Docs: fill documentation gaps found in user questions

Add pages on class-hierarchy/smart-pointer/variant/chrono recipes, working
without exceptions, and large, streamed and partial input. Extend the FAQ
(23 entries, Known bugs first), parse error documentation (empty-input
checklist, line/column, diagnostic positions), element access, conversions,
creating values, ADL troubleshooting, memory, and build/distribution notes.
Add 14 examples with generated output. Correct the statement that parse errors
cannot be recovered from with -fno-exceptions.

The topics come from recurring questions on Stack Overflow, Reddit, Hacker
News, YouTube, and the project's GitHub discussions and issues.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/examples/no_exceptions_access.cpp

@@ -0,0 +1,42 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    json j = json::parse(R"({"name": "Mary", "age": 42})");
+
+    // look up the key, then test the type: neither step throws
+    for (const char* key : {"name", "age", "city"})
+    {
+        const auto it = j.find(key);
+        if (it == j.end())
+        {
+            std::cout << key << ": missing\n";
+        }
+        else if (it->is_string())
+        {
+            std::cout << key << ": string \"" << it->get_ref<const std::string&>() << "\"\n";
+        }
+        else
+        {
+            std::cout << key << ": not a string, but " << it->type_name() << '\n';
+        }
+    }
+
+    // get_ptr returns a null pointer if the value has another type
+    const std::string* name = j["name"].get_ptr<const std::string*>();
+    const std::string* age = j["age"].get_ptr<const std::string*>();
+    std::cout << "get_ptr<string*>: name = " << (name != nullptr) << ", age = " << (age != nullptr) << '\n';
+
+    // value() is NOT exception-free: it throws if the key exists with a different type
+    try
+    {
+        std::cout << j.value("name", 0) << '\n';
+    }
+    catch (const json::type_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/no_exceptions_access.output

@@ -0,0 +1,5 @@
+name: string "Mary"
+age: not a string, but number
+city: missing
+get_ptr<string*>: name = 1, age = 0
+[json.exception.type_error.302] type must be number, but is string

docs/mkdocs/docs/examples/no_exceptions_convert.c++17.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <optional>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+struct person
+{
+    std::string name;
+    int age;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, age)
+
+// Compile this function with exceptions enabled and call it from code that does not use them.
+std::optional<person> to_person(const json& j)
+{
+    try
+    {
+        return j.get<person>();
+    }
+    catch (const json::exception&)
+    {
+        return std::nullopt;
+    }
+}
+
+int main()
+{
+    const json good = {{"name", "Mary"}, {"age", 42}};
+    const json bad = {{"name", "Mary"}, {"age", "forty-two"}};
+    const json incomplete = {{"name", "Mary"}};
+
+    for (const json& j : {good, bad, incomplete})
+    {
+        if (const auto p = to_person(j))
+        {
+            std::cout << "person: " << p->name << ", " << p->age << '\n';
+        }
+        else
+        {
+            std::cout << "not a person: " << j << '\n';
+        }
+    }
+}

docs/mkdocs/docs/examples/no_exceptions_convert.c++17.output

@@ -0,0 +1,3 @@
+person: Mary, 42
+not a person: {"age":"forty-two","name":"Mary"}
+not a person: {"name":"Mary"}

docs/mkdocs/docs/examples/no_exceptions_parse.cpp

@@ -0,0 +1,28 @@
+#include <cstdint>
+#include <iostream>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// None of the calls below throws, so this example also works with -fno-exceptions.
+int main()
+{
+    const std::string invalid = R"({"name": "Mary", "age": )";
+
+    // parse() with allow_exceptions = false returns a discarded value
+    json j = json::parse(invalid, nullptr, false);
+    std::cout << std::boolalpha << "parse: discarded = " << j.is_discarded() << '\n';
+
+    // accept() only tells whether the input is valid JSON
+    std::cout << "accept: " << json::accept(invalid) << '\n';
+
+    // the binary formats have the same parameter
+    const std::vector<std::uint8_t> truncated_cbor = {0x83, 0x01};
+    json c = json::from_cbor(truncated_cbor, true, false);
+    std::cout << "from_cbor: discarded = " << c.is_discarded() << '\n';
+
+    // valid input is parsed as usual
+    json valid = json::parse(R"({"name": "Mary"})", nullptr, false);
+    std::cout << "valid input: " << valid << '\n';
+}

docs/mkdocs/docs/examples/no_exceptions_parse.output

@@ -0,0 +1,4 @@
+parse: discarded = true
+accept: false
+from_cbor: discarded = true
+valid input: {"name":"Mary"}

docs/mkdocs/docs/examples/parse_error_position.cpp

@@ -0,0 +1,42 @@
+#include <iostream>
+#include <utility>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// line and column (both starting at 1) of a byte index in a text
+std::pair<std::size_t, std::size_t> line_column(const std::string& input, std::size_t byte)
+{
+    std::size_t line = 1;
+    std::size_t column = 1;
+    for (std::size_t i = 0; i + 1 < byte && i < input.size(); ++i)
+    {
+        if (input[i] == '\n')
+        {
+            ++line;
+            column = 1;
+        }
+        else
+        {
+            ++column;
+        }
+    }
+    return {line, column};
+}
+
+int main()
+{
+    const std::string input = "{\n  \"a\": 1,\n  \"b\": ]\n}";
+
+    try
+    {
+        const json j = json::parse(input);
+        std::cout << j << '\n';
+    }
+    catch (const json::parse_error& e)
+    {
+        const auto position = line_column(input, e.byte);
+        std::cout << e.what() << '\n';
+        std::cout << "byte " << e.byte << " = line " << position.first << ", column " << position.second << '\n';
+    }
+}

docs/mkdocs/docs/examples/parse_error_position.output

@@ -0,0 +1,2 @@
+[json.exception.parse_error.101] parse error at line 3, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+byte 20 = line 3, column 8

docs/mkdocs/docs/examples/parse_error_position_diagnostic.cpp

@@ -0,0 +1,46 @@
+#define JSON_DIAGNOSTIC_POSITIONS 1
+#include <iostream>
+#include <utility>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// line and column (both starting at 1) of a byte index in a text
+std::pair<std::size_t, std::size_t> line_column(const std::string& input, std::size_t byte)
+{
+    std::size_t line = 1;
+    std::size_t column = 1;
+    for (std::size_t i = 0; i + 1 < byte && i < input.size(); ++i)
+    {
+        if (input[i] == '\n')
+        {
+            ++line;
+            column = 1;
+        }
+        else
+        {
+            ++column;
+        }
+    }
+    return {line, column};
+}
+
+int main()
+{
+    const std::string input = "{\n  \"name\": \"Mary\",\n  \"age\": \"forty-two\"\n}";
+    const json j = json::parse(input); // the input is valid JSON ...
+
+    try
+    {
+        const int age = j["age"]; // ... but the value has the wrong type
+        std::cout << age << '\n';
+    }
+    catch (const json::exception& e)
+    {
+        std::cout << e.what() << '\n';
+
+        // start_pos() is a 0-based index into the input; the helper expects a 1-based byte index
+        const auto position = line_column(input, j["age"].start_pos() + 1);
+        std::cout << "the value starts at line " << position.first << ", column " << position.second << '\n';
+    }
+}

docs/mkdocs/docs/examples/parse_error_position_diagnostic.output

@@ -0,0 +1,2 @@
+[json.exception.type_error.302] (bytes 29-40) type must be number, but is string
+the value starts at line 3, column 10

docs/mkdocs/docs/examples/partial_input_buffering.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+std::string buffer;
+
+// call for every chunk; returns true and sets `value` once the buffer holds one complete JSON value
+bool push(const std::string& chunk, json& value)
+{
+    buffer += chunk;
+    try
+    {
+        value = json::parse(buffer);
+        buffer.clear();
+        return true;
+    }
+    catch (const json::parse_error& e)
+    {
+        if (e.byte == buffer.size() + 1)
+        {
+            return false; // the input ends prematurely: wait for more data
+        }
+        throw; // a real syntax error
+    }
+}
+
+int main()
+{
+    json value;
+    for (const std::string chunk : {"{\"na", "me\": \"Ma", "ry\", \"l", "ist\": [1, 2", ", 3]}"})
+    {
+        std::cout << "chunk " << chunk << " -> " << (push(chunk, value) ? "complete" : "incomplete") << '\n';
+    }
+    std::cout << value << '\n';
+
+    // a syntax error in the middle is not mistaken for missing data
+    try
+    {
+        push("[1, ]", value);
+    }
+    catch (const json::parse_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/partial_input_buffering.output

@@ -0,0 +1,7 @@
+chunk {"na -> incomplete
+chunk me": "Ma -> incomplete
+chunk ry", "l -> incomplete
+chunk ist": [1, 2 -> incomplete
+chunk , 3]} -> complete
+{"list":[1,2,3],"name":"Mary"}
+[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal

docs/mkdocs/docs/examples/partial_input_cbor.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a CBOR value followed by other data
+    const std::vector<std::uint8_t> cbor = json::to_cbor(json{1, 2, 3});
+    std::string data(cbor.begin(), cbor.end());
+    data += "TRAILING";
+
+    std::istringstream input(data);
+    json j = json::from_cbor(input, false); // strict = false: stop after the first value
+
+    std::cout << "value: " << j << '\n';
+    std::cout << "bytes used: " << input.tellg() << '\n';
+
+    std::string rest;
+    input >> rest;
+    std::cout << "remaining input: " << rest << '\n';
+}

docs/mkdocs/docs/examples/partial_input_cbor.output

@@ -0,0 +1,3 @@
+value: [1,2,3]
+bytes used: 4
+remaining input: TRAILING

docs/mkdocs/docs/examples/partial_input_concatenated.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    std::istringstream input(R"({"a":1} [2,3] 4 "s")");
+
+    // check for the end of the stream before each read, because a read at the end throws
+    json j;
+    while (input >> std::ws && input.peek() != std::char_traits<char>::eof())
+    {
+        input >> j;
+        std::cout << j << '\n';
+    }
+}

docs/mkdocs/docs/examples/partial_input_concatenated.output

@@ -0,0 +1,4 @@
+{"a":1}
+[2,3]
+4
+"s"

docs/mkdocs/docs/examples/partial_input_discard_records.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+void handle(const json& record)
+{
+    std::cout << "handling " << record << '\n';
+}
+
+int main()
+{
+    std::istringstream file(R"([{"id": 1}, {"id": 2}, {"id": 3}])");
+
+    json result = json::parse(file, [](int depth, json::parse_event_t event, json & record)
+    {
+        if (depth == 1 && event == json::parse_event_t::object_end)
+        {
+            handle(record);
+            return false; // discard the record
+        }
+        return true;
+    });
+
+    std::cout << "result: " << result << '\n';
+}

docs/mkdocs/docs/examples/partial_input_discard_records.output

@@ -0,0 +1,4 @@
+handling {"id":1}
+handling {"id":2}
+handling {"id":3}
+result: []

docs/mkdocs/docs/examples/partial_input_sax_stop.cpp

@@ -0,0 +1,81 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+struct find_id : nlohmann::json_sax<json>
+{
+    bool next_is_id = false;
+    json::number_unsigned_t id = 0;
+
+    bool key(std::string& name) override
+    {
+        next_is_id = (name == "id");
+        return true;
+    }
+
+    bool number_unsigned(json::number_unsigned_t value) override
+    {
+        if (next_is_id)
+        {
+            id = value;
+            return false; // found: stop parsing
+        }
+        return true;
+    }
+
+    bool null() override
+    {
+        return true;
+    }
+    bool boolean(bool /*val*/) override
+    {
+        return true;
+    }
+    bool number_integer(json::number_integer_t /*val*/) override
+    {
+        return true;
+    }
+    bool number_float(json::number_float_t /*val*/, const std::string& /*s*/) override
+    {
+        return true;
+    }
+    bool string(std::string& /*val*/) override
+    {
+        return true;
+    }
+    bool binary(json::binary_t& /*val*/) override
+    {
+        return true;
+    }
+    bool start_object(std::size_t /*elements*/) override
+    {
+        return true;
+    }
+    bool end_object() override
+    {
+        return true;
+    }
+    bool start_array(std::size_t /*elements*/) override
+    {
+        return true;
+    }
+    bool end_array() override
+    {
+        return true;
+    }
+    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const json::exception& /*ex*/) override
+    {
+        return false;
+    }
+};
+
+int main()
+{
+    find_id handler;
+    const bool completed = json::sax_parse(R"({"x": [1, 2, 3], "id": 42, "rest": [4, 5, 6]})", &handler);
+
+    std::cout << std::boolalpha;
+    std::cout << "parse completed: " << completed << '\n';
+    std::cout << "id: " << handler.id << '\n';
+}

docs/mkdocs/docs/examples/partial_input_sax_stop.output

@@ -0,0 +1,2 @@
+parse completed: false
+id: 42

docs/mkdocs/docs/examples/type_recipes_chrono.cpp

@@ -0,0 +1,56 @@
+#include <chrono>
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+namespace nlohmann
+{
+template <typename Rep, typename Period>
+struct adl_serializer<std::chrono::duration<Rep, Period>>
+{
+    static void to_json(json& j, const std::chrono::duration<Rep, Period>& d)
+    {
+        j = d.count();
+    }
+
+    static void from_json(const json& j, std::chrono::duration<Rep, Period>& d)
+    {
+        d = std::chrono::duration<Rep, Period>(j.get<Rep>());
+    }
+};
+
+template <typename Duration>
+struct adl_serializer<std::chrono::time_point<std::chrono::system_clock, Duration>>
+{
+    static void to_json(json& j, const std::chrono::time_point<std::chrono::system_clock, Duration>& t)
+    {
+        j = t.time_since_epoch();
+    }
+
+    static void from_json(const json& j, std::chrono::time_point<std::chrono::system_clock, Duration>& t)
+    {
+        t = std::chrono::time_point<std::chrono::system_clock, Duration>(j.get<Duration>());
+    }
+};
+} // namespace nlohmann
+
+int main()
+{
+    using namespace std::chrono;
+
+    std::cout << std::boolalpha;
+
+    // the unit is not part of the JSON value
+    const json timeout = milliseconds(1500);
+    std::cout << "duration: " << timeout << '\n';
+    std::cout << "as milliseconds: " << timeout.get<milliseconds>().count() << '\n';
+
+    // a system_clock time point is the time since the Unix epoch
+    const time_point<system_clock, milliseconds> t(milliseconds(1700000000123));
+    const json stamp = t;
+    std::cout << "time point: " << stamp << '\n';
+
+    const auto back = stamp.get<time_point<system_clock, milliseconds>>();
+    std::cout << "round trip: " << (back == t) << '\n';
+}

docs/mkdocs/docs/examples/type_recipes_chrono.output

@@ -0,0 +1,4 @@
+duration: 1500
+as milliseconds: 1500
+time point: 1700000000123
+round trip: true

docs/mkdocs/docs/examples/type_recipes_class_hierarchy.c++14.cpp

@@ -0,0 +1,99 @@
+#include <iostream>
+#include <memory>
+#include <stdexcept>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+struct shape
+{
+    virtual ~shape() = default;
+    virtual json serialize() const = 0;
+};
+
+struct circle : shape
+{
+    double radius;
+
+    explicit circle(double r) : radius(r) {}
+
+    json serialize() const override
+    {
+        return {{"type", "circle"}, {"radius", radius}};
+    }
+};
+
+struct rectangle : shape
+{
+    double width;
+    double height;
+
+    rectangle(double w, double h) : width(w), height(h) {}
+
+    json serialize() const override
+    {
+        return {{"type", "rectangle"}, {"width", width}, {"height", height}};
+    }
+};
+
+namespace nlohmann
+{
+template <>
+struct adl_serializer<std::unique_ptr<shape>>
+{
+    static void to_json(json& j, const std::unique_ptr<shape>& p)
+    {
+        j = p ? p->serialize() : json(nullptr);
+    }
+
+    static void from_json(const json& j, std::unique_ptr<shape>& p)
+    {
+        if (j.is_null())
+        {
+            p.reset();
+            return;
+        }
+
+        const auto& type = j.at("type").get_ref<const std::string&>();
+        if (type == "circle")
+        {
+            p = std::make_unique<circle>(j.at("radius").get<double>());
+        }
+        else if (type == "rectangle")
+        {
+            p = std::make_unique<rectangle>(j.at("width").get<double>(), j.at("height").get<double>());
+        }
+        else
+        {
+            throw std::invalid_argument("unknown shape type: " + type);
+        }
+    }
+};
+} // namespace nlohmann
+
+int main()
+{
+    std::vector<std::unique_ptr<shape>> shapes;
+    shapes.push_back(std::make_unique<circle>(1.5));
+    shapes.push_back(std::make_unique<rectangle>(2, 3));
+
+    const json j = shapes;
+    std::cout << j << '\n';
+
+    // reading creates objects of the derived types
+    const auto back = j.get<std::vector<std::unique_ptr<shape>>>();
+    std::cout << std::boolalpha;
+    std::cout << "first is a circle: " << (dynamic_cast<circle*>(back[0].get()) != nullptr) << '\n';
+    std::cout << "second is a rectangle: " << (dynamic_cast<rectangle*>(back[1].get()) != nullptr) << '\n';
+
+    // an unknown type tag is reported
+    try
+    {
+        json{{"type", "star"}}.get<std::unique_ptr<shape>>();
+    }
+    catch (const std::invalid_argument& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/type_recipes_class_hierarchy.c++14.output

@@ -0,0 +1,4 @@
+[{"radius":1.5,"type":"circle"},{"height":3.0,"type":"rectangle","width":2.0}]
+first is a circle: true
+second is a rectangle: true
+unknown shape type: star

docs/mkdocs/docs/examples/type_recipes_smart_pointers.c++14.cpp

@@ -0,0 +1,90 @@
+#include <iostream>
+#include <memory>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+namespace nlohmann
+{
+template <typename T>
+struct adl_serializer<std::shared_ptr<T>>
+{
+    static void to_json(json& j, const std::shared_ptr<T>& p)
+    {
+        if (p)
+        {
+            j = *p;
+        }
+        else
+        {
+            j = nullptr;
+        }
+    }
+
+    static void from_json(const json& j, std::shared_ptr<T>& p)
+    {
+        if (j.is_null())
+        {
+            p = nullptr;
+        }
+        else
+        {
+            p = std::make_shared<T>(j.get<typename std::remove_const<T>::type>());
+        }
+    }
+};
+
+template <typename T>
+struct adl_serializer<std::unique_ptr<T>>
+{
+    static void to_json(json& j, const std::unique_ptr<T>& p)
+    {
+        if (p)
+        {
+            j = *p;
+        }
+        else
+        {
+            j = nullptr;
+        }
+    }
+
+    static void from_json(const json& j, std::unique_ptr<T>& p)
+    {
+        if (j.is_null())
+        {
+            p = nullptr;
+        }
+        else
+        {
+            p = std::make_unique<T>(j.get<T>());
+        }
+    }
+};
+} // namespace nlohmann
+
+struct point
+{
+    int x;
+    int y;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(point, x, y)
+
+int main()
+{
+    // an empty pointer is written as null
+    const std::vector<std::shared_ptr<point>> points = {std::make_shared<point>(point{1, 2}), nullptr};
+    const json j = points;
+    std::cout << j << '\n';
+
+    // reading allocates new objects
+    const auto back = j.get<std::vector<std::shared_ptr<point>>>();
+    std::cout << back[0]->x << ", " << back[0]->y << ", " << (back[1] == nullptr) << '\n';
+
+    // pointers to const and unique_ptr work as well
+    const auto const_ptr = j[0].get<std::shared_ptr<const point>>();
+    const auto unique = j[0].get<std::unique_ptr<point>>();
+    std::cout << const_ptr->y << ", " << unique->x << '\n';
+}

docs/mkdocs/docs/examples/type_recipes_smart_pointers.c++14.output

@@ -0,0 +1,3 @@
+[{"x":1,"y":2},null]
+1, 2, 1
+2, 1

docs/mkdocs/docs/examples/type_recipes_variant.c++17.cpp

@@ -0,0 +1,63 @@
+#include <iostream>
+#include <stdexcept>
+#include <variant>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+namespace geo
+{
+struct circ
+{
+    double radius;
+};
+
+struct rect
+{
+    double width;
+    double height;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(circ, radius)
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(rect, width, height)
+
+using figure = std::variant<circ, rect>;
+
+void to_json(json& j, const figure& f)
+{
+    std::visit([&j](const auto & alternative)
+    {
+        j = alternative;
+    }, f);
+    j["type"] = std::holds_alternative<circ>(f) ? "circ" : "rect";
+}
+
+void from_json(const json& j, figure& f)
+{
+    const auto& type = j.at("type").get_ref<const std::string&>();
+    if (type == "circ")
+    {
+        f = j.get<circ>();
+    }
+    else if (type == "rect")
+    {
+        f = j.get<rect>();
+    }
+    else
+    {
+        throw std::invalid_argument("unknown figure type: " + type);
+    }
+}
+} // namespace geo
+
+int main()
+{
+    const std::vector<geo::figure> figures = {geo::circ{2}, geo::rect{3, 4}};
+
+    const json j = figures;
+    std::cout << j << '\n';
+
+    const auto back = j.get<std::vector<geo::figure>>();
+    std::cout << "alternatives read back: " << back[0].index() << ", " << back[1].index() << '\n';
+}

docs/mkdocs/docs/examples/type_recipes_variant.c++17.output

@@ -0,0 +1,2 @@
+[{"radius":2.0,"type":"circ"},{"height":4.0,"type":"rect","width":3.0}]
+alternatives read back: 0, 1

docs/mkdocs/docs/features/arbitrary_types.md

@@ -409,6 +409,32 @@ namespace nlohmann {
 }
 ```
 
+## Why isn't my `to_json` or `from_json` found?
+
+The library calls `to_json` and `from_json` without qualification, so the compiler finds them by
+[argument-dependent lookup](https://en.cppreference.com/w/cpp/language/adl) in the namespace of the type, or in the
+namespaces of its template arguments. The usual reasons for a function that is "not found" are:
+
+- **The type is an alias of a standard type.** After `#!cpp using Hash = std::array<std::uint8_t, 6>;` the type
+  *is* `std::array<std::uint8_t, 6>`, which lives in namespace `std`. A `to_json(json&, const Hash&)` in your namespace
+  is never selected. Either give the type its own identity, for example `#!cpp struct Hash : std::array<std::uint8_t, 6> {};`
+  (the function is then found in `Hash`'s namespace), or specialize
+  [`adl_serializer<Hash>`](#how-do-i-convert-third-party-types).
+- **The function is in the wrong namespace.** It must be in the namespace of the type (a global type needs a global
+  function), not in the namespace of the code that calls the conversion. Specializations of `adl_serializer` belong in
+  namespace `nlohmann`.
+- **It is declared too late.** A conversion can only use what has been declared when it is instantiated. If
+  `#!cpp json j = std::vector<third_party::string>{...};` appears before the `adl_serializer` specialization, the
+  compiler reports an error such as "explicit specialization of `adl_serializer<...>` after instantiation". Put the
+  specialization in a small header that every file includes **before** it uses the type with `json`.
+- **It is a template.** For `template <class T> struct box`, write `template <class T> void to_json(json&, const box<T>&)`,
+  not an overload for one `T`.
+- **It worked by accident.** Some versions found `to_json` overloads in `nlohmann::detail` through argument-dependent
+  lookup of the base class of `basic_json`. Do not rely on this; it is not part of the interface.
+
+For smart pointers, class hierarchies, `std::variant`, and `std::chrono`, see
+[Recipes for common types](type_recipes.md).
+
 ## Why can't I convert to/from `std::any`?
 
 `std::any` is intentionally excluded from `get<T>()`/generic conversion support, so `get<std::any>()` and
@@ -505,6 +531,7 @@ struct bad_serializer
 
 ## See also
 
+- [Recipes for common types](type_recipes.md) - smart pointers, class hierarchies, `std::variant`, and `std::chrono`
 - [Converting values](conversions.md) - the general overview of `get`/`get_to` and implicit conversions
 - [Specializing enum conversion](enum_conversion.md) - map enums to JSON strings instead of integers
 - [Supported macros](macros.md) - reference for `NLOHMANN_DEFINE_TYPE_*` and related macros

docs/mkdocs/docs/features/assertions.md

@@ -7,7 +7,9 @@ detect bugs in client code.
 ## Switch off runtime assertions
 
 Runtime assertions can be switched off by defining the preprocessor macro `NDEBUG` (see the
-[documentation of assert](https://en.cppreference.com/w/cpp/error/assert)) which is the default for release builds.
+[documentation of assert](https://en.cppreference.com/w/cpp/error/assert)) which is the default for release builds. Without `NDEBUG`, the assertions are compiled in and contain the name of the source
+file (`__FILE__`); see [notes for builds and distribution](../integration/index.md#notes-for-builds-and-distribution)
+if that path must not end up in your binaries.
 
 ## Change assertion behavior
 

docs/mkdocs/docs/features/conversions.md

@@ -112,6 +112,29 @@ Implicit conversions are convenient but can be surprising (for example, in overl
 be disabled by defining [`JSON_USE_IMPLICIT_CONVERSIONS`](../api/macros/json_use_implicit_conversions.md) to `#!cpp 0`,
 which forces the explicit `get` form and can catch unintended conversions at compile time.
 
+!!! warning "`auto` copies the JSON value; it does not convert it"
+
+    The type of `#!cpp j["name"]` is `json`, not the C++ type of the value inside. `#!cpp auto` therefore deduces
+    `json`:
+
+    ```cpp
+    json j = {{"name", "Mary"}, {"age", 42}};
+
+    auto name = j["name"];                       // json: a copy of the value; prints as "Mary" (with quotes)
+    std::string s1 = j["name"];                  // std::string: implicit conversion
+    auto s2 = j["name"].get<std::string>();      // std::string: explicit conversion
+    auto& age = j["age"];                        // json&: a reference, no copy
+    age = 43;                                    // changes j
+    ```
+
+    This is also why `#!cpp std::cout << j["name"]` prints the quotes (see
+    [getting a string without quotes](#getting-values-out)), and why a `json` value cannot be passed to `printf`: the
+    argument is not an `int` or a `char*`, and a compiler either rejects passing it through `...` (Clang does) or
+    compiles it and prints garbage. Convert first: `#!cpp std::printf("%d", j["age"].get<int>());`.
+
+    Prefer `get<T>()` over `auto` when you want the C++ value, and `auto&` or `const auto&` when you want to avoid a
+    copy of a large value.
+
 !!! warning "Conversions do not range-check numbers"
 
     Just like C++ itself, the `get` family performs numeric conversions without range checks — retrieving a

docs/mkdocs/docs/features/creating_values.md

@@ -59,6 +59,25 @@ with a string as the first element is treated as an object, everything else as a
     [FAQ](../home/faq.md#brace-initialization-yields-arrays) for details and the opt-in
     [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) macro.
 
+### What does this produce?
+
+The following table shows how some common spellings are interpreted. When in doubt, use `#!cpp json::array()`,
+`#!cpp json::object()`, or the `#!cpp json(value)` form with parentheses.
+
+| code                                            | result                       | note                                         |
+|-------------------------------------------------|------------------------------|----------------------------------------------|
+| `#!cpp json j = {};` / `#!cpp json j{};`        | `#!json null`                | use `json::object()` or `json::array()`      |
+| `#!cpp json j = json::object();`                | `#!json {}`                  |                                              |
+| `#!cpp json j = json::array();`                 | `#!json []`                  |                                              |
+| `#!cpp json j(true);`                           | `#!json true`                | parentheses create the value itself          |
+| `#!cpp json j = {true};`                        | `#!json [true]`              | braces create a one-element array (`#!cpp json j{true};` depends on the compiler, see the [FAQ](../home/faq.md#brace-initialization-yields-arrays)) |
+| `#!cpp json j = {{"a", 1}};`                    | `#!json {"a":1}`             | all elements are `[string, value]` pairs: object |
+| `#!cpp json j = {{"a", 1}, {"b"}};`             | `#!json [["a",1],["b"]]`     | one element is not a pair: array             |
+| `#!cpp json j = {{"a", 1}, 2};`                 | `#!json [["a",1],2]`         | a plain value among pairs: array             |
+| `#!cpp json j = {{"a", 1, 2}};`                 | `#!json [["a",1,2]]`         | a three-element list is not a pair: array    |
+| `#!cpp json j = "{\"a\":1}";`                   | `#!json "{\"a\":1}"`           | a string **value**; it is not parsed         |
+| `#!cpp json j = json::parse("{\"a\":1}");`      | `#!json {"a":1}`             | parse text with `parse` or `_json`           |
+
 ## Building incrementally
 
 A value can also be built up piece by piece. Accessing a non-existing object key or array index with

docs/mkdocs/docs/features/element_access/index.md

@@ -21,3 +21,42 @@ flowchart TD
     A --> F{"just testing first?"}
     F -->|"yes"| G["contains() / find()"]
 ```
+
+## Does this key exist?
+
+Use [`contains`](../../api/basic_json/contains.md) to test for a key; it does not modify the value and does not throw:
+
+```cpp
+json j = {{"name", "Mary"}, {"address", {{"city", "Berlin"}}}};
+
+j.contains("name");                   // true
+j.contains("age");                    // false
+j.contains("city");                   // false: contains() only looks at the top level
+j["address"].contains("city");        // true
+j.contains(json::json_pointer("/address/city"));  // true: a JSON pointer tests a nested path in one call
+```
+
+If the value is needed afterwards, [`find`](../../api/basic_json/find.md) tests and accesses with a single lookup:
+
+```cpp
+if (auto it = j.find("name"); it != j.end())
+{
+    std::cout << *it << '\n';
+}
+```
+
+`contains` also returns `true` for a key whose value is `null`; use `j.contains("k") && !j["k"].is_null()` if a
+`null` should count as missing. To read a value with a fallback instead, see [`value`](default_value.md).
+
+!!! warning "`operator[]` inserts missing keys"
+
+    Like `#!cpp std::map::operator[]`, the non-const [`operator[]`](unchecked_access.md) adds a `null` value if the key
+    is missing. Testing a key with it therefore *changes the object*:
+
+    ```cpp
+    json j = {{"foo", 1}};
+    bool absent = j["bar"].is_null();   // true, but j is now {"bar": null, "foo": 1}
+    ```
+
+    Use `contains`/`find` to test, and [`at`](checked_access.md) to access a value that must exist (it throws an
+    [`out_of_range`](../../home/exceptions.md#out-of-range) exception otherwise).

docs/mkdocs/docs/features/no_exceptions.md

@@ -0,0 +1,113 @@
+# Working Without Exceptions
+
+By default, the library reports errors by throwing exceptions (see [Exceptions](../home/exceptions.md)). This page
+collects what to use when exceptions are unwanted or unavailable, for example in embedded systems, game engines, or
+code compiled with `-fno-exceptions`.
+
+## Two different questions
+
+1. **Can my code avoid *catching* exceptions?** Yes. For parsing and for accessing values there are functions that
+   report failure through a return value. They work in a normal build and need no `#!cpp try`/`#!cpp catch`.
+2. **Can the library be *compiled* without exceptions?** Yes, with `-fno-exceptions` or by defining
+   [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md). Both have the same effect: every `#!cpp throw` in the
+   library becomes a call to `std::abort()`. The functions listed below never reach a `#!cpp throw` for the failures
+   they report, so they keep working in this configuration. Anything else that fails aborts the program.
+
+## Parsing
+
+| function                                                                                    | on invalid input                                    |
+|---------------------------------------------------------------------------------------------|-----------------------------------------------------|
+| `#!cpp json::parse(input, nullptr, false)`                                                  | returns a *discarded* value; test with `is_discarded()` |
+| [`accept`](../api/basic_json/accept.md)                                                     | returns `#!cpp false`                               |
+| `#!cpp json::from_cbor(input, true, false)` (and the other `from_*` functions)              | returns a *discarded* value                         |
+| [`sax_parse`](../api/basic_json/sax_parse.md) with your own handler                         | returns `#!cpp false` after calling `parse_error`   |
+
+??? example "Example: parse and validate without exceptions"
+
+    ```cpp
+    --8<-- "examples/no_exceptions_parse.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/no_exceptions_parse.output"
+    ```
+
+None of the calls in this example throws, so it also compiles and runs with `-fno-exceptions`.
+
+The discarded value carries no message. If you need the position or the reason, use the SAX interface; see
+[Parsing and exceptions](parsing/parse_exceptions.md).
+
+## Accessing values
+
+The access functions are not equally safe. Only some of them never throw:
+
+| expression                          | if the key is missing or the type is wrong                                    |
+|-------------------------------------|-------------------------------------------------------------------------------|
+| `#!cpp j.contains("k")`             | returns `#!cpp false` for a missing key; never throws                         |
+| `#!cpp j.find("k")`                 | returns `end()` for a missing key; never throws                               |
+| `#!cpp j.is_string()`, ...          | the `is_*` functions test the type; never throw                               |
+| `#!cpp j.get_ptr<const std::string*>()` | returns `#!cpp nullptr` for a different type; never throws                |
+| `#!cpp j.at("k")`                   | throws `out_of_range.403` for a missing key                                   |
+| `#!cpp j.get<int>()`                | throws `type_error.302` for a value that is not a number                      |
+| `#!cpp j.value("k", 0)`             | returns the default for a missing key, but **throws `type_error.302` if `k` exists with another type** |
+| `#!cpp j["k"]` (non-const)          | inserts `null` for a missing key                                              |
+| `#!cpp j["k"]` (const)              | undefined behavior for a missing key                                          |
+
+So reading a value that may be absent or of the wrong type without exceptions takes two steps: look up, then test the
+type.
+
+??? example "Example: look up a key and test its type"
+
+    ```cpp
+    --8<-- "examples/no_exceptions_access.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/no_exceptions_access.output"
+    ```
+
+The last lines of the example show why `value` is not on the safe list: it returns the default only for a *missing*
+key.
+
+For numbers, test with `is_number()` (or `is_number_integer()`, `is_number_unsigned()`, `is_number_float()`) before
+calling `get<int>()`, and see [number handling](types/number_handling.md) for range and precision. Whether a value
+fits into the target type is not checked by `get`.
+
+## Converting to your own types
+
+`from_json` functions (including the ones generated by the
+[`NLOHMANN_DEFINE_TYPE_*` macros](arbitrary_types.md#simplify-your-life-with-macros)) report problems by throwing.
+There is no variant that returns an error code. Without exceptions you have two options:
+
+- Validate the JSON value yourself, as shown above, and fill your struct field by field.
+- Convert in a function that is compiled **with** exceptions enabled and catches them at the boundary, returning
+  `std::optional` or an error code to the rest of your code:
+
+??? example "Example: convert to a struct and report failure as std::optional"
+
+    ```cpp
+    --8<-- "examples/no_exceptions_convert.c++17.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/no_exceptions_convert.c++17.output"
+    ```
+
+## Overriding what happens instead of an exception
+
+With exceptions off, you can replace the `abort()` by your own code, for example to log the message first. See
+[Switch off exceptions](../home/exceptions.md#switch-off-exceptions) and
+[`JSON_THROW_USER`](../api/macros/json_throw_user.md). The handler must not return normally.
+
+## See also
+
+- [Exceptions](../home/exceptions.md) - all exceptions and their ids
+- [Parsing and exceptions](parsing/parse_exceptions.md) - the parsing alternatives in detail
+- [Parsing untrusted input](parsing/untrusted_input.md)
+- [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md)

docs/mkdocs/docs/features/parsing/index.md

@@ -33,7 +33,9 @@ json data = json::parse(f);
 ```
 
 The input must be encoded in UTF-8; other encodings are not supported. A single input may contain only one JSON value.
-Inputs consisting of multiple values separated by newlines are handled by the [JSON Lines](json_lines.md) format.
+Inputs consisting of multiple values separated by newlines are handled by the [JSON Lines](json_lines.md) format; input
+that arrives in chunks or contains several values is covered in
+[Large, streamed, and partial input](large_and_partial_input.md).
 
 By default, the library rejects comments and trailing commas. Both can be enabled with parameters of the `parse`
 function — see [comments](../comments.md) and [trailing commas](../trailing_commas.md).
@@ -85,7 +87,7 @@ again without changing any result.
 
 ## SAX vs. DOM parsing
 
-The library offers two parsing models:
+The library offers two parsing models, and a third, read-only alternative:
 
 - **DOM parsing** (the default): the complete input is read and stored as an in-memory `basic_json` value that can be
   traversed and modified freely. This is what [`parse`](../../api/basic_json/parse.md) does, and it is the right choice
@@ -95,6 +97,13 @@ The library offers two parsing models:
   inputs or when you only need to extract parts of the input. See the [SAX interface](sax_interface.md) for details and
   [`sax_parse`](../../api/basic_json/sax_parse.md) for the API.
 
+- **Document and views** (`#!cpp <nlohmann/json_view.hpp>`, added in version 3.13.0): [`json_document::parse`](../../api/basic_json_document/parse.md)
+  reads the same JSON grammar but builds a flat, read-only index of the values instead of a `basic_json` tree. Strings and
+  floating-point numbers are read from the text on demand, and only the parts you
+  [`materialize()`](../../api/basic_json_view/materialize.md) become `basic_json` values. This avoids most of the work when you
+  need only a few values from a large or frequently parsed text; see [Zero-copy JSON views](../json_view.md). It is read-only, so use
+  `parse` when you need to modify the value.
+
 You can influence a DOM parse without switching to the SAX interface by passing a
 [parser callback](parser_callbacks.md), which is called during parsing and can, for example, discard parts of the input.
 
@@ -111,7 +120,9 @@ options.
 - [`accept`](../../api/basic_json/accept.md) - check if the input is valid JSON
 - [`sax_parse`](../../api/basic_json/sax_parse.md) - generate SAX events
 - [JSON Lines](json_lines.md) - parse newline-delimited JSON
+- [Large, streamed, and partial input](large_and_partial_input.md) - chunked, concatenated, and very large input
 - [parser callbacks](parser_callbacks.md) - influence the parsing by a callback function
 - [SAX interface](sax_interface.md) - implement a custom SAX handler
+- [Zero-copy JSON views](../json_view.md) - parse into a read-only document and read it through views
 - [parsing and exceptions](parse_exceptions.md) - control error handling
 - [parsing untrusted input](untrusted_input.md) - what to consider when parsing input from untrusted sources

docs/mkdocs/docs/features/parsing/large_and_partial_input.md

@@ -0,0 +1,154 @@
+# Large, Streamed, and Partial Input
+
+[`parse`](../../api/basic_json/parse.md) reads exactly one complete JSON value and builds it in memory. It cannot be
+paused and resumed, and it does not hand back a half-parsed value when the input ends early. This page shows what to do
+when the input does not fit that model: it arrives in pieces, it contains several values, or it is too large to hold
+as a `json` value.
+
+```mermaid
+flowchart TD
+    A["my input is..."] --> B{"several JSON values in one stream?"}
+    B -->|"yes"| C["read them one at a time"]
+    A --> D{"arriving in chunks (socket, pipe)?"}
+    D -->|"yes"| E["frame the messages, or buffer until complete"]
+    A --> F{"too large to keep in memory?"}
+    F -->|"yes"| G["discard parts with a callback, or use SAX"]
+    A --> H{"only a small part is needed?"}
+    H -->|"yes"| I["stop early with SAX, or read through a view"]
+```
+
+## Several values in one stream
+
+For newline-delimited input, read line by line and parse each line, as described in [JSON Lines](json_lines.md). For
+values that are simply concatenated, [`operator>>`](../../api/operator_gtgt.md) reads one value and leaves the stream
+positioned after it. Check for the end of the stream before each read, because a read at the end throws:
+
+??? example "Example: read concatenated values"
+
+    ```cpp
+    --8<-- "examples/partial_input_concatenated.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_concatenated.output"
+    ```
+
+The same works for binary formats. [`from_cbor`](../../api/basic_json/from_cbor.md) and its relatives accept
+`#!cpp strict = false` to stop after the first value and leave the rest of the stream untouched; `tellg()` then reports
+how many bytes the value took:
+
+??? example "Example: read one CBOR value and find out how many bytes it used"
+
+    ```cpp
+    --8<-- "examples/partial_input_cbor.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_cbor.output"
+    ```
+
+## Input arriving in chunks
+
+A socket, pipe, or HTTP body hands over data in pieces of arbitrary size, and a piece can end in the middle of a
+number, a string, or an object. The parser does not keep state between calls, so there are two ways to deal with this.
+
+**Frame the messages.** The most robust approach is a protocol that says where a value ends: one value per line
+([JSON Lines](json_lines.md)), a length prefix, or a delimiter. Collect the bytes of one message and parse them when
+the frame is complete. Prefer this whenever you control the protocol.
+
+**Buffer until the value is complete.** If the data has no framing, append every chunk to a buffer and try to parse
+it. A parse error at the very end of the buffer means that the input ended prematurely, while an error anywhere else is
+a real syntax error. The member `byte` of the [`parse_error`](../../home/exceptions.md#jsonexceptionparse_error101)
+exception is one past the buffer size in the first case:
+
+??? example "Example: buffer chunks until the value is complete"
+
+    ```cpp
+    --8<-- "examples/partial_input_buffering.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_buffering.output"
+    ```
+
+The example feeds a document in five chunks. The first four are reported as incomplete, and a syntax error is reported as
+such, not as missing data.
+
+!!! warning "Limits of buffering"
+
+    - The buffer must contain exactly one value. Data that belongs to the next value is a syntax error. Use framing if
+      values follow each other without a separator.
+    - A number at the end of the buffer is a complete value, even if more digits are still to come (`12` may be the
+      start of `123`). Buffering cannot detect this; use framing for top-level numbers.
+    - Every attempt parses the buffer from the beginning, so the total work grows quadratically with the size of the
+      value. Limit the size of the buffer for input you do not trust (see [untrusted input](untrusted_input.md)).
+
+## Input too large for memory
+
+The input does not have to become one huge `json` value. The two tools below process it piece by piece.
+
+### Handle and discard elements with a callback
+
+A [parser callback](parser_callbacks.md) is called for every finished value. If it returns `#!cpp false`, the value is
+discarded and its memory is released at once. For a file that consists of one huge array (or one huge object) of
+records, handle each record at depth 1 and discard it:
+
+??? example "Example: handle and discard each record of a large array"
+
+    ```cpp
+    --8<-- "examples/partial_input_discard_records.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_discard_records.output"
+    ```
+
+Only one record is in memory at any time. The same recipe, with more detail, is in the
+[parser callbacks](parser_callbacks.md#recipe-streaming-a-large-homogeneous-array) page. To skip entire members you do not
+need, discard them when their key is read; see the [example](parser_callbacks.md) for `parse_event_t::key`.
+
+### Extract a few values and stop with SAX
+
+With the [SAX interface](sax_interface.md), no value is built at all, and **returning `#!cpp false` from any handler
+function stops the parser**. [`sax_parse`](../../api/basic_json/sax_parse.md) then returns `#!cpp false`, and the rest
+of the input is not read. The example finds the first `id` in a document without parsing the remainder:
+
+??? example "Example: stop parsing as soon as a value is found"
+
+    ```cpp
+    --8<-- "examples/partial_input_sax_stop.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_sax_stop.output"
+    ```
+
+Note that `sax_parse` returns `#!cpp false` both when a handler stopped the parse and when the input is invalid, so
+record the reason in the handler (here: `id`) if you need to tell the two apart.
+
+### Read parts of a large document with a view
+
+If the whole text is available and you only need to read some of it, a [`json_document`](../json_view.md) from
+`<nlohmann/json_view.hpp>` (added in version 3.13.0) avoids the `basic_json` tree altogether: it keeps the text, builds a flat index of the values,
+and gives read-only [views](../../api/basic_json_view/index.md) of the parts you look at. Only what you
+[`materialize()`](../../api/basic_json_view/materialize.md) becomes a `basic_json` value. See
+[Zero-copy JSON views](../json_view.md) for details and for the lifetime rules.
+
+## See also
+
+- [Parsing](index.md) - overview of the parsing functions
+- [JSON Lines](json_lines.md) - newline-delimited JSON
+- [Parser callbacks](parser_callbacks.md) - discard values while parsing
+- [SAX interface](sax_interface.md) - event-based parsing
+- [Zero-copy JSON views](../json_view.md) - read parts of a large document without building a tree
+- [Untrusted input](untrusted_input.md) - limits for input you do not control

docs/mkdocs/docs/features/parsing/parse_exceptions.md

@@ -21,6 +21,10 @@ catch (json::parse_error& ex)
 In case exceptions are undesired or not supported by the environment, there are different ways to proceed:
 
 
+!!! tip
+
+    [Working without exceptions](../no_exceptions.md) also covers accessing values and converting to your own types.
+
 ## Switch off exceptions
 
 The [`parse()`](../../api/basic_json/parse.md) function accepts a `#!cpp bool` parameter `allow_exceptions` which
@@ -81,3 +85,61 @@ The return value indicates whether the parsing should continue, so the function
     ```
     --8<-- "examples/sax_no_exception.output"
     ```
+
+## Where did the error occur?
+
+The message of a [`parse_error`](../../home/exceptions.md#jsonexceptionparse_error101) for JSON text contains the line
+and column of the error:
+
+```
+[json.exception.parse_error.101] parse error at line 3, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+```
+
+The exception object itself only stores the **byte index** of the last read character in the member `byte` (the first
+byte of the input has index 1). The same index is passed to `parse_error` in the [SAX interface](sax_interface.md). If
+you need the line and column as numbers, for example to show them in an editor, compute them from the input:
+
+??? example "Example: compute line and column of a parse error"
+
+    ```cpp
+    --8<-- "examples/parse_error_position.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/parse_error_position.output"
+    ```
+
+Columns count bytes, so a line with multi-byte UTF-8 characters before the error may differ from the column your editor
+shows.
+
+### Where is the value that caused a later error?
+
+A `parse_error` is raised while the text is read. Many mistakes show up later: the text is valid JSON, but a value has
+the wrong type when you convert it (`type_error.302`), or a key is missing (`out_of_range.403`). The exception then says
+what is wrong, but not where in the input the value was. Define
+[`JSON_DIAGNOSTIC_POSITIONS`](../../api/macros/json_diagnostic_positions.md) before including the library to add the
+byte range of the offending value to such messages (since version 3.12.0), and to query the range of any value with
+[`start_pos()`](../../api/basic_json/start_pos.md) and [`end_pos()`](../../api/basic_json/end_pos.md):
+
+??? example "Example: locate a value with diagnostic positions"
+
+    ```cpp
+    --8<-- "examples/parse_error_position_diagnostic.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/parse_error_position_diagnostic.output"
+    ```
+
+Positions are only available for values created by [`parse`](../../api/basic_json/parse.md), they are not updated when a
+value is changed, and the macro makes every value 16 bytes larger on 64-bit platforms, so use it where the cost is
+acceptable, for example for configuration files. Note that `start_pos()` is a 0-based index into the input, whereas
+`byte` of a `parse_error` starts at 1.
+
+For binary formats such as CBOR, there are no lines; `byte` is the position in the byte sequence. To find out how many
+bytes a successfully parsed value used, see
+[Several values in one stream](large_and_partial_input.md#several-values-in-one-stream).

docs/mkdocs/docs/features/parsing/untrusted_input.md

@@ -26,9 +26,11 @@ several alternatives; see [Parsing and exceptions](parse_exceptions.md) for the
   [example](parse_exceptions.md#user-defined-sax-interface) that overrides it to print instead of throw.
 
 If exceptions are unavailable entirely (`-fno-exceptions`, or [`JSON_NOEXCEPTION`](../../api/macros/json_noexception.md)
-defined), every `#!cpp throw` in the library becomes a call to `std::abort()` -- there is no way to recover from a
-parse error of untrusted input in that configuration; see
-[Switch off exceptions](../../home/exceptions.md#switch-off-exceptions) for the details and for overriding this with
+defined), every `#!cpp throw` in the library becomes a call to `std::abort()`. The alternatives above do not throw, so
+`parse()` with `allow_exceptions` set to `#!cpp false` (and likewise `accept()` and the `from_*` functions with
+`allow_exceptions` set to `#!cpp false`) can still reject invalid input in that configuration; a plain `parse()` call
+aborts on invalid input. See [Working without exceptions](../no_exceptions.md) and
+[Switch off exceptions](../../home/exceptions.md#switch-off-exceptions) for the details and for overriding the abort with
 `JSON_THROW_USER`.
 
 ## Nesting depth

docs/mkdocs/docs/features/performance.md

@@ -122,7 +122,9 @@ an adapter, since their template argument order does not match what `basic_json`
   [linear in its size](../api/basic_json/basic_json.md#complexity) for the copy constructor but
   [constant](../api/basic_json/basic_json.md#complexity) for the move constructor. The same applies to assigning a
   large `#!cpp std::string`, `#!cpp std::vector`, or other container into a value: pass it as `#!cpp std::move(x)`
-  rather than `x` whenever `x` is no longer needed afterwards.
+  rather than `x` whenever `x` is no longer needed afterwards. Since version 3.13.0, converting an rvalue container
+  (`#!cpp json j = std::move(vec);`) moves the elements instead of copying them; the source is then left in a valid but
+  unspecified state.
 - **Access without copying.** [`get<T>()`](../api/basic_json/get.md) returns a copy of the stored value converted to
   `T`. When a reference or pointer to the value already stored inside the `basic_json` is enough,
   [`get_ref()`](../api/basic_json/get_ref.md) and [`get_ptr()`](../api/basic_json/get_ptr.md) access it directly:
@@ -151,6 +153,29 @@ an adapter, since their template argument order does not match what `basic_json`
   ["reserving array capacity"](element_access/unchecked_access.md#performance-reserving-array-capacity) for the
   one-line recipe.
 
+## Memory
+
+- **A value is small, its content is on the heap.** A `basic_json` is 16 bytes on a 64-bit platform (a type tag and a
+  union). Strings, arrays, objects, and binary values are allocated on the heap and owned by the value. Destroying the
+  value frees everything it owns.
+- **Copies are deep.** After `#!cpp json b = a;`, changing `b` does not change `a`, and both own their memory. Copying a
+  large value therefore doubles its memory; see [Avoiding copies](#avoiding-copies). `#!cpp auto x = j["key"];` is a
+  copy, `#!cpp auto& x = j["key"];` is not.
+- **A moved-from value is `null`.** After `#!cpp json c = std::move(a);` the value `a` is `#!json null` and owns nothing.
+- **Reading does not require a tree.** If you only read the data, parse it into a [`json_document`](json_view.md)
+  (`#!cpp <nlohmann/json_view.hpp>`, added in version 3.13.0) instead of a `basic_json`. It stores 16 bytes per value, does not copy floating-point
+  numbers or strings without escape sequences out of the text, and creates no `basic_json` value except for the parts
+  you [`materialize()`](../api/basic_json_view/materialize.md). A document that borrows the text needs the text to
+  outlive it; see [Zero-copy JSON views](json_view.md).
+- **Containers keep their capacity.** `clear()` and `erase()` on an array remove the elements, but the underlying
+  `#!cpp std::vector` keeps its allocated capacity, like `#!cpp std::vector::clear` does. To give the memory back,
+  assign a new value (`#!cpp j = json::array();`) or destroy the value.
+- **Freed memory does not always go back to the operating system.** The library returns memory to the allocator
+  (`#!cpp std::allocator` by default, or the [one you configured](types/template_parameters.md)). Whether the process
+  size shrinks then depends on the allocator and the platform, as for any C++ program. A process that parses a large
+  document and drops it is not leaking if its resident size stays high; run it under a tool such as
+  [Valgrind](https://valgrind.org) or the sanitizers to tell a leak from retained memory.
+
 ## Serialization
 
 [`dump()`](../api/basic_json/dump.md) with the default `#!cpp indent = -1` selects "the most compact representation"

docs/mkdocs/docs/features/type_recipes.md

@@ -0,0 +1,122 @@
+# Recipes for Common Types
+
+The library converts the standard containers, strings, numbers, tuples, `std::optional`, and `std::filesystem::path`
+(the last two since version 3.12.0, C++17) out of the box, and your own types once you write conversion functions or use
+the macros (see [Arbitrary type conversions](arbitrary_types.md)). It deliberately does **not** convert smart pointers,
+`std::variant`, `std::chrono` types, or class hierarchies, because there is more than one reasonable JSON
+representation for each of them. This page shows a representation for each that you can copy and adapt.
+
+All recipes use a specialization of [`adl_serializer`](../api/adl_serializer/index.md), which you may provide for types
+you do not own, or free `to_json`/`from_json` functions in the namespace of the type. Place them where they are
+visible before any code that converts the type; see
+[Why isn't my `to_json` found?](arbitrary_types.md#why-isnt-my-to_json-or-from_json-found).
+
+## Smart pointers
+
+A `std::shared_ptr<T>` or `std::unique_ptr<T>` is written as the value it points to, or as `#!json null` for an empty
+pointer, and read back by allocating a new `T`:
+
+??? example "Example: serialize shared_ptr and unique_ptr"
+
+    ```cpp
+    --8<-- "examples/type_recipes_smart_pointers.c++14.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_smart_pointers.c++14.output"
+    ```
+
+With this, containers of smart pointers, pointers to `const`, and members of these types in your own structs convert as
+usual. A pointer to a base class cannot be filled this way, because `T` would have
+to be created as a derived type; see the next section.
+
+Reading creates a new object. Two `shared_ptr`s that pointed to the same object are written twice and read back as two
+separate objects.
+
+## Class hierarchies
+
+!!! tip "Derived classes whose type is known at compile time"
+
+    If you only need to serialize the data members of a derived class, and the code always knows the concrete type, you do
+    not need a type tag. The [`NLOHMANN_DEFINE_DERIVED_TYPE_*` macros](arbitrary_types.md#simplify-your-life-with-macros)
+    (since version 3.12.0) add the members of the derived class to those of its base class. This section is for the case
+    where the concrete type is only known at run time, such as a `std::unique_ptr<shape>` that holds a circle or a
+    rectangle.
+
+JSON has no notion of types, so a value in a hierarchy needs a **type tag** that says which derived class to create.
+Write the tag in the object, and select the class from it when reading:
+
+??? example "Example: serialize a class hierarchy with a type tag"
+
+    ```cpp
+    --8<-- "examples/type_recipes_class_hierarchy.c++14.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_class_hierarchy.c++14.output"
+    ```
+
+A `#!cpp std::vector<std::unique_ptr<shape>>` converts to an array of tagged objects and back, creating a `circle`
+and a `rectangle`. The same works for `std::shared_ptr<shape>`. Remember the virtual destructor: without it, deleting a
+derived object through the base pointer is undefined behavior.
+
+## `std::variant`
+
+A variant has the same problem: the alternative must be recorded. If the alternatives are your own types, write a type
+tag next to their members, exactly as for a hierarchy:
+
+??? example "Example: serialize a std::variant with a type tag"
+
+    ```cpp
+    --8<-- "examples/type_recipes_variant.c++17.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_variant.c++17.output"
+    ```
+
+In the example, the functions are found
+because `geo` is the namespace of the template arguments of `#!cpp std::variant<circ, rect>`; for a variant of only
+standard types (for example `#!cpp std::variant<int, std::string>`) there is no such namespace, and you need an
+`adl_serializer` specialization or a wrapper type of your own.
+
+If the alternatives are JSON-native (numbers, strings, ...), a variant such as `#!cpp std::variant<int, std::string>`
+can instead be written as the plain value, and read by testing the JSON type (`is_number_integer()`, `is_string()`)
+to choose the alternative.
+
+## `std::chrono`
+
+A duration is written as its count and read back with the same representation and period. The **unit is not part of
+the JSON value**, so document it, for example in the member name (`timeout_ms`):
+
+??? example "Example: serialize durations and system_clock time points"
+
+    ```cpp
+    --8<-- "examples/type_recipes_chrono.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_chrono.output"
+    ```
+
+A `system_clock::time_point` with millisecond precision is written as the number of milliseconds since the Unix epoch.
+The time point serializer is limited to `system_clock`,
+because the epoch of other clocks (for example `steady_clock`) has no meaning outside the running program.
+
+If you prefer a text representation such as ISO 8601 (`2023-11-14T22:13:20Z`), write the string with
+`#!cpp std::format("{:%FT%TZ}", t)` and read it with `std::chrono::parse` (both C++20), or with a date library, in the
+same two functions.
+
+## See also
+
+- [Arbitrary type conversions](arbitrary_types.md) - the conversion mechanism and macros
+- [Why isn't my `to_json` found?](arbitrary_types.md#why-isnt-my-to_json-or-from_json-found)
+- [Converting values](conversions.md) - `get`, implicit conversions, and `std::optional`

docs/mkdocs/docs/home/exceptions.md

@@ -39,6 +39,8 @@ classDiagram
 
 Exceptions are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md). In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `#!cpp throw`), `JSON_TRY_USER` (overriding `#!cpp try`), and `JSON_CATCH_USER` (overriding `#!cpp catch`).
 
+See [Working without exceptions](../features/no_exceptions.md) for the functions that report errors without throwing.
+
 Note that [`JSON_THROW_USER`](../api/macros/json_throw_user.md) should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.
 
 ??? example "Example: switch off exceptions and log errors before aborting"
@@ -192,6 +194,34 @@ This error indicates a syntax error while deserializing a JSON text. The error m
     - Make sure the input is correctly read. Try to write the input to standard output to check if, for instance, the input file was successfully opened.
     - Paste the input to a JSON validator like <https://jsonlint.com> or a tool like [jq](https://jqlang.github.io/jq/).
 
+??? info "Parsing a file fails at line 1, column 1 (or \"unexpected end of input\")"
+
+    The messages `attempting to parse an empty input` (since version 3.11.3) and `unexpected end of input` (also the message of
+    earlier versions for an empty input) at the very start of the input mean
+    that the parser did not see a single character. The library only reads from the stream it is given: it does not
+    open files and cannot tell a missing file from an empty one. The usual causes are:
+
+    - **The file was not opened.** A relative path is resolved against the *working directory of the running program*,
+      not against the source file or the project. IDEs and build tools often start the program in a build directory
+      (for example `build/` or `cmake-build-debug/`), so `"example.json"` may need to be `"../example.json"`. Use an
+      absolute path to rule this out.
+    - **The file is empty**, or a previous run truncated it (for example when it was opened for writing).
+    - **The stream was already read.** A stream whose content has been consumed (by printing it with
+      `std::cout << file.rdbuf()`, or by an earlier `accept`/`parse`/`>>`) is at its end. Parse it once, or rewind it
+      with `seekg(0)` after clearing the state with `clear()`.
+
+    Check the stream before parsing it:
+
+    ```cpp
+    std::ifstream f("example.json");
+    if (!f.is_open())
+    {
+        std::cerr << "cannot open example.json\n";
+        return 1;
+    }
+    json data = json::parse(f);
+    ```
+
 ### json.exception.parse_error.102
 
 JSON uses the `\uxxxx` format to describe Unicode characters. Code points above 0xFFFF are split into two `\uxxxx` entries ("surrogate pairs"). This error indicates that the surrogate pair is incomplete or contains an invalid code point.

docs/mkdocs/docs/home/faq.md

@@ -58,6 +58,208 @@ json j{obj};   // -> {"key":"value"}  (copy, not array)
 
 Without the macro (default behavior), `json j{obj}` creates `[{"key":"value"}]`. This opt-in macro fixes issue #5074 while preserving backwards compatibility for existing code.
 
+## Getting started
+
+### Which file do I need?
+
+!!! question
+
+    Do I have to clone the repository or build the library?
+
+No. The library is header-only: the single file [`json.hpp`](https://github.com/nlohmann/json/releases) from the
+releases page is all you need, including the `_json` literals. Put it in a directory `nlohmann` on your include path.
+Companion headers (`json_fwd.hpp`, `json_view.hpp`, `json_literals.hpp`) are only needed if you use them. See
+[Integration](../integration/index.md#header-only).
+
+### Using CMake or a package manager
+
+!!! question
+
+    How do I add the library with CMake, Conan, vcpkg, Homebrew, or another tool?
+
+See [CMake](../integration/cmake.md) for `find_package`, `add_subdirectory`, and `FetchContent`, and
+[Package managers](../integration/package_managers.md) for the list of supported package managers.
+
+### The IDE cannot open the header
+
+!!! question
+
+    The compiler finds `nlohmann/json.hpp`, but my IDE reports "cannot open source file". Why?
+
+The compiler's include path is set correctly, but the IDE's is not. Add the same directory to the include paths of the
+IDE (or of its language server); the build itself is not affected.
+
+### Compile times
+
+!!! question
+
+    Including the library slows down my build. What can I do?
+
+Include [`json_fwd.hpp`](../integration/compile_times.md#include-json_fwdhpp-in-headers) in headers and `json.hpp` only
+in the source files that need it, instantiate `basic_json` once, and consider precompiled headers or
+[C++20 modules](../features/modules.md). See [Compile times](../integration/compile_times.md).
+
+## Parsing
+
+### Parsing a file fails with "unexpected end of input"
+
+!!! question
+
+    `json::parse(file)` throws `parse_error.101` at line 1, column 1 for a file that is valid JSON. Why?
+
+The parser did not see any character: the file was most likely not opened. A relative path is resolved against the
+working directory of the running program, which is often the build directory of your IDE, not the source directory.
+Check `is_open()` and try an absolute path. Other causes are an empty file and a stream that was already read. See
+[`parse_error.101`](exceptions.md#jsonexceptionparse_error101).
+
+### Input that arrives in chunks
+
+!!! question
+
+    My data comes from a socket in pieces. How do I parse it?
+
+The parser cannot be resumed. Frame the messages (one value per line, a length prefix) and parse each complete frame, or
+buffer the chunks until the value is complete; a `parse_error` at the end of the buffer means the input ended
+prematurely. See [Large, streamed, and partial input](../features/parsing/large_and_partial_input.md#input-arriving-in-chunks).
+
+### Several values in one stream
+
+!!! question
+
+    How do I read concatenated JSON values or one value per line?
+
+Read newline-delimited input line by line ([JSON Lines](../features/parsing/json_lines.md)). For concatenated values, use
+`operator>>` and check for the end of the stream before each read, as shown in
+[Several values in one stream](../features/parsing/large_and_partial_input.md#several-values-in-one-stream).
+
+### Files that are too large for memory
+
+!!! question
+
+    How do I process a huge JSON file?
+
+Handle and discard the records of a large array with a [parser callback](../features/parsing/parser_callbacks.md), stop
+early with the [SAX interface](../features/parsing/sax_interface.md), or read parts of the text through a
+[`json_document`](../features/json_view.md) (added in version 3.13.0). See
+[Input too large for memory](../features/parsing/large_and_partial_input.md#input-too-large-for-memory).
+
+### Position of a parse error
+
+!!! question
+
+    How do I get the line and column of a parse error?
+
+The message contains them. The exception stores the byte index in `byte`, from which you can compute both; see
+[Where did the error occur?](../features/parsing/parse_exceptions.md#where-did-the-error-occur). To locate a value that
+causes a *later* error, such as a `type_error`, use
+[`JSON_DIAGNOSTIC_POSITIONS`](../features/parsing/parse_exceptions.md#where-is-the-value-that-caused-a-later-error).
+
+### Comments and trailing commas
+
+!!! question
+
+    Can the parser read JSON with comments or trailing commas?
+
+Yes, when asked to: see [Comments](../features/comments.md) and [Trailing commas](../features/trailing_commas.md). Both
+are rejected by default.
+
+## Accessing and creating values
+
+### Reading a value into a variable
+
+!!! question
+
+    How do I get a C++ value out of a `json` value?
+
+Use [`get<T>()`](../api/basic_json/get.md), for example `#!cpp int age = j["age"].get<int>();`, or an implicit conversion.
+`#!cpp auto x = j["age"];` is **not** a conversion: it copies the `json` value. See
+[Converting values](../features/conversions.md).
+
+### Strings are printed with quotes
+
+!!! question
+
+    `std::cout << j["name"]` prints `"Mary"` with quotes. How do I get the string?
+
+The value is a `json`, and printing it produces JSON text. Convert it first: `#!cpp j["name"].get<std::string>()`. See
+[Getting a string without quotes](../features/conversions.md#getting-values-out).
+
+### Testing whether a key exists
+
+!!! question
+
+    How do I check if a key exists, without changing the object?
+
+Use `contains` or `find`. Do not test with the non-const `operator[]`: like `std::map::operator[]`, it inserts a `null`
+value for a missing key. See [Does this key exist?](../features/element_access/index.md#does-this-key-exist).
+
+### Reading a value with a fallback
+
+!!! question
+
+    How do I read a value that may be missing?
+
+Use [`value`](../features/element_access/default_value.md), which returns a default for a missing key. It still throws if
+the key exists with a different type; see [Working without exceptions](../features/no_exceptions.md).
+
+### Iterating and nested values
+
+!!! question
+
+    How do I loop over an array or object, or reach a nested value?
+
+See [Iterators](../features/iterators.md) and [`items()`](../api/basic_json/items.md) for loops, and
+[JSON Pointer](../features/json_pointer.md) to address or test a nested value by path.
+
+### Unexpected arrays when creating values
+
+!!! question
+
+    Why does `json j{x}` or `{{"a", 1}, {"b"}}` produce an array instead of what I expected?
+
+Braces create arrays and objects based on their content, and single-element braces create a one-element array. See
+[Brace initialization yields arrays](#brace-initialization-yields-arrays) and the table in
+[Creating values](../features/creating_values.md#what-does-this-produce).
+
+### Keeping the order of object keys
+
+!!! question
+
+    The keys of my object come out sorted. How do I keep the insertion order?
+
+Use `ordered_json`, and call `ordered_json::parse` when reading. See [Object order](../features/object_order.md).
+
+## Converting your own types
+
+### Structs, enums, and optional fields
+
+!!! question
+
+    How do I convert my own types to and from JSON?
+
+Write `to_json`/`from_json` functions or use the `NLOHMANN_DEFINE_TYPE_*` macros; see
+[Arbitrary type conversions](../features/arbitrary_types.md). Enums can be mapped to strings
+([Enum conversion](../features/enum_conversion.md)), and an empty `std::optional` can be omitted
+([Omitting a field](../features/conversions.md#omitting-a-field-when-serializing-stdoptional)).
+
+### Smart pointers, variants, chrono, and class hierarchies
+
+!!! question
+
+    Why can't I convert `std::shared_ptr`, `std::variant`, `std::chrono` types, or a pointer to a base class?
+
+There is more than one sensible JSON representation for them, so the library leaves the choice to you.
+[Recipes for common types](../features/type_recipes.md) shows one for each.
+
+### My `to_json` is not found
+
+!!! question
+
+    I wrote `to_json`/`from_json`, but the compiler does not find them. Why?
+
+Typical causes are a type alias of a standard type, a function in the wrong namespace, or a declaration that comes too
+late. See [Why isn't my `to_json` found?](../features/arbitrary_types.md#why-isnt-my-to_json-or-from_json-found).
+
 ## Limitations
 
 ### Relaxed parsing
@@ -202,6 +404,36 @@ Not directly, but the companion project [json-schema-validator](https://github.c
 builds JSON Schema (draft 7; draft 4 in its older, now-superseded 1.x releases) validation on top of this library
 and is a common recommendation for this use case.
 
+### Memory use
+
+!!! question
+
+    Does the library leak memory? My process stays large after I free a `json` value.
+
+Destroying a value frees everything it owns. Freed memory is returned to the allocator, which does not necessarily give
+it back to the operating system, so a high resident size alone is not a leak. Copies are deep, and `clear()` keeps the
+capacity of an array. See [Memory](../features/performance.md#memory), and use Valgrind or the sanitizers to tell a leak
+from retained memory.
+
+### Reproducible builds
+
+!!! question
+
+    The header path ends up in my binary. How do I get path-independent builds?
+
+The runtime assertions embed `__FILE__`. Define `NDEBUG` (the default for release builds) or map the path prefix; see
+[Notes for builds and distribution](../integration/index.md#notes-for-builds-and-distribution).
+
+### Slow debug builds
+
+!!! question
+
+    Parsing a large file is very slow in my debug build. Can I compile the library with optimizations?
+
+The library is header-only, so there is no separate source file. Keep the code that uses `json` in its own source file and
+compile that file with optimizations; see
+[Notes for builds and distribution](../integration/index.md#notes-for-builds-and-distribution).
+
 ## Exceptions
 
 ### Parsing without exceptions
@@ -210,7 +442,8 @@ and is a common recommendation for this use case.
 
     Is it possible to indicate a parse error without throwing an exception?
 
-Yes, see [Parsing and exceptions](../features/parsing/parse_exceptions.md).
+Yes, see [Parsing and exceptions](../features/parsing/parse_exceptions.md) and
+[Working without exceptions](../features/no_exceptions.md).
 
 
 ### Key name in exceptions

docs/mkdocs/docs/index.md

@@ -29,6 +29,10 @@ int main()
     j["name"] = "Niels";
     j["list"] = {1, 0, 2};
 
+    // read a value into a C++ variable and use it
+    double pi = j["pi"].get<double>();
+    std::cout << "2 * pi = " << 2 * pi << '\n';
+
     // serialize with an indent of 4 spaces
     std::cout << j.dump(4) << '\n';
 }

docs/mkdocs/docs/integration/index.md

@@ -43,6 +43,21 @@ using json = nlohmann::json;
 to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and
 Clang).
 
+!!! tip "Which file do I download?"
+
+    For a project without a package manager, the library itself, including the `_json` literals, is **one file**:
+    [`json.hpp`](https://github.com/nlohmann/json/releases/latest/download/json.hpp) from the
+    [releases page](https://github.com/nlohmann/json/releases). You do not need to clone the repository, build
+    anything, or link a library. Put the file in a directory named `nlohmann` that is on your include path (for
+    example `third_party/nlohmann/json.hpp` with `-I third_party`), so that `#include <nlohmann/json.hpp>` works.
+    Download the companion headers listed below only if you use them: `json_view.hpp` for the
+    [zero-copy views](../features/json_view.md), `json_fwd.hpp` for forward declarations, and `json_literals.hpp` if
+    you define `JSON_NO_AUTOMATIC_UDLS`. Keep them in the same `nlohmann` directory.
+
+    Do not copy only parts of the repository's `include/` directory: the headers in it include each other and must be
+    kept together. If your IDE reports "cannot open source file" while the compiler succeeds, the compiler's include
+    path is set correctly but the IDE's is not; add the same directory to the IDE's include paths.
+
 You can further use file
 [`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp)
 for forward declarations (see [Compile times](compile_times.md)), and file
@@ -54,3 +69,21 @@ For the read-only, non-owning [`basic_json_document`](../api/basic_json_document
 types, additionally include
 [`single_include/nlohmann/json_view.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_view.hpp);
 see [Zero-copy JSON views](../features/json_view.md).
+
+## Notes for builds and distribution
+
+**Reproducible and path-independent builds.** The runtime assertions use `assert`, which embeds the name of the source
+file (`__FILE__`) in the binary. Release builds do not contain them, because they define `NDEBUG`. If you compile with
+assertions enabled and need binaries that do not depend on the build directory, either define `NDEBUG` or map the
+prefix of the path with the compiler option `-ffile-prefix-map=<old>=<new>` (GCC 8 and later, Clang 10 and later). See
+[Runtime assertions](../features/assertions.md).
+
+**There is no separate source file to compile.** The library is header-only, so there is no `.cpp` that could be
+built with different options than the code that includes it. It is also not available as a precompiled library. To
+compile the library with optimizations in an otherwise unoptimized build (for example to parse large files in a debug
+build, which is slow because of the unoptimized code and the checks of the debug standard library), keep the code that
+uses `json` in a separate source file and set the options for that file only. [Compile times](compile_times.md)
+shows how to [instantiate `basic_json` once](compile_times.md#instantiate-basic_json-once).
+
+**Debugger visualization.** The Natvis file works with the Visual Studio debugger, including the `cppvsdbg` engine in
+Visual Studio Code, but not with debuggers that wrap LLDB, such as `codelldb`; see [Debugging](../home/debugging.md).

docs/mkdocs/mkdocs.yml

@@ -60,6 +60,7 @@ nav:
   - Features:
       - features/index.md
       - features/arbitrary_types.md
+      - features/type_recipes.md
       - Binary Formats:
           - features/binary_formats/index.md
           - features/binary_formats/bjdata.md
@@ -84,11 +85,13 @@ nav:
       - features/modifying_values.md
       - features/modules.md
       - 'nlohmann Namespace': features/namespace.md
+      - features/no_exceptions.md
       - features/object_order.md
       - features/performance.md
       - Parsing:
           - features/parsing/index.md
           - features/parsing/json_lines.md
+          - features/parsing/large_and_partial_input.md
           - features/parsing/parse_exceptions.md
           - features/parsing/parser_callbacks.md
           - features/parsing/sax_interface.md

include/nlohmann/detail/conversions/from_json.hpp

@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include <algorithm> // min, transform
+#include <algorithm> // transform
 #include <array> // array
 #include <forward_list> // forward_list
 #include <iterator> // inserter, front_inserter, end
@@ -69,10 +69,12 @@ void from_json(const BasicJsonType& j, std::optional<T>& opt)
 }
 #endif // JSON_HAS_CPP_17
 
-// read a number value of any of the three number types into val;
-// returns false (leaving val untouched) if j is not a number
-template<typename BasicJsonType, typename ArithmeticType>
-bool get_number_value(const BasicJsonType& j, ArithmeticType& val)
+// overloads for basic_json template parameters
+template < typename BasicJsonType, typename ArithmeticType,
+           enable_if_t < std::is_arithmetic<ArithmeticType>::value&&
+                         !std::is_same<ArithmeticType, typename BasicJsonType::boolean_t>::value,
+                         int > = 0 >
+void get_arithmetic_value(const BasicJsonType& j, ArithmeticType& val)
 {
     switch (static_cast<value_t>(j))
     {
@@ -83,17 +85,17 @@ bool get_number_value(const BasicJsonType& j, ArithmeticType& val)
             const auto* ptr = j.template get_ptr<const typename BasicJsonType::number_unsigned_t*>();
             JSON_ASSERT(ptr != nullptr);
             val = static_cast<ArithmeticType>(*ptr);
-            return true;
+            break;
         }
         case value_t::number_integer:
         {
             val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_integer_t*>());
-            return true;
+            break;
         }
         case value_t::number_float:
         {
             val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_float_t*>());
-            return true;
+            break;
         }
 
         case value_t::null:
@@ -104,20 +106,7 @@ bool get_number_value(const BasicJsonType& j, ArithmeticType& val)
         case value_t::binary:
         case value_t::discarded:
         default:
-            return false;
-    }
-}
-
-// overloads for basic_json template parameters
-template < typename BasicJsonType, typename ArithmeticType,
-           enable_if_t < std::is_arithmetic<ArithmeticType>::value&&
-                         !std::is_same<ArithmeticType, typename BasicJsonType::boolean_t>::value,
-                         int > = 0 >
-void get_arithmetic_value(const BasicJsonType& j, ArithmeticType& val)
-{
-    if (JSON_HEDLEY_UNLIKELY(!get_number_value(j, val)))
-    {
-        throw_type_must_be("number", j);
+            throw_type_must_be("number", j);
     }
 }
 
@@ -256,44 +245,29 @@ inline void from_json_array_impl(const BasicJsonType& j, typename BasicJsonType:
     arr = *j.template get_ptr<const typename BasicJsonType::array_t*>();
 }
 
-// fill a std::array from the JSON array j: the size is checked once and the
-// elements are read in order, so a short array converts the elements it has and
-// then throws the out_of_range error at() would throw for the first missing one
-template<typename BasicJsonType, typename T, std::size_t N>
-void from_json_std_array(const BasicJsonType& j, std::array<T, N>& arr)
-{
-    const auto& inner_array = *j.template get_ptr<const typename BasicJsonType::array_t*>();
-    const std::size_t size = (std::min)(N, inner_array.size());
-    for (std::size_t i = 0; i < size; ++i)
-    {
-        arr[i] = inner_array[i].template get<T>();
-    }
-    if (JSON_HEDLEY_UNLIKELY(size < N))
-    {
-        static_cast<void>(j.at(size));
-    }
-}
-
 template<typename BasicJsonType, typename T, std::size_t N>
 auto from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr,
                           priority_tag<2> /*unused*/)
 -> decltype(j.template get<T>(), void())
 {
-    from_json_std_array(j, arr);
+    for (std::size_t i = 0; i < N; ++i)
+    {
+        arr[i] = j.at(i).template get<T>();
+    }
 }
 
-// reserve() is called through this pair (used for arrays and objects alike)
-// so from_json_array_impl and the object from_json have a single body for both
-// containers that support reserve() and those that don't.
-template<typename ConstructibleContainerType>
-auto reserve_if_possible(ConstructibleContainerType& c, typename ConstructibleContainerType::size_type size, priority_tag<1> /*unused*/)
--> decltype(c.reserve(size), void())
+// reserve() is called through this pair (modeled on from_json_object_reserve)
+// so from_json_array_impl below has a single body for both ConstructibleArrayType
+// that support reserve() and those that don't.
+template<typename ConstructibleArrayType>
+auto from_json_array_reserve(ConstructibleArrayType& arr, typename ConstructibleArrayType::size_type size, priority_tag<1> /*unused*/)
+-> decltype(arr.reserve(size), void())
 {
-    c.reserve(size);
+    arr.reserve(size);
 }
 
-template<typename ConstructibleContainerType>
-void reserve_if_possible(ConstructibleContainerType& /*c*/, std::size_t /*size*/, priority_tag<0> /*unused*/)
+template<typename ConstructibleArrayType>
+void from_json_array_reserve(ConstructibleArrayType& /*arr*/, std::size_t /*size*/, priority_tag<0> /*unused*/)
 {}
 
 // append through push_back() where available; containers without it (such as
@@ -323,7 +297,7 @@ auto from_json_array_impl(const BasicJsonType& j, ConstructibleArrayType& arr, p
 {
     ConstructibleArrayType ret;
     const auto* inner_array = j.template get_ptr<const typename BasicJsonType::array_t*>();
-    reserve_if_possible(ret, inner_array->size(), priority_tag<1> {});
+    from_json_array_reserve(ret, inner_array->size(), priority_tag<1> {});
     for (const auto& elem : *inner_array)
     {
         // get<BasicJsonType>() returns *this, this won't call a from_json
@@ -362,37 +336,6 @@ std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(const BasicJsonType&
     return { { j.at(Idx).template get<T>()... } };
 }
 
-// std::is_trivial is deprecated in C++26 (see binary_writer::to_char_type);
-// a struct rather than an alias, as astyle indents an #ifdef block of aliases
-template<typename T>
-struct is_trivial_element
-#ifdef JSON_HAS_CPP_26
-    : conjunction<std::is_trivially_copyable<T>, std::is_trivially_default_constructible<T>>
-#else
-    : std::is_trivial<T>
-#endif
-{};
-
-// the element type may not be default constructible: construct every element
-// in place (a pack expansion that is unrolled N times)
-template<typename BasicJsonType, typename T, std::size_t N>
-std::array<T, N> from_json_make_array(const BasicJsonType& j, identity_tag<std::array<T, N>> tag,
-                                      std::false_type /*is_trivial_element*/)
-{
-    return from_json_inplace_array_impl(j, tag, make_index_sequence<N> {});
-}
-
-// a trivial element type cannot tell default construction plus assignment from
-// construction in place, so use a loop instead of unrolling N conversions
-template<typename BasicJsonType, typename T, std::size_t N>
-std::array<T, N> from_json_make_array(const BasicJsonType& j, identity_tag<std::array<T, N>> /*unused*/,
-                                      std::true_type /*is_trivial_element*/)
-{
-    std::array<T, N> arr; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): every element is assigned or an exception is thrown
-    from_json_std_array(j, arr);
-    return arr;
-}
-
 template < typename BasicJsonType, typename T, std::size_t N >
 auto from_json(const BasicJsonType& j, identity_tag<std::array<T, N>> tag)
 -> decltype(from_json_inplace_array_impl(j, tag, make_index_sequence<N> {}))
@@ -402,7 +345,7 @@ auto from_json(const BasicJsonType& j, identity_tag<std::array<T, N>> tag)
         throw_type_must_be("array", j);
     }
 
-    return from_json_make_array(j, tag, is_trivial_element<T> {});
+    return from_json_inplace_array_impl(j, tag, make_index_sequence<N> {});
 }
 
 template<typename BasicJsonType>
@@ -435,6 +378,17 @@ inline void from_json(const BasicJsonType& j, CompatibleArrayType& bin)
     }
 }
 
+template<typename ConstructibleObjectType>
+auto from_json_object_reserve(ConstructibleObjectType& obj, typename ConstructibleObjectType::size_type size, priority_tag<1> /*unused*/)
+-> decltype(obj.reserve(size), void())
+{
+    obj.reserve(size);
+}
+
+template<typename ConstructibleObjectType>
+inline void from_json_object_reserve(ConstructibleObjectType& /*obj*/, std::size_t /*size*/, priority_tag<0> /*unused*/)
+{}
+
 // the keys of the source are sorted for the usual object types, so hinting the
 // end makes every insertion constant-time (for containers that order their keys
 // the same way); containers without emplace_hint() (such as ordered_map) fall
@@ -463,7 +417,7 @@ inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
 
     ConstructibleObjectType ret;
     const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
-    reserve_if_possible(ret, inner_object->size(), priority_tag<1> {});
+    from_json_object_reserve(ret, inner_object->size(), priority_tag<1> {});
     for (const auto& p : *inner_object)
     {
         from_json_object_emplace(ret, p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>(), priority_tag<1> {});
@@ -483,17 +437,42 @@ template < typename BasicJsonType, typename ArithmeticType,
                int > = 0 >
 inline void from_json(const BasicJsonType& j, ArithmeticType& val)
 {
-    if (get_number_value(j, val))
+    switch (static_cast<value_t>(j))
     {
-        return;
-    }
+        case value_t::number_unsigned:
+        {
+            // never null: a basic_json whose number_unsigned_t is number_integer_t
+            // stores no number_unsigned values (#2573)
+            const auto* ptr = j.template get_ptr<const typename BasicJsonType::number_unsigned_t*>();
+            JSON_ASSERT(ptr != nullptr);
+            val = static_cast<ArithmeticType>(*ptr);
+            break;
+        }
+        case value_t::number_integer:
+        {
+            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_integer_t*>());
+            break;
+        }
+        case value_t::number_float:
+        {
+            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_float_t*>());
+            break;
+        }
+        case value_t::boolean:
+        {
+            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::boolean_t*>());
+            break;
+        }
 
-    // unlike get_arithmetic_value(), a boolean is accepted here
-    if (JSON_HEDLEY_UNLIKELY(!j.is_boolean()))
-    {
-        throw_type_must_be("number", j);
+        case value_t::null:
+        case value_t::object:
+        case value_t::array:
+        case value_t::string:
+        case value_t::binary:
+        case value_t::discarded:
+        default:
+            throw_type_must_be("number", j);
     }
-    val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::boolean_t*>());
 }
 
 template<typename BasicJsonType, typename Type>

include/nlohmann/detail/exceptions.hpp

@@ -66,7 +66,6 @@ enum class exception_id : int
     invalid_string_or_size = 113, ///< a binary input contains an invalid string or size specification
     bson_unsupported_type = 114, ///< a BSON record type is not supported
     invalid_high_precision_number = 115, ///< a UBJSON/BJData high-precision number cannot be parsed
-    invalid_document_image = 116, ///< json_document::load() rejects an image
     // invalid_iterator
     iterators_incompatible = 201, ///< the iterators of a range belong to different values
     iterator_from_other_value = 202, ///< an iterator does not belong to the value it is used with
@@ -101,8 +100,6 @@ enum class exception_id : int
     invalid_utf8 = 316, ///< dump() finds a string that is not valid UTF-8
     type_not_serializable = 317, ///< a value cannot be serialized to the requested binary format
     enum_key_duplicate = 318, ///< an enum-keyed map has two keys that serialize to the same string
-    document_binary_value = 319, ///< a binary value is stored in a json_document
-    document_image_unsupported = 320, ///< a json_document image cannot be saved or loaded (discarded document, big-endian target)
     discarded_value_used = 321, ///< a discarded value is used
     // out_of_range
     array_index_out_of_range = 401, ///< an array index is out of range
@@ -120,7 +117,6 @@ enum class exception_id : int
     patch_remove_parent_not_container = 413, ///< the parent of a JSON Patch 'remove' target is not a container
     patch_move_into_child = 414, ///< a JSON Patch 'move' moves a value into one of its children
     subtype_out_of_range = 415, ///< a binary subtype does not fit into one byte
-    document_too_large = 416, ///< a json_document input, its edit storage, or an image reaches the 32-bit (4 GiB) limit
     // other_error
     internal_error = 500, ///< unreachable code was reached
     patch_test_failed = 501, ///< a JSON Patch 'test' operation failed
@@ -150,13 +146,6 @@ class exception : public std::exception
         return concat("[json.exception.", ename, '.', std::to_string(id_), "] ");
     }
 
-    /// build the message "[json.exception.<ename>.<id>] <diagnostics><what_arg>"
-    template<typename BasicJsonContext>
-    static std::string what_impl(const std::string& ename, int id_, const std::string& what_arg, BasicJsonContext context)
-    {
-        return concat(name(ename, id_), diagnostics(context), what_arg);
-    }
-
     static std::string diagnostics(std::nullptr_t /*leaf_element*/)
     {
         return "";
@@ -169,33 +158,48 @@ class exception : public std::exception
         std::vector<std::string> tokens;
         for (const auto* current = leaf_element; current != nullptr && current->m_parent != nullptr; current = current->m_parent)
         {
-            const auto* parent = current->m_parent;
-            if (parent->is_array())
+            switch (current->m_parent->type())
             {
-                for (std::size_t i = 0; i < parent->m_data.m_value.array->size(); ++i)
+                case value_t::array:
                 {
-                    if (&parent->m_data.m_value.array->operator[](i) == current)
+                    for (std::size_t i = 0; i < current->m_parent->m_data.m_value.array->size(); ++i)
                     {
-                        tokens.emplace_back(std::to_string(i));
-                        break;
+                        if (&current->m_parent->m_data.m_value.array->operator[](i) == current)
+                        {
+                            tokens.emplace_back(std::to_string(i));
+                            break;
+                        }
                     }
+                    break;
                 }
-            }
-            else if (parent->is_object())
-            {
-                for (const auto& element : *parent->m_data.m_value.object)
+
+                case value_t::object:
                 {
-                    if (&element.second == current)
+                    for (const auto& element : *current->m_parent->m_data.m_value.object)
                     {
-                        // data() is null-terminated, so a key containing
-                        // a null byte is cut short here rather than
-                        // truncating the whole message at what()
-                        tokens.emplace_back(element.first.data());
-                        break;
+                        if (&element.second == current)
+                        {
+                            // data() is null-terminated, so a key containing
+                            // a null byte is cut short here rather than
+                            // truncating the whole message at what()
+                            tokens.emplace_back(element.first.data());
+                            break;
+                        }
                     }
+                    break;
                 }
+
+                case value_t::null: // LCOV_EXCL_LINE
+                case value_t::string: // LCOV_EXCL_LINE
+                case value_t::boolean: // LCOV_EXCL_LINE
+                case value_t::number_integer: // LCOV_EXCL_LINE
+                case value_t::number_unsigned: // LCOV_EXCL_LINE
+                case value_t::number_float: // LCOV_EXCL_LINE
+                case value_t::binary: // LCOV_EXCL_LINE
+                case value_t::discarded: // LCOV_EXCL_LINE
+                default:   // LCOV_EXCL_LINE
+                    break; // LCOV_EXCL_LINE
             }
-            // all other parent types (primitives) contribute no token
         }
 
         if (tokens.empty())
@@ -311,7 +315,7 @@ class invalid_iterator : public exception
     template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
     static invalid_iterator create(int id_, const std::string& what_arg, BasicJsonContext context)
     {
-        const std::string w = exception::what_impl("invalid_iterator", id_, what_arg, context);
+        const std::string w = concat(exception::name("invalid_iterator", id_), exception::diagnostics(context), what_arg);
         return {id_, w.c_str()};
     }
 
@@ -335,7 +339,7 @@ class type_error : public exception
     template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
     static type_error create(int id_, const std::string& what_arg, BasicJsonContext context)
     {
-        const std::string w = exception::what_impl("type_error", id_, what_arg, context);
+        const std::string w = concat(exception::name("type_error", id_), exception::diagnostics(context), what_arg);
         return {id_, w.c_str()};
     }
 
@@ -358,7 +362,7 @@ class out_of_range : public exception
     template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
     static out_of_range create(int id_, const std::string& what_arg, BasicJsonContext context)
     {
-        const std::string w = exception::what_impl("out_of_range", id_, what_arg, context);
+        const std::string w = concat(exception::name("out_of_range", id_), exception::diagnostics(context), what_arg);
         return {id_, w.c_str()};
     }
 
@@ -381,7 +385,7 @@ class other_error : public exception
     template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
     static other_error create(int id_, const std::string& what_arg, BasicJsonContext context)
     {
-        const std::string w = exception::what_impl("other_error", id_, what_arg, context);
+        const std::string w = concat(exception::name("other_error", id_), exception::diagnostics(context), what_arg);
         return {id_, w.c_str()};
     }
 

include/nlohmann/detail/input/binary_reader.hpp

@@ -293,40 +293,6 @@ class binary_reader
         return is_object ? sax->end_object() : sax->end_array();
     }
 
-    /*!
-    @brief close the innermost open container and report whether that
-           completed the value being read
-
-    The value begun by the driver is complete once its container is not
-    inside another one.
-
-    @param[out] value_complete  whether no container is left open
-    @return whether the SAX parser accepted the end event
-    */
-    bool leave_container_and_check(bool& value_complete)
-    {
-        if (JSON_HEDLEY_UNLIKELY(!leave_container()))
-        {
-            return false;
-        }
-        value_complete = container_stack.empty();
-        return true;
-    }
-
-    /*!
-    @brief read an object key and pass it to the SAX parser
-
-    @tparam GetKey  member function that reads the key into a string
-    @param[in,out] key  string the key is read into; cleared first
-    @return whether reading the key and the SAX event succeeded
-    */
-    template<bool (binary_reader::*GetKey)(string_t&)>
-    bool read_object_key(string_t& key)
-    {
-        key.clear();
-        return (this->*GetKey)(key) && sax->key(key);
-    }
-
     //////////
     // BSON //
     //////////
@@ -1098,34 +1064,6 @@ class binary_reader
         return last_byte_error(exception_id::invalid_string_or_size, concat("indefinite-length ", type_name, " is not allowed inside indefinite-length ", type_name, "; last byte: 0x", get_token_string()), context);
     }
 
-    /*!
-    @brief report an object key that is not a string
-
-    @param[in] found  description of what was found instead of a string key
-    @return false
-    */
-    bool unsupported_key_type(const char* found) const
-    {
-        return last_byte_error(exception_id::invalid_string_or_size, "only string keys are supported, but found ", "object key", found);
-    }
-
-    /*!
-    @brief read the length of a CBOR string or byte array and then its bytes
-
-    @tparam NumberType    the type of the length field
-    @tparam ContainerType the destination container (string_t or binary_t)
-    @param[in] context  further context information (for diagnostics)
-    @param[out] result  container the bytes are appended to
-
-    @return whether reading completed
-    */
-    template<typename NumberType, typename ContainerType>
-    bool get_cbor_sized_bytes(const char* context, ContainerType& result)
-    {
-        NumberType len{};
-        return get_number(len) && get_bytes(len, context, result);
-    }
-
     /*!
     @brief reads a definite-length CBOR string
 
@@ -1176,22 +1114,26 @@ class binary_reader
 
             case 0x78: // UTF-8 string (one-byte uint8_t for n follows)
             {
-                return get_cbor_sized_bytes<std::uint8_t>("string", result);
+                std::uint8_t len{};
+                return get_number(len) && get_string(len, result);
             }
 
             case 0x79: // UTF-8 string (two-byte uint16_t for n follow)
             {
-                return get_cbor_sized_bytes<std::uint16_t>("string", result);
+                std::uint16_t len{};
+                return get_number(len) && get_string(len, result);
             }
 
             case 0x7A: // UTF-8 string (four-byte uint32_t for n follow)
             {
-                return get_cbor_sized_bytes<std::uint32_t>("string", result);
+                std::uint32_t len{};
+                return get_number(len) && get_string(len, result);
             }
 
             case 0x7B: // UTF-8 string (eight-byte uint64_t for n follow)
             {
-                return get_cbor_sized_bytes<std::uint64_t>("string", result);
+                std::uint64_t len{};
+                return get_number(len) && get_string(len, result);
             }
 
             default:
@@ -1326,7 +1268,7 @@ class binary_reader
                 break;
         }
 
-        return unsupported_key_type(found);
+        return last_byte_error(exception_id::invalid_string_or_size, "only string keys are supported, but found ", "object key", found);
     }
 
     /*!
@@ -1379,22 +1321,30 @@ class binary_reader
 
             case 0x58: // Binary data (one-byte uint8_t for n follows)
             {
-                return get_cbor_sized_bytes<std::uint8_t>("binary", result);
+                std::uint8_t len{};
+                return get_number(len) &&
+                       get_binary(len, result);
             }
 
             case 0x59: // Binary data (two-byte uint16_t for n follow)
             {
-                return get_cbor_sized_bytes<std::uint16_t>("binary", result);
+                std::uint16_t len{};
+                return get_number(len) &&
+                       get_binary(len, result);
             }
 
             case 0x5A: // Binary data (four-byte uint32_t for n follow)
             {
-                return get_cbor_sized_bytes<std::uint32_t>("binary", result);
+                std::uint32_t len{};
+                return get_number(len) &&
+                       get_binary(len, result);
             }
 
             case 0x5B: // Binary data (eight-byte uint64_t for n follow)
             {
-                return get_cbor_sized_bytes<std::uint64_t>("binary", result);
+                std::uint64_t len{};
+                return get_number(len) &&
+                       get_binary(len, result);
             }
 
             default:
@@ -1609,12 +1559,12 @@ class binary_reader
 
                 if (at_end)
                 {
-                    bool value_complete = false;
-                    if (JSON_HEDLEY_UNLIKELY(!leave_container_and_check(value_complete)))
+                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
                     {
                         return false;
                     }
-                    if (value_complete)
+                    // the value begun here is complete once its container is
+                    if (container_stack.empty())
                     {
                         return true;
                     }
@@ -1623,7 +1573,8 @@ class binary_reader
 
                 if (top.is_object)
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!read_object_key<&binary_reader::get_cbor_object_key>(key)))
+                    key.clear();
+                    if (JSON_HEDLEY_UNLIKELY(!get_cbor_object_key(key) || !sax->key(key)))
                     {
                         return false;
                     }
@@ -2094,17 +2045,20 @@ class binary_reader
 
             case 0xD9: // str 8
             {
-                return get_string_with_length<std::uint8_t>(result, context);
+                std::uint8_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             case 0xDA: // str 16
             {
-                return get_string_with_length<std::uint16_t>(result, context);
+                std::uint16_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             case 0xDB: // str 32
             {
-                return get_string_with_length<std::uint32_t>(result, context);
+                std::uint32_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             default:
@@ -2201,7 +2155,7 @@ class binary_reader
                 break;
         }
 
-        return unsupported_key_type(found);
+        return last_byte_error(exception_id::invalid_string_or_size, "only string keys are supported, but found ", "object key", found);
     }
 
     /*!
@@ -2346,12 +2300,12 @@ class binary_reader
 
                 if (container_stack.back().remaining == 0)
                 {
-                    bool value_complete = false;
-                    if (JSON_HEDLEY_UNLIKELY(!leave_container_and_check(value_complete)))
+                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
                     {
                         return false;
                     }
-                    if (value_complete)
+                    // the value begun here is complete once its container is
+                    if (container_stack.empty())
                     {
                         return true;
                     }
@@ -2364,7 +2318,8 @@ class binary_reader
                 if (is_object)
                 {
                     get();
-                    if (JSON_HEDLEY_UNLIKELY(!read_object_key<&binary_reader::get_msgpack_object_key>(key)))
+                    key.clear();
+                    if (JSON_HEDLEY_UNLIKELY(!get_msgpack_object_key(key) || !sax->key(key)))
                     {
                         return false;
                     }
@@ -2548,7 +2503,8 @@ class binary_reader
         {
             case 'U':
             {
-                return get_string_with_length<std::uint8_t>(result, context);
+                std::uint8_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             case 'i':
@@ -2581,7 +2537,8 @@ class binary_reader
                 {
                     break;
                 }
-                return get_string_with_length<std::uint16_t>(result, context);
+                std::uint16_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             case 'm':
@@ -2590,7 +2547,8 @@ class binary_reader
                 {
                     break;
                 }
-                return get_string_with_length<std::uint32_t>(result, context);
+                std::uint32_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             case 'M':
@@ -2599,7 +2557,8 @@ class binary_reader
                 {
                     break;
                 }
-                return get_string_with_length<std::uint64_t>(result, context);
+                std::uint64_t len{};
+                return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
             }
 
             default:
@@ -3415,12 +3374,12 @@ class binary_reader
 
                 if (at_end)
                 {
-                    bool value_complete = false;
-                    if (JSON_HEDLEY_UNLIKELY(!leave_container_and_check(value_complete)))
+                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
                     {
                         return false;
                     }
-                    if (value_complete)
+                    // the value begun here is complete once its container is
+                    if (container_stack.empty())
                     {
                         return true;
                     }
@@ -3429,7 +3388,8 @@ class binary_reader
 
                 if (top.is_object)
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!read_object_key<&binary_reader::get_bon8_key>(key)))
+                    key.clear();
+                    if (JSON_HEDLEY_UNLIKELY(!get_bon8_key(key) || !sax->key(key)))
                     {
                         return false;
                     }
@@ -4169,22 +4129,6 @@ class binary_reader
         return true;
     }
 
-    /*!
-    @brief read a length of type @a NumberType, then a string of that many bytes
-
-    @tparam NumberType  the type of the length field
-    @param[out] result  string the bytes are appended to
-    @param[in] context  further context information (for diagnostics)
-
-    @return whether reading and validating the string succeeded
-    */
-    template<typename NumberType>
-    bool get_string_with_length(string_t& result, const char* context)
-    {
-        NumberType len{};
-        return get_number(len) && get_string(len, result) && check_string_utf8(result, context);
-    }
-
     /*!
     @brief create a byte array by reading bytes from the input
 
@@ -4394,7 +4338,37 @@ class binary_reader
                                   const std::string& context) const
     {
         std::string error_msg = "syntax error while parsing ";
-        error_msg += input_format_name(input_format);
+
+        switch (input_format)
+        {
+            case input_format_t::cbor:
+                error_msg += "CBOR";
+                break;
+
+            case input_format_t::msgpack:
+                error_msg += "MessagePack";
+                break;
+
+            case input_format_t::ubjson:
+                error_msg += "UBJSON";
+                break;
+
+            case input_format_t::bson:
+                error_msg += "BSON";
+                break;
+
+            case input_format_t::bjdata:
+                error_msg += "BJData";
+                break;
+
+            case input_format_t::bon8:
+                error_msg += "BON8";
+                break;
+
+            case input_format_t::json: // LCOV_EXCL_LINE
+            default:            // LCOV_EXCL_LINE
+                JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
+        }
 
         return concat(error_msg, ' ', context, ": ", detail);
     }

include/nlohmann/detail/input/input_adapters.hpp

@@ -67,36 +67,6 @@ namespace detail
 /// the supported input formats
 enum class input_format_t { json, cbor, msgpack, ubjson, bson, bjdata, bon8 };
 
-/// @return the name of a binary input format, as used in exception messages
-inline const char* input_format_name(const input_format_t format) noexcept
-{
-    switch (format)
-    {
-        case input_format_t::cbor:
-            return "CBOR";
-        case input_format_t::msgpack:
-            return "MessagePack";
-        case input_format_t::ubjson:
-            return "UBJSON";
-        case input_format_t::bson:
-            return "BSON";
-        case input_format_t::bjdata:
-            return "BJData";
-        case input_format_t::bon8:
-            return "BON8";
-        case input_format_t::json: // LCOV_EXCL_LINE
-        default:            // LCOV_EXCL_LINE
-            JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
-            return ""; // LCOV_EXCL_LINE
-    }
-}
-
-/// @return the message of the parse_error thrown or reported for an empty input
-inline const char* empty_input_message() noexcept
-{
-    return "attempting to parse an empty input; check that your input string or stream contains the expected JSON";
-}
-
 ////////////////////
 // input adapters //
 ////////////////////
@@ -1298,7 +1268,7 @@ inline file_input_adapter input_adapter(std::FILE* file)
 {
     if (file == nullptr)
     {
-        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, empty_input_message(), nullptr));
+        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
     }
     return file_input_adapter(file);
 }
@@ -1307,7 +1277,7 @@ inline input_stream_adapter input_adapter(std::istream& stream)
 {
     if (stream.rdbuf() == nullptr)
     {
-        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, empty_input_message(), nullptr));
+        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
     }
     return input_stream_adapter(stream);
 }
@@ -1332,7 +1302,7 @@ contiguous_bytes_input_adapter input_adapter(CharT b)
 {
     if (b == nullptr)
     {
-        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, empty_input_message(), nullptr));
+        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
     }
     auto length = std::strlen(reinterpret_cast<const char*>(b));
     const auto* ptr = reinterpret_cast<const char*>(b);

include/nlohmann/detail/input/json_sax.hpp

@@ -321,52 +321,6 @@ struct diagnostic_positions
 };
 #endif
 
-/*!
-@brief error state shared by the DOM-building SAX parsers
-
-Holds whether a parse error occurred and whether errors are thrown, and
-implements the parse_error() and is_errored() members of the SAX interface for
-json_sax_dom_parser and json_sax_dom_callback_parser.
-*/
-class json_sax_dom_error_state
-{
-  public:
-    explicit json_sax_dom_error_state(const bool allow_exceptions_) noexcept
-        : allow_exceptions(allow_exceptions_)
-    {}
-
-    // make class move-only
-    json_sax_dom_error_state(const json_sax_dom_error_state&) = delete;
-    json_sax_dom_error_state(json_sax_dom_error_state&&) = default; // NOLINT(hicpp-noexcept-move,performance-noexcept-move-constructor)
-    json_sax_dom_error_state& operator=(const json_sax_dom_error_state&) = delete;
-    json_sax_dom_error_state& operator=(json_sax_dom_error_state&&) = delete; // the const member prevents assignment
-    ~json_sax_dom_error_state() = default;
-
-    template<class Exception>
-    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/,
-                     const Exception& ex)
-    {
-        errored = true;
-        static_cast<void>(ex);
-        if (allow_exceptions)
-        {
-            JSON_THROW(ex);
-        }
-        return false;
-    }
-
-    bool is_errored() const
-    {
-        return errored;
-    }
-
-  private:
-    /// whether a syntax error occurred
-    bool errored = false;
-    /// whether to throw exceptions in case of errors
-    const bool allow_exceptions = true;
-};
-
 /*!
 @brief a hash table that finds the position of a key in an object whose
        elements are kept in a vector (ordered_map)
@@ -475,7 +429,7 @@ read up to it.
                  parse error)
 */
 template<typename BasicJsonType, typename InputAdapterType, bool Collect = false>
-class json_sax_dom_parser : public json_sax_dom_error_state
+class json_sax_dom_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -491,7 +445,7 @@ class json_sax_dom_parser : public json_sax_dom_error_state
     @param[in] allow_exceptions_  whether parse errors yield exceptions
     */
     explicit json_sax_dom_parser(BasicJsonType& r, const bool allow_exceptions_ = true, lexer_t* lexer_ = nullptr)
-        : json_sax_dom_error_state(allow_exceptions_), root(r), m_lexer_ref(lexer_)
+        : root(r), allow_exceptions(allow_exceptions_), m_lexer_ref(lexer_)
     {}
 
     // make class move-only
@@ -642,6 +596,24 @@ class json_sax_dom_parser : public json_sax_dom_error_state
         return true;
     }
 
+    template<class Exception>
+    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/,
+                     const Exception& ex)
+    {
+        errored = true;
+        static_cast<void>(ex);
+        if (allow_exceptions)
+        {
+            JSON_THROW(ex);
+        }
+        return false;
+    }
+
+    constexpr bool is_errored() const
+    {
+        return errored;
+    }
+
   private:
     using object_t = typename BasicJsonType::object_t;
     using array_t = typename BasicJsonType::array_t;
@@ -937,8 +909,6 @@ class json_sax_dom_parser : public json_sax_dom_error_state
     /// directly if the value was the one too many.
     void place_container(const frame& f, frame* enclosing, BasicJsonType&& value, const bool enclosing_is_innermost)
     {
-        // only a container with a slot may have no enclosing container
-        JSON_ASSERT(f.slot != nullptr || enclosing != nullptr);
         if (f.slot != nullptr)
         {
             *f.slot = std::move(value);
@@ -1355,6 +1325,10 @@ class json_sax_dom_parser : public json_sax_dom_error_state
     /// the array that stores the elements of the innermost array as they
     /// arrive (frames.back().array), or nullptr
     array_t* stored_array = nullptr;
+    /// whether a syntax error occurred
+    bool errored = false;
+    /// whether to throw exceptions in case of errors
+    const bool allow_exceptions = true;
     /// the lexer reference to obtain the current position
     lexer_t* m_lexer_ref = nullptr;
 };
@@ -1379,7 +1353,7 @@ constructor contains the parsed value.
 @tparam BasicJsonType  the JSON type
 */
 template<typename BasicJsonType, typename InputAdapterType>
-class json_sax_dom_binary_parser : public json_sax_dom_error_state
+class json_sax_dom_binary_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -1395,7 +1369,7 @@ class json_sax_dom_binary_parser : public json_sax_dom_error_state
     @param[in] allow_exceptions_  whether parse errors yield exceptions
     */
     explicit json_sax_dom_binary_parser(BasicJsonType& r, const bool allow_exceptions_ = true, lexer_t* lexer_ = nullptr)
-        : json_sax_dom_error_state(allow_exceptions_), root(r), m_lexer_ref(lexer_)
+        : root(r), allow_exceptions(allow_exceptions_), m_lexer_ref(lexer_)
     {}
 
     // make class move-only
@@ -1524,6 +1498,24 @@ class json_sax_dom_binary_parser : public json_sax_dom_error_state
         return true;
     }
 
+    template<class Exception>
+    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/,
+                     const Exception& ex)
+    {
+        errored = true;
+        static_cast<void>(ex);
+        if (allow_exceptions)
+        {
+            JSON_THROW(ex);
+        }
+        return false;
+    }
+
+    constexpr bool is_errored() const
+    {
+        return errored;
+    }
+
   private:
 
     /*!
@@ -1577,12 +1569,16 @@ class json_sax_dom_binary_parser : public json_sax_dom_error_state
     std::vector<BasicJsonType*> ref_stack {};
     /// helper to hold the reference for the next object element
     BasicJsonType* object_element = nullptr;
+    /// whether a syntax error occurred
+    bool errored = false;
+    /// whether to throw exceptions in case of errors
+    const bool allow_exceptions = true;
     /// the lexer reference to obtain the current position
     lexer_t* m_lexer_ref = nullptr;
 };
 
 template<typename BasicJsonType, typename InputAdapterType>
-class json_sax_dom_callback_parser : public json_sax_dom_error_state
+class json_sax_dom_callback_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -1598,7 +1594,7 @@ class json_sax_dom_callback_parser : public json_sax_dom_error_state
                                  parser_callback_t cb,
                                  const bool allow_exceptions_ = true,
                                  lexer_t* lexer_ = nullptr)
-        : json_sax_dom_error_state(allow_exceptions_), root(r), callback(std::move(cb)), m_lexer_ref(lexer_)
+        : root(r), callback(std::move(cb)), allow_exceptions(allow_exceptions_), m_lexer_ref(lexer_)
     {
         keep_stack.push_back(true);
     }
@@ -1862,6 +1858,24 @@ class json_sax_dom_callback_parser : public json_sax_dom_error_state
         return true;
     }
 
+    template<class Exception>
+    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/,
+                     const Exception& ex)
+    {
+        errored = true;
+        static_cast<void>(ex);
+        if (allow_exceptions)
+        {
+            JSON_THROW(ex);
+        }
+        return false;
+    }
+
+    constexpr bool is_errored() const
+    {
+        return errored;
+    }
+
   private:
 
     /*!
@@ -2128,8 +2142,12 @@ class json_sax_dom_callback_parser : public json_sax_dom_error_state
     /// value is later rejected by the callback, instead of erasing the
     /// member entirely
     std::vector<std::pair<BasicJsonType*, BasicJsonType>> duplicate_key_stash {};
+    /// whether a syntax error occurred
+    bool errored = false;
     /// callback function
     const parser_callback_t callback = nullptr;
+    /// whether to throw exceptions in case of errors
+    const bool allow_exceptions = true;
     /// a discarded value for the callback
     BasicJsonType discarded = BasicJsonType::value_t::discarded;
     /// the value of the key event for the callback (see key_value())

include/nlohmann/detail/input/lexer.hpp

@@ -657,74 +657,194 @@ class lexer : public lexer_base<BasicJsonType>
 
                 // invalid control characters
                 case 0x00:
+                {
+                    error_message = "invalid string: control character U+0000 (NUL) must be escaped to \\u0000";
+                    return token_type::parse_error;
+                }
+
                 case 0x01:
+                {
+                    error_message = "invalid string: control character U+0001 (SOH) must be escaped to \\u0001";
+                    return token_type::parse_error;
+                }
+
                 case 0x02:
+                {
+                    error_message = "invalid string: control character U+0002 (STX) must be escaped to \\u0002";
+                    return token_type::parse_error;
+                }
+
                 case 0x03:
+                {
+                    error_message = "invalid string: control character U+0003 (ETX) must be escaped to \\u0003";
+                    return token_type::parse_error;
+                }
+
                 case 0x04:
+                {
+                    error_message = "invalid string: control character U+0004 (EOT) must be escaped to \\u0004";
+                    return token_type::parse_error;
+                }
+
                 case 0x05:
+                {
+                    error_message = "invalid string: control character U+0005 (ENQ) must be escaped to \\u0005";
+                    return token_type::parse_error;
+                }
+
                 case 0x06:
+                {
+                    error_message = "invalid string: control character U+0006 (ACK) must be escaped to \\u0006";
+                    return token_type::parse_error;
+                }
+
                 case 0x07:
+                {
+                    error_message = "invalid string: control character U+0007 (BEL) must be escaped to \\u0007";
+                    return token_type::parse_error;
+                }
+
                 case 0x08:
+                {
+                    error_message = "invalid string: control character U+0008 (BS) must be escaped to \\u0008 or \\b";
+                    return token_type::parse_error;
+                }
+
                 case 0x09:
+                {
+                    error_message = "invalid string: control character U+0009 (HT) must be escaped to \\u0009 or \\t";
+                    return token_type::parse_error;
+                }
+
                 case 0x0A:
+                {
+                    error_message = "invalid string: control character U+000A (LF) must be escaped to \\u000A or \\n";
+                    return token_type::parse_error;
+                }
+
                 case 0x0B:
+                {
+                    error_message = "invalid string: control character U+000B (VT) must be escaped to \\u000B";
+                    return token_type::parse_error;
+                }
+
                 case 0x0C:
+                {
+                    error_message = "invalid string: control character U+000C (FF) must be escaped to \\u000C or \\f";
+                    return token_type::parse_error;
+                }
+
                 case 0x0D:
+                {
+                    error_message = "invalid string: control character U+000D (CR) must be escaped to \\u000D or \\r";
+                    return token_type::parse_error;
+                }
+
                 case 0x0E:
+                {
+                    error_message = "invalid string: control character U+000E (SO) must be escaped to \\u000E";
+                    return token_type::parse_error;
+                }
+
                 case 0x0F:
+                {
+                    error_message = "invalid string: control character U+000F (SI) must be escaped to \\u000F";
+                    return token_type::parse_error;
+                }
+
                 case 0x10:
+                {
+                    error_message = "invalid string: control character U+0010 (DLE) must be escaped to \\u0010";
+                    return token_type::parse_error;
+                }
+
                 case 0x11:
+                {
+                    error_message = "invalid string: control character U+0011 (DC1) must be escaped to \\u0011";
+                    return token_type::parse_error;
+                }
+
                 case 0x12:
+                {
+                    error_message = "invalid string: control character U+0012 (DC2) must be escaped to \\u0012";
+                    return token_type::parse_error;
+                }
+
                 case 0x13:
+                {
+                    error_message = "invalid string: control character U+0013 (DC3) must be escaped to \\u0013";
+                    return token_type::parse_error;
+                }
+
                 case 0x14:
+                {
+                    error_message = "invalid string: control character U+0014 (DC4) must be escaped to \\u0014";
+                    return token_type::parse_error;
+                }
+
                 case 0x15:
+                {
+                    error_message = "invalid string: control character U+0015 (NAK) must be escaped to \\u0015";
+                    return token_type::parse_error;
+                }
+
                 case 0x16:
+                {
+                    error_message = "invalid string: control character U+0016 (SYN) must be escaped to \\u0016";
+                    return token_type::parse_error;
+                }
+
                 case 0x17:
+                {
+                    error_message = "invalid string: control character U+0017 (ETB) must be escaped to \\u0017";
+                    return token_type::parse_error;
+                }
+
                 case 0x18:
+                {
+                    error_message = "invalid string: control character U+0018 (CAN) must be escaped to \\u0018";
+                    return token_type::parse_error;
+                }
+
                 case 0x19:
+                {
+                    error_message = "invalid string: control character U+0019 (EM) must be escaped to \\u0019";
+                    return token_type::parse_error;
+                }
+
                 case 0x1A:
+                {
+                    error_message = "invalid string: control character U+001A (SUB) must be escaped to \\u001A";
+                    return token_type::parse_error;
+                }
+
                 case 0x1B:
+                {
+                    error_message = "invalid string: control character U+001B (ESC) must be escaped to \\u001B";
+                    return token_type::parse_error;
+                }
+
                 case 0x1C:
+                {
+                    error_message = "invalid string: control character U+001C (FS) must be escaped to \\u001C";
+                    return token_type::parse_error;
+                }
+
                 case 0x1D:
+                {
+                    error_message = "invalid string: control character U+001D (GS) must be escaped to \\u001D";
+                    return token_type::parse_error;
+                }
+
                 case 0x1E:
+                {
+                    error_message = "invalid string: control character U+001E (RS) must be escaped to \\u001E";
+                    return token_type::parse_error;
+                }
+
                 case 0x1F:
                 {
-                    static const std::array<const char*, 32> control_character_messages = {{
-                            "invalid string: control character U+0000 (NUL) must be escaped to \\u0000",
-                            "invalid string: control character U+0001 (SOH) must be escaped to \\u0001",
-                            "invalid string: control character U+0002 (STX) must be escaped to \\u0002",
-                            "invalid string: control character U+0003 (ETX) must be escaped to \\u0003",
-                            "invalid string: control character U+0004 (EOT) must be escaped to \\u0004",
-                            "invalid string: control character U+0005 (ENQ) must be escaped to \\u0005",
-                            "invalid string: control character U+0006 (ACK) must be escaped to \\u0006",
-                            "invalid string: control character U+0007 (BEL) must be escaped to \\u0007",
-                            "invalid string: control character U+0008 (BS) must be escaped to \\u0008 or \\b",
-                            "invalid string: control character U+0009 (HT) must be escaped to \\u0009 or \\t",
-                            "invalid string: control character U+000A (LF) must be escaped to \\u000A or \\n",
-                            "invalid string: control character U+000B (VT) must be escaped to \\u000B",
-                            "invalid string: control character U+000C (FF) must be escaped to \\u000C or \\f",
-                            "invalid string: control character U+000D (CR) must be escaped to \\u000D or \\r",
-                            "invalid string: control character U+000E (SO) must be escaped to \\u000E",
-                            "invalid string: control character U+000F (SI) must be escaped to \\u000F",
-                            "invalid string: control character U+0010 (DLE) must be escaped to \\u0010",
-                            "invalid string: control character U+0011 (DC1) must be escaped to \\u0011",
-                            "invalid string: control character U+0012 (DC2) must be escaped to \\u0012",
-                            "invalid string: control character U+0013 (DC3) must be escaped to \\u0013",
-                            "invalid string: control character U+0014 (DC4) must be escaped to \\u0014",
-                            "invalid string: control character U+0015 (NAK) must be escaped to \\u0015",
-                            "invalid string: control character U+0016 (SYN) must be escaped to \\u0016",
-                            "invalid string: control character U+0017 (ETB) must be escaped to \\u0017",
-                            "invalid string: control character U+0018 (CAN) must be escaped to \\u0018",
-                            "invalid string: control character U+0019 (EM) must be escaped to \\u0019",
-                            "invalid string: control character U+001A (SUB) must be escaped to \\u001A",
-                            "invalid string: control character U+001B (ESC) must be escaped to \\u001B",
-                            "invalid string: control character U+001C (FS) must be escaped to \\u001C",
-                            "invalid string: control character U+001D (GS) must be escaped to \\u001D",
-                            "invalid string: control character U+001E (RS) must be escaped to \\u001E",
-                            "invalid string: control character U+001F (US) must be escaped to \\u001F"
-                        }
-                    };
-                    error_message = control_character_messages[static_cast<std::size_t>(current)];
+                    error_message = "invalid string: control character U+001F (US) must be escaped to \\u001F";
                     return token_type::parse_error;
                 }
 

include/nlohmann/detail/input/parser.hpp

@@ -165,10 +165,23 @@ class parser
 
         if (result)
         {
-            return finish_input(*sax, strict);
+            if (strict)
+            {
+                // strict mode: next byte must be EOF
+                if (get_token() != token_type::end_of_input)
+                {
+                    return syntax_error(*sax, exception_message(token_type::end_of_input, "value"));
+                }
+            }
+            else
+            {
+                // the caller keeps using the input: position it right after
+                // the value by leaving the character that terminated it
+                m_lexer.release_lookahead();
+            }
         }
 
-        return false;
+        return result;
     }
 
   private:
@@ -189,39 +202,6 @@ class parser
         return m_lexer.get_string();
     }
 
-    /*!
-    @brief apply the end-of-input handling after a value was parsed
-
-    In strict mode, the next token must be the end of the input; otherwise
-    parse_error.101 is reported through @a sax. In non-strict mode, the
-    lookahead is released so the caller can keep reading the input right after
-    the parsed value.
-
-    @param[in,out] sax  the SAX parser to report an error to
-    @param[in] strict   whether to expect the last token to be EOF
-    @return true, or what @a sax returned for the error
-    */
-    template<typename SAX>
-    bool finish_input(SAX& sax, const bool strict)
-    {
-        if (strict)
-        {
-            // strict mode: next byte must be EOF
-            if (get_token() != token_type::end_of_input)
-            {
-                return syntax_error(sax, exception_message(token_type::end_of_input, "value"));
-            }
-        }
-        else
-        {
-            // the caller keeps using the input: position it right after
-            // the value by leaving the character that terminated it
-            m_lexer.release_lookahead();
-        }
-
-        return true;
-    }
-
     /*!
     @brief run a DOM SAX parser to completion and position the lexer
 
@@ -241,7 +221,20 @@ class parser
     {
         sax_parse_internal(&sdp);
 
-        static_cast<void>(finish_input(sdp, strict));
+        if (strict)
+        {
+            // in strict mode, input must be completely read
+            if (get_token() != token_type::end_of_input)
+            {
+                syntax_error(sdp, exception_message(token_type::end_of_input, "value"));
+            }
+        }
+        else
+        {
+            // the caller keeps using the input: position it right after
+            // the value by leaving the character that terminated it
+            m_lexer.release_lookahead();
+        }
 
         return !sdp.is_errored();
     }
@@ -418,7 +411,7 @@ class parser
                     {
                         if (JSON_HEDLEY_UNLIKELY(m_lexer.get_chars_read_total() == 1))
                         {
-                            return syntax_error(*sax, empty_input_message());
+                            return syntax_error(*sax, "attempting to parse an empty input; check that your input string or stream contains the expected JSON");
                         }
 
                         return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));

include/nlohmann/detail/input/string_scan.hpp

@@ -96,7 +96,7 @@ JSON_HEDLEY_ALWAYS_INLINE std::size_t find_string_special(const unsigned char* d
 // printable ASCII except '"' and '\\' - is emitted unchanged. Note this differs
 // from is_string_special() only in that 0x7F is also a stop (it is escaped as
 // \u007f under ensure_ascii).
-constexpr bool is_ascii_copyable(unsigned char c) noexcept
+inline bool is_ascii_copyable(unsigned char c) noexcept
 {
     return c >= 0x20u && c < 0x7Fu && c != '"' && c != '\\';
 }

include/nlohmann/detail/iterators/iter_impl.hpp

@@ -108,18 +108,33 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
     {
         JSON_ASSERT(m_object != nullptr);
 
-        if (m_object->is_object())
+        switch (m_object->m_data.m_type)
         {
-            m_it.object_iterator = typename object_t::iterator();
-        }
-        else if (m_object->is_array())
-        {
-            m_it.array_iterator = typename array_t::iterator();
-        }
-        else
-        {
-            // primitive (is_primitive(), including discarded)
-            m_it.primitive_iterator = primitive_iterator_t();
+            case value_t::object:
+            {
+                m_it.object_iterator = typename object_t::iterator();
+                break;
+            }
+
+            case value_t::array:
+            {
+                m_it.array_iterator = typename array_t::iterator();
+                break;
+            }
+
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+            {
+                m_it.primitive_iterator = primitive_iterator_t();
+                break;
+            }
         }
     }
 
@@ -234,28 +249,33 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
     {
         JSON_ASSERT(m_object != nullptr);
 
-        if (m_object->is_object())
+        switch (m_object->m_data.m_type)
         {
-            m_it.object_iterator = m_object->m_data.m_value.object->end();
-        }
-        else if (m_object->is_array())
-        {
-            m_it.array_iterator = m_object->m_data.m_value.array->end();
-        }
-        else
-        {
-            // primitive (is_primitive(), including discarded)
-            m_it.primitive_iterator.set_end();
-        }
-    }
+            case value_t::object:
+            {
+                m_it.object_iterator = m_object->m_data.m_value.object->end();
+                break;
+            }
 
-    /// @throw invalid_iterator.212 if @a other points to another container
-    template<typename IterImpl>
-    JSON_HEDLEY_ALWAYS_INLINE void check_same_container(const IterImpl& other) const
-    {
-        if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
-        {
-            throw_literal<invalid_iterator>(exception_id::iterators_compare_different_values, "cannot compare iterators of different containers", m_object);
+            case value_t::array:
+            {
+                m_it.array_iterator = m_object->m_data.m_value.array->end();
+                break;
+            }
+
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+            {
+                m_it.primitive_iterator.set_end();
+                break;
+            }
         }
     }
 
@@ -404,7 +424,10 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
     bool operator==(const IterImpl& other) const
     {
         // if objects are not the same, the comparison is undefined
-        check_same_container(other);
+        if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
+        {
+            throw_literal<invalid_iterator>(exception_id::iterators_compare_different_values, "cannot compare iterators of different containers", m_object);
+        }
 
         // value-initialized forward iterators can be compared, and must compare equal to other value-initialized iterators of the same type #4493
         if (m_object == nullptr)
@@ -443,7 +466,10 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
     bool operator<(const iter_impl& other) const
     {
         // if objects are not the same, the comparison is undefined
-        check_same_container(other);
+        if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
+        {
+            throw_literal<invalid_iterator>(exception_id::iterators_compare_different_values, "cannot compare iterators of different containers", m_object);
+        }
 
         // value-initialized forward iterators can be compared, and must compare equal to other value-initialized iterators of the same type #4493
         if (m_object == nullptr)
@@ -452,18 +478,25 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
             return false;
         }
 
-        if (m_object->is_object())
+        switch (m_object->m_data.m_type)
         {
-            throw_literal<invalid_iterator>(exception_id::iterator_order_on_object, "cannot compare order of object iterators", m_object);
-        }
+            case value_t::object:
+                throw_literal<invalid_iterator>(exception_id::iterator_order_on_object, "cannot compare order of object iterators", m_object);
 
-        if (m_object->is_array())
-        {
-            return (m_it.array_iterator < other.m_it.array_iterator);
-        }
+            case value_t::array:
+                return (m_it.array_iterator < other.m_it.array_iterator);
 
-        // primitive (is_primitive(), including discarded)
-        return (m_it.primitive_iterator < other.m_it.primitive_iterator);
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+                return (m_it.primitive_iterator < other.m_it.primitive_iterator);
+        }
     }
 
     /*!
@@ -501,19 +534,30 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
     {
         JSON_ASSERT(m_object != nullptr);
 
-        if (m_object->is_object())
+        switch (m_object->m_data.m_type)
         {
-            throw_literal<invalid_iterator>(exception_id::iterator_arithmetic_on_object, "cannot use offsets with object iterators", m_object);
-        }
+            case value_t::object:
+                throw_literal<invalid_iterator>(exception_id::iterator_arithmetic_on_object, "cannot use offsets with object iterators", m_object);
 
-        if (m_object->is_array())
-        {
-            std::advance(m_it.array_iterator, i);
-        }
-        else
-        {
-            // primitive (is_primitive(), including discarded)
-            m_it.primitive_iterator += i;
+            case value_t::array:
+            {
+                std::advance(m_it.array_iterator, i);
+                break;
+            }
+
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+            {
+                m_it.primitive_iterator += i;
+                break;
+            }
         }
 
         return *this;
@@ -569,18 +613,25 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
     {
         JSON_ASSERT(m_object != nullptr);
 
-        if (m_object->is_object())
+        switch (m_object->m_data.m_type)
         {
-            throw_literal<invalid_iterator>(exception_id::iterator_arithmetic_on_object, "cannot use offsets with object iterators", m_object);
-        }
+            case value_t::object:
+                throw_literal<invalid_iterator>(exception_id::iterator_arithmetic_on_object, "cannot use offsets with object iterators", m_object);
 
-        if (m_object->is_array())
-        {
-            return m_it.array_iterator - other.m_it.array_iterator;
-        }
+            case value_t::array:
+                return m_it.array_iterator - other.m_it.array_iterator;
 
-        // primitive (is_primitive(), including discarded)
-        return m_it.primitive_iterator - other.m_it.primitive_iterator;
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+                return m_it.primitive_iterator - other.m_it.primitive_iterator;
+        }
     }
 
     /*!

include/nlohmann/detail/iterators/iteration_proxy.hpp

@@ -109,25 +109,35 @@ template<typename IteratorType> class iteration_proxy_value
     {
         JSON_ASSERT(anchor.m_object != nullptr);
 
-        if (anchor.m_object->is_array())
+        switch (anchor.m_object->type())
         {
             // use integer array index as key
-            if (array_index != array_index_last)
+            case value_t::array:
             {
-                int_to_string( array_index_str, array_index );
-                array_index_last = array_index;
+                if (array_index != array_index_last)
+                {
+                    int_to_string( array_index_str, array_index );
+                    array_index_last = array_index;
+                }
+                return array_index_str;
             }
-            return array_index_str;
-        }
 
-        if (anchor.m_object->is_object())
-        {
             // use key from the object
-            return anchor.key();
-        }
+            case value_t::object:
+                return anchor.key();
 
-        // use an empty key for all primitive types
-        return empty_str;
+            // use an empty key for all primitive types
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+                return empty_str;
+        }
     }
 
     /// return value of the iterator

include/nlohmann/detail/json_pointer.hpp

@@ -38,102 +38,6 @@ NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
 struct json_pointer_access;
-
-/*!
-@brief result of parse_array_index()
-
-json_pointer::array_index() maps each value to the corresponding
-parse_error/out_of_range exception; json_pointer::contains() and
-get_checked_or_null(), which must not throw for an out-of-range or
-unrepresentable index, and the json_view pointer resolution switch on it
-directly instead.
-*/
-enum class array_index_status
-{
-    ok,                ///< @a s is a valid, representable array index
-    leading_zero,      ///< @a s begins with '0' but has more than one character
-    not_a_number,      ///< @a s is neither empty nor "-" and does not begin with a digit
-    unresolved,        ///< @a s could not be converted to an integer
-    exceeds_size_type  ///< @a s converts to an integer that exceeds SizeType
-};
-
-/*!
-@brief convert a JSON Pointer reference token into an array index (RFC 6901, Sect. 4)
-
-@param[in] s    reference token to be converted into an array index; its data()
-                must be NUL-terminated
-@param[out] idx the integer representation of @a s if array_index_status::ok
-                is returned; left unchanged otherwise
-
-@return whether @a s is a valid array index, and if not, why
-
-@note this function never throws; json_pointer::array_index(), the callers that
-      must not throw, and the json_view pointer resolution build on it instead
-      of each re-implementing the RFC 6901 digit rules and the range check
-@note force-inlined: as a free function template it is no longer inlined into
-      the pointer resolution, which makes JsonPointerAt up to 17% slower (#5891)
-*/
-template<typename SizeType, typename StringType>
-JSON_HEDLEY_ALWAYS_INLINE array_index_status parse_array_index(const StringType& s, SizeType& idx) noexcept
-{
-    // error condition (cf. RFC 6901, Sect. 4)
-    if (JSON_HEDLEY_UNLIKELY(s.size() > 1 && s[0] == '0'))
-    {
-        return array_index_status::leading_zero;
-    }
-
-    // error condition (cf. RFC 6901, Sect. 4); this also covers single-
-    // character tokens, so "/x" and "/xy" fail alike; "-" and the empty
-    // token are left to the conversion below and are reported as unresolved
-    if (JSON_HEDLEY_UNLIKELY(!s.empty() && !(s.size() == 1 && s[0] == '-') && !(s[0] >= '0' && s[0] <= '9')))
-    {
-        return array_index_status::not_a_number;
-    }
-
-    // fast path: up to 18 decimal digits cannot overflow unsigned long long or
-    // SizeType (9 digits for a 32-bit SizeType), so strtoull and errno are not needed
-    constexpr std::size_t max_fast_digits = sizeof(SizeType) >= 8 ? 18 : 9;
-    if (!s.empty() && s.size() <= max_fast_digits)
-    {
-        SizeType acc = 0;
-        for (std::size_t i = 0; i < s.size(); ++i)
-        {
-            const char c = s[i];
-            if (JSON_HEDLEY_UNLIKELY(c < '0' || c > '9'))
-            {
-                break; // not a plain number: let strtoull decide
-            }
-            acc = static_cast<SizeType>((acc * 10) + static_cast<SizeType>(c - '0'));
-            if (JSON_HEDLEY_UNLIKELY(i == s.size() - 1))
-            {
-                idx = acc;
-                return array_index_status::ok;
-            }
-        }
-    }
-
-    const char* p = s.data();
-    char* p_end = nullptr; // NOLINT(misc-const-correctness)
-    errno = 0; // strtoull doesn't reset errno
-    const unsigned long long res = std::strtoull(p, &p_end, 10); // NOLINT(runtime/int)
-    if (p == p_end // invalid input or empty string
-            || errno == ERANGE // out of range
-            || JSON_HEDLEY_UNLIKELY(static_cast<std::size_t>(p_end - p) != s.size())) // incomplete read
-    {
-        return array_index_status::unresolved;
-    }
-
-    // the index does not fit into SizeType; on 64-bit platforms this is
-    // only SIZE_MAX itself (see #2203 and #5395)
-    if (res >= static_cast<unsigned long long>((std::numeric_limits<SizeType>::max)()))  // NOLINT(runtime/int)
-    {
-        return array_index_status::exceeds_size_type;
-    }
-
-    idx = static_cast<SizeType>(res);
-    return array_index_status::ok;
-}
-
 }  // namespace detail
 
 /// @brief JSON Pointer defines a string syntax for identifying a specific value within a JSON document
@@ -398,28 +302,6 @@ class json_pointer
         JSON_THROW(detail::out_of_range::create(detail::exception_id::patch_on_root, "JSON pointer has no parent", nullptr));
     }
 
-    /// whether the '~' at @a pos of @a s is not followed by '0' or '1'
-    JSON_HEDLEY_ALWAYS_INLINE static bool is_invalid_escape(const string_t& s, std::size_t pos)
-    {
-        return pos == s.size() - 1 || (s[pos + 1] != '0' && s[pos + 1] != '1');
-    }
-
-    /// @throw parse_error.107 always
-    JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE static void throw_missing_slash(const string_t& pointer)
-    {
-        static_cast<void>(pointer); // unused when JSON_NOEXCEPTION is defined
-        JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_missing_slash, 1, detail::concat("JSON pointer must be empty or begin with '/' - was: '", pointer, "'"), nullptr));
-    }
-
-    /// @throw parse_error.107 if a nonempty @a pointer does not begin with '/'
-    JSON_HEDLEY_ALWAYS_INLINE static void check_begins_with_slash(const string_t& pointer)
-    {
-        if (JSON_HEDLEY_UNLIKELY(pointer[0] != '/'))
-        {
-            throw_missing_slash(pointer);
-        }
-    }
-
     /// @throw out_of_range.404 always
     template<typename BasicJsonContext>
     JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE static void throw_unresolved(const string_t& reference_token, BasicJsonContext context)
@@ -429,7 +311,21 @@ class json_pointer
         JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_unresolved, detail::concat("unresolved reference token '", reference_token, "'"), context));
     }
 
-    using array_index_status = detail::array_index_status;
+    /*!
+    @brief result of @ref parse_array_index
+
+    @ref array_index maps each value to the corresponding parse_error/out_of_range
+    exception; @ref contains and @ref get_checked_or_null, which must not throw for
+    an out-of-range or unrepresentable index, switch on it directly instead.
+    */
+    enum class array_index_status
+    {
+        ok,                ///< @a s is a valid, representable array index
+        leading_zero,      ///< @a s begins with '0' but has more than one character
+        not_a_number,      ///< @a s is neither empty nor "-" and does not begin with a digit
+        unresolved,        ///< @a s could not be converted to an integer
+        exceeds_size_type  ///< @a s converts to an integer that exceeds size_type
+    };
 
     /// whether a reference token is "-" (a plain comparison with a string literal is not always inlined)
     static bool is_dash(const string_t& s) noexcept
@@ -437,11 +333,78 @@ class json_pointer
         return s.size() == 1 && s[0] == '-';
     }
 
-    /// detail::parse_array_index() for the size_type of @a BasicJsonType
+    /*!
+    @param[in] s    reference token to be converted into an array index
+    @param[out] idx the integer representation of @a s if @ref array_index_status::ok
+                     is returned; left unchanged otherwise
+
+    @return whether @a s is a valid array index, and if not, why
+
+    @note this function never throws; @ref array_index and the callers that must not
+          throw (@ref contains, @ref get_checked_or_null) build on it instead of each
+          re-implementing the RFC 6901 digit rules and the @a size_type range check
+    */
     template<typename BasicJsonType>
     static array_index_status parse_array_index(const string_t& s, typename BasicJsonType::size_type& idx) noexcept
     {
-        return detail::parse_array_index(s, idx);
+        using size_type = typename BasicJsonType::size_type;
+
+        // error condition (cf. RFC 6901, Sect. 4)
+        if (JSON_HEDLEY_UNLIKELY(s.size() > 1 && s[0] == '0'))
+        {
+            return array_index_status::leading_zero;
+        }
+
+        // error condition (cf. RFC 6901, Sect. 4); this also covers single-
+        // character tokens, so "/x" and "/xy" fail alike; "-" and the empty
+        // token are left to the conversion below and are reported as unresolved
+        if (JSON_HEDLEY_UNLIKELY(!s.empty() && !is_dash(s) && !(s[0] >= '0' && s[0] <= '9')))
+        {
+            return array_index_status::not_a_number;
+        }
+
+        // fast path: up to 18 decimal digits cannot overflow unsigned long long or
+        // size_type (9 digits for a 32-bit size_type), so strtoull and errno are not needed
+        constexpr std::size_t max_fast_digits = sizeof(size_type) >= 8 ? 18 : 9;
+        if (!s.empty() && s.size() <= max_fast_digits)
+        {
+            size_type acc = 0;
+            for (std::size_t i = 0; i < s.size(); ++i)
+            {
+                const char c = s[i];
+                if (JSON_HEDLEY_UNLIKELY(c < '0' || c > '9'))
+                {
+                    break; // not a plain number: let strtoull decide
+                }
+                acc = static_cast<size_type>((acc * 10) + static_cast<size_type>(c - '0'));
+                if (JSON_HEDLEY_UNLIKELY(i == s.size() - 1))
+                {
+                    idx = acc;
+                    return array_index_status::ok;
+                }
+            }
+        }
+
+        const char* p = s.data();
+        char* p_end = nullptr; // NOLINT(misc-const-correctness)
+        errno = 0; // strtoull doesn't reset errno
+        const unsigned long long res = std::strtoull(p, &p_end, 10); // NOLINT(runtime/int)
+        if (p == p_end // invalid input or empty string
+                || errno == ERANGE // out of range
+                || JSON_HEDLEY_UNLIKELY(static_cast<std::size_t>(p_end - p) != s.size())) // incomplete read
+        {
+            return array_index_status::unresolved;
+        }
+
+        // the index does not fit into size_type; on 64-bit platforms this is
+        // only SIZE_MAX itself (see #2203 and #5395)
+        if (res >= static_cast<unsigned long long>((std::numeric_limits<size_type>::max)()))  // NOLINT(runtime/int)
+        {
+            return array_index_status::exceeds_size_type;
+        }
+
+        idx = static_cast<size_type>(res);
+        return array_index_status::ok;
     }
 
     /*!
@@ -491,7 +454,10 @@ class json_pointer
             return reference_tokens.empty();
         }
 
-        check_begins_with_slash(reference_string);
+        if (JSON_HEDLEY_UNLIKELY(reference_string[0] != '/'))
+        {
+            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_missing_slash, 1, detail::concat("JSON pointer must be empty or begin with '/' - was: '", reference_string, "'"), nullptr));
+        }
 
         // the whole string is validated, whether or not it matches
         const std::size_t size = reference_string.size();
@@ -499,7 +465,7 @@ class json_pointer
                 pos != string_t::npos;
                 pos = reference_string.find_first_of('~', pos + 1))
         {
-            if (JSON_HEDLEY_UNLIKELY(is_invalid_escape(reference_string, pos)))
+            if (JSON_HEDLEY_UNLIKELY(pos == size - 1 || (reference_string[pos + 1] != '0' && reference_string[pos + 1] != '1')))
             {
                 JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_invalid_escape, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
             }
@@ -777,7 +743,10 @@ class json_pointer
         }
 
         const char* const data = key.data();
-        check_begins_with_slash(key);
+        if (JSON_HEDLEY_UNLIKELY(data[0] != '/'))
+        {
+            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_missing_slash, 1, detail::concat("JSON pointer must be empty or begin with '/' - was: '", key, "'"), nullptr));
+        }
 
         // The beginning of the key that it has in common with the previous
         // one, which was checked already, is skipped: the scan starts with
@@ -810,7 +779,7 @@ class json_pointer
             else if (data[i] == '~')
             {
                 // ~ must be followed by 0 or 1
-                if (JSON_HEDLEY_UNLIKELY(is_invalid_escape(key, i)))
+                if (JSON_HEDLEY_UNLIKELY(i + 1 == size || (data[i + 1] != '0' && data[i + 1] != '1')))
                 {
                     JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_invalid_escape, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
                 }
@@ -909,46 +878,58 @@ class json_pointer
                 ++end;
             }
 
-            if (ptr->is_object())
+            switch (ptr->type())
             {
-                token.clear();
-                token.append(begin, static_cast<std::size_t>(end - begin));
-                const auto it = ptr->m_data.m_value.object->find(token);
-                if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                case detail::value_t::object:
                 {
-                    return nullptr;
-                }
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                // an index of up to 18 digits without a leading zero fits into size_type
-                // (9 digits for a 32-bit size_type); everything else is left to json_pointer
-                constexpr std::size_t max_digits = sizeof(typename BasicJsonType::size_type) >= 8 ? 18 : 9;
-                const auto digits = static_cast<std::size_t>(end - begin);
-                if (JSON_HEDLEY_UNLIKELY(digits == 0 || digits > max_digits || (digits > 1 && *begin == '0')))
-                {
-                    return nullptr;
-                }
-                typename BasicJsonType::size_type idx = 0;
-                for (const char* c = begin; c != end; ++c)
-                {
-                    if (JSON_HEDLEY_UNLIKELY(*c < '0' || *c > '9'))
+                    token.clear();
+                    token.append(begin, static_cast<std::size_t>(end - begin));
+                    const auto it = ptr->m_data.m_value.object->find(token);
+                    if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
                     {
                         return nullptr;
                     }
-                    idx = static_cast<typename BasicJsonType::size_type>((idx * 10) + static_cast<typename BasicJsonType::size_type>(*c - '0'));
+                    ptr = &it->second;
+                    break;
                 }
-                if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
+
+                case detail::value_t::array:
                 {
-                    return nullptr;
+                    // an index of up to 18 digits without a leading zero fits into size_type
+                    // (9 digits for a 32-bit size_type); everything else is left to json_pointer
+                    constexpr std::size_t max_digits = sizeof(typename BasicJsonType::size_type) >= 8 ? 18 : 9;
+                    const auto digits = static_cast<std::size_t>(end - begin);
+                    if (JSON_HEDLEY_UNLIKELY(digits == 0 || digits > max_digits || (digits > 1 && *begin == '0')))
+                    {
+                        return nullptr;
+                    }
+                    typename BasicJsonType::size_type idx = 0;
+                    for (const char* c = begin; c != end; ++c)
+                    {
+                        if (JSON_HEDLEY_UNLIKELY(*c < '0' || *c > '9'))
+                        {
+                            return nullptr;
+                        }
+                        idx = static_cast<typename BasicJsonType::size_type>((idx * 10) + static_cast<typename BasicJsonType::size_type>(*c - '0'));
+                    }
+                    if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
+                    {
+                        return nullptr;
+                    }
+                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    break;
                 }
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else
-            {
-                // primitive value with a reference token left
-                return nullptr;
+
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
+                    return nullptr;
             }
             pos = static_cast<std::size_t>(end - path.data());
             steps.emplace_back(pos, ptr);
@@ -998,28 +979,40 @@ class json_pointer
                        : detail::value_t::object;
             }
 
-            if (ptr->is_object())
+            switch (ptr->type())
             {
-                // use unchecked object access
-                ptr = &object_member(*ptr, reference_token);
-            }
-            else if (ptr->is_array())
-            {
-                if (reference_token == "-")
+                case detail::value_t::object:
                 {
-                    // explicitly treat "-" as index beyond the end
-                    ptr = &ptr->operator[](ptr->m_data.m_value.array->size());
+                    // use unchecked object access
+                    ptr = &object_member(*ptr, reference_token);
+                    break;
                 }
-                else
+
+                case detail::value_t::array:
                 {
-                    // convert array index to number; unchecked access
-                    ptr = &ptr->operator[](array_index<BasicJsonType>(reference_token));
+                    if (reference_token == "-")
+                    {
+                        // explicitly treat "-" as index beyond the end
+                        ptr = &ptr->operator[](ptr->m_data.m_value.array->size());
+                    }
+                    else
+                    {
+                        // convert array index to number; unchecked access
+                        ptr = &ptr->operator[](array_index<BasicJsonType>(reference_token));
+                    }
+                    break;
                 }
-            }
-            else
-            {
-                // primitive value with a reference token left
-                throw_unresolved(reference_token, ptr);
+
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
+                    throw_unresolved(reference_token, ptr);
             }
         }
 
@@ -1037,39 +1030,51 @@ class json_pointer
     {
         for (const auto& reference_token : reference_tokens)
         {
-            if (ptr->is_object())
+            switch (ptr->type())
             {
-                const auto it = ptr->m_data.m_value.object->find(reference_token);
-                if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                case detail::value_t::object:
                 {
-                    // at() throws out_of_range.403 with the usual message
-                    ptr->at(reference_token);
-                }
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
-                {
-                    // "-" always fails the range check
-                    JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_past_the_end_index, detail::concat(
-                            "array index '-' (", std::to_string(ptr->m_data.m_value.array->size()),
-                            ") is out of range"), ptr));
+                    const auto it = ptr->m_data.m_value.object->find(reference_token);
+                    if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                    {
+                        // at() throws out_of_range.403 with the usual message
+                        ptr->at(reference_token);
+                    }
+                    ptr = &it->second;
+                    break;
                 }
 
-                const auto idx = array_index<BasicJsonType>(reference_token);
-                // Bounds check before access to avoid exception with JSON_NOEXCEPTION
-                if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
+                case detail::value_t::array:
                 {
-                    JSON_THROW(detail::out_of_range::create(detail::exception_id::array_index_out_of_range, detail::concat(
-                            "array index ", std::to_string(idx), " is out of range"), ptr));
+                    if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
+                    {
+                        // "-" always fails the range check
+                        JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_past_the_end_index, detail::concat(
+                                "array index '-' (", std::to_string(ptr->m_data.m_value.array->size()),
+                                ") is out of range"), ptr));
+                    }
+
+                    const auto idx = array_index<BasicJsonType>(reference_token);
+                    // Bounds check before access to avoid exception with JSON_NOEXCEPTION
+                    if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
+                    {
+                        JSON_THROW(detail::out_of_range::create(detail::exception_id::array_index_out_of_range, detail::concat(
+                                "array index ", std::to_string(idx), " is out of range"), ptr));
+                    }
+                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    break;
                 }
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else
-            {
-                // primitive value with a reference token left
-                throw_unresolved(reference_token, ptr);
+
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
+                    throw_unresolved(reference_token, ptr);
             }
         }
 
@@ -1098,32 +1103,44 @@ class json_pointer
     {
         for (const auto& reference_token : reference_tokens)
         {
-            if (ptr->is_object())
+            switch (ptr->type())
             {
-                // use unchecked object access; the const operator[]
-                // asserts that the key exists
-                const auto it = ptr->m_data.m_value.object->find(reference_token);
-                JSON_ASSERT(it != ptr->m_data.m_value.object->end());
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
+                case detail::value_t::object:
                 {
-                    // "-" cannot be used for const access
-                    JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_past_the_end_index, detail::concat("array index '-' (", std::to_string(ptr->m_data.m_value.array->size()), ") is out of range"), ptr));
+                    // use unchecked object access; the const operator[]
+                    // asserts that the key exists
+                    const auto it = ptr->m_data.m_value.object->find(reference_token);
+                    JSON_ASSERT(it != ptr->m_data.m_value.object->end());
+                    ptr = &it->second;
+                    break;
                 }
 
-                // use unchecked array access; the const operator[]
-                // asserts that the index exists
-                const auto idx = array_index<BasicJsonType>(reference_token);
-                JSON_ASSERT(idx < ptr->m_data.m_value.array->size());
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else
-            {
-                // primitive value with a reference token left
-                throw_unresolved(reference_token, ptr);
+                case detail::value_t::array:
+                {
+                    if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
+                    {
+                        // "-" cannot be used for const access
+                        JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_past_the_end_index, detail::concat("array index '-' (", std::to_string(ptr->m_data.m_value.array->size()), ") is out of range"), ptr));
+                    }
+
+                    // use unchecked array access; the const operator[]
+                    // asserts that the index exists
+                    const auto idx = array_index<BasicJsonType>(reference_token);
+                    JSON_ASSERT(idx < ptr->m_data.m_value.array->size());
+                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    break;
+                }
+
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
+                    throw_unresolved(reference_token, ptr);
             }
         }
 
@@ -1147,54 +1164,66 @@ class json_pointer
     {
         for (const auto& reference_token : reference_tokens)
         {
-            if (ptr->is_object())
+            switch (ptr->type())
             {
-                const auto it = ptr->m_data.m_value.object->find(reference_token);
-                if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                case detail::value_t::object:
                 {
-                    return nullptr;
-                }
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
-                {
-                    // "-" always fails the range check
-                    return nullptr;
-                }
-
-                // a malformed index throws parse_error.106/109; an
-                // index that is syntactically valid but cannot be
-                // represented (out_of_range.404/410) is treated like an
-                // out-of-range index below
-                typename BasicJsonType::size_type idx{};
-                switch (parse_array_index<BasicJsonType>(reference_token, idx))
-                {
-                    // the branches differ in their messages, not after JSON_THROW's expansion
-                    // NOLINTNEXTLINE(bugprone-branch-clone)
-                    case array_index_status::leading_zero:
-                        JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_leading_zero, 0, detail::concat("array index '", reference_token, "' must not begin with '0'"), nullptr));
-                    case array_index_status::not_a_number:
-                        JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_not_a_number, 0, detail::concat("array index '", reference_token, "' is not a number"), nullptr));
-                    case array_index_status::unresolved:
-                    case array_index_status::exceeds_size_type:
+                    const auto it = ptr->m_data.m_value.object->find(reference_token);
+                    if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                    {
                         return nullptr;
-                    case array_index_status::ok:
-                    default:
-                        break;
+                    }
+                    ptr = &it->second;
+                    break;
                 }
 
-                if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
+                case detail::value_t::array:
                 {
-                    return nullptr;
+                    if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
+                    {
+                        // "-" always fails the range check
+                        return nullptr;
+                    }
+
+                    // a malformed index throws parse_error.106/109; an
+                    // index that is syntactically valid but cannot be
+                    // represented (out_of_range.404/410) is treated like an
+                    // out-of-range index below
+                    typename BasicJsonType::size_type idx{};
+                    switch (parse_array_index<BasicJsonType>(reference_token, idx))
+                    {
+                        // the branches differ in their messages, not after JSON_THROW's expansion
+                        // NOLINTNEXTLINE(bugprone-branch-clone)
+                        case array_index_status::leading_zero:
+                            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_leading_zero, 0, detail::concat("array index '", reference_token, "' must not begin with '0'"), nullptr));
+                        case array_index_status::not_a_number:
+                            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_not_a_number, 0, detail::concat("array index '", reference_token, "' is not a number"), nullptr));
+                        case array_index_status::unresolved:
+                        case array_index_status::exceeds_size_type:
+                            return nullptr;
+                        case array_index_status::ok:
+                        default:
+                            break;
+                    }
+
+                    if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
+                    {
+                        return nullptr;
+                    }
+                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    break;
                 }
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else
-            {
-                // primitive value with a reference token left
-                return nullptr;
+
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
+                    return nullptr;
             }
         }
 
@@ -1210,48 +1239,63 @@ class json_pointer
     {
         for (const auto& reference_token : reference_tokens)
         {
-            if (ptr->is_object())
+            switch (ptr->type())
             {
-                const auto it = ptr->m_data.m_value.object->find(reference_token);
-                if (it == ptr->m_data.m_value.object->end())
+                case detail::value_t::object:
                 {
-                    // we did not find the key in the object
-                    return false;
+                    const auto it = ptr->m_data.m_value.object->find(reference_token);
+                    if (it == ptr->m_data.m_value.object->end())
+                    {
+                        // we did not find the key in the object
+                        return false;
+                    }
+
+                    ptr = &it->second;
+                    break;
                 }
 
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
+                case detail::value_t::array:
                 {
-                    // "-" always fails the range check
-                    return false;
+                    if (JSON_HEDLEY_UNLIKELY(is_dash(reference_token)))
+                    {
+                        // "-" always fails the range check
+                        return false;
+                    }
+
+                    // any parse failure (malformed index, or one that is syntactically
+                    // valid but not representable as size_type) means the reference
+                    // token cannot denote an existing array element -- contains() must
+                    // not throw (see #5395), so it is treated as "not found"
+                    typename BasicJsonType::size_type idx{};
+                    if (JSON_HEDLEY_UNLIKELY(parse_array_index<BasicJsonType>(reference_token, idx) != array_index_status::ok))
+                    {
+                        return false;
+                    }
+
+                    if (idx >= ptr->m_data.m_value.array->size())
+                    {
+                        // index out of range
+                        return false;
+                    }
+
+                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    break;
                 }
 
-                // any parse failure (malformed index, or one that is syntactically
-                // valid but not representable as size_type) means the reference
-                // token cannot denote an existing array element -- contains() must
-                // not throw (see #5395), so it is treated as "not found"
-                typename BasicJsonType::size_type idx{};
-                if (JSON_HEDLEY_UNLIKELY(parse_array_index<BasicJsonType>(reference_token, idx) != array_index_status::ok))
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
                 {
+                    // we do not expect primitive values if there is still a
+                    // reference token to process
                     return false;
                 }
-
-                if (idx >= ptr->m_data.m_value.array->size())
-                {
-                    // index out of range
-                    return false;
-                }
-
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else
-            {
-                // we do not expect primitive values if there is still a
-                // reference token to process
-                return false;
             }
         }
 
@@ -1279,7 +1323,10 @@ class json_pointer
         }
 
         // check if a nonempty reference string begins with slash
-        check_begins_with_slash(reference_string);
+        if (JSON_HEDLEY_UNLIKELY(reference_string[0] != '/'))
+        {
+            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_missing_slash, 1, detail::concat("JSON pointer must be empty or begin with '/' - was: '", reference_string, "'"), nullptr));
+        }
 
         // every slash starts a reference token
         const std::size_t size = reference_string.size();
@@ -1320,7 +1367,9 @@ class json_pointer
                     JSON_ASSERT(reference_token[pos] == '~');
 
                     // ~ must be followed by 0 or 1
-                    if (JSON_HEDLEY_UNLIKELY(is_invalid_escape(reference_token, pos)))
+                    if (JSON_HEDLEY_UNLIKELY(pos == reference_token.size() - 1 ||
+                                             (reference_token[pos + 1] != '0' &&
+                                              reference_token[pos + 1] != '1')))
                     {
                         JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_invalid_escape, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
                     }
@@ -1477,34 +1526,50 @@ class json_pointer
         auto hint = object.end();
         const auto enter = [&stack, &path, &object, &hint](const BasicJsonType & v)
         {
-            if (v.is_array())
+            switch (v.type())
             {
-                if (v.m_data.m_value.array->empty())
+                case detail::value_t::array:
                 {
-                    // flatten empty array as null
-                    add_flattened(object, hint, path, nullptr, detail::priority_tag<2> {});
+                    if (v.m_data.m_value.array->empty())
+                    {
+                        // flatten empty array as null
+                        add_flattened(object, hint, path, nullptr, detail::priority_tag<2> {});
+                    }
+                    else
+                    {
+                        stack.emplace_back(&v, object_const_iterator(), path.size());
+                    }
+                    return;
                 }
-                else
+
+                case detail::value_t::object:
                 {
-                    stack.emplace_back(&v, object_const_iterator(), path.size());
+                    if (v.m_data.m_value.object->empty())
+                    {
+                        // flatten empty object as null
+                        add_flattened(object, hint, path, nullptr, detail::priority_tag<2> {});
+                    }
+                    else
+                    {
+                        stack.emplace_back(&v, v.m_data.m_value.object->begin(), path.size());
+                    }
+                    return;
                 }
-            }
-            else if (v.is_object())
-            {
-                if (v.m_data.m_value.object->empty())
+
+                case detail::value_t::null:
+                case detail::value_t::string:
+                case detail::value_t::boolean:
+                case detail::value_t::number_integer:
+                case detail::value_t::number_unsigned:
+                case detail::value_t::number_float:
+                case detail::value_t::binary:
+                case detail::value_t::discarded:
+                default:
                 {
-                    // flatten empty object as null
-                    add_flattened(object, hint, path, nullptr, detail::priority_tag<2> {});
+                    // add a primitive value with its reference string
+                    add_flattened(object, hint, path, v, detail::priority_tag<2> {});
+                    return;
                 }
-                else
-                {
-                    stack.emplace_back(&v, v.m_data.m_value.object->begin(), path.size());
-                }
-            }
-            else
-            {
-                // add a primitive value with its reference string
-                add_flattened(object, hint, path, v, detail::priority_tag<2> {});
             }
         };
 

include/nlohmann/detail/output/binary_writer.hpp

@@ -21,7 +21,6 @@
 
 #include <nlohmann/detail/bit_ops.hpp>
 #include <nlohmann/detail/input/binary_reader.hpp>
-#include <nlohmann/detail/input/input_adapters.hpp>
 #include <nlohmann/detail/input/string_scan.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/output/error_handler.hpp>
@@ -312,7 +311,9 @@ class binary_writer
                 write_cbor_head(0x40, N);
 
                 // step 2: write each element
-                write_bytes(j.m_data.m_value.binary->data(), N);
+                oa.write_characters(
+                      reinterpret_cast<const CharType*>(j.m_data.m_value.binary->data()),
+                      N);
 
                 break;
             }
@@ -325,7 +326,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                throw_on_discarded(j, input_format_t::cbor);
+                throw_on_discarded(j, "CBOR");
         }
     }
 
@@ -525,7 +526,9 @@ class binary_writer
                 }
 
                 // step 2: write the byte string
-                write_bytes(j.m_data.m_value.binary->data(), N);
+                oa.write_characters(
+                      reinterpret_cast<const CharType*>(j.m_data.m_value.binary->data()),
+                      N);
 
                 break;
             }
@@ -539,7 +542,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                throw_on_discarded(j, input_format_t::msgpack);
+                throw_on_discarded(j, "MessagePack");
         }
     }
 
@@ -623,7 +626,7 @@ class binary_writer
             case value_t::array:
             {
                 bool prefix_required = true;
-                const bool write_closer = write_ubjson_start_container<true>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
+                const bool write_closer = write_ubjson_start_array(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
 
                 {
                     const auto& array = *j.m_data.m_value.array;
@@ -673,7 +676,9 @@ class binary_writer
 
                 if (use_type)
                 {
-                    write_bytes(j.m_data.m_value.binary->data(), j.m_data.m_value.binary->size());
+                    oa.write_characters(
+                          reinterpret_cast<const CharType*>(j.m_data.m_value.binary->data()),
+                          j.m_data.m_value.binary->size());
                 }
                 else
                 {
@@ -699,7 +704,7 @@ class binary_writer
                 }
 
                 bool prefix_required = true;
-                const bool write_closer = write_ubjson_start_container<false>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
+                const bool write_closer = write_ubjson_start_object(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
 
                 write_ubjson_members(j, use_count, use_type, prefix_required, use_bjdata, bjdata_version, depth);
 
@@ -713,7 +718,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                throw_on_discarded(j, use_bjdata ? input_format_t::bjdata : input_format_t::ubjson);
+                throw_on_discarded(j, use_bjdata ? "BJData" : "UBJSON");
         }
     }
 
@@ -739,11 +744,11 @@ class binary_writer
     @brief throws because @a j is discarded and cannot be serialized
     @throw type_error.321 always
     */
-    JSON_HEDLEY_NO_RETURN static void throw_on_discarded(const BasicJsonType& j, const input_format_t format)
+    JSON_HEDLEY_NO_RETURN static void throw_on_discarded(const BasicJsonType& j, const char* format_name)
     {
         static_cast<void>(j); // unused when JSON_NOEXCEPTION is defined
-        static_cast<void>(format);
-        JSON_THROW(type_error::create(exception_id::discarded_value_used, concat("cannot serialize discarded value to ", input_format_name(format)), &j));
+        static_cast<void>(format_name);
+        JSON_THROW(type_error::create(exception_id::discarded_value_used, concat("cannot serialize discarded value to ", format_name), &j));
     }
 
     /// how the range of integer type @a NumberType relates to that of @a TargetType
@@ -863,11 +868,11 @@ class binary_writer
     }
 
     /*!
-    @brief throws because the integer @a j is too large for @a format
+    @brief throws because the integer @a j is too large for @a format_name
     @throw out_of_range.407 always
     */
     JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE
-    static void throw_integer_out_of_range(const BasicJsonType& j, const input_format_t format, const char* range)
+    static void throw_integer_out_of_range(const BasicJsonType& j, const char* format_name, const char* range)
     {
         // neither std::to_string(), which has no overload for integer types
         // wider than 64 bits, nor dump(), which would also instantiate the
@@ -878,9 +883,9 @@ class binary_writer
                                    ? integer_to_string(j.m_data.m_value.number_unsigned, std::integral_constant<bool, unsigned_limits::is_signed>())
                                    : integer_to_string(j.m_data.m_value.number_integer, std::integral_constant<bool, integer_limits::is_signed>());
         static_cast<void>(number); // unused when JSON_NOEXCEPTION is defined
-        static_cast<void>(format);
+        static_cast<void>(format_name);
         static_cast<void>(range);
-        JSON_THROW(out_of_range::create(exception_id::integer_too_large, concat("integer number ", number, " cannot be represented by ", input_format_name(format), " as it does not fit ", range), &j));
+        JSON_THROW(out_of_range::create(exception_id::integer_too_large, concat("integer number ", number, " cannot be represented by ", format_name, " as it does not fit ", range), &j));
     }
 
     // The exceptions below are thrown from functions of their own, out of line:
@@ -923,56 +928,53 @@ class binary_writer
         JSON_THROW(other_error::create(exception_id::size_marker_required, "use_type requires use_size = true", &j));
     }
 
-    /// @brief write @a size bytes starting at @a data to the output adapter
-    JSON_HEDLEY_ALWAYS_INLINE
-    void write_bytes(const void* data, const std::size_t size)
-    {
-        oa.write_characters(static_cast<const CharType*>(data), size);
-    }
-
-    /// @brief write the MessagePack prefix of an array or object with @a N
-    ///        elements: the fix marker @a fix_marker | n, or @a marker_16 or
-    ///        @a marker_32 followed by the length
-    JSON_HEDLEY_ALWAYS_INLINE
-    void write_msgpack_container_prefix(const std::size_t N, const BasicJsonType& j,
-                                        const std::uint8_t fix_marker, const std::uint8_t marker_16, const std::uint8_t marker_32)
+    void write_msgpack_array_prefix(const std::size_t N, const BasicJsonType& j)
     {
         const auto n = to_msgpack_length(N, j);
         if (n <= 15)
         {
-            // fixarray, fixmap
-            oa.write_character(to_char_type(static_cast<std::uint8_t>(fix_marker | n)));
+            // fixarray
+            oa.write_character(to_char_type(static_cast<std::uint8_t>(0x90 | n)));
         }
         else if (n <= (std::numeric_limits<std::uint16_t>::max)())
         {
-            // array 16, map 16
-            oa.write_character(to_char_type(marker_16));
+            // array 16
+            oa.write_character(to_char_type(0xDC));
             write_number(static_cast<std::uint16_t>(n));
         }
         else
         {
-            // array 32, map 32
-            oa.write_character(to_char_type(marker_32));
+            // array 32
+            oa.write_character(to_char_type(0xDD));
             write_number(static_cast<std::uint32_t>(n));
         }
     }
 
-    JSON_HEDLEY_ALWAYS_INLINE
-    void write_msgpack_array_prefix(const std::size_t N, const BasicJsonType& j)
-    {
-        write_msgpack_container_prefix(N, j, 0x90, 0xDC, 0xDD);
-    }
-
-    JSON_HEDLEY_ALWAYS_INLINE
     void write_msgpack_object_prefix(const std::size_t N, const BasicJsonType& j)
     {
-        write_msgpack_container_prefix(N, j, 0x80, 0xDE, 0xDF);
+        const auto n = to_msgpack_length(N, j);
+        if (n <= 15)
+        {
+            // fixmap
+            oa.write_character(to_char_type(static_cast<std::uint8_t>(0x80 | (n & 0xF))));
+        }
+        else if (n <= (std::numeric_limits<std::uint16_t>::max)())
+        {
+            // map 16
+            oa.write_character(to_char_type(0xDE));
+            write_number(static_cast<std::uint16_t>(n));
+        }
+        else
+        {
+            // map 32
+            oa.write_character(to_char_type(0xDF));
+            write_number(static_cast<std::uint32_t>(n));
+        }
     }
 
-    /// @brief a CBOR, MessagePack, BON8, or (as the base of @ref ubjson_frame)
-    ///        UBJSON array or object whose elements @ref write_container_iterative,
-    ///        @ref write_bon8_iterative, or @ref write_ubjson_iterative is still
-    ///        writing
+    /// @brief a CBOR, MessagePack, or BON8 array or object whose elements
+    ///        @ref write_cbor_iterative, @ref write_msgpack_iterative, or
+    ///        @ref write_bon8_iterative is still writing
     struct binary_container_frame
     {
         explicit binary_container_frame(const BasicJsonType* value_) noexcept
@@ -1008,82 +1010,19 @@ class binary_writer
         typename BasicJsonType::array_t::const_iterator array_it{};
     };
 
-    /// @brief the CBOR specifics of @ref write_container_iterative
-    struct cbor_walk
-    {
-        static void array_head(binary_writer& w, const BasicJsonType& j)
-        {
-            w.write_cbor_head(0x80, j.m_data.m_value.array->size());
-        }
-
-        static void object_head(binary_writer& w, const BasicJsonType& j)
-        {
-            w.write_cbor_head(0xA0, j.m_data.m_value.object->size());
-        }
-
-        static void scalar(binary_writer& w, const BasicJsonType& j)
-        {
-            w.write_cbor(j);
-        }
-
-        static void string(binary_writer& w, const string_t& key, const BasicJsonType& context)
-        {
-            w.write_cbor_string(key, context);
-        }
-
-        template<typename KeyType>
-        static void key(binary_writer& w, const KeyType& k, const BasicJsonType& object)
-        {
-            w.write_cbor_key(k, object);
-        }
-    };
-
-    /// @brief the MessagePack specifics of @ref write_container_iterative
-    struct msgpack_walk
-    {
-        static void array_head(binary_writer& w, const BasicJsonType& j)
-        {
-            w.write_msgpack_array_prefix(j.m_data.m_value.array->size(), j);
-        }
-
-        static void object_head(binary_writer& w, const BasicJsonType& j)
-        {
-            w.write_msgpack_object_prefix(j.m_data.m_value.object->size(), j);
-        }
-
-        static void scalar(binary_writer& w, const BasicJsonType& j)
-        {
-            w.write_msgpack(j);
-        }
-
-        static void string(binary_writer& w, const string_t& key, const BasicJsonType& context)
-        {
-            w.write_msgpack_string(key, context);
-        }
-
-        template<typename KeyType>
-        static void key(binary_writer& w, const KeyType& k, const BasicJsonType& object)
-        {
-            w.write_msgpack_key(k, object);
-        }
-    };
-
     /*!
-    @brief write @a j with @a Walk::scalar, or write its header and push a
-           frame for @ref write_container_iterative to continue with its
-           elements
+    @brief write @a j with @ref write_cbor, or write its header and push a
+           frame for @ref write_cbor_iterative to continue with its elements
 
     A scalar, and an empty array or object, are written out in full: there is
-    nothing below them for @ref write_container_iterative to come back to, so
+    nothing below them for @ref write_cbor_iterative to come back to, so
     nothing is pushed for them.
     */
-    template<typename Walk>
-    JSON_HEDLEY_ALWAYS_INLINE
-    void write_container_value_or_push(const BasicJsonType& j, std::vector<binary_container_frame>& stack)
+    void write_cbor_value_or_push(const BasicJsonType& j, std::vector<binary_container_frame>& stack)
     {
         if (j.is_array())
         {
-            Walk::array_head(*this, j);
+            write_cbor_head(0x80, j.m_data.m_value.array->size());
             if (!j.m_data.m_value.array->empty())
             {
                 stack.emplace_back(&j);
@@ -1093,7 +1032,7 @@ class binary_writer
 
         if (j.is_object())
         {
-            Walk::object_head(*this, j);
+            write_cbor_head(0xA0, j.m_data.m_value.object->size());
             if (!j.m_data.m_value.object->empty())
             {
                 stack.emplace_back(&j);
@@ -1101,26 +1040,22 @@ class binary_writer
             return;
         }
 
-        Walk::scalar(*this, j);
+        write_cbor(j);
     }
 
     /*!
     @brief write out @a root and everything below it without the call stack
 
-    Emits the same bytes as the recursive writer, keeping the containers it has
+    Emits the same bytes as @ref write_cbor, keeping the containers it has
     entered on an explicit stack instead of descending into them. Only reached
     for values nested deeper than @ref recursion_depth_limit, which is why it
-    is not written for speed. Shared by CBOR and MessagePack, which differ only
-    in the @a Walk policy (@ref cbor_walk, @ref msgpack_walk); BON8 has its own
-    walker, as it tracks an open string run and closes a container with a
-    marker.
+    is not written for speed.
     */
-    template<typename Walk>
-    void write_container_iterative(const BasicJsonType& root)
+    void write_cbor_iterative(const BasicJsonType& root)
     {
-        // only a container with elements is ever pushed; see write_container_value_or_push
+        // only a container with elements is ever pushed; see write_cbor_value_or_push
         std::vector<binary_container_frame> stack;
-        write_container_value_or_push<Walk>(root, stack);
+        write_cbor_value_or_push(root, stack);
 
         while (!stack.empty())
         {
@@ -1138,7 +1073,7 @@ class binary_writer
                 // read the child before pushing: entering it can move every frame
                 const BasicJsonType* child = &(*current.array_it);
                 ++stack.back().array_it;
-                write_container_value_or_push<Walk>(*child, stack);
+                write_cbor_value_or_push(*child, stack);
             }
             else
             {
@@ -1150,53 +1085,110 @@ class binary_writer
                 }
 
                 // the key is written directly (not via a temporary basic_json),
-                // with the object as diagnostics context, as in the recursive writer
-                Walk::key(*this, current.object_it->first, *current.value);
+                // with the object as diagnostics context, as in write_cbor
+                write_cbor_key(current.object_it->first, *current.value);
                 const BasicJsonType* child = &(current.object_it->second);
                 ++stack.back().object_it;
-                write_container_value_or_push<Walk>(*child, stack);
+                write_cbor_value_or_push(*child, stack);
             }
         }
     }
 
-    void write_cbor_iterative(const BasicJsonType& root)
-    {
-        write_container_iterative<cbor_walk>(root);
-    }
+    /*!
+    @brief write @a j with @ref write_msgpack, or write its header and push a
+           frame for @ref write_msgpack_iterative to continue with its elements
 
-    void write_msgpack_iterative(const BasicJsonType& root)
+    @sa @ref write_cbor_value_or_push
+    */
+    void write_msgpack_value_or_push(const BasicJsonType& j, std::vector<binary_container_frame>& stack)
     {
-        write_container_iterative<msgpack_walk>(root);
+        if (j.is_array())
+        {
+            write_msgpack_array_prefix(j.m_data.m_value.array->size(), j);
+            if (!j.m_data.m_value.array->empty())
+            {
+                stack.emplace_back(&j);
+            }
+            return;
+        }
+
+        if (j.is_object())
+        {
+            write_msgpack_object_prefix(j.m_data.m_value.object->size(), j);
+            if (!j.m_data.m_value.object->empty())
+            {
+                stack.emplace_back(&j);
+            }
+            return;
+        }
+
+        write_msgpack(j);
     }
 
     /*!
-    @brief write the start of an array (@a IsArray) or object: its opening
-           marker, the optimized type, and the count
+    @brief write out @a root and everything below it without the call stack
 
-    @return true when a closing ']' or '}' still has to be written after the
-            elements
+    @sa @ref write_cbor_iterative
     */
-    template<bool IsArray>
-    bool write_ubjson_start_container(const BasicJsonType& j, const bool use_count, const bool use_type,
-                                      const bool add_prefix, const bool use_bjdata, bool& prefix_required)
+    void write_msgpack_iterative(const BasicJsonType& root)
+    {
+        std::vector<binary_container_frame> stack;
+        write_msgpack_value_or_push(root, stack);
+
+        while (!stack.empty())
+        {
+            const binary_container_frame current = stack.back();
+
+            if (current.value->is_array())
+            {
+                const auto& array = *current.value->m_data.m_value.array;
+                if (current.array_it == array.cend())
+                {
+                    stack.pop_back();
+                    continue;
+                }
+
+                const BasicJsonType* child = &(*current.array_it);
+                ++stack.back().array_it;
+                write_msgpack_value_or_push(*child, stack);
+            }
+            else
+            {
+                const auto& object = *current.value->m_data.m_value.object;
+                if (current.object_it == object.cend())
+                {
+                    stack.pop_back();
+                    continue;
+                }
+
+                // as in write_cbor_iterative, the key is written directly with
+                // the object as diagnostics context
+                write_msgpack_key(current.object_it->first, *current.value);
+                const BasicJsonType* child = &(current.object_it->second);
+                ++stack.back().object_it;
+                write_msgpack_value_or_push(*child, stack);
+            }
+        }
+    }
+
+    /// @return true when a closing ']' still has to be written after the elements
+    bool write_ubjson_start_array(const BasicJsonType& j, const bool use_count, const bool use_type,
+                                  const bool add_prefix, const bool use_bjdata, bool& prefix_required)
     {
         prefix_required = true;
         if (add_prefix)
         {
-            oa.write_character(to_char_type(IsArray ? '[' : '{'));
+            oa.write_character(to_char_type('['));
         }
 
-        const std::size_t size = IsArray ? j.m_data.m_value.array->size() : j.m_data.m_value.object->size();
-
-        if (use_type && size != 0)
+        if (use_type && !j.m_data.m_value.array->empty())
         {
             if (!use_count)
             {
                 throw_size_marker_required(j);
             }
             const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
-            // the first element of an array has been compared with itself
-            const bool same_prefix = std::all_of(IsArray ? j.begin() + 1 : j.begin(), j.end(),
+            const bool same_prefix = std::all_of(j.begin() + 1, j.end(),
                                                  [this, first_prefix, use_bjdata](const BasicJsonType & v)
             {
                 return ubjson_prefix(v, use_bjdata) == first_prefix;
@@ -1208,9 +1200,8 @@ class binary_writer
             // those, at one byte per element, so the result can be read back.
             // Objects are not affected: every element is preceded by its key.
             const bool valueless_type = (first_prefix == 'Z' || first_prefix == 'T' || first_prefix == 'F');
-            const bool excessive_valueless = IsArray
-                                             && valueless_type
-                                             && size > detail::max_valueless_container_size;
+            const bool excessive_valueless = valueless_type
+                                             && j.m_data.m_value.array->size() > detail::max_valueless_container_size;
 
             if (same_prefix && !excessive_valueless
                     && !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
@@ -1223,7 +1214,46 @@ class binary_writer
 
         if (use_count)
         {
-            write_ubjson_count(size, use_bjdata);
+            write_ubjson_count(j.m_data.m_value.array->size(), use_bjdata);
+        }
+
+        return !use_count;
+    }
+
+    /// @return true when a closing '}' still has to be written after the elements
+    bool write_ubjson_start_object(const BasicJsonType& j, const bool use_count, const bool use_type,
+                                   const bool add_prefix, const bool use_bjdata, bool& prefix_required)
+    {
+        prefix_required = true;
+        if (add_prefix)
+        {
+            oa.write_character(to_char_type('{'));
+        }
+
+        if (use_type && !j.m_data.m_value.object->empty())
+        {
+            if (!use_count)
+            {
+                throw_size_marker_required(j);
+            }
+            const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
+            const bool same_prefix = std::all_of(j.begin(), j.end(),
+                                                 [this, first_prefix, use_bjdata](const BasicJsonType & v)
+            {
+                return ubjson_prefix(v, use_bjdata) == first_prefix;
+            });
+
+            if (same_prefix && !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
+            {
+                prefix_required = false;
+                oa.write_character(to_char_type('$'));
+                oa.write_character(first_prefix);
+            }
+        }
+
+        if (use_count)
+        {
+            write_ubjson_count(j.m_data.m_value.object->size(), use_bjdata);
         }
 
         return !use_count;
@@ -1251,12 +1281,21 @@ class binary_writer
 
     /// @brief an object or array @ref write_ubjson_iterative is still writing
     ///        the elements of
-    struct ubjson_frame : binary_container_frame
+    struct ubjson_frame
     {
         ubjson_frame(const BasicJsonType* value_, const bool prefix_required_) noexcept
-            : binary_container_frame(value_)
+            : value(value_)
             , prefix_required(prefix_required_)
-        {}
+        {
+            if (value->is_object())
+            {
+                object_it = value->m_data.m_value.object->cbegin();
+            }
+            else
+            {
+                array_it = value->m_data.m_value.array->cbegin();
+            }
+        }
 
         // declared for GCC's -Weffc++, which asks for them in a class with
         // pointer members and a non-trivial destructor; the exception
@@ -1268,9 +1307,13 @@ class binary_writer
         ubjson_frame& operator=(ubjson_frame&&) = default;
         ~ubjson_frame() = default;
 
+        /// the array or object being written
+        const BasicJsonType* value;
         /// whether value's elements each carry their own type marker; an
         /// optimized ($type) container writes it once for all of them instead
         bool prefix_required;
+        typename BasicJsonType::object_t::const_iterator object_it{};
+        typename BasicJsonType::array_t::const_iterator array_it{};
     };
 
     /*!
@@ -1281,7 +1324,7 @@ class binary_writer
                elements of an optimized container, and everything below the
                top level, never repeat it)
 
-    @sa @ref write_container_value_or_push
+    @sa @ref write_cbor_value_or_push
     */
     void write_ubjson_value_or_push(const BasicJsonType& j, const bool add_prefix, const bool use_count,
                                     const bool use_type, const bool use_bjdata, const bjdata_version_t bjdata_version,
@@ -1304,11 +1347,11 @@ class binary_writer
         bool prefix_required = true;
         if (is_array)
         {
-            write_ubjson_start_container<true>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
+            write_ubjson_start_array(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
         }
         else
         {
-            write_ubjson_start_container<false>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
+            write_ubjson_start_object(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
         }
 
         const bool empty = is_array ? j.m_data.m_value.array->empty() : j.m_data.m_value.object->empty();
@@ -1318,7 +1361,7 @@ class binary_writer
             return;
         }
 
-        // write_ubjson_start_container returns !use_count, i.e. whether a
+        // write_ubjson_start_array/_object return !use_count, i.e. whether a
         // closer still has to be written; use_count is constant for the whole
         // document, so that is recomputed here instead of being carried along
         if (!use_count)
@@ -1507,15 +1550,14 @@ class binary_writer
     {
         oa.write_character(to_char_type(element_type));
 
-        if (JSON_HEDLEY_LIKELY(error_handler == error_handler_t::keep || error_handler == error_handler_t::strict))
+        if (error_handler == error_handler_t::keep || error_handler == error_handler_t::strict || is_valid_utf8(name))
         {
-            write_bytes(name.data(), name.size());
+            oa.write_characters(reinterpret_cast<const CharType*>(name.data()), name.size());
         }
         else
         {
-            string_t storage;
-            const string_t& written = sanitize_utf8_for_bson_write(name, storage);
-            write_bytes(written.data(), written.size());
+            const string_t sanitized = sanitize_utf8(name, error_handler);
+            oa.write_characters(reinterpret_cast<const CharType*>(sanitized.data()), sanitized.size());
         }
 
         // the terminating null byte is written explicitly rather than taken
@@ -1591,11 +1633,16 @@ class binary_writer
     {
         write_bson_entry_header(name, 0x02);
 
-        string_t storage;
-        const string_t& written = sanitize_utf8_for_bson_write(value, storage);
+        const bool sanitize = error_handler != error_handler_t::keep
+                              && error_handler != error_handler_t::strict
+                              && !is_valid_utf8(value);
+        const string_t sanitized = sanitize ? sanitize_utf8(value, error_handler) : string_t{};
+        const string_t& written = sanitize ? sanitized : value;
 
         write_number<std::int32_t>(to_bson_length(written.size() + 1ul), true);
-        write_bytes(written.data(), written.size());
+        oa.write_characters(
+              reinterpret_cast<const CharType*>(written.data()),
+              written.size());
         // the terminating null byte is written explicitly rather than taken
         // from the buffer, so that string_t::data() need not be null-terminated
         oa.write_character(to_char_type(0x00));
@@ -1701,7 +1748,7 @@ class binary_writer
 
         write_number(value.has_subtype() ? static_cast<std::uint8_t>(value.subtype()) : static_cast<std::uint8_t>(0x00));
 
-        write_bytes(value.data(), value.size());
+        oa.write_characters(reinterpret_cast<const CharType*>(value.data()), value.size());
     }
 
     /*!
@@ -1731,14 +1778,14 @@ class binary_writer
             case value_t::number_integer:
                 if (JSON_HEDLEY_UNLIKELY(!integer_fits<std::int64_t>(j.m_data.m_value.number_integer)))
                 {
-                    throw_integer_out_of_range(j, input_format_t::bson, "int64");
+                    throw_integer_out_of_range(j, "BSON", "int64");
                 }
                 return calc_bson_integer_size(static_cast<std::int64_t>(j.m_data.m_value.number_integer));
 
             case value_t::number_unsigned:
                 if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::uint64_t>(j.m_data.m_value.number_unsigned)))
                 {
-                    throw_integer_out_of_range(j, input_format_t::bson, "uint64");
+                    throw_integer_out_of_range(j, "BSON", "uint64");
                 }
                 return calc_bson_unsigned_size(conditional_static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
 
@@ -1749,7 +1796,7 @@ class binary_writer
                 return 0ul;
 
             case value_t::discarded:
-                throw_on_discarded(j, input_format_t::bson);
+                throw_on_discarded(j, "BSON");
 
             // LCOV_EXCL_START
             case value_t::object:
@@ -1913,7 +1960,7 @@ class binary_writer
             // the terminating null byte is written explicitly rather than
             // taken from the buffer, so that string_t::data() need not be
             // null-terminated
-            write_bytes(value.data(), value.size());
+            oa.write_characters(reinterpret_cast<const CharType*>(value.data()), value.size());
             oa.write_character(to_char_type(0x00));
             return true;
         }
@@ -1930,7 +1977,7 @@ class binary_writer
             p += sizeof(std::int32_t);
             *p++ = value.has_subtype() ? to_char_type(static_cast<std::uint8_t>(value.subtype())) : to_char_type(0x00);
             oa.commit(static_cast<std::size_t>(p - out));
-            write_bytes(value.data(), value.size());
+            oa.write_characters(reinterpret_cast<const CharType*>(value.data()), value.size());
             return true;
         }
 
@@ -1978,7 +2025,7 @@ class binary_writer
                 return write_bson_null(name);
 
             case value_t::discarded:
-                throw_on_discarded(j, input_format_t::bson);
+                throw_on_discarded(j, "BSON");
 
             // LCOV_EXCL_START
             case value_t::object:
@@ -2759,7 +2806,7 @@ class binary_writer
         {
             if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::uint64_t>(j.m_data.m_value.number_unsigned)))
             {
-                throw_integer_out_of_range(j, input_format_t::cbor, "uint64");
+                throw_integer_out_of_range(j, "CBOR", "uint64");
             }
             write_cbor_head(0x00, conditional_static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
             return;
@@ -2769,7 +2816,7 @@ class binary_writer
         {
             if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::uint64_t>(j.m_data.m_value.number_integer)))
             {
-                throw_integer_out_of_range(j, input_format_t::cbor, "[-2^64, 2^64-1]");
+                throw_integer_out_of_range(j, "CBOR", "[-2^64, 2^64-1]");
             }
             // CBOR does not differentiate between positive signed
             // integers and unsigned integers
@@ -2780,7 +2827,7 @@ class binary_writer
             // a negative integer n is encoded as -1 - n
             if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::uint64_t>(-1 - j.m_data.m_value.number_integer)))
             {
-                throw_integer_out_of_range(j, input_format_t::cbor, "[-2^64, 2^64-1]");
+                throw_integer_out_of_range(j, "CBOR", "[-2^64, 2^64-1]");
             }
             write_cbor_head(0x20, static_cast<std::uint64_t>(-1 - j.m_data.m_value.number_integer));
         }
@@ -2856,7 +2903,7 @@ class binary_writer
         {
             if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::uint64_t>(j.m_data.m_value.number_unsigned)))
             {
-                throw_integer_out_of_range(j, input_format_t::msgpack, "uint64");
+                throw_integer_out_of_range(j, "MessagePack", "uint64");
             }
             write_msgpack_unsigned(static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
             return;
@@ -2866,7 +2913,7 @@ class binary_writer
         {
             if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::uint64_t>(j.m_data.m_value.number_integer)))
             {
-                throw_integer_out_of_range(j, input_format_t::msgpack, "[-2^63, 2^64-1]");
+                throw_integer_out_of_range(j, "MessagePack", "[-2^63, 2^64-1]");
             }
             // MessagePack does not differentiate between positive
             // signed integers and unsigned integers.
@@ -2876,7 +2923,7 @@ class binary_writer
         {
             if (JSON_HEDLEY_UNLIKELY(!integer_fits_min<std::int64_t>(j.m_data.m_value.number_integer)))
             {
-                throw_integer_out_of_range(j, input_format_t::msgpack, "[-2^63, 2^64-1]");
+                throw_integer_out_of_range(j, "MessagePack", "[-2^63, 2^64-1]");
             }
             if (j.m_data.m_value.number_integer >= -32)
             {
@@ -3010,37 +3057,40 @@ class binary_writer
     }
 
     /*!
-    @brief write an object key as a CBOR or MessagePack string (@a Walk)
+    @brief write an object key as a CBOR text string
 
     A key convertible to string_t is written directly. Other key types (only
     an explicit conversion, or only a to_json overload) go through a temporary
     basic_json, as in version 3.12.0; the temporary is then the diagnostics
     context for strict UTF-8 checks.
     */
-    template<typename Walk, typename Key = typename BasicJsonType::object_t::key_type,
+    template<typename Key = typename BasicJsonType::object_t::key_type,
              enable_if_t<std::is_convertible<Key, string_t>::value, int> = 0>
-    void write_object_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& context)
-    {
-        Walk::string(*this, key, context);
-    }
-
-    template<typename Walk, typename Key = typename BasicJsonType::object_t::key_type,
-             enable_if_t<negation<std::is_convertible<Key, string_t>>::value, int> = 0>
-    void write_object_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& /*context*/)
-    {
-        Walk::scalar(*this, BasicJsonType(key));
-    }
-
-    /// @brief write an object key as a CBOR text string
     void write_cbor_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& context)
     {
-        write_object_key<cbor_walk>(key, context);
+        write_cbor_string(key, context);
     }
 
-    /// @brief write an object key as a MessagePack str
+    template < typename Key = typename BasicJsonType::object_t::key_type,
+               enable_if_t < !std::is_convertible<Key, string_t>::value, int > = 0 >
+    void write_cbor_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& /*context*/)
+    {
+        write_cbor(BasicJsonType(key));
+    }
+
+    /// @brief write an object key as a MessagePack str, as in @ref write_cbor_key
+    template<typename Key = typename BasicJsonType::object_t::key_type,
+             enable_if_t<std::is_convertible<Key, string_t>::value, int> = 0>
     void write_msgpack_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& context)
     {
-        write_object_key<msgpack_walk>(key, context);
+        write_msgpack_string(key, context);
+    }
+
+    template < typename Key = typename BasicJsonType::object_t::key_type,
+               enable_if_t < !std::is_convertible<Key, string_t>::value, int > = 0 >
+    void write_msgpack_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& /*context*/)
+    {
+        write_msgpack(BasicJsonType(key));
     }
 
     /// the longest string that is written, with its head of one or two
@@ -3115,7 +3165,9 @@ class binary_writer
         write_cbor_head(0x60, sanitized.size());
 
         // step 2: write the string
-        write_bytes(sanitized.data(), sanitized.size());
+        oa.write_characters(
+              reinterpret_cast<const CharType*>(sanitized.data()),
+              sanitized.size());
     }
 
     /////////////
@@ -3196,7 +3248,9 @@ class binary_writer
         }
 
         // step 2: write the string
-        write_bytes(sanitized.data(), sanitized.size());
+        oa.write_characters(
+              reinterpret_cast<const CharType*>(sanitized.data()),
+              sanitized.size());
     }
 
     ////////////
@@ -3479,7 +3533,9 @@ class binary_writer
             oa.write_character(to_char_type('S'));
         }
         write_number_with_ubjson_prefix(sanitized.size(), true, use_bjdata);
-        write_bytes(sanitized.data(), sanitized.size());
+        oa.write_characters(
+              reinterpret_cast<const CharType*>(sanitized.data()),
+              sanitized.size());
     }
 
     /*!
@@ -4279,7 +4335,7 @@ class binary_writer
             {
                 if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::int64_t>(j.m_data.m_value.number_unsigned)))
                 {
-                    throw_integer_out_of_range(j, input_format_t::bon8, "int64");
+                    throw_integer_out_of_range(j, "BON8", "int64");
                 }
                 write_bon8_integer(static_cast<std::int64_t>(j.m_data.m_value.number_unsigned));
                 string_open = false;
@@ -4290,7 +4346,7 @@ class binary_writer
             {
                 if (JSON_HEDLEY_UNLIKELY(!integer_fits<std::int64_t>(j.m_data.m_value.number_integer)))
                 {
-                    throw_integer_out_of_range(j, input_format_t::bon8, "int64");
+                    throw_integer_out_of_range(j, "BON8", "int64");
                 }
                 write_bon8_integer(static_cast<std::int64_t>(j.m_data.m_value.number_integer));
                 string_open = false;
@@ -4358,7 +4414,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                throw_on_discarded(j, input_format_t::bon8);
+                throw_on_discarded(j, "BON8");
         }
     }
 
@@ -4369,7 +4425,7 @@ class binary_writer
     A scalar, and an empty array or object, are written out in full and not
     pushed.
 
-    @sa @ref write_container_value_or_push
+    @sa @ref write_cbor_value_or_push
     */
     void write_bon8_value_or_push(const BasicJsonType& j, bool& string_open, std::vector<binary_container_frame>& stack)
     {
@@ -4755,7 +4811,7 @@ class binary_writer
         }
         else
         {
-            write_bytes(s.data(), s.size());
+            oa.write_characters(reinterpret_cast<const CharType*>(s.data()), s.size());
             string_open = true;
         }
     }
@@ -4846,31 +4902,6 @@ class binary_writer
         }
     }
 
-    /*!
-    @brief the write-pass counterpart of @ref sanitize_utf8_for_write for BSON
-
-    The size pass (@ref calc_bson_entry_header_size, @ref
-    calc_bson_string_size) has already validated @a s, and thrown for @ref
-    error_handler_t::strict if it was ill-formed. Here, @ref
-    error_handler_t::strict therefore behaves like @ref error_handler_t::keep,
-    and @ref error_handler_t::replace / @ref error_handler_t::ignore produce
-    exactly the bytes the size pass measured. Hence no context is needed.
-
-    @param[in] s        the string (value or object key) to write
-    @param[out] storage  backing storage for a sanitized copy
-
-    @return a reference to @a s, or to @a storage once it holds a sanitized copy
-    */
-    const string_t& sanitize_utf8_for_bson_write(const string_t& s, string_t& storage) const
-    {
-        if (error_handler == error_handler_t::keep || error_handler == error_handler_t::strict || is_valid_utf8(s))
-        {
-            return s; // NOLINT(bugprone-return-const-ref-from-parameter): callers pass lvalues that outlive the call
-        }
-        storage = sanitize_utf8(s, error_handler);
-        return storage;
-    }
-
     /// deleted: anything but a string_t would bind a temporary that dies before the returned reference is used
     template < typename T, enable_if_t < !std::is_same<T, string_t>::value, int > = 0 >
     const string_t& sanitize_utf8_for_write(const T& /*s*/, const BasicJsonType& /*context*/, string_t& /*storage*/) const = delete; // NOLINT(hicpp-use-equals-delete,modernize-use-equals-delete): a private helper's guard, not part of the interface

include/nlohmann/detail/output/serializer.hpp

@@ -966,28 +966,6 @@ class serializer
         }
     }
 
-    /// write out the bytes pending in @ref string_buffer and reset @a bytes
-    JSON_HEDLEY_ALWAYS_INLINE void emit_pending(std::size_t& bytes)
-    {
-        if (bytes != 0)
-        {
-            put_buffer(string_buffer, bytes);
-            bytes = 0;
-        }
-    }
-
-    /// write buffer and reset index if fewer than 13 bytes are left, as this
-    /// is the maximal number of bytes to be written ("\uxxxx\uxxxx\0") for one
-    /// code point
-    JSON_HEDLEY_ALWAYS_INLINE void reserve_string_buffer(std::size_t& bytes)
-    {
-        if (string_buffer.size() - bytes < 13)
-        {
-            put_buffer(string_buffer, bytes);
-            bytes = 0;
-        }
-    }
-
     /*!
     @brief worker for @ref dump_escaped
 
@@ -1046,7 +1024,11 @@ class serializer
                 {
                     // emit any bytes still pending in string_buffer first to
                     // preserve output order, then write the run directly
-                    emit_pending(bytes);
+                    if (bytes != 0)
+                    {
+                        put_buffer(string_buffer, bytes);
+                        bytes = 0;
+                    }
                     put_run(s, i, run);
                     bytes_after_last_accept = 0;
                     undumped_chars = 0;
@@ -1067,10 +1049,11 @@ class serializer
                 {
                     // emit any bytes still pending in string_buffer first to
                     // preserve output order
-                    emit_pending(bytes);
-                    // deliberately not put_buffer(): a fixed 8-byte memcpy
-                    // has no asserts and no write-through branch, which
-                    // matters on the hot path
+                    if (bytes != 0)
+                    {
+                        put_buffer(string_buffer, bytes);
+                        bytes = 0;
+                    }
                     const auto& escape = ascii_escapes()[data[i]];
                     if (JSON_HEDLEY_UNLIKELY(write_buffer.size() - write_buffer_pos < escape.size()))
                     {
@@ -1145,7 +1128,14 @@ class serializer
                         string_buffer[bytes++] = s[i];
                     }
 
-                    reserve_string_buffer(bytes);
+                    // write buffer and reset index; there must be 13 bytes
+                    // left, as this is the maximal number of bytes to be
+                    // written ("\uxxxx\uxxxx\0") for one code point
+                    if (string_buffer.size() - bytes < 13)
+                    {
+                        put_buffer(string_buffer, bytes);
+                        bytes = 0;
+                    }
 
                     // remember the byte position of this accept
                     bytes_after_last_accept = bytes;
@@ -1197,7 +1187,14 @@ class serializer
                                     string_buffer[bytes++] = '\xBD';
                                 }
 
-                                reserve_string_buffer(bytes);
+                                // write buffer and reset index; there must be 13 bytes
+                                // left, as this is the maximal number of bytes to be
+                                // written ("\uxxxx\uxxxx\0") for one code point
+                                if (string_buffer.size() - bytes < 13)
+                                {
+                                    put_buffer(string_buffer, bytes);
+                                    bytes = 0;
+                                }
 
                                 bytes_after_last_accept = bytes;
                             }
@@ -1230,7 +1227,14 @@ class serializer
                                 string_buffer[bytes++] = s[i];
                             }
 
-                            reserve_string_buffer(bytes);
+                            // write buffer and reset index; there must be 13 bytes
+                            // left, as this is the maximal number of bytes to be
+                            // written ("\uxxxx\uxxxx\0") for one code point
+                            if (string_buffer.size() - bytes < 13)
+                            {
+                                put_buffer(string_buffer, bytes);
+                                bytes = 0;
+                            }
 
                             bytes_after_last_accept = bytes;
                             undumped_chars = 0;
@@ -1596,17 +1600,30 @@ class serializer
     */
     static const std::array<std::uint8_t, 256>& ascii_copyable() noexcept
     {
-        // constant-initialized from the predicate: no runtime loop, no guard
-        static constexpr std::array<std::uint8_t, 256> copyable = make_ascii_copyable(make_index_sequence<256> {});
+        static const std::array<std::uint8_t, 256> copyable =
+        {
+            {
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x00
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x10
+                1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x20
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x30
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x40
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, // 0x50
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x60
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, // 0x70
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x80
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x90
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xA0
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xB0
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xC0
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xD0
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0xE0
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 // 0xF0
+            }
+        };
         return copyable;
     }
 
-    template<std::size_t... Is>
-    static constexpr std::array<std::uint8_t, 256> make_ascii_copyable(index_sequence<Is...> /*unused*/) noexcept
-    {
-        return {{ static_cast<std::uint8_t>(is_ascii_copyable(static_cast<unsigned char>(Is)) ? 1 : 0)... }};
-    }
-
     /*!
     @brief the JSON form of each character below 0x60
 
@@ -1735,6 +1752,7 @@ class serializer
     */
     JSON_HEDLEY_NEVER_INLINE std::size_t write_u_escapes(const unsigned char* data, std::size_t n)
     {
+        constexpr const char* nibble_to_hex = "0123456789abcdef";
         std::size_t i = 0;
         while (i < n && data[i] >= 0x80)
         {
@@ -1771,21 +1789,26 @@ class serializer
             char* d = write_buffer.data() + write_buffer_pos;
             if (codepoint > 0xFFFFu)
             {
-                d = put_u_escape(d, static_cast<std::uint16_t>(0xD7C0u + (codepoint >> 10u)));
+                d = put_u_escape(d, static_cast<std::uint16_t>(0xD7C0u + (codepoint >> 10u)), nibble_to_hex);
                 codepoint = 0xDC00u + (codepoint & 0x3FFu);
             }
-            d = put_u_escape(d, static_cast<std::uint16_t>(codepoint));
+            d = put_u_escape(d, static_cast<std::uint16_t>(codepoint), nibble_to_hex);
             write_buffer_pos = static_cast<std::size_t>(d - write_buffer.data());
             i += length;
         }
         return i;
     }
 
-    static char* put_u_escape(char* d, const std::uint16_t codeunit) noexcept
+    static char* put_u_escape(char* d, const std::uint16_t codeunit, const char* nibble_to_hex) noexcept
     {
+        const auto unit = static_cast<std::uint32_t>(codeunit);
         d[0] = '\\';
         d[1] = 'u';
-        return hex4_lower(codeunit, d + 2);
+        d[2] = nibble_to_hex[(unit >> 12u) & 0x0Fu];
+        d[3] = nibble_to_hex[(unit >> 8u) & 0x0Fu];
+        d[4] = nibble_to_hex[(unit >> 4u) & 0x0Fu];
+        d[5] = nibble_to_hex[unit & 0x0Fu];
+        return d + 6;
     }
 
     /*!
@@ -1794,7 +1817,7 @@ class serializer
      * Branch-free replacement for `snprintf(buf, 7, "\\u%04x", codeunit)` in the
      * string escaping hot path. It writes exactly six characters ('\\', 'u' and
      * four hex digits) at position @a pos of @a string_buffer via a nibble
-     * lookup table (@ref hex4_lower), avoiding the format-string parsing and locale machinery of
+     * lookup table, avoiding the format-string parsing and locale machinery of
      * `snprintf`. Advances @a pos by the number of bytes written (6).
      *
      * @param[in] pos       position in @a string_buffer to write at; there must
@@ -1804,9 +1827,13 @@ class serializer
     void write_u_escape(std::size_t& pos, std::uint16_t codeunit) noexcept
     {
         JSON_ASSERT(string_buffer.size() - pos >= 6);
+        constexpr const char* nibble_to_hex = "0123456789abcdef";
         string_buffer[pos + 0] = '\\';
         string_buffer[pos + 1] = 'u';
-        hex4_lower(codeunit, &string_buffer[pos + 2]);
+        string_buffer[pos + 2] = nibble_to_hex[(codeunit >> 12u) & 0x0Fu];
+        string_buffer[pos + 3] = nibble_to_hex[(codeunit >> 8u) & 0x0Fu];
+        string_buffer[pos + 4] = nibble_to_hex[(codeunit >> 4u) & 0x0Fu];
+        string_buffer[pos + 5] = nibble_to_hex[codeunit & 0x0Fu];
         pos += 6;
     }
 

include/nlohmann/detail/string_utils.hpp

@@ -48,24 +48,6 @@ inline std::string hex_byte(const std::uint8_t byte)
     return result;
 }
 
-/*!
-@brief write a UTF-16 code unit as four lowercase hexadecimal digits
-
-The lowercase counterpart of hex_byte(), used for the `\\uXXXX` escapes of the
-serializers, whose output is lowercase. Writes exactly four characters to
-@a out and returns the pointer past them.
-*/
-JSON_HEDLEY_ALWAYS_INLINE char* hex4_lower(const std::uint16_t codeunit, char* out) noexcept
-{
-    constexpr const char* nibble_to_hex = "0123456789abcdef";
-    const unsigned int unit = codeunit;
-    out[0] = nibble_to_hex[(unit >> 12u) & 0x0Fu];
-    out[1] = nibble_to_hex[(unit >> 8u) & 0x0Fu];
-    out[2] = nibble_to_hex[(unit >> 4u) & 0x0Fu];
-    out[3] = nibble_to_hex[unit & 0x0Fu];
-    return out + 4;
-}
-
 ///////////////////
 // UTF-8 encoding //
 ///////////////////
@@ -121,66 +103,6 @@ void encode_utf8(std::uint32_t cp, const Out& out)
     }
 }
 
-/*!
-@brief the shape of a well-formed UTF-8 sequence, by its lead byte
-
-@a length is 1 for ASCII, 2 to 4 for a valid lead byte, and 0 for a byte that
-cannot start a well-formed sequence (a continuation byte, 0xC0, 0xC1, or 0xF5
-to 0xFF). For a multibyte sequence, the second byte must lie in
-[@a second_lo, @a second_hi], and every later byte in [0x80, 0xBF]
-(RFC 3629, section 4; Unicode Table 3-7). The narrower second-byte ranges
-exclude overlong forms (0xE0, 0xF0), surrogates (0xED), and code points
-beyond U+10FFFF (0xF4).
-*/
-struct utf8_sequence_shape
-{
-    std::uint8_t length;
-    std::uint8_t second_lo;
-    std::uint8_t second_hi;
-};
-
-/// @return the shape of a UTF-8 sequence starting with @a lead, see utf8_sequence_shape
-inline utf8_sequence_shape utf8_shape(const std::uint8_t lead) noexcept
-{
-    if (lead < 0x80u)
-    {
-        return {1, 0, 0};
-    }
-    if (lead < 0xC2u)
-    {
-        return {0, 0, 0};
-    }
-    if (lead <= 0xDFu)
-    {
-        return {2, 0x80u, 0xBFu};
-    }
-    if (lead == 0xE0u)
-    {
-        return {3, 0xA0u, 0xBFu};
-    }
-    if (lead == 0xEDu)
-    {
-        return {3, 0x80u, 0x9Fu};
-    }
-    if (lead <= 0xEFu)
-    {
-        return {3, 0x80u, 0xBFu};
-    }
-    if (lead == 0xF0u)
-    {
-        return {4, 0x90u, 0xBFu};
-    }
-    if (lead <= 0xF3u)
-    {
-        return {4, 0x80u, 0xBFu};
-    }
-    if (lead == 0xF4u)
-    {
-        return {4, 0x80u, 0x8Fu};
-    }
-    return {0, 0, 0};
-}
-
 ///////////////////
 // UTF-8 decoding //
 ///////////////////
@@ -196,7 +118,7 @@ This is a single-byte step of a "shift-based" UTF-8 decoder originally
 written by Björn Hoehrmann. See
 http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
 
-The library checks UTF-8 well-formedness (RFC 3629, section 4) in five
+The library checks UTF-8 well-formedness (RFC 3629, section 4) in three
 places, which differ in speed, diagnostics, and how they read the input:
 
 - decode() below: the serializer, to escape and, in strict mode, reject
@@ -210,15 +132,10 @@ places, which differ in speed, diagnostics, and how they read the input:
   bulk string scan, the bulk path of the BON8 reader, and the BON8 writer.
   They must accept exactly what the lexer's switch accepts.
 - the byte path of binary_reader::get_bon8_string(): BON8 input without bulk
-  access, and the bytes the bulk path leaves to it. It keeps its own ranges:
-  taking them from utf8_shape() made BON8 decoding 2-3% slower (#5891).
-- check_utf8() in detail/view/edit.hpp: strings stored in an editable
-  json_document, with the index of the offending byte. It also uses
-  utf8_shape().
+  access, and the bytes the bulk path leaves to it.
 
-All five must accept the same set of sequences, which the test "UTF-8
-validators accept the same sequences" in unit-class_lexer.cpp checks
-exhaustively against decode() and utf8_shape().
+All four must accept the same set of sequences, so a change to one needs a
+matching change to the others.
 
 @param[in,out] state  the current decoder state
 @param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)

include/nlohmann/detail/value_t.hpp

@@ -177,36 +177,6 @@ inline bool owns_memory(const value_t t) noexcept
     }
 }
 
-/*!
-@brief whether a value of the given type is neither an object nor an array
-
-Unlike basic_json::is_primitive(), this includes value_t::discarded: it names
-the types that iterators walk with a primitive_iterator_t (a single value, or no
-value for null and discarded) and that JSON Pointer resolution and the
-serializer treat as leaves. Every enumerator is listed so that -Wswitch-enum
-flags this function when a new type is added.
-*/
-inline bool is_primitive(const value_t t) noexcept
-{
-    switch (t)
-    {
-        case value_t::object:
-        case value_t::array:
-            return false;
-
-        case value_t::null:
-        case value_t::string:
-        case value_t::boolean:
-        case value_t::number_integer:
-        case value_t::number_unsigned:
-        case value_t::number_float:
-        case value_t::binary:
-        case value_t::discarded:
-        default:
-            return true;
-    }
-}
-
 
 /*!
 @brief compare an integer with a floating point number without precision loss

include/nlohmann/detail/view/edit.hpp

@@ -51,6 +51,11 @@ struct first_true<false, Conditions...> : std::integral_constant < int, 1 + firs
 inline void check_utf8(const char* s, std::size_t n)
 {
     const auto* const p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    const auto hex = [](unsigned char c)
+    {
+        constexpr const char* digits = "0123456789ABCDEF";
+        return std::string{digits[c >> 4u], digits[c & 0xFu]};
+    };
     for (std::size_t i = 0; i < n;)
     {
         const unsigned char c = p[i];
@@ -59,22 +64,39 @@ inline void check_utf8(const char* s, std::size_t n)
             ++i;
             continue;
         }
-        const utf8_sequence_shape shape = utf8_shape(c);
-        const std::size_t len = shape.length;
-        if (len == 0)
+        std::size_t len = 0;
+        unsigned char lo = 0x80;
+        unsigned char hi = 0xBF;
+        if (c >= 0xC2 && c <= 0xDF)
         {
-            throw_type_error(exception_id::invalid_utf8, concat("invalid UTF-8 byte at index ", std::to_string(i), ": 0x", hex_byte(c)));
+            len = 2;
+        }
+        else if (c >= 0xE0 && c <= 0xEF)
+        {
+            len = 3;
+            lo = c == 0xE0 ? 0xA0 : 0x80;
+            hi = c == 0xED ? 0x9F : 0xBF;
+        }
+        else if (c >= 0xF0 && c <= 0xF4)
+        {
+            len = 4;
+            lo = c == 0xF0 ? 0x90 : 0x80;
+            hi = c == 0xF4 ? 0x8F : 0xBF;
+        }
+        else
+        {
+            throw_type_error(316, concat("invalid UTF-8 byte at index ", std::to_string(i), ": 0x", hex(c)));
         }
         for (std::size_t k = 1; k < len; ++k)
         {
             if (i + k == n)
             {
-                throw_type_error(exception_id::invalid_utf8, concat("incomplete UTF-8 string; last byte: 0x", hex_byte(p[n - 1])));
+                throw_type_error(316, concat("incomplete UTF-8 string; last byte: 0x", hex(p[n - 1])));
             }
             const unsigned char b = p[i + k];
-            if (b < (k == 1 ? shape.second_lo : 0x80) || b > (k == 1 ? shape.second_hi : 0xBF))
+            if (b < (k == 1 ? lo : 0x80) || b > (k == 1 ? hi : 0xBF))
             {
-                throw_type_error(exception_id::invalid_utf8, concat("invalid UTF-8 byte at index ", std::to_string(i + k), ": 0x", hex_byte(b)));
+                throw_type_error(316, concat("invalid UTF-8 byte at index ", std::to_string(i + k), ": 0x", hex(b)));
             }
         }
         i += len;
@@ -122,7 +144,7 @@ class editor
         node* const o = own(object);
         if (o->kind != static_cast<std::uint8_t>(value_t::object) && o->kind != static_cast<std::uint8_t>(value_t::null))
         {
-            throw_type_error(exception_id::subscript_wrong_type, "cannot use operator[] with a string argument with ", object.type_name());
+            throw_type_error(305, "cannot use operator[] with a string argument with ", object.type_name());
         }
         check_utf8(key.data(), key.size());
         const encoded e = encode(std::forward<V>(value));
@@ -173,7 +195,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array))
         {
-            throw_type_error(exception_id::subscript_wrong_type, "cannot use operator[] with a numeric argument with ", array.type_name());
+            throw_type_error(305, "cannot use operator[] with a numeric argument with ", array.type_name());
         }
         check_index(idx, a->len);
         const encoded e = encode(std::forward<V>(value));
@@ -190,7 +212,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array) && a->kind != static_cast<std::uint8_t>(value_t::null))
         {
-            throw_type_error(exception_id::push_back_wrong_type, "cannot use push_back() with ", array.type_name());
+            throw_type_error(308, "cannot use push_back() with ", array.type_name());
         }
         const encoded e = encode(std::forward<V>(value));
         if (a->kind == static_cast<std::uint8_t>(value_t::null))
@@ -214,7 +236,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array))
         {
-            throw_type_error(exception_id::insert_wrong_type, "cannot use insert() with ", array.type_name());
+            throw_type_error(309, "cannot use insert() with ", array.type_name());
         }
         check_index(idx, a->len + 1);
         const encoded e = encode(std::forward<V>(value));
@@ -234,7 +256,7 @@ class editor
         node* const o = own(object);
         if (o->kind != static_cast<std::uint8_t>(value_t::object))
         {
-            throw_type_error(exception_id::erase_wrong_type, "cannot use erase() with ", object.type_name());
+            throw_type_error(307, "cannot use erase() with ", object.type_name());
         }
         for (const node* k = nav::first(m_doc, o), *end = nav::end(m_doc, o); k != end; k = document_data::after(k + 1))
         {
@@ -252,7 +274,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array))
         {
-            throw_type_error(exception_id::erase_wrong_type, "cannot use erase() with ", array.type_name());
+            throw_type_error(307, "cannot use erase() with ", array.type_name());
         }
         check_index(idx, a->len);
         node* const h = block_of(m_doc, a, 0);
@@ -275,7 +297,7 @@ class editor
     {
         if (NLOHMANN_VIEW_UNLIKELY(v.m_doc != &m_doc || v.m_node == nullptr))
         {
-            throw_invalid_iterator(exception_id::iterator_from_other_value, "view does not belong to this document");
+            throw_invalid_iterator(202, "view does not belong to this document");
         }
         edit_state_of(m_doc);
         return const_cast<node*>(v.m_node); // NOLINT(cppcoreguidelines-pro-type-const-cast): the nodes belong to this document
@@ -285,7 +307,7 @@ class editor
     {
         if (idx >= limit)
         {
-            throw_array_index_out_of_range(idx);
+            throw_out_of_range(401, concat("array index ", std::to_string(idx), " is out of range"));
         }
     }
 
@@ -426,7 +448,7 @@ class editor
     {
         if (NLOHMANN_VIEW_UNLIKELY(v.m_node == nullptr))
         {
-            throw_type_error(exception_id::type_mismatch, "type must be a value, but is ", "discarded");
+            throw_type_error(302, "type must be a value, but is ", "discarded");
         }
         encoded r;
         if (!is_container(*v.m_node))
@@ -576,7 +598,7 @@ class editor
     {
         if (NLOHMANN_VIEW_UNLIKELY(len >= 0xFFFFFFFFu))
         {
-            throw_out_of_range(exception_id::document_too_large, "strings of 4 GiB or more are not supported by json_document"); // LCOV_EXCL_LINE
+            throw_out_of_range(416, "strings of 4 GiB or more are not supported by json_document"); // LCOV_EXCL_LINE
         }
         node n = plain_node(value_t::string);
         n.flags = static_cast<std::uint8_t>(n.flags | node_flags::edited);
@@ -651,12 +673,12 @@ class editor
                 return string_node(s.data(), s.size());
             }
             case value_t::binary:
-                throw_type_error(exception_id::document_binary_value, "cannot store a binary value in a json_document", "");
+                throw_type_error(319, "cannot store a binary value in a json_document", "");
             case value_t::discarded:
             case value_t::object:
             case value_t::array:
             default:
-                throw_type_error(exception_id::type_mismatch, "type must be a value, but is ", "discarded");
+                throw_type_error(302, "type must be a value, but is ", "discarded");
         }
     }
 

include/nlohmann/detail/view/edit_storage.hpp

@@ -84,7 +84,7 @@ inline std::size_t text_capacity(std::size_t cap, std::size_t used, std::size_t
     constexpr std::size_t limit = 0xFFFFFFFFu;
     if (NLOHMANN_VIEW_UNLIKELY(used > limit || n > limit - used))
     {
-        throw_out_of_range(exception_id::document_too_large, "edits of 4 GiB or more are not supported by json_document");
+        throw_out_of_range(416, "edits of 4 GiB or more are not supported by json_document");
     }
     const std::size_t needed = used + n;
     const std::size_t wanted = needed + (std::min)(limit - needed, std::size_t{256});
@@ -135,7 +135,7 @@ inline void reserve_moved(document_data& d)
     document_data::edit_state& e = edit_state_of(d);
     if (e.moved.size() >= 0xFFFFFFFFu)
     {
-        throw_out_of_range(exception_id::document_too_large, "more than 4294967295 edited arrays and objects are not supported by json_document"); // LCOV_EXCL_LINE
+        throw_out_of_range(416, "more than 4294967295 edited arrays and objects are not supported by json_document"); // LCOV_EXCL_LINE
     }
     if (e.moved.size() == e.moved.capacity() || e.moved_cap.size() == e.moved_cap.capacity())
     {

include/nlohmann/detail/view/errors.hpp

@@ -25,52 +25,32 @@ namespace view
 // Exceptions are thrown out of line, so that the accessors that may throw stay
 // small enough to be inlined.
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(exception_id id, const char* prefix, const char* type)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(int id, const char* prefix, const char* type)
 {
     NLOHMANN_VIEW_THROW(type_error::create(id, concat(prefix, type), nullptr));
 }
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(exception_id id, const std::string& msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(int id, const std::string& msg)
 {
     NLOHMANN_VIEW_THROW(type_error::create(id, msg, nullptr));
 }
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_out_of_range(exception_id id, const std::string& msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_out_of_range(int id, const std::string& msg)
 {
     NLOHMANN_VIEW_THROW(out_of_range::create(id, msg, nullptr));
 }
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_iterator(exception_id id, const char* msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_iterator(int id, const char* msg)
 {
     NLOHMANN_VIEW_THROW(invalid_iterator::create(id, msg, nullptr));
 }
 
 /// a parse error without a position (as those of json_pointer)
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_parse_error(exception_id id, const std::string& msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_parse_error(int id, const std::string& msg)
 {
     NLOHMANN_VIEW_THROW(parse_error::create(id, 0, msg, nullptr));
 }
 
-/// out_of_range.401: the array index @a idx is not below the size
-template<typename Index>
-[[noreturn]] NLOHMANN_VIEW_NOINLINE void throw_array_index_out_of_range(const Index idx)
-{
-    throw_out_of_range(exception_id::array_index_out_of_range, concat("array index ", std::to_string(idx), " is out of range"));
-}
-
-/// out_of_range.402: the JSON Pointer token '-' of an array of @a size elements
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_array_index_past_end(std::size_t size)
-{
-    throw_out_of_range(exception_id::pointer_past_the_end_index, concat("array index '-' (", std::to_string(size), ") is out of range"));
-}
-
-/// out_of_range.403: the object has no member @a key
-template<typename Key>
-[[noreturn]] NLOHMANN_VIEW_NOINLINE void throw_key_not_found(const Key& key)
-{
-    throw_out_of_range(exception_id::key_not_found, concat("key '", key, "' not found"));
-}
-
 /// SAX handler of the error replay: accepts every event without storing it,
 /// and throws the exception the parser reports
 template<typename BasicJsonType>
@@ -169,7 +149,7 @@ template<typename BasicJsonType>
     if (f.code == error_code::input_too_large)
     {
         // (the limit is detail::view::max_input_size(): 4 GiB minus 16 bytes)
-        NLOHMANN_VIEW_THROW(out_of_range::create(exception_id::document_too_large, "input of 4294967280 bytes or more is not supported by json_document", nullptr));
+        NLOHMANN_VIEW_THROW(out_of_range::create(416, "input of 4294967280 bytes or more is not supported by json_document", nullptr));
     }
     throwing_sax<BasicJsonType> sax;
     const bool accepted = BasicJsonType::sax_parse(src, src + size, &sax, input_format_t::json, true, ignore_comments, ignore_trailing_commas);
@@ -189,7 +169,7 @@ template<typename BasicJsonType>
         }
     }
     pos.chars_read_current_line = off + 1 - line_start;
-    NLOHMANN_VIEW_THROW(parse_error::create(exception_id::syntax_error, pos, "syntax error while parsing value", nullptr));
+    NLOHMANN_VIEW_THROW(parse_error::create(101, pos, "syntax error while parsing value", nullptr));
     // LCOV_EXCL_STOP
 }
 

include/nlohmann/detail/view/image.hpp

@@ -186,7 +186,7 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
 inline std::vector<std::uint8_t> save_image(const document_data& d)
 {
 #if !NLOHMANN_VIEW_LITTLE_ENDIAN
-    throw_type_error(exception_id::document_image_unsupported, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
+    throw_type_error(320, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
 #endif
     const std::size_t arena_size = d.arena_size;
     std::vector<node> compacted;
@@ -203,7 +203,7 @@ inline std::vector<std::uint8_t> save_image(const document_data& d)
     if (NLOHMANN_VIEW_UNLIKELY(text_size >= image_limit || total_arena >= image_limit || count >= image_limit))
     {
         // LCOV_EXCL_START (4 GiB)
-        throw_out_of_range(exception_id::document_too_large, "images of 4 GiB or more are not supported by json_document");
+        throw_out_of_range(416, "images of 4 GiB or more are not supported by json_document");
         // LCOV_EXCL_STOP
     }
     image_header h{};
@@ -660,7 +660,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
 
 [[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_image(const char* what)
 {
-    throw_parse_error(exception_id::invalid_document_image, concat("invalid json_document image: ", what));
+    throw_parse_error(116, concat("invalid json_document image: ", what));
 }
 
 /// Read an image into d. The text and the decoded strings stay in the image;
@@ -668,7 +668,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
 inline void load_image(document_data& d, const std::uint8_t* image, std::size_t size, image_check check)
 {
 #if !NLOHMANN_VIEW_LITTLE_ENDIAN
-    throw_type_error(exception_id::document_image_unsupported, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
+    throw_type_error(320, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
 #endif
     if (image == nullptr || size < sizeof(image_header))
     {

include/nlohmann/detail/view/iterator.hpp

@@ -110,7 +110,7 @@ class view_iterator
     {
         if (NLOHMANN_VIEW_UNLIKELY(m_value_offset == 0))
         {
-            throw_invalid_iterator(exception_id::iterator_key_not_object, "cannot use key() for non-object iterators");
+            throw_invalid_iterator(207, "cannot use key() for non-object iterators");
         }
         return string_view_t(m_doc->str(*m_pos), m_pos->len);
     }

include/nlohmann/detail/view/materialize.hpp

@@ -143,6 +143,8 @@ BasicJsonType materialize(const document_data& d, const node* n)
             case value_t::binary:
             case value_t::discarded:
             default:
+                // false positive: the parser's frame stack points into its own storage (never null)
+                // @infer-ignore NULLPTR_DEREFERENCE
                 sax.null();
                 break;
         }

include/nlohmann/detail/view/pointer.hpp

@@ -32,15 +32,51 @@ enum class pointer_mode
     contains,  ///< as basic_json::contains(): no exceptions at all
 };
 
-/// the outcome of reading an array index: detail::parse_array_index(), shared with json_pointer
-using index_status = detail::array_index_status;
+/// the outcome of reading an array index from a reference token
+enum class index_status
+{
+    ok,
+    leading_zero, ///< parse_error.106
+    not_number,   ///< parse_error.109
+    unresolved,   ///< out_of_range.404
+    too_large,    ///< out_of_range.410
+};
 
 /// reads an array index like json_pointer::array_index (RFC 6901, Sect. 4),
 /// but reports errors instead of throwing them
 template<typename StringType>
 index_status array_index(const StringType& s, std::size_t& idx) noexcept
 {
-    return detail::parse_array_index(s, idx);
+    // as basic_json: the empty token and "-" (past the last element) are
+    // unresolved rather than not a number
+    if (s.empty() || (s.size() == 1 && s[0] == '-'))
+    {
+        return index_status::unresolved;
+    }
+    if (s[0] < '0' || s[0] > '9')
+    {
+        return index_status::not_number;
+    }
+    if (s.size() > 1 && s[0] == '0')
+    {
+        return index_status::leading_zero;
+    }
+    std::uint64_t v = 0;
+    for (const auto c : s)
+    {
+        const auto d = static_cast<unsigned>(static_cast<unsigned char>(c)) - '0';
+        if (d > 9 || v > ((std::numeric_limits<std::uint64_t>::max)() - d) / 10)
+        {
+            return index_status::unresolved; // not a number, or beyond unsigned long long
+        }
+        v = (v * 10) + d;
+    }
+    if (v >= (std::numeric_limits<std::size_t>::max)()) // (std::size_t converts to std::uint64_t implicitly)
+    {
+        return index_status::too_large;
+    }
+    idx = static_cast<std::size_t>(v);
+    return index_status::ok;
 }
 
 /// throws the exception json_pointer::array_index throws for this status
@@ -50,15 +86,15 @@ template<typename StringType>
     switch (status)
     {
         case index_status::leading_zero:
-            throw_parse_error(exception_id::pointer_index_leading_zero, concat("array index '", s, "' must not begin with '0'"));
-        case index_status::not_a_number:
-            throw_parse_error(exception_id::pointer_index_not_a_number, concat("array index '", s, "' is not a number"));
-        case index_status::exceeds_size_type:
-            throw_out_of_range(exception_id::value_out_of_range, concat("array index ", s, " exceeds size_type")); // LCOV_EXCL_LINE
+            throw_parse_error(106, concat("array index '", s, "' must not begin with '0'"));
+        case index_status::not_number:
+            throw_parse_error(109, concat("array index '", s, "' is not a number"));
+        case index_status::too_large:
+            throw_out_of_range(410, concat("array index ", s, " exceeds size_type")); // LCOV_EXCL_LINE
         case index_status::unresolved:
         case index_status::ok:
         default:
-            throw_out_of_range(exception_id::pointer_unresolved, concat("unresolved reference token '", s, "'"));
+            throw_out_of_range(404, concat("unresolved reference token '", s, "'"));
     }
 }
 
@@ -83,7 +119,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             {
                 if (mode == pointer_mode::checked)
                 {
-                    throw_key_not_found(token);
+                    throw_out_of_range(403, concat("key '", token, "' not found"));
                 }
                 return View();
             }
@@ -95,7 +131,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             {
                 if (throwing)
                 {
-                    throw_array_index_past_end(cur.size());
+                    throw_out_of_range(402, concat("array index '-' (", std::to_string(cur.size()), ") is out of range"));
                 }
                 return View();
             }
@@ -103,7 +139,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             const index_status status = array_index(token, idx);
             if (status != index_status::ok)
             {
-                const bool parse_error = status == index_status::leading_zero || status == index_status::not_a_number;
+                const bool parse_error = status == index_status::leading_zero || status == index_status::not_number;
                 if (throwing || (mode == pointer_mode::value && parse_error))
                 {
                     throw_array_index_error(status, token);
@@ -114,7 +150,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             {
                 if (mode == pointer_mode::checked)
                 {
-                    throw_array_index_out_of_range(idx);
+                    throw_out_of_range(401, concat("array index ", std::to_string(idx), " is out of range"));
                 }
                 return View();
             }
@@ -124,7 +160,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
         {
             if (throwing)
             {
-                throw_out_of_range(exception_id::pointer_unresolved, concat("unresolved reference token '", token, "'"));
+                throw_out_of_range(404, concat("unresolved reference token '", token, "'"));
             }
             return View();
         }

include/nlohmann/detail/view/serializer.hpp

@@ -1073,17 +1073,21 @@ class view_serializer
             m_out.put("null");
             return;
         }
-        write_float(x, std::integral_constant<bool, ::nlohmann::detail::has_native_float_format<number_float_t>::value>());
+        static constexpr bool is_ieee_single_or_double
+            = std::numeric_limits<number_float_t>::is_iec559
+              && ((std::numeric_limits<number_float_t>::digits == 24 && std::numeric_limits<number_float_t>::max_exponent == 128)
+                  || (std::numeric_limits<number_float_t>::digits == 53 && std::numeric_limits<number_float_t>::max_exponent == 1024));
+        write_float(x, std::integral_constant<bool, is_ieee_single_or_double>());
     }
 
-    void write_float(number_float_t x, std::true_type /*has_native_float_format*/)
+    void write_float(number_float_t x, std::true_type /*is_ieee_single_or_double*/)
     {
         std::array<char, 64> buf{};
         const char* const end = ::nlohmann::detail::to_chars(buf.data(), buf.data() + buf.size(), x);
         m_out.put(buf.data(), static_cast<std::size_t>(end - buf.data()));
     }
 
-    void write_float(number_float_t x, std::false_type /*has_native_float_format*/)
+    void write_float(number_float_t x, std::false_type /*is_ieee_single_or_double*/)
     {
         // other types (e.g. long double) are rare: the library writes them
         const string_t s = BasicJsonType(x).dump();
@@ -1144,8 +1148,8 @@ class view_serializer
 
     void write_u_escape(std::uint32_t u)
     {
-        std::array<char, 6> e = {{'\\', 'u', 0, 0, 0, 0}};
-        hex4_lower(static_cast<std::uint16_t>(u), &e[2]);
+        static constexpr const char* hex = "0123456789abcdef";
+        const std::array<char, 6> e = {{'\\', 'u', hex[(u >> 12u) & 0xFu], hex[(u >> 8u) & 0xFu], hex[(u >> 4u) & 0xFu], hex[u & 0xFu]}};
         m_out.put(e.data(), e.size());
     }
 

include/nlohmann/detail/view/value.hpp

@@ -60,7 +60,7 @@ NLOHMANN_VIEW_ALWAYS_INLINE T arithmetic_value(const document_data& d, const nod
         case value_t::binary:
         case value_t::discarded:
         default:
-            throw_type_error(exception_id::type_mismatch, "type must be number, but is ", value_type_name(static_cast<value_t>(n.kind)));
+            throw_type_error(302, "type must be number, but is ", value_type_name(static_cast<value_t>(n.kind)));
     }
 }
 
@@ -70,7 +70,7 @@ std::vector<U, A> vector_value(const View& v)
 {
     if (NLOHMANN_VIEW_UNLIKELY(!v.is_array()))
     {
-        throw_type_error(exception_id::type_mismatch, "type must be array, but is ", v.type_name());
+        throw_type_error(302, "type must be array, but is ", v.type_name());
     }
     std::vector<U, A> r;
     r.reserve(v.size());
@@ -88,7 +88,7 @@ Map map_value(const View& v)
 {
     if (NLOHMANN_VIEW_UNLIKELY(!v.is_object()))
     {
-        throw_type_error(exception_id::type_mismatch, "type must be object, but is ", v.type_name());
+        throw_type_error(302, "type must be object, but is ", v.type_name());
     }
     Map r;
     for (auto it = v.begin(); it != v.end(); ++it)

include/nlohmann/json.hpp

@@ -55,7 +55,7 @@
 #include <nlohmann/detail/abi_macros.hpp> // IWYU pragma: export
 #include <nlohmann/detail/conversions/from_json.hpp> // IWYU pragma: keep
 #include <nlohmann/detail/conversions/to_json.hpp> // IWYU pragma: keep
-#include <nlohmann/detail/exceptions.hpp> // IWYU pragma: export
+#include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/hash.hpp>
 #include <nlohmann/detail/input/binary_reader.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
@@ -376,9 +376,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         result["name"] = "JSON for Modern C++";
         result["url"] = "https://github.com/nlohmann/json";
         result["version"]["string"] =
-            detail::concat<string_t>(detail::to_string<string_t>(static_cast<std::size_t>(NLOHMANN_JSON_VERSION_MAJOR)), '.',
-                                     detail::to_string<string_t>(static_cast<std::size_t>(NLOHMANN_JSON_VERSION_MINOR)), '.',
-                                     detail::to_string<string_t>(static_cast<std::size_t>(NLOHMANN_JSON_VERSION_PATCH)));
+            detail::concat(std::to_string(NLOHMANN_JSON_VERSION_MAJOR), '.',
+                           std::to_string(NLOHMANN_JSON_VERSION_MINOR), '.',
+                           std::to_string(NLOHMANN_JSON_VERSION_PATCH));
         result["version"]["major"] = NLOHMANN_JSON_VERSION_MAJOR;
         result["version"]["minor"] = NLOHMANN_JSON_VERSION_MINOR;
         result["version"]["patch"] = NLOHMANN_JSON_VERSION_PATCH;
@@ -400,10 +400,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 #elif defined(__clang__)
         result["compiler"] = {{"family", "clang"}, {"version", __clang_version__}};
 #elif defined(__GNUC__) || defined(__GNUG__)
-        result["compiler"] = {{"family", "gcc"}, {"version", detail::concat<string_t>(
-                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC__)), '.',
-                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC_MINOR__)), '.',
-                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC_PATCHLEVEL__)))
+        result["compiler"] = {{"family", "gcc"}, {"version", detail::concat(
+                    std::to_string(__GNUC__), '.',
+                    std::to_string(__GNUC_MINOR__), '.',
+                    std::to_string(__GNUC_PATCHLEVEL__))
             }
         };
 #elif defined(__HP_aCC)
@@ -421,9 +421,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 #endif
 
 #if defined(_MSVC_LANG)
-        result["compiler"]["c++"] = detail::to_string<string_t>(static_cast<std::size_t>(_MSVC_LANG));
+        result["compiler"]["c++"] = std::to_string(_MSVC_LANG);
 #elif defined(__cplusplus)
-        result["compiler"]["c++"] = detail::to_string<string_t>(static_cast<std::size_t>(__cplusplus));
+        result["compiler"]["c++"] = std::to_string(__cplusplus);
 #else
         result["compiler"]["c++"] = "unknown";
 #endif
@@ -734,15 +734,23 @@ private:
         // true if v is not an array/object, or is an already-empty one
         static bool has_no_children(const basic_json& v) noexcept
         {
-            if (v.m_data.m_type == value_t::array)
+            switch (v.m_data.m_type)
             {
-                return v.m_data.m_value.array->empty();
+                case value_t::array:
+                    return v.m_data.m_value.array->empty();
+                case value_t::object:
+                    return v.m_data.m_value.object->empty();
+                case value_t::null:
+                case value_t::string:
+                case value_t::boolean:
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                case value_t::binary:
+                case value_t::discarded:
+                default:
+                    return true;
             }
-            if (v.m_data.m_type == value_t::object)
-            {
-                return v.m_data.m_value.object->empty();
-            }
-            return true;
         }
 
         // true if no child of the non-empty array/object v has children of
@@ -847,17 +855,28 @@ private:
         }
 
 public:
-        template<typename T>
-        static void destroy_pointer(T*& ptr) noexcept
+        void destroy_string() noexcept
         {
-            if (ptr == nullptr)
+            if (string == nullptr)
             {
                 // not initialized (e.g., due to exception in the ctor)
                 return;
             }
-            AllocatorType<T> alloc;
-            std::allocator_traits<decltype(alloc)>::destroy(alloc, ptr);
-            std::allocator_traits<decltype(alloc)>::deallocate(alloc, ptr, 1);
+            AllocatorType<string_t> alloc;
+            std::allocator_traits<decltype(alloc)>::destroy(alloc, string);
+            std::allocator_traits<decltype(alloc)>::deallocate(alloc, string, 1);
+        }
+
+        void destroy_binary() noexcept
+        {
+            if (binary == nullptr)
+            {
+                // not initialized (e.g., due to exception in the ctor)
+                return;
+            }
+            AllocatorType<binary_t> alloc;
+            std::allocator_traits<decltype(alloc)>::destroy(alloc, binary);
+            std::allocator_traits<decltype(alloc)>::deallocate(alloc, binary, 1);
         }
 
         // t must be value_t::array or value_t::object
@@ -1023,11 +1042,11 @@ public:
             switch (t)
             {
                 case value_t::string:
-                    destroy_pointer(string);
+                    destroy_string();
                     break;
 
                 case value_t::binary:
-                    destroy_pointer(binary);
+                    destroy_binary();
                     break;
 
                 case value_t::object:
@@ -1089,19 +1108,36 @@ public:
     void set_parents()
     {
 #if JSON_DIAGNOSTICS
-        if (m_data.m_type == value_t::array)
+        switch (m_data.m_type)
         {
-            for (auto& element : *m_data.m_value.array)
+            case value_t::array:
             {
-                element.m_parent = this;
+                for (auto& element : *m_data.m_value.array)
+                {
+                    element.m_parent = this;
+                }
+                break;
             }
-        }
-        else if (m_data.m_type == value_t::object)
-        {
-            for (auto& element : *m_data.m_value.object)
+
+            case value_t::object:
             {
-                element.second.m_parent = this;
+                for (auto& element : *m_data.m_value.object)
+                {
+                    element.second.m_parent = this;
+                }
+                break;
             }
+
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+                break;
         }
 #endif
     }
@@ -2549,7 +2585,8 @@ public:
             case value_t::string:
             case value_t::binary:
             {
-                if (JSON_HEDLEY_UNLIKELY(!primitive_range_is_complete(first, last)))
+                if (JSON_HEDLEY_UNLIKELY(!first.m_it.primitive_iterator.is_begin()
+                                         || !last.m_it.primitive_iterator.is_end()))
                 {
                     detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_range_out_of_range, "iterators out of range", first.m_object);
                 }
@@ -3023,134 +3060,6 @@ public:
         JSON_THROW(std::length_error(detail::concat("array index ", std::to_string(idx), " exceeds size_type")));
     }
 
-    /// @throw type_error.309 always, as insert() is not defined for the type of @a j
-    JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE
-    static void throw_insert_wrong_type(const basic_json& j)
-    {
-        detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", j);
-    }
-
-    /// @throw invalid_iterator.202 always, as an iterator belongs to another value than @a obj
-    JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE
-    static void throw_iterator_from_other_value(const basic_json* obj)
-    {
-        detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", obj);
-    }
-
-    /// @throw type_error.310 always, as swap() with the given operand is not defined for the type of @a j
-    JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE
-    static void throw_swap_wrong_type(const char* operation, const basic_json& j)
-    {
-        detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, operation, j);
-    }
-
-    /// exchange the stored @a Stored value (if the value has that type) with @a other
-    template<typename Stored, typename Other>
-    void swap_impl(Other& other, const char* operation)
-    {
-        Stored* const stored = get_impl_ptr(static_cast<Stored*>(nullptr));
-        if (JSON_HEDLEY_UNLIKELY(stored == nullptr))
-        {
-            throw_swap_wrong_type(operation, *this);
-        }
-
-        using std::swap;
-        swap(*stored, other);
-    }
-
-    /// whether [first, last) spans the whole of a primitive value
-    template<typename IteratorType>
-    JSON_HEDLEY_ALWAYS_INLINE
-    static bool primitive_range_is_complete(const IteratorType& first, const IteratorType& last) noexcept
-    {
-        return first.m_it.primitive_iterator.is_begin() && last.m_it.primitive_iterator.is_end();
-    }
-
-    /// destroy the current (primitive) value and become null
-    void reset_to_null_impl()
-    {
-        m_data.m_value.destroy(m_data.m_type);
-        m_data.m_value = {};
-        m_data.m_type = value_t::null;
-        assert_invariant();
-    }
-
-    /// append @a val (moved or copied) to the array; a null value becomes an array
-    template<typename ValueType>
-    JSON_HEDLEY_ALWAYS_INLINE
-    void push_back_array_impl(ValueType&& val)
-    {
-        // push_back only works for null objects or arrays
-        if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_array())))
-        {
-            detail::throw_cannot_use_with(detail::exception_id::push_back_wrong_type, "push_back()", *this);
-        }
-
-        // transform a null object into an array
-        if (is_null())
-        {
-            convert_null_to<array_t>();
-        }
-
-        // add the element to the array
-        const auto old_capacity = container_capacity();
-        m_data.m_value.array->push_back(std::forward<ValueType>(val));
-        set_parent_after_insert(m_data.m_value.array->back(), old_capacity);
-    }
-
-    /// parse the input behind an already created adapter
-    template<typename InputAdapterType>
-    static basic_json parse_impl(InputAdapterType&& adapter,
-                                 parser_callback_t cb,
-                                 const bool allow_exceptions,
-                                 const bool ignore_comments,
-                                 const bool ignore_trailing_commas)
-    {
-        basic_json result;
-        parser(std::forward<InputAdapterType>(adapter), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas).parse(true, result);
-        return result;
-    }
-
-    /// check the input behind an already created adapter
-    template<typename InputAdapterType>
-    static bool accept_impl(InputAdapterType&& adapter,
-                            const bool ignore_comments,
-                            const bool ignore_trailing_commas)
-    {
-        return parser(std::forward<InputAdapterType>(adapter), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
-    }
-
-    /// generate SAX events from the input behind an already created adapter
-    template<typename InputAdapterType, typename SAX>
-    static bool sax_parse_impl(InputAdapterType ia, SAX* sax,
-                               const input_format_t format,
-                               const bool strict,
-                               const bool ignore_comments,
-                               const bool ignore_trailing_commas,
-                               const cbor_tag_handler_t tag_handler)
-    {
-        if (format == input_format_t::json)
-        {
-            return parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict);
-        }
-        return detail::binary_reader<basic_json, InputAdapterType, SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
-    }
-
-    /// serialize @a j into a new vector; @a write receives the vector-backed writer
-    template<typename WriteFunction>
-    static std::vector<std::uint8_t> to_binary_vector(const basic_json& j, const error_handler_t error_handler, WriteFunction write)
-    {
-        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_initial_capacity(j));
-        {
-            // the sink sets the size of result when it is destroyed, which
-            // must happen before result is returned (without NRVO, it is moved)
-            auto writer = vector_writer(result, error_handler);
-            write(writer);
-        }
-        return result;
-    }
-
     /// @throw out_of_range.401 always, as @a idx is out of range of @a j
     JSON_HEDLEY_NO_RETURN JSON_HEDLEY_NEVER_INLINE
     static void throw_array_index_out_of_range(size_type idx, const basic_json& j)
@@ -4133,7 +4042,7 @@ public:
         // make sure the iterator fits the current value
         if (JSON_HEDLEY_UNLIKELY(this != pos.m_object))
         {
-            throw_iterator_from_other_value(this);
+            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this);
         }
 
         IteratorType result = end();
@@ -4152,7 +4061,10 @@ public:
                     detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_out_of_range, "iterator out of range", this);
                 }
 
-                reset_to_null_impl();
+                m_data.m_value.destroy(m_data.m_type);
+                m_data.m_value = {};
+                m_data.m_type = value_t::null;
+                assert_invariant();
                 break;
             }
 
@@ -4202,12 +4114,16 @@ public:
             case value_t::string:
             case value_t::binary:
             {
-                if (JSON_HEDLEY_UNLIKELY(!primitive_range_is_complete(first, last)))
+                if (JSON_HEDLEY_UNLIKELY(!first.m_it.primitive_iterator.is_begin()
+                                         || !last.m_it.primitive_iterator.is_end()))
                 {
                     detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_range_out_of_range, "iterators out of range", this);
                 }
 
-                reset_to_null_impl();
+                m_data.m_value.destroy(m_data.m_type);
+                m_data.m_value = {};
+                m_data.m_type = value_t::null;
+                assert_invariant();
                 break;
             }
 
@@ -4688,20 +4604,34 @@ public:
     JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type max_size() const noexcept
     {
-        if (m_data.m_type == value_t::array)
+        switch (m_data.m_type)
         {
-            // delegate call to array_t::max_size()
-            return m_data.m_value.array->max_size();
-        }
+            case value_t::array:
+            {
+                // delegate call to array_t::max_size()
+                return m_data.m_value.array->max_size();
+            }
 
-        if (m_data.m_type == value_t::object)
-        {
-            // delegate call to object_t::max_size()
-            return m_data.m_value.object->max_size();
-        }
+            case value_t::object:
+            {
+                // delegate call to object_t::max_size()
+                return m_data.m_value.object->max_size();
+            }
 
-        // all other types have max_size() == size()
-        return size();
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+            {
+                // all other types have max_size() == size()
+                return size();
+            }
+        }
     }
 
     /// @}
@@ -4779,7 +4709,22 @@ public:
     /// @sa https://json.nlohmann.me/api/basic_json/push_back/
     void push_back(basic_json&& val)
     {
-        push_back_array_impl(std::move(val));
+        // push_back only works for null objects or arrays
+        if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_array())))
+        {
+            detail::throw_cannot_use_with(detail::exception_id::push_back_wrong_type, "push_back()", *this);
+        }
+
+        // transform a null object into an array
+        if (is_null())
+        {
+            convert_null_to<array_t>();
+        }
+
+        // add the element to the array (move semantics)
+        const auto old_capacity = container_capacity();
+        m_data.m_value.array->push_back(std::move(val));
+        set_parent_after_insert(m_data.m_value.array->back(), old_capacity);
         // if val is moved from, basic_json move constructor marks it null, so we do not call the destructor
     }
 
@@ -4795,7 +4740,22 @@ public:
     /// @sa https://json.nlohmann.me/api/basic_json/push_back/
     void push_back(const basic_json& val)
     {
-        push_back_array_impl(val);
+        // push_back only works for null objects or arrays
+        if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_array())))
+        {
+            detail::throw_cannot_use_with(detail::exception_id::push_back_wrong_type, "push_back()", *this);
+        }
+
+        // transform a null object into an array
+        if (is_null())
+        {
+            convert_null_to<array_t>();
+        }
+
+        // add the element to the array
+        const auto old_capacity = container_capacity();
+        m_data.m_value.array->push_back(val);
+        set_parent_after_insert(m_data.m_value.array->back(), old_capacity);
     }
 
     /// @brief add an object to an array
@@ -4941,13 +4901,13 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            throw_insert_wrong_type(*this);
+            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            throw_iterator_from_other_value(this);
+            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this);
         }
 
         // insert to array and return iterator
@@ -4961,13 +4921,13 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            throw_insert_wrong_type(*this);
+            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            throw_iterator_from_other_value(this);
+            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this);
         }
 
         // moving into a local first keeps this safe even if val aliases
@@ -4983,13 +4943,13 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            throw_insert_wrong_type(*this);
+            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            throw_iterator_from_other_value(this);
+            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this);
         }
 
         // insert to array and return iterator
@@ -5003,13 +4963,13 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            throw_insert_wrong_type(*this);
+            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            throw_iterator_from_other_value(this);
+            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this);
         }
 
         // check if range iterators belong to the same JSON object
@@ -5040,13 +5000,13 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            throw_insert_wrong_type(*this);
+            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            throw_iterator_from_other_value(this);
+            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this);
         }
 
         // copy the values first: ilist may refer to elements of this array
@@ -5068,7 +5028,7 @@ public:
         // insert only works for objects
         if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            throw_insert_wrong_type(*this);
+            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
         }
 
         // check if range iterators belong to the same JSON object
@@ -5310,37 +5270,82 @@ public:
     /// @sa https://json.nlohmann.me/api/basic_json/swap/
     void swap(array_t& other) // NOLINT(bugprone-exception-escape,cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
     {
-        swap_impl<array_t>(other, "swap(array_t&)");
-        set_parents();
+        // swap only works for arrays
+        if (JSON_HEDLEY_LIKELY(is_array()))
+        {
+            using std::swap;
+            swap(*(m_data.m_value.array), other);
+            set_parents();
+        }
+        else
+        {
+            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(array_t&)", *this);
+        }
     }
 
     /// @brief exchanges the values
     /// @sa https://json.nlohmann.me/api/basic_json/swap/
     void swap(object_t& other) // NOLINT(bugprone-exception-escape,cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
     {
-        swap_impl<object_t>(other, "swap(object_t&)");
-        set_parents();
+        // swap only works for objects
+        if (JSON_HEDLEY_LIKELY(is_object()))
+        {
+            using std::swap;
+            swap(*(m_data.m_value.object), other);
+            set_parents();
+        }
+        else
+        {
+            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(object_t&)", *this);
+        }
     }
 
     /// @brief exchanges the values
     /// @sa https://json.nlohmann.me/api/basic_json/swap/
     void swap(string_t& other) // NOLINT(bugprone-exception-escape,cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
     {
-        swap_impl<string_t>(other, "swap(string_t&)");
+        // swap only works for strings
+        if (JSON_HEDLEY_LIKELY(is_string()))
+        {
+            using std::swap;
+            swap(*(m_data.m_value.string), other);
+        }
+        else
+        {
+            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(string_t&)", *this);
+        }
     }
 
     /// @brief exchanges the values
     /// @sa https://json.nlohmann.me/api/basic_json/swap/
     void swap(binary_t& other) // NOLINT(bugprone-exception-escape,cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
     {
-        swap_impl<binary_t>(other, "swap(binary_t&)");
+        // swap only works for binary values
+        if (JSON_HEDLEY_LIKELY(is_binary()))
+        {
+            using std::swap;
+            swap(*(m_data.m_value.binary), other);
+        }
+        else
+        {
+            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(binary_t&)", *this);
+        }
     }
 
     /// @brief exchanges the values
     /// @sa https://json.nlohmann.me/api/basic_json/swap/
     void swap(typename binary_t::container_type& other) // NOLINT(bugprone-exception-escape)
     {
-        swap_impl<binary_t>(other, "swap(binary_t::container_type&)");
+        // swap only works for binary values
+        if (JSON_HEDLEY_LIKELY(is_binary()))
+        {
+            using std::swap;
+            swap(*(m_data.m_value.binary), other);
+        }
+        else
+        {
+            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(binary_t::container_type&)", *this);
+        }
     }
 
     /// @}
@@ -6021,7 +6026,10 @@ public:
                             const bool ignore_comments = false,
                             const bool ignore_trailing_commas = false)
     {
-        return parse_impl(detail::input_adapter(std::forward<InputType>(i)), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
+        basic_json result;
+        auto p = parser(detail::input_adapter(std::forward<InputType>(i)), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
+        p.parse(true, result);
+        return result;
     }
 
     /// @brief deserialize from a pair of character iterators (or an iterator+sentinel pair, C++20 ranges support)
@@ -6036,7 +6044,10 @@ public:
                             const bool ignore_comments = false,
                             const bool ignore_trailing_commas = false)
     {
-        return parse_impl(detail::input_adapter(std::move(first), std::move(last)), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
+        basic_json result;
+        auto p = parser(detail::input_adapter(std::move(first), std::move(last)), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
+        p.parse(true, result);
+        return result;
     }
 
     JSON_HEDLEY_WARN_UNUSED_RESULT
@@ -6050,7 +6061,10 @@ public:
         = delete;
 #else
     {
-        return parse_impl(i.get(), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
+        basic_json result;
+        auto p = parser(i.get(), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
+        p.parse(true, result);
+        return result;
     }
 #endif
 
@@ -6062,7 +6076,7 @@ public:
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return accept_impl(detail::input_adapter(std::forward<InputType>(i)), ignore_comments, ignore_trailing_commas);
+        return parser(detail::input_adapter(std::forward<InputType>(i)), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
     }
 
     /// @brief check if the input is valid JSON (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -6074,7 +6088,7 @@ public:
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
     {
-        return accept_impl(detail::input_adapter(std::move(first), std::move(last)), ignore_comments, ignore_trailing_commas);
+        return parser(detail::input_adapter(std::move(first), std::move(last)), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
     }
 
     JSON_HEDLEY_WARN_UNUSED_RESULT
@@ -6086,7 +6100,7 @@ public:
         = delete;
 #else
     {
-        return accept_impl(i.get(), ignore_comments, ignore_trailing_commas);
+        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
     }
 #endif
 
@@ -6101,7 +6115,10 @@ public:
                           const bool ignore_trailing_commas = false,
                           const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
     {
-        return sax_parse_impl(detail::input_adapter(std::forward<InputType>(i)), sax, format, strict, ignore_comments, ignore_trailing_commas, tag_handler);
+        auto ia = detail::input_adapter(std::forward<InputType>(i));
+        return format == input_format_t::json
+               ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
+               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
     }
 
     /// @brief generate SAX events (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -6116,7 +6133,10 @@ public:
                           const bool ignore_trailing_commas = false,
                           const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
     {
-        return sax_parse_impl(detail::input_adapter(std::move(first), std::move(last)), sax, format, strict, ignore_comments, ignore_trailing_commas, tag_handler);
+        auto ia = detail::input_adapter(std::move(first), std::move(last));
+        return format == input_format_t::json
+               ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
+               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
     }
 
     /// @brief generate SAX events
@@ -6150,7 +6170,12 @@ public:
     = delete;
 #else
     {
-        return sax_parse_impl(i.get(), sax, format, strict, ignore_comments, ignore_trailing_commas, tag_handler);
+        auto ia = i.get();
+        return format == input_format_t::json
+               // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
+               ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
+               // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
+               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
     }
 #endif
 #if defined(__clang__)
@@ -6298,10 +6323,10 @@ public:
     static std::vector<std::uint8_t> to_cbor(const basic_json& j,
             const error_handler_t error_handler = detail::binary_writer_default_error_handler())
     {
-        return to_binary_vector(j, error_handler, [&](vector_binary_writer<std::uint8_t>& w)
-        {
-            w.write_cbor(j);
-        });
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_initial_capacity(j));
+        vector_writer(result, error_handler).write_cbor(j);
+        return result;
     }
 
     /// @brief create a CBOR serialization of a given JSON value
@@ -6329,10 +6354,10 @@ public:
     static std::vector<std::uint8_t> to_msgpack(const basic_json& j,
             const error_handler_t error_handler = error_handler_t::keep)
     {
-        return to_binary_vector(j, error_handler, [&](vector_binary_writer<std::uint8_t>& w)
-        {
-            w.write_msgpack(j);
-        });
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_initial_capacity(j));
+        vector_writer(result, error_handler).write_msgpack(j);
+        return result;
     }
 
     /// @brief create a MessagePack serialization of a given JSON value
@@ -6362,10 +6387,10 @@ public:
             const bool use_type = false,
             const error_handler_t error_handler = detail::binary_writer_default_error_handler())
     {
-        return to_binary_vector(j, error_handler, [&](vector_binary_writer<std::uint8_t>& w)
-        {
-            w.write_ubjson(j, use_size, use_type);
-        });
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_initial_capacity(j));
+        vector_writer(result, error_handler).write_ubjson(j, use_size, use_type);
+        return result;
     }
 
     /// @brief create a UBJSON serialization of a given JSON value
@@ -6398,10 +6423,10 @@ public:
             const bjdata_version_t version = bjdata_version_t::draft2,
             const error_handler_t error_handler = detail::binary_writer_default_error_handler())
     {
-        return to_binary_vector(j, error_handler, [&](vector_binary_writer<std::uint8_t>& w)
-        {
-            w.write_ubjson(j, use_size, use_type, true, true, version);
-        });
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_initial_capacity(j));
+        vector_writer(result, error_handler).write_ubjson(j, use_size, use_type, true, true, version);
+        return result;
     }
 
     /// @brief create a BJData serialization of a given JSON value
@@ -6433,10 +6458,10 @@ public:
     static std::vector<std::uint8_t> to_bson(const basic_json& j,
             const error_handler_t error_handler = detail::binary_writer_default_error_handler())
     {
-        return to_binary_vector(j, error_handler, [&](vector_binary_writer<std::uint8_t>& w)
-        {
-            w.write_bson(j);
-        });
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_initial_capacity(j));
+        vector_writer(result, error_handler).write_bson(j);
+        return result;
     }
 
     /// @brief create a BSON serialization of a given JSON value
@@ -6463,10 +6488,10 @@ public:
     /// @sa https://json.nlohmann.me/api/basic_json/to_bon8/
     static std::vector<std::uint8_t> to_bon8(const basic_json& j)
     {
-        return to_binary_vector(j, detail::binary_writer_default_error_handler(), [&](vector_binary_writer<std::uint8_t>& w)
-        {
-            w.write_bon8(j);
-        });
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_initial_capacity(j));
+        vector_writer(result).write_bon8(j);
+        return result;
     }
 
     /// @brief create a BON8 serialization of a given JSON value
@@ -7802,68 +7827,82 @@ public:
             return;
         }
 
-        if (detail::is_primitive(source.type()))
+        switch (source.type())
         {
-            // both primitive types: replace value
-            diff_replace(result, path, target);
-            return;
-        }
-
-        if (source.is_array())
-        {
-            const std::size_t path_length = path.size();
-
-            // first pass: traverse common elements
-            std::size_t i = 0;
-            while (i < source.size() && i < target.size())
+            case value_t::array:
             {
-                // recursive call to compare array values at index i
-                if (!(source[i] == target[i]))
+                const std::size_t path_length = path.size();
+
+                // first pass: traverse common elements
+                std::size_t i = 0;
+                while (i < source.size() && i < target.size())
                 {
-                    diff_append_index(path, i);
-                    diff_unequal(result, source[i], target[i], path, depth + 1);
-                    path.resize(path_length);
+                    // recursive call to compare array values at index i
+                    if (!(source[i] == target[i]))
+                    {
+                        diff_append_index(path, i);
+                        diff_unequal(result, source[i], target[i], path, depth + 1);
+                        path.resize(path_length);
+                    }
+                    ++i;
                 }
-                ++i;
+
+                // We now reached the end of at least one array
+                // in a second pass, traverse the remaining elements
+                diff_array_tails(result, source, target, path, i);
+                break;
             }
 
-            // We now reached the end of at least one array
-            // in a second pass, traverse the remaining elements
-            diff_array_tails(result, source, target, path, i);
-        }
-        else
-        {
-            diff_target_values target_values;
-            std::vector<const_iterator> added;
-            if (diff_object_keys(result, source, target, path, target_values, added))
+            case value_t::object:
             {
-                // fast path: target_values holds, for every member of
-                // source in order, its value in target -- so no further
-                // lookup is needed. Deleted keys are interleaved here
-                // too, in source's original order, to match the
-                // historical (pre-reordering-aware) output order.
-                const std::size_t path_length = path.size();
-                std::size_t i = 0;
-                for (auto it = source.cbegin(); it != source.cend(); ++it, ++i)
+                diff_target_values target_values;
+                std::vector<const_iterator> added;
+                if (diff_object_keys(result, source, target, path, target_values, added))
                 {
-                    if (target_values[i] != nullptr)
+                    // fast path: target_values holds, for every member of
+                    // source in order, its value in target -- so no further
+                    // lookup is needed. Deleted keys are interleaved here
+                    // too, in source's original order, to match the
+                    // historical (pre-reordering-aware) output order.
+                    const std::size_t path_length = path.size();
+                    std::size_t i = 0;
+                    for (auto it = source.cbegin(); it != source.cend(); ++it, ++i)
                     {
-                        if (!(it.value() == *target_values[i]))
+                        if (target_values[i] != nullptr)
                         {
-                            diff_append_key(path, it.key());
-                            diff_unequal(result, it.value(), *target_values[i], path, depth + 1);
-                            path.resize(path_length);
+                            if (!(it.value() == *target_values[i]))
+                            {
+                                diff_append_key(path, it.key());
+                                diff_unequal(result, it.value(), *target_values[i], path, depth + 1);
+                                path.resize(path_length);
+                            }
+                        }
+                        else
+                        {
+                            // found a key that is not in target -> remove it
+                            diff_remove(result, diff_key_path(path, it.key()));
                         }
                     }
-                    else
-                    {
-                        // found a key that is not in target -> remove it
-                        diff_remove(result, diff_key_path(path, it.key()));
-                    }
-                }
 
-                // append the "add" operations for brand-new keys
-                diff_added(result, added, path);
+                    // append the "add" operations for brand-new keys
+                    diff_added(result, added, path);
+                }
+                break;
+            }
+
+            case value_t::null:
+            case value_t::string:
+            case value_t::boolean:
+            case value_t::number_integer:
+            case value_t::number_unsigned:
+            case value_t::number_float:
+            case value_t::binary:
+            case value_t::discarded:
+            default:
+            {
+                // both primitive types: replace value
+                diff_replace(result, path, target);
+                break;
             }
         }
     }
@@ -7909,31 +7948,46 @@ public:
                 return;
             }
 
-            if (detail::is_primitive(s.type()))
+            switch (s.type())
             {
-                // both primitive types: replace value
-                diff_replace(result, current_path, t);
-                return;
-            }
+                case value_t::array:
+                {
+                    stack.emplace_back(&s, &t, current_path.size());
+                    return;
+                }
 
-            if (s.is_array())
-            {
-                stack.emplace_back(&s, &t, current_path.size());
-                return;
+                case value_t::object:
+                {
+                    std::vector<const basic_json*> target_values;
+                    std::vector<const_iterator> added;
+                    if (diff_object_keys(result, s, t, current_path, target_values, added))
+                    {
+                        // fast path: the frame walks source in lockstep with
+                        // common_keys, as diff_recursively does, and appends
+                        // added_ops once all members are done
+                        stack.emplace_back(&s, &t, current_path.size());
+                        stack.back().member = s.cbegin();
+                        stack.back().target_values = std::move(target_values);
+                        stack.back().added = std::move(added);
+                    }
+                    return;
+                }
+
+                case value_t::null:
+                case value_t::string:
+                case value_t::boolean:
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                case value_t::binary:
+                case value_t::discarded:
+                default:
+                {
+                    // both primitive types: replace value
+                    diff_replace(result, current_path, t);
+                    return;
+                }
             }
-            std::vector<const basic_json*> target_values;
-            std::vector<const_iterator> added;
-            if (diff_object_keys(result, s, t, current_path, target_values, added))
-            {
-                // fast path: the frame walks source in lockstep with
-                // common_keys, as diff_recursively does, and appends
-                // added_ops once all members are done
-                stack.emplace_back(&s, &t, current_path.size());
-                stack.back().member = s.cbegin();
-                stack.back().target_values = std::move(target_values);
-                stack.back().added = std::move(added);
-            }
-            return;
         };
 
         enter(source, target);

include/nlohmann/json_view.hpp

@@ -268,7 +268,7 @@ class basic_json_view
             {
                 return {};
             }
-            detail::view::throw_type_error(detail::exception_id::subscript_wrong_type, "cannot use operator[] with a string argument with ", type_name());
+            detail::view::throw_type_error(305, "cannot use operator[] with a string argument with ", type_name());
         }
         return lookup(key);
     }
@@ -294,7 +294,7 @@ class basic_json_view
             {
                 return {};
             }
-            detail::view::throw_type_error(detail::exception_id::subscript_wrong_type, "cannot use operator[] with a numeric argument with ", type_name());
+            detail::view::throw_type_error(305, "cannot use operator[] with a numeric argument with ", type_name());
         }
         return idx < m_node->len ? element(idx) : basic_json_view();
     }
@@ -327,12 +327,12 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
-            detail::view::throw_type_error(detail::exception_id::at_wrong_type, "cannot use at() with ", type_name());
+            detail::view::throw_type_error(304, "cannot use at() with ", type_name());
         }
         const basic_json_view r = lookup(key);
         if (NLOHMANN_VIEW_UNLIKELY(r.is_discarded()))
         {
-            detail::view::throw_key_not_found(std::string(key.data(), key.size()));
+            detail::view::throw_out_of_range(403, detail::concat("key '", std::string(key.data(), key.size()), "' not found"));
         }
         return r;
     }
@@ -353,11 +353,11 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_array()))
         {
-            detail::view::throw_type_error(detail::exception_id::at_wrong_type, "cannot use at() with ", type_name());
+            detail::view::throw_type_error(304, "cannot use at() with ", type_name());
         }
         if (NLOHMANN_VIEW_UNLIKELY(idx >= m_node->len))
         {
-            detail::view::throw_array_index_out_of_range(idx);
+            detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
         }
         return element(idx);
     }
@@ -385,7 +385,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = lookup(key);
         return r.is_discarded() ? default_value : r.template get<T>();
@@ -395,7 +395,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         // (the default is made only if there is no such member)
         const basic_json_view r = lookup(key);
@@ -410,7 +410,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_structured()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::value);
         return r.is_discarded() ? default_value : r.template get<T>();
@@ -420,7 +420,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_structured()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::value);
         return r.is_discarded() ? string_t(default_value) : r.template get<string_t>();
@@ -433,7 +433,7 @@ class basic_json_view
         const iterator it = begin();
         if (NLOHMANN_VIEW_UNLIKELY(it == end()))
         {
-            detail::view::throw_invalid_iterator(detail::exception_id::iterator_value_unavailable, "cannot get value");
+            detail::view::throw_invalid_iterator(214, "cannot get value");
         }
         return *it;
     }
@@ -586,7 +586,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_string()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be string, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be string, but is ", type_name());
         }
         return {m_doc->str(*m_node), m_node->len};
     }
@@ -598,7 +598,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_number()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be number, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be number, but is ", type_name());
         }
         return {m_doc->str(*m_node), detail::view::number_length(*m_node)};
     }
@@ -855,7 +855,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_boolean()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be boolean, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be boolean, but is ", type_name());
         }
         return (m_node->flags & detail::view::node_flags::is_true) != 0;
     }
@@ -865,7 +865,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(m_node == nullptr))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be number, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be number, but is ", type_name());
         }
         return detail::view::arithmetic_value<T, BasicJsonType>(*m_doc, *m_node);
     }
@@ -874,7 +874,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_null()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be null, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be null, but is ", type_name());
         }
         return nullptr;
     }
@@ -1183,7 +1183,7 @@ class basic_json_document
     {
         if (NLOHMANN_VIEW_UNLIKELY(!m_data || m_data->discarded))
         {
-            detail::view::throw_type_error(detail::exception_id::document_image_unsupported, "cannot save a discarded json_document");
+            detail::view::throw_type_error(320, "cannot save a discarded json_document");
         }
         return detail::view::save_image(*m_data);
     }
@@ -1284,7 +1284,7 @@ class basic_json_document
                 const std::size_t idx = pointer_index(token);
                 if (idx >= 0xFFFFFFFFu)
                 {
-                    detail::view::throw_array_index_out_of_range(idx);
+                    detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
                 }
                 for (std::size_t i = 0; i < idx; ++i)
                 {
@@ -1340,7 +1340,7 @@ class basic_json_document
     {
         if (ptr.empty())
         {
-            detail::view::throw_out_of_range(detail::exception_id::patch_on_root, "JSON pointer has no parent");
+            detail::view::throw_out_of_range(405, "JSON pointer has no parent");
         }
         const view_type parent = root().at(ptr.parent_pointer());
         const auto& token = ptr.back();
@@ -1360,7 +1360,7 @@ class basic_json_document
         static_assert(Editable, "only an editable document can be edited: use basic_json_document<BasicJsonType, true> (json_editable_document)");
         if (NLOHMANN_VIEW_UNLIKELY(!m_data || m_data->discarded))
         {
-            detail::view::throw_invalid_iterator(detail::exception_id::iterator_from_other_value, "view does not belong to this document");
+            detail::view::throw_invalid_iterator(202, "view does not belong to this document");
         }
         return detail::view::editor<BasicJsonType, view_type>(*m_data);
     }
@@ -1377,7 +1377,7 @@ class basic_json_document
     {
         if (idx < 0)
         {
-            detail::view::throw_array_index_out_of_range(idx);
+            detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
         }
         return static_cast<std::size_t>(idx);
     }

include/nlohmann/ordered_map.hpp

@@ -125,19 +125,6 @@ private:
         Container::pop_back();
     }
 
-    /// @brief remove the entry with the given key; returns the number of removed entries
-    template<class K>
-    size_type erase_impl(const K& key)
-    {
-        const auto it = find_impl(*this, key);
-        if (it != this->end())
-        {
-            erase_at(it);
-            return 1;
-        }
-        return 0;
-    }
-
 public:
     template<class V, detail::enable_if_t<
                  detail::is_constructible<T, V>::value, int> = 0>
@@ -227,14 +214,26 @@ public:
 
     size_type erase(const key_type& key)
     {
-        return erase_impl(key);
+        const auto it = find_impl(*this, key);
+        if (it != this->end())
+        {
+            erase_at(it);
+            return 1;
+        }
+        return 0;
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     size_type erase(KeyType && key) // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        return erase_impl(key);
+        const auto it = find_impl(*this, key);
+        if (it != this->end())
+        {
+            erase_at(it);
+            return 1;
+        }
+        return 0;
     }
 
     iterator erase(iterator pos)

single_include/nlohmann/json_view.hpp

@@ -2819,52 +2819,32 @@ namespace view
 // Exceptions are thrown out of line, so that the accessors that may throw stay
 // small enough to be inlined.
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(exception_id id, const char* prefix, const char* type)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(int id, const char* prefix, const char* type)
 {
     NLOHMANN_VIEW_THROW(type_error::create(id, concat(prefix, type), nullptr));
 }
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(exception_id id, const std::string& msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(int id, const std::string& msg)
 {
     NLOHMANN_VIEW_THROW(type_error::create(id, msg, nullptr));
 }
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_out_of_range(exception_id id, const std::string& msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_out_of_range(int id, const std::string& msg)
 {
     NLOHMANN_VIEW_THROW(out_of_range::create(id, msg, nullptr));
 }
 
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_iterator(exception_id id, const char* msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_iterator(int id, const char* msg)
 {
     NLOHMANN_VIEW_THROW(invalid_iterator::create(id, msg, nullptr));
 }
 
 /// a parse error without a position (as those of json_pointer)
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_parse_error(exception_id id, const std::string& msg)
+[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_parse_error(int id, const std::string& msg)
 {
     NLOHMANN_VIEW_THROW(parse_error::create(id, 0, msg, nullptr));
 }
 
-/// out_of_range.401: the array index @a idx is not below the size
-template<typename Index>
-[[noreturn]] NLOHMANN_VIEW_NOINLINE void throw_array_index_out_of_range(const Index idx)
-{
-    throw_out_of_range(exception_id::array_index_out_of_range, concat("array index ", std::to_string(idx), " is out of range"));
-}
-
-/// out_of_range.402: the JSON Pointer token '-' of an array of @a size elements
-[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_array_index_past_end(std::size_t size)
-{
-    throw_out_of_range(exception_id::pointer_past_the_end_index, concat("array index '-' (", std::to_string(size), ") is out of range"));
-}
-
-/// out_of_range.403: the object has no member @a key
-template<typename Key>
-[[noreturn]] NLOHMANN_VIEW_NOINLINE void throw_key_not_found(const Key& key)
-{
-    throw_out_of_range(exception_id::key_not_found, concat("key '", key, "' not found"));
-}
-
 /// SAX handler of the error replay: accepts every event without storing it,
 /// and throws the exception the parser reports
 template<typename BasicJsonType>
@@ -2963,7 +2943,7 @@ template<typename BasicJsonType>
     if (f.code == error_code::input_too_large)
     {
         // (the limit is detail::view::max_input_size(): 4 GiB minus 16 bytes)
-        NLOHMANN_VIEW_THROW(out_of_range::create(exception_id::document_too_large, "input of 4294967280 bytes or more is not supported by json_document", nullptr));
+        NLOHMANN_VIEW_THROW(out_of_range::create(416, "input of 4294967280 bytes or more is not supported by json_document", nullptr));
     }
     throwing_sax<BasicJsonType> sax;
     const bool accepted = BasicJsonType::sax_parse(src, src + size, &sax, input_format_t::json, true, ignore_comments, ignore_trailing_commas);
@@ -2983,7 +2963,7 @@ template<typename BasicJsonType>
         }
     }
     pos.chars_read_current_line = off + 1 - line_start;
-    NLOHMANN_VIEW_THROW(parse_error::create(exception_id::syntax_error, pos, "syntax error while parsing value", nullptr));
+    NLOHMANN_VIEW_THROW(parse_error::create(101, pos, "syntax error while parsing value", nullptr));
     // LCOV_EXCL_STOP
 }
 
@@ -3058,7 +3038,7 @@ inline std::size_t text_capacity(std::size_t cap, std::size_t used, std::size_t
     constexpr std::size_t limit = 0xFFFFFFFFu;
     if (NLOHMANN_VIEW_UNLIKELY(used > limit || n > limit - used))
     {
-        throw_out_of_range(exception_id::document_too_large, "edits of 4 GiB or more are not supported by json_document");
+        throw_out_of_range(416, "edits of 4 GiB or more are not supported by json_document");
     }
     const std::size_t needed = used + n;
     const std::size_t wanted = needed + (std::min)(limit - needed, std::size_t{256});
@@ -3109,7 +3089,7 @@ inline void reserve_moved(document_data& d)
     document_data::edit_state& e = edit_state_of(d);
     if (e.moved.size() >= 0xFFFFFFFFu)
     {
-        throw_out_of_range(exception_id::document_too_large, "more than 4294967295 edited arrays and objects are not supported by json_document"); // LCOV_EXCL_LINE
+        throw_out_of_range(416, "more than 4294967295 edited arrays and objects are not supported by json_document"); // LCOV_EXCL_LINE
     }
     if (e.moved.size() == e.moved.capacity() || e.moved_cap.size() == e.moved_cap.capacity())
     {
@@ -3739,6 +3719,11 @@ struct first_true<false, Conditions...> : std::integral_constant < int, 1 + firs
 inline void check_utf8(const char* s, std::size_t n)
 {
     const auto* const p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    const auto hex = [](unsigned char c)
+    {
+        constexpr const char* digits = "0123456789ABCDEF";
+        return std::string{digits[c >> 4u], digits[c & 0xFu]};
+    };
     for (std::size_t i = 0; i < n;)
     {
         const unsigned char c = p[i];
@@ -3747,22 +3732,39 @@ inline void check_utf8(const char* s, std::size_t n)
             ++i;
             continue;
         }
-        const utf8_sequence_shape shape = utf8_shape(c);
-        const std::size_t len = shape.length;
-        if (len == 0)
+        std::size_t len = 0;
+        unsigned char lo = 0x80;
+        unsigned char hi = 0xBF;
+        if (c >= 0xC2 && c <= 0xDF)
         {
-            throw_type_error(exception_id::invalid_utf8, concat("invalid UTF-8 byte at index ", std::to_string(i), ": 0x", hex_byte(c)));
+            len = 2;
+        }
+        else if (c >= 0xE0 && c <= 0xEF)
+        {
+            len = 3;
+            lo = c == 0xE0 ? 0xA0 : 0x80;
+            hi = c == 0xED ? 0x9F : 0xBF;
+        }
+        else if (c >= 0xF0 && c <= 0xF4)
+        {
+            len = 4;
+            lo = c == 0xF0 ? 0x90 : 0x80;
+            hi = c == 0xF4 ? 0x8F : 0xBF;
+        }
+        else
+        {
+            throw_type_error(316, concat("invalid UTF-8 byte at index ", std::to_string(i), ": 0x", hex(c)));
         }
         for (std::size_t k = 1; k < len; ++k)
         {
             if (i + k == n)
             {
-                throw_type_error(exception_id::invalid_utf8, concat("incomplete UTF-8 string; last byte: 0x", hex_byte(p[n - 1])));
+                throw_type_error(316, concat("incomplete UTF-8 string; last byte: 0x", hex(p[n - 1])));
             }
             const unsigned char b = p[i + k];
-            if (b < (k == 1 ? shape.second_lo : 0x80) || b > (k == 1 ? shape.second_hi : 0xBF))
+            if (b < (k == 1 ? lo : 0x80) || b > (k == 1 ? hi : 0xBF))
             {
-                throw_type_error(exception_id::invalid_utf8, concat("invalid UTF-8 byte at index ", std::to_string(i + k), ": 0x", hex_byte(b)));
+                throw_type_error(316, concat("invalid UTF-8 byte at index ", std::to_string(i + k), ": 0x", hex(b)));
             }
         }
         i += len;
@@ -3810,7 +3812,7 @@ class editor
         node* const o = own(object);
         if (o->kind != static_cast<std::uint8_t>(value_t::object) && o->kind != static_cast<std::uint8_t>(value_t::null))
         {
-            throw_type_error(exception_id::subscript_wrong_type, "cannot use operator[] with a string argument with ", object.type_name());
+            throw_type_error(305, "cannot use operator[] with a string argument with ", object.type_name());
         }
         check_utf8(key.data(), key.size());
         const encoded e = encode(std::forward<V>(value));
@@ -3861,7 +3863,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array))
         {
-            throw_type_error(exception_id::subscript_wrong_type, "cannot use operator[] with a numeric argument with ", array.type_name());
+            throw_type_error(305, "cannot use operator[] with a numeric argument with ", array.type_name());
         }
         check_index(idx, a->len);
         const encoded e = encode(std::forward<V>(value));
@@ -3878,7 +3880,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array) && a->kind != static_cast<std::uint8_t>(value_t::null))
         {
-            throw_type_error(exception_id::push_back_wrong_type, "cannot use push_back() with ", array.type_name());
+            throw_type_error(308, "cannot use push_back() with ", array.type_name());
         }
         const encoded e = encode(std::forward<V>(value));
         if (a->kind == static_cast<std::uint8_t>(value_t::null))
@@ -3902,7 +3904,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array))
         {
-            throw_type_error(exception_id::insert_wrong_type, "cannot use insert() with ", array.type_name());
+            throw_type_error(309, "cannot use insert() with ", array.type_name());
         }
         check_index(idx, a->len + 1);
         const encoded e = encode(std::forward<V>(value));
@@ -3922,7 +3924,7 @@ class editor
         node* const o = own(object);
         if (o->kind != static_cast<std::uint8_t>(value_t::object))
         {
-            throw_type_error(exception_id::erase_wrong_type, "cannot use erase() with ", object.type_name());
+            throw_type_error(307, "cannot use erase() with ", object.type_name());
         }
         for (const node* k = nav::first(m_doc, o), *end = nav::end(m_doc, o); k != end; k = document_data::after(k + 1))
         {
@@ -3940,7 +3942,7 @@ class editor
         node* const a = own(array);
         if (a->kind != static_cast<std::uint8_t>(value_t::array))
         {
-            throw_type_error(exception_id::erase_wrong_type, "cannot use erase() with ", array.type_name());
+            throw_type_error(307, "cannot use erase() with ", array.type_name());
         }
         check_index(idx, a->len);
         node* const h = block_of(m_doc, a, 0);
@@ -3963,7 +3965,7 @@ class editor
     {
         if (NLOHMANN_VIEW_UNLIKELY(v.m_doc != &m_doc || v.m_node == nullptr))
         {
-            throw_invalid_iterator(exception_id::iterator_from_other_value, "view does not belong to this document");
+            throw_invalid_iterator(202, "view does not belong to this document");
         }
         edit_state_of(m_doc);
         return const_cast<node*>(v.m_node); // NOLINT(cppcoreguidelines-pro-type-const-cast): the nodes belong to this document
@@ -3973,7 +3975,7 @@ class editor
     {
         if (idx >= limit)
         {
-            throw_array_index_out_of_range(idx);
+            throw_out_of_range(401, concat("array index ", std::to_string(idx), " is out of range"));
         }
     }
 
@@ -4114,7 +4116,7 @@ class editor
     {
         if (NLOHMANN_VIEW_UNLIKELY(v.m_node == nullptr))
         {
-            throw_type_error(exception_id::type_mismatch, "type must be a value, but is ", "discarded");
+            throw_type_error(302, "type must be a value, but is ", "discarded");
         }
         encoded r;
         if (!is_container(*v.m_node))
@@ -4264,7 +4266,7 @@ class editor
     {
         if (NLOHMANN_VIEW_UNLIKELY(len >= 0xFFFFFFFFu))
         {
-            throw_out_of_range(exception_id::document_too_large, "strings of 4 GiB or more are not supported by json_document"); // LCOV_EXCL_LINE
+            throw_out_of_range(416, "strings of 4 GiB or more are not supported by json_document"); // LCOV_EXCL_LINE
         }
         node n = plain_node(value_t::string);
         n.flags = static_cast<std::uint8_t>(n.flags | node_flags::edited);
@@ -4339,12 +4341,12 @@ class editor
                 return string_node(s.data(), s.size());
             }
             case value_t::binary:
-                throw_type_error(exception_id::document_binary_value, "cannot store a binary value in a json_document", "");
+                throw_type_error(319, "cannot store a binary value in a json_document", "");
             case value_t::discarded:
             case value_t::object:
             case value_t::array:
             default:
-                throw_type_error(exception_id::type_mismatch, "type must be a value, but is ", "discarded");
+                throw_type_error(302, "type must be a value, but is ", "discarded");
         }
     }
 
@@ -4972,7 +4974,7 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
 inline std::vector<std::uint8_t> save_image(const document_data& d)
 {
 #if !NLOHMANN_VIEW_LITTLE_ENDIAN
-    throw_type_error(exception_id::document_image_unsupported, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
+    throw_type_error(320, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
 #endif
     const std::size_t arena_size = d.arena_size;
     std::vector<node> compacted;
@@ -4989,7 +4991,7 @@ inline std::vector<std::uint8_t> save_image(const document_data& d)
     if (NLOHMANN_VIEW_UNLIKELY(text_size >= image_limit || total_arena >= image_limit || count >= image_limit))
     {
         // LCOV_EXCL_START (4 GiB)
-        throw_out_of_range(exception_id::document_too_large, "images of 4 GiB or more are not supported by json_document");
+        throw_out_of_range(416, "images of 4 GiB or more are not supported by json_document");
         // LCOV_EXCL_STOP
     }
     image_header h{};
@@ -5446,7 +5448,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
 
 [[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_image(const char* what)
 {
-    throw_parse_error(exception_id::invalid_document_image, concat("invalid json_document image: ", what));
+    throw_parse_error(116, concat("invalid json_document image: ", what));
 }
 
 /// Read an image into d. The text and the decoded strings stay in the image;
@@ -5454,7 +5456,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
 inline void load_image(document_data& d, const std::uint8_t* image, std::size_t size, image_check check)
 {
 #if !NLOHMANN_VIEW_LITTLE_ENDIAN
-    throw_type_error(exception_id::document_image_unsupported, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
+    throw_type_error(320, "json_document images need a little-endian target"); // LCOV_EXCL_LINE
 #endif
     if (image == nullptr || size < sizeof(image_header))
     {
@@ -5842,7 +5844,7 @@ class view_iterator
     {
         if (NLOHMANN_VIEW_UNLIKELY(m_value_offset == 0))
         {
-            throw_invalid_iterator(exception_id::iterator_key_not_object, "cannot use key() for non-object iterators");
+            throw_invalid_iterator(207, "cannot use key() for non-object iterators");
         }
         return string_view_t(m_doc->str(*m_pos), m_pos->len);
     }
@@ -6150,6 +6152,8 @@ BasicJsonType materialize(const document_data& d, const node* n)
             case value_t::binary:
             case value_t::discarded:
             default:
+                // false positive: the parser's frame stack points into its own storage (never null)
+                // @infer-ignore NULLPTR_DEREFERENCE
                 sax.null();
                 break;
         }
@@ -6234,15 +6238,51 @@ enum class pointer_mode
     contains,  ///< as basic_json::contains(): no exceptions at all
 };
 
-/// the outcome of reading an array index: detail::parse_array_index(), shared with json_pointer
-using index_status = detail::array_index_status;
+/// the outcome of reading an array index from a reference token
+enum class index_status
+{
+    ok,
+    leading_zero, ///< parse_error.106
+    not_number,   ///< parse_error.109
+    unresolved,   ///< out_of_range.404
+    too_large,    ///< out_of_range.410
+};
 
 /// reads an array index like json_pointer::array_index (RFC 6901, Sect. 4),
 /// but reports errors instead of throwing them
 template<typename StringType>
 index_status array_index(const StringType& s, std::size_t& idx) noexcept
 {
-    return detail::parse_array_index(s, idx);
+    // as basic_json: the empty token and "-" (past the last element) are
+    // unresolved rather than not a number
+    if (s.empty() || (s.size() == 1 && s[0] == '-'))
+    {
+        return index_status::unresolved;
+    }
+    if (s[0] < '0' || s[0] > '9')
+    {
+        return index_status::not_number;
+    }
+    if (s.size() > 1 && s[0] == '0')
+    {
+        return index_status::leading_zero;
+    }
+    std::uint64_t v = 0;
+    for (const auto c : s)
+    {
+        const auto d = static_cast<unsigned>(static_cast<unsigned char>(c)) - '0';
+        if (d > 9 || v > ((std::numeric_limits<std::uint64_t>::max)() - d) / 10)
+        {
+            return index_status::unresolved; // not a number, or beyond unsigned long long
+        }
+        v = (v * 10) + d;
+    }
+    if (v >= (std::numeric_limits<std::size_t>::max)()) // (std::size_t converts to std::uint64_t implicitly)
+    {
+        return index_status::too_large;
+    }
+    idx = static_cast<std::size_t>(v);
+    return index_status::ok;
 }
 
 /// throws the exception json_pointer::array_index throws for this status
@@ -6252,15 +6292,15 @@ template<typename StringType>
     switch (status)
     {
         case index_status::leading_zero:
-            throw_parse_error(exception_id::pointer_index_leading_zero, concat("array index '", s, "' must not begin with '0'"));
-        case index_status::not_a_number:
-            throw_parse_error(exception_id::pointer_index_not_a_number, concat("array index '", s, "' is not a number"));
-        case index_status::exceeds_size_type:
-            throw_out_of_range(exception_id::value_out_of_range, concat("array index ", s, " exceeds size_type")); // LCOV_EXCL_LINE
+            throw_parse_error(106, concat("array index '", s, "' must not begin with '0'"));
+        case index_status::not_number:
+            throw_parse_error(109, concat("array index '", s, "' is not a number"));
+        case index_status::too_large:
+            throw_out_of_range(410, concat("array index ", s, " exceeds size_type")); // LCOV_EXCL_LINE
         case index_status::unresolved:
         case index_status::ok:
         default:
-            throw_out_of_range(exception_id::pointer_unresolved, concat("unresolved reference token '", s, "'"));
+            throw_out_of_range(404, concat("unresolved reference token '", s, "'"));
     }
 }
 
@@ -6285,7 +6325,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             {
                 if (mode == pointer_mode::checked)
                 {
-                    throw_key_not_found(token);
+                    throw_out_of_range(403, concat("key '", token, "' not found"));
                 }
                 return View();
             }
@@ -6297,7 +6337,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             {
                 if (throwing)
                 {
-                    throw_array_index_past_end(cur.size());
+                    throw_out_of_range(402, concat("array index '-' (", std::to_string(cur.size()), ") is out of range"));
                 }
                 return View();
             }
@@ -6305,7 +6345,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             const index_status status = array_index(token, idx);
             if (status != index_status::ok)
             {
-                const bool parse_error = status == index_status::leading_zero || status == index_status::not_a_number;
+                const bool parse_error = status == index_status::leading_zero || status == index_status::not_number;
                 if (throwing || (mode == pointer_mode::value && parse_error))
                 {
                     throw_array_index_error(status, token);
@@ -6316,7 +6356,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
             {
                 if (mode == pointer_mode::checked)
                 {
-                    throw_array_index_out_of_range(idx);
+                    throw_out_of_range(401, concat("array index ", std::to_string(idx), " is out of range"));
                 }
                 return View();
             }
@@ -6326,7 +6366,7 @@ View resolve_pointer(View cur, const Tokens& tokens, pointer_mode mode)
         {
             if (throwing)
             {
-                throw_out_of_range(exception_id::pointer_unresolved, concat("unresolved reference token '", token, "'"));
+                throw_out_of_range(404, concat("unresolved reference token '", token, "'"));
             }
             return View();
         }
@@ -7419,17 +7459,21 @@ class view_serializer
             m_out.put("null");
             return;
         }
-        write_float(x, std::integral_constant<bool, ::nlohmann::detail::has_native_float_format<number_float_t>::value>());
+        static constexpr bool is_ieee_single_or_double
+            = std::numeric_limits<number_float_t>::is_iec559
+              && ((std::numeric_limits<number_float_t>::digits == 24 && std::numeric_limits<number_float_t>::max_exponent == 128)
+                  || (std::numeric_limits<number_float_t>::digits == 53 && std::numeric_limits<number_float_t>::max_exponent == 1024));
+        write_float(x, std::integral_constant<bool, is_ieee_single_or_double>());
     }
 
-    void write_float(number_float_t x, std::true_type /*has_native_float_format*/)
+    void write_float(number_float_t x, std::true_type /*is_ieee_single_or_double*/)
     {
         std::array<char, 64> buf{};
         const char* const end = ::nlohmann::detail::to_chars(buf.data(), buf.data() + buf.size(), x);
         m_out.put(buf.data(), static_cast<std::size_t>(end - buf.data()));
     }
 
-    void write_float(number_float_t x, std::false_type /*has_native_float_format*/)
+    void write_float(number_float_t x, std::false_type /*is_ieee_single_or_double*/)
     {
         // other types (e.g. long double) are rare: the library writes them
         const string_t s = BasicJsonType(x).dump();
@@ -7490,8 +7534,8 @@ class view_serializer
 
     void write_u_escape(std::uint32_t u)
     {
-        std::array<char, 6> e = {{'\\', 'u', 0, 0, 0, 0}};
-        hex4_lower(static_cast<std::uint16_t>(u), &e[2]);
+        static constexpr const char* hex = "0123456789abcdef";
+        const std::array<char, 6> e = {{'\\', 'u', hex[(u >> 12u) & 0xFu], hex[(u >> 8u) & 0xFu], hex[(u >> 4u) & 0xFu], hex[u & 0xFu]}};
         m_out.put(e.data(), e.size());
     }
 
@@ -7688,7 +7732,7 @@ NLOHMANN_VIEW_ALWAYS_INLINE T arithmetic_value(const document_data& d, const nod
         case value_t::binary:
         case value_t::discarded:
         default:
-            throw_type_error(exception_id::type_mismatch, "type must be number, but is ", value_type_name(static_cast<value_t>(n.kind)));
+            throw_type_error(302, "type must be number, but is ", value_type_name(static_cast<value_t>(n.kind)));
     }
 }
 
@@ -7698,7 +7742,7 @@ std::vector<U, A> vector_value(const View& v)
 {
     if (NLOHMANN_VIEW_UNLIKELY(!v.is_array()))
     {
-        throw_type_error(exception_id::type_mismatch, "type must be array, but is ", v.type_name());
+        throw_type_error(302, "type must be array, but is ", v.type_name());
     }
     std::vector<U, A> r;
     r.reserve(v.size());
@@ -7716,7 +7760,7 @@ Map map_value(const View& v)
 {
     if (NLOHMANN_VIEW_UNLIKELY(!v.is_object()))
     {
-        throw_type_error(exception_id::type_mismatch, "type must be object, but is ", v.type_name());
+        throw_type_error(302, "type must be object, but is ", v.type_name());
     }
     Map r;
     for (auto it = v.begin(); it != v.end(); ++it)
@@ -7955,7 +7999,7 @@ class basic_json_view
             {
                 return {};
             }
-            detail::view::throw_type_error(detail::exception_id::subscript_wrong_type, "cannot use operator[] with a string argument with ", type_name());
+            detail::view::throw_type_error(305, "cannot use operator[] with a string argument with ", type_name());
         }
         return lookup(key);
     }
@@ -7981,7 +8025,7 @@ class basic_json_view
             {
                 return {};
             }
-            detail::view::throw_type_error(detail::exception_id::subscript_wrong_type, "cannot use operator[] with a numeric argument with ", type_name());
+            detail::view::throw_type_error(305, "cannot use operator[] with a numeric argument with ", type_name());
         }
         return idx < m_node->len ? element(idx) : basic_json_view();
     }
@@ -8014,12 +8058,12 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
-            detail::view::throw_type_error(detail::exception_id::at_wrong_type, "cannot use at() with ", type_name());
+            detail::view::throw_type_error(304, "cannot use at() with ", type_name());
         }
         const basic_json_view r = lookup(key);
         if (NLOHMANN_VIEW_UNLIKELY(r.is_discarded()))
         {
-            detail::view::throw_key_not_found(std::string(key.data(), key.size()));
+            detail::view::throw_out_of_range(403, detail::concat("key '", std::string(key.data(), key.size()), "' not found"));
         }
         return r;
     }
@@ -8040,11 +8084,11 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_array()))
         {
-            detail::view::throw_type_error(detail::exception_id::at_wrong_type, "cannot use at() with ", type_name());
+            detail::view::throw_type_error(304, "cannot use at() with ", type_name());
         }
         if (NLOHMANN_VIEW_UNLIKELY(idx >= m_node->len))
         {
-            detail::view::throw_array_index_out_of_range(idx);
+            detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
         }
         return element(idx);
     }
@@ -8072,7 +8116,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = lookup(key);
         return r.is_discarded() ? default_value : r.template get<T>();
@@ -8082,7 +8126,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         // (the default is made only if there is no such member)
         const basic_json_view r = lookup(key);
@@ -8097,7 +8141,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_structured()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::value);
         return r.is_discarded() ? default_value : r.template get<T>();
@@ -8107,7 +8151,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_structured()))
         {
-            detail::view::throw_type_error(detail::exception_id::value_wrong_type, "cannot use value() with ", type_name());
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::value);
         return r.is_discarded() ? string_t(default_value) : r.template get<string_t>();
@@ -8120,7 +8164,7 @@ class basic_json_view
         const iterator it = begin();
         if (NLOHMANN_VIEW_UNLIKELY(it == end()))
         {
-            detail::view::throw_invalid_iterator(detail::exception_id::iterator_value_unavailable, "cannot get value");
+            detail::view::throw_invalid_iterator(214, "cannot get value");
         }
         return *it;
     }
@@ -8273,7 +8317,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_string()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be string, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be string, but is ", type_name());
         }
         return {m_doc->str(*m_node), m_node->len};
     }
@@ -8285,7 +8329,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_number()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be number, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be number, but is ", type_name());
         }
         return {m_doc->str(*m_node), detail::view::number_length(*m_node)};
     }
@@ -8542,7 +8586,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_boolean()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be boolean, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be boolean, but is ", type_name());
         }
         return (m_node->flags & detail::view::node_flags::is_true) != 0;
     }
@@ -8552,7 +8596,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(m_node == nullptr))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be number, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be number, but is ", type_name());
         }
         return detail::view::arithmetic_value<T, BasicJsonType>(*m_doc, *m_node);
     }
@@ -8561,7 +8605,7 @@ class basic_json_view
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_null()))
         {
-            detail::view::throw_type_error(detail::exception_id::type_mismatch, "type must be null, but is ", type_name());
+            detail::view::throw_type_error(302, "type must be null, but is ", type_name());
         }
         return nullptr;
     }
@@ -8870,7 +8914,7 @@ class basic_json_document
     {
         if (NLOHMANN_VIEW_UNLIKELY(!m_data || m_data->discarded))
         {
-            detail::view::throw_type_error(detail::exception_id::document_image_unsupported, "cannot save a discarded json_document");
+            detail::view::throw_type_error(320, "cannot save a discarded json_document");
         }
         return detail::view::save_image(*m_data);
     }
@@ -8971,7 +9015,7 @@ class basic_json_document
                 const std::size_t idx = pointer_index(token);
                 if (idx >= 0xFFFFFFFFu)
                 {
-                    detail::view::throw_array_index_out_of_range(idx);
+                    detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
                 }
                 for (std::size_t i = 0; i < idx; ++i)
                 {
@@ -9027,7 +9071,7 @@ class basic_json_document
     {
         if (ptr.empty())
         {
-            detail::view::throw_out_of_range(detail::exception_id::patch_on_root, "JSON pointer has no parent");
+            detail::view::throw_out_of_range(405, "JSON pointer has no parent");
         }
         const view_type parent = root().at(ptr.parent_pointer());
         const auto& token = ptr.back();
@@ -9047,7 +9091,7 @@ class basic_json_document
         static_assert(Editable, "only an editable document can be edited: use basic_json_document<BasicJsonType, true> (json_editable_document)");
         if (NLOHMANN_VIEW_UNLIKELY(!m_data || m_data->discarded))
         {
-            detail::view::throw_invalid_iterator(detail::exception_id::iterator_from_other_value, "view does not belong to this document");
+            detail::view::throw_invalid_iterator(202, "view does not belong to this document");
         }
         return detail::view::editor<BasicJsonType, view_type>(*m_data);
     }
@@ -9064,7 +9108,7 @@ class basic_json_document
     {
         if (idx < 0)
         {
-            detail::view::throw_array_index_out_of_range(idx);
+            detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
         }
         return static_cast<std::size_t>(idx);
     }

tests/src/unit-class_lexer.cpp

@@ -2042,118 +2042,3 @@ TEST_CASE("string scanning kernels")
     CHECK(nlohmann::detail::read_eight_bytes(bytes.data() + 8) == 0xFF0F0E0D0C0B0A09u);
     CHECK(nlohmann::detail::read_eight_bytes(reinterpret_cast<const char*>(bytes.data()) + 3) == 0x0B0A090807060504u);
 }
-
-TEST_CASE("find_ascii_copyable_run agrees with is_ascii_copyable for every byte")
-{
-    // the SWAR mask in find_ascii_copyable_run() encodes the predicate a
-    // second time; check every byte value at every position of a 24-byte buffer
-    // (three words) and for several lengths, with the byte at the end or inside
-    for (unsigned int value = 0; value < 256; ++value)
-    {
-        for (std::size_t position = 0; position < 24; ++position)
-        {
-            std::array<unsigned char, 24> buffer{};
-            buffer.fill(static_cast<unsigned char>('a'));
-            buffer[position] = static_cast<unsigned char>(value);
-            const bool copyable = nlohmann::detail::is_ascii_copyable(static_cast<unsigned char>(value));
-            for (const std::size_t n :
-                    {
-                        position, position + 1, std::size_t{24}
-                    })
-            {
-                if (n > 24)
-                {
-                    continue;
-                }
-                const std::size_t expected = (copyable || n <= position) ? n : position;
-                CAPTURE(value)
-                CAPTURE(position)
-                CAPTURE(n)
-                CHECK(nlohmann::detail::find_ascii_copyable_run(buffer.data(), n) == expected);
-            }
-        }
-    }
-}
-
-TEST_CASE("UTF-8 validators accept the same sequences")
-{
-    // The library checks UTF-8 in several places: detail::decode (serializer),
-    // the per-lead-byte switch of the lexer (json::accept), validate_one_utf8
-    // (bulk string scan), utf8_shape, and the byte path of the BON8 reader.
-    // They must accept exactly the same sequences (RFC 3629, section 4).
-    using nlohmann::json;
-
-    // bytes for the third and fourth position: the first two pairs are checked
-    // against all validators, the others only against the cheap ones
-    const std::array<std::array<unsigned char, 2>, 6> tails =
-    {
-        {
-            {{0x80, 0x80}}, {{0xBF, 0xBF}}, {{0x7F, 0x80}}, {{0xC0, 0x80}}, {{0x80, 0x7F}}, {{0x80, 0xC0}}
-        }
-    };
-
-    for (unsigned lead = 0x80; lead <= 0xFF; ++lead)
-    {
-        const auto shape = nlohmann::detail::utf8_shape(static_cast<std::uint8_t>(lead));
-        for (unsigned second = 0; second <= 0xFF; ++second)
-        {
-            for (std::size_t t = 0; t < tails.size(); ++t)
-            {
-                const std::array<unsigned char, 4> bytes = {{static_cast<unsigned char>(lead), static_cast<unsigned char>(second), tails[t][0], tails[t][1]}};
-
-                // expectation from the shape: the sequence is bytes[0..length)
-                const std::size_t length = shape.length;
-                bool expected = length >= 2 && second >= shape.second_lo && second <= shape.second_hi;
-                for (std::size_t i = 2; expected && i < length; ++i)
-                {
-                    expected = bytes[i] >= 0x80 && bytes[i] <= 0xBF;
-                }
-
-                // the DFA of the serializer
-                bool dfa = length >= 2;
-                if (dfa)
-                {
-                    std::uint8_t state = nlohmann::detail::UTF8_ACCEPT;
-                    std::uint32_t codep = 0;
-                    for (std::size_t i = 0; i < length; ++i)
-                    {
-                        nlohmann::detail::decode(state, codep, bytes[i]);
-                    }
-                    dfa = state == nlohmann::detail::UTF8_ACCEPT;
-                }
-
-                // the bulk path: exactly the sequence, and one byte short
-                const std::size_t bulk = nlohmann::detail::validate_one_utf8(bytes.data(), length);
-                const std::size_t bulk_short = length > 0 ? nlohmann::detail::validate_one_utf8(bytes.data(), length - 1) : 0;
-
-                CAPTURE(lead)
-                CAPTURE(second)
-                CAPTURE(t)
-                CHECK((dfa == expected && bulk == (expected ? length : 0) && bulk_short == 0));
-
-                if (t < 2 && length >= 2)
-                {
-                    // the lexer's byte path
-                    const std::string sequence(reinterpret_cast<const char*>(bytes.data()), length); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-                    CHECK(json::accept("\"" + sequence + "\"") == expected);
-
-                    // the byte path of the BON8 reader (a string ends at 0xFF)
-                    if (lead >= 0xC2 && lead <= 0xF7)
-                    {
-                        std::vector<std::uint8_t> packed(bytes.begin(), bytes.begin() + static_cast<std::ptrdiff_t>(length));
-                        packed.push_back(0xFF);
-                        const json j = json::from_bon8(packed, true, false);
-                        if (expected)
-                        {
-                            CHECK(j == json(sequence));
-                        }
-                        else
-                        {
-                            CHECK_FALSE((j.is_string() && j.get<std::string>() == sequence));
-                        }
-                    }
-                }
-            }
-        }
-    }
-}

tests/src/unit-constructor1.cpp

@@ -361,40 +361,6 @@ TEST_CASE("constructors")
             CHECK_THROWS_WITH_AS((j.get<std::pair<int, int>>()), "[json.exception.out_of_range.401] array index 1 is out of range", json::out_of_range&);
             CHECK_THROWS_WITH_AS((j.get<std::tuple<int, int>>()), "[json.exception.out_of_range.401] array index 1 is out of range", json::out_of_range&);
             CHECK_THROWS_WITH_AS((j.get<std::array<int, 3>>()), "[json.exception.out_of_range.401] array index 1 is out of range", json::out_of_range&);
-#if JSON_DIAGNOSTICS
-            // the exception names the element that has the wrong type
-            CHECK_THROWS_WITH_AS((j.get<std::array<std::string, 3>>()), "[json.exception.type_error.302] (/0) type must be string, but is number", json::type_error&);
-#else
-            CHECK_THROWS_WITH_AS((j.get<std::array<std::string, 3>>()), "[json.exception.type_error.302] type must be string, but is number", json::type_error&);
-#endif
-
-            // the elements are converted in order, so a type error comes before a missing element
-            json const j2{1, "two"};
-            std::array<int, 3> a{{0, 0, 0}};
-#if JSON_DIAGNOSTICS
-            CHECK_THROWS_WITH_AS((j2.get<std::array<int, 3>>()), "[json.exception.type_error.302] (/1) type must be number, but is string", json::type_error&);
-            CHECK_THROWS_WITH_AS(j2.get_to(a), "[json.exception.type_error.302] (/1) type must be number, but is string", json::type_error&);
-#else
-            CHECK_THROWS_WITH_AS((j2.get<std::array<int, 3>>()), "[json.exception.type_error.302] type must be number, but is string", json::type_error&);
-            CHECK_THROWS_WITH_AS(j2.get_to(a), "[json.exception.type_error.302] type must be number, but is string", json::type_error&);
-#endif
-            CHECK_THROWS_WITH_AS(j.get_to(a), "[json.exception.out_of_range.401] array index 1 is out of range", json::out_of_range&);
-#if !defined(JSON_NOEXCEPTION) // without exceptions, the get_to calls in CHECK_THROWS_WITH_AS do not run
-            CHECK(a[0] == 1);
-#endif
-
-            json const j3{"one", "two"};
-            CHECK_THROWS_WITH_AS((j3.get<std::array<std::string, 3>>()), "[json.exception.out_of_range.401] array index 2 is out of range", json::out_of_range&);
-        }
-
-        SECTION("std::array from a longer array or from booleans")
-        {
-            json const j{1, 2.5, true, 4u};
-            CHECK(j.get<std::array<int, 3>>() == (std::array<int, 3> {{1, 2, 1}}));
-            std::array<int, 4> a{{0, 0, 0, 0}};
-            j.get_to(a);
-            CHECK(a == (std::array<int, 4> {{1, 2, 1, 4}}));
-            CHECK(j.get<std::array<int, 0>>().empty());
         }
 
         SECTION("std::forward_list<json>")