Update cppcheck to 1.5.2 (Cppcheck 2.20) and fix its new findings

Cppcheck 2.20 rejects invocations of unknown function-like macros in #if
conditions instead of evaluating them as 0. default_defines.hpp expands
the Hedley macros to the compiler's feature-test operators (__has_attribute
etc.), so define them as 0 in a generated include file.

It also reports a false bufferAccessOutOfBounds in the float overload of
float_from_bits, sizing the parameter as the double overload's; use the
size of the source instead (equal by the static_assert).

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

cmake/ci.cmake

@@ -485,6 +485,13 @@ add_custom_target(ci_clang_analyze
 # Check code with Cppcheck.
 ###############################################################################
 
+# default_defines.hpp expands the Hedley macros to the compiler's feature-test operators, which Cppcheck does not know.
+# Since Cppcheck 2.20, it rejects their invocations in #if conditions instead of evaluating them as 0.
+file(WRITE ${CMAKE_BINARY_DIR}/cppcheck_feature_tests.hpp "")
+foreach(OPERATOR __has_attribute __has_builtin __has_cpp_attribute __has_declspec_attribute __has_extension __has_feature __has_include __has_warning)
+    file(APPEND ${CMAKE_BINARY_DIR}/cppcheck_feature_tests.hpp "#define ${OPERATOR}(x) 0\n")
+endforeach()
+
 add_custom_target(ci_cppcheck
     COMMAND mkdir -p cppcheck
     COMMAND clang -dM -E -x c++ -std=c++11 ${CMAKE_SOURCE_DIR}/include/nlohmann/thirdparty/hedley/hedley.hpp > default_defines.hpp 2> /dev/null
@@ -493,7 +500,7 @@ add_custom_target(ci_cppcheck
     COMMAND venv_cppcheck/bin/cppcheck --enable=warning --check-level=exhaustive --inline-suppr --inconclusive --force
             --std=c++11 ${PROJECT_SOURCE_DIR}/include/nlohmann/json.hpp -I ${CMAKE_SOURCE_DIR}/include
             --error-exitcode=1 --relative-paths=${PROJECT_SOURCE_DIR} -j ${N} --include=default_defines.hpp
-            --cppcheck-build-dir=cppcheck
+            --include=${CMAKE_BINARY_DIR}/cppcheck_feature_tests.hpp --cppcheck-build-dir=cppcheck
             -UJSON_CATCH_USER -UJSON_TRY_USER -UJSON_ASSERT -UJSON_INTERNAL_CATCH -UJSON_THROW
             -DJSON_HAS_CPP_11 -UJSON_HAS_CPP_14 -UJSON_HAS_CPP_17 -UJSON_HAS_CPP_20 -UJSON_HAS_THREE_WAY_COMPARISON
     COMMENT "Check code with Cppcheck"

cmake/requirements/requirements-cppcheck.txt

@@ -1 +1 @@
-cppcheck==1.5.1
+cppcheck==1.5.2

docs/mkdocs/docs/api/basic_json/array_t.md

@@ -27,7 +27,7 @@ To store objects in C++, a type is defined by the template parameters explained
 
 ### Default type
 
-With the default values for `ArrayType` (`std::vector`) and `AllocatorType` (`std::allocator`), the default type for
+With the default values for `ArrayType` (`std::vector`) and `AllocatorType` (`std::allocator`), the default value for
 `array_t` is:
 
 ```cpp

docs/mkdocs/docs/api/basic_json/boolean_t.md

@@ -23,7 +23,7 @@ To store boolean values in C++, a type is defined by the template parameter  `Bo
 
 ### Default type
 
-With the default values for `BooleanType` (`#!cpp bool`), the default type for `boolean_t` is `#!cpp bool`.
+With the default values for `BooleanType` (`#!cpp bool`), the default value for `boolean_t` is `#!cpp bool`.
 
 ### Storage
 

docs/mkdocs/docs/api/basic_json/number_float_t.md

@@ -35,7 +35,7 @@ type to use.
 
 ### Default type
 
-With the default values for `NumberFloatType` (`double`), the default type for `number_float_t` is `#!cpp double`.
+With the default values for `NumberFloatType` (`double`), the default value for `number_float_t` is `#!cpp double`.
 
 ### Default behavior
 
@@ -52,9 +52,8 @@ With the default values for `NumberFloatType` (`double`), the default type for `
 > interoperability can be achieved by implementations that expect no more precision or range than these provide, in the
 > sense that implementations will approximate JSON numbers within the expected precision.
 
-This implementation does exactly follow this approach, as it uses double precision floating-point numbers by default.
-Note that with the default `double`, numbers smaller than `-1.79769313486232e+308` or greater than
-`1.79769313486232e+308` are rejected during parsing with
+This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note that
+numbers smaller than `-1.79769313486232e+308` or greater than `1.79769313486232e+308` are rejected during parsing with
 [`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406). Non-finite values (NaN and infinity) can
 only be stored by assigning them directly and are serialized to `null`.
 

docs/mkdocs/docs/api/basic_json/number_integer_t.md

@@ -31,7 +31,7 @@ to use.
 
 ### Default type
 
-With the default values for `NumberIntegerType` (`std::int64_t`), the default type for `number_integer_t` is
+With the default values for `NumberIntegerType` (`std::int64_t`), the default value for `number_integer_t` is
 `#!cpp std::int64_t`.
 
 ### Default behavior

docs/mkdocs/docs/api/basic_json/number_unsigned_t.md

@@ -32,7 +32,7 @@ the type to use.
 
 ### Default type
 
-With the default values for `NumberUnsignedType` (`std::uint64_t`), the default type for `number_unsigned_t` is
+With the default values for `NumberUnsignedType` (`std::uint64_t`), the default value for `number_unsigned_t` is
 `#!cpp std::uint64_t`.
 
 ### Default behavior

docs/mkdocs/docs/api/basic_json/object_t.md

@@ -36,7 +36,7 @@ To store objects in C++, a type is defined by the template parameters described
 ### Default type
 
 With the default values for `ObjectType` (`std::map`), `StringType` (`std::string`), and `AllocatorType`
-(`std::allocator`), the default type for `object_t` is:
+(`std::allocator`), the default value for `object_t` is:
 
 ```cpp
 // until C++14

docs/mkdocs/docs/api/basic_json/string_t.md

@@ -32,7 +32,7 @@ JSON class into byte-sized characters during deserialization.
 
 ### Default type
 
-With the default values for `StringType` (`std::string`), the default type for `string_t` is `#!cpp std::string`.
+With the default values for `StringType` (`std::string`), the default value for `string_t` is `#!cpp std::string`.
 
 ### Encoding
 

docs/mkdocs/docs/features/types/index.md

@@ -120,7 +120,7 @@ requirements are collected in [Template Parameter Requirements](template_paramet
 
 ### Default type
 
-With the default values for *ObjectType* (`std::map`), *StringType* (`std::string`), and *AllocatorType* (`std::allocator`), the default type for `object_t` is:
+With the default values for *ObjectType* (`std::map`), *StringType* (`std::string`), and *AllocatorType* (`std::allocator`), the default value for `object_t` is:
 
 ```cpp
 std::map<
@@ -177,7 +177,7 @@ json j = m;
 
 ### Default type
 
-With the default values for *ArrayType* (`std::vector`) and *AllocatorType* (`std::allocator`), the default type for `array_t` is:
+With the default values for *ArrayType* (`std::vector`) and *AllocatorType* (`std::allocator`), the default value for `array_t` is:
 
 ```cpp
 std::vector<
@@ -209,7 +209,7 @@ Unicode values are split by the JSON class into byte-sized characters during des
 
 ### Default type
 
-With the default values for *StringType* (`std::string`), the default type for `string_t` is `#!cpp std::string`.
+With the default values for *StringType* (`std::string`), the default value for `string_t` is `#!cpp std::string`.
 
 ### Encoding
 
@@ -234,7 +234,7 @@ String values are stored as pointers in a `basic_json` type. That is, for any ac
 
 ### Default type
 
-With the default values for *BooleanType* (`#!cpp bool`), the default type for `boolean_t` is `#!cpp bool`.
+With the default values for *BooleanType* (`#!cpp bool`), the default value for `boolean_t` is `#!cpp bool`.
 
 ### Storage
 
@@ -252,9 +252,9 @@ This description includes both integer and floating-point numbers. However, C++
 
 ### Default types
 
-With the default values for *NumberIntegerType* (`std::int64_t`), the default type for `number_integer_t` is `std::int64_t`.
-With the default values for *NumberUnsignedType* (`std::uint64_t`), the default type for `number_unsigned_t` is `std::uint64_t`.
-With the default values for *NumberFloatType* (`#!cpp double`), the default type for `number_float_t` is `#!cpp double`.
+With the default values for *NumberIntegerType* (`std::int64_t`), the default value for `number_integer_t` is `std::int64_t`.
+With the default values for *NumberUnsignedType* (`std::uint64_t`), the default value for `number_unsigned_t` is `std::uint64_t`.
+With the default values for *NumberFloatType* (`#!cpp double`), the default value for `number_float_t` is `#!cpp double`.
 
 ### Default behavior
 
@@ -281,7 +281,7 @@ As this range is a subrange of the exactly supported range [`INT64_MIN`, `INT64_
 
 > This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.
 
-This implementation does exactly follow this approach, as it uses double precision floating-point numbers by default (see *NumberFloatType* above). Note that with the default `#!cpp double`, numbers smaller than `#!c -1.79769313486232e+308` or greater than `#!c 1.79769313486232e+308` are rejected during parsing with [`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406). Non-finite values (NaN and infinity) can only be stored by assigning them directly and are serialized to `#!json null`.
+This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note that numbers smaller than `#!c -1.79769313486232e+308` or greater than `#!c 1.79769313486232e+308` are rejected during parsing with [`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406). Non-finite values (NaN and infinity) can only be stored by assigning them directly and are serialized to `#!json null`.
 
 ### Storage
 

include/nlohmann/detail/input/json_sax.hpp

@@ -674,19 +674,16 @@ class json_sax_dom_callback_parser
         if (keep && ref_stack.back())
         {
             auto& obj = *ref_stack.back()->m_data.m_value.object;
-            // a single lookup: insert the placeholder, or find the existing member
-            const auto inserted = obj.emplace(val, discarded);
-            const auto it = inserted.first;
-            if (!inserted.second)
+            const auto it = obj.find(val);
+            if (it != obj.end())
             {
                 // this is a duplicate key (legal in JSON); remember its
                 // current value so it can be restored later if the new
                 // value is rejected by the callback, instead of being
                 // erased together with the discarded placeholder
                 duplicate_key_stash.emplace_back(&(it->second), it->second);
-                it->second = discarded;
             }
-            object_element = &(it->second);
+            object_element = &(obj[val] = discarded);
         }
 
         return true;

include/nlohmann/detail/input/number_parse.hpp

@@ -704,7 +704,7 @@ inline void float_from_bits(std::uint64_t bits, float& value) noexcept
 {
     static_assert(sizeof(float) == sizeof(std::uint32_t), "float must have 32 bits");
     const auto bits32 = static_cast<std::uint32_t>(bits);
-    std::memcpy(&value, &bits32, sizeof(value));
+    std::memcpy(&value, &bits32, sizeof(bits32));
 }
 
 /// the powers of ten that are exact in binary64 (up to 10^22)

include/nlohmann/detail/json_pointer.hpp

@@ -16,6 +16,8 @@
     #include <iosfwd> // ostream
 #endif  // JSON_NO_IO
 #include <limits> // max
+#include <map> // map
+#include <numeric> // accumulate
 #include <string> // string
 #include <utility> // move
 #include <vector> // vector
@@ -67,21 +69,12 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/to_string/
     string_t to_string() const
     {
-        // one buffer: every token adds its escaped form (at least its length) and a slash
-        std::size_t length = 0;
-        for (const auto& reference_token : reference_tokens)
+        return std::accumulate(reference_tokens.begin(), reference_tokens.end(),
+                               string_t{},
+                               [](const string_t& a, const string_t& b)
         {
-            length += reference_token.size() + 1;
-        }
-
-        string_t result;
-        result.reserve(length);
-        for (const auto& reference_token : reference_tokens)
-        {
-            result.append("/", 1);
-            detail::escape_into(result, reference_token);
-        }
-        return result;
+            return detail::concat<string_t>(a, '/', detail::escape(b));
+        });
     }
 
     /// @brief return a string representation of the JSON pointer
@@ -136,29 +129,21 @@ class json_pointer
     friend json_pointer operator/(const json_pointer& lhs,
                                   const json_pointer& rhs)
     {
-        json_pointer result;
-        result.reference_tokens.reserve(lhs.reference_tokens.size() + rhs.reference_tokens.size());
-        result.reference_tokens.insert(result.reference_tokens.end(), lhs.reference_tokens.begin(), lhs.reference_tokens.end());
-        result.reference_tokens.insert(result.reference_tokens.end(), rhs.reference_tokens.begin(), rhs.reference_tokens.end());
-        return result;
+        return json_pointer(lhs) /= rhs;
     }
 
     /// @brief create a new JSON pointer by appending the unescaped token at the end of the JSON pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slash/
     friend json_pointer operator/(const json_pointer& lhs, string_t token) // NOLINT(performance-unnecessary-value-param)
     {
-        json_pointer result;
-        result.reference_tokens.reserve(lhs.reference_tokens.size() + 1);
-        result.reference_tokens.insert(result.reference_tokens.end(), lhs.reference_tokens.begin(), lhs.reference_tokens.end());
-        result.reference_tokens.push_back(std::move(token));
-        return result;
+        return json_pointer(lhs) /= std::move(token);
     }
 
     /// @brief create a new JSON pointer by appending the array-index-token at the end of the JSON pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slash/
     friend json_pointer operator/(const json_pointer& lhs, std::size_t array_idx)
     {
-        return lhs / detail::to_string<string_t>(array_idx);
+        return json_pointer(lhs) /= array_idx;
     }
 
     /// @brief returns the parent of this JSON pointer
@@ -170,8 +155,8 @@ class json_pointer
             return *this;
         }
 
-        json_pointer res;
-        res.reference_tokens = std::vector<string_t>(reference_tokens.begin(), reference_tokens.end() - 1);
+        json_pointer res = *this;
+        res.pop_back();
         return res;
     }
 
@@ -260,14 +245,14 @@ class json_pointer
 
   private:
     /// @throw out_of_range.405 always
-    JSON_HEDLEY_NEVER_INLINE JSON_HEDLEY_NO_RETURN static void throw_no_parent()
+    JSON_HEDLEY_NO_RETURN static void throw_no_parent()
     {
         JSON_THROW(detail::out_of_range::create(detail::exception_id::patch_on_root, "JSON pointer has no parent", nullptr));
     }
 
     /// @throw out_of_range.404 always
     template<typename BasicJsonContext>
-    JSON_HEDLEY_NEVER_INLINE JSON_HEDLEY_NO_RETURN static void throw_unresolved(const string_t& reference_token, BasicJsonContext context)
+    JSON_HEDLEY_NO_RETURN static void throw_unresolved(const string_t& reference_token, BasicJsonContext context)
     {
         static_cast<void>(reference_token); // unused when JSON_NOEXCEPTION is defined
         static_cast<void>(context);
@@ -320,28 +305,6 @@ class json_pointer
             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
@@ -398,83 +361,6 @@ class json_pointer
         return idx;
     }
 
-    /*!
-    @brief compare with a JSON pointer string without splitting it into tokens
-
-    @throw parse_error.107  if the string is not empty or begins with '/'
-    @throw parse_error.108  if character '~' is not followed by '0' or '1'
-    */
-    bool equals_string(const string_t& reference_string) const
-    {
-        if (reference_string.empty())
-        {
-            return reference_tokens.empty();
-        }
-
-        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();
-        for (std::size_t pos = reference_string.find_first_of('~');
-                pos != string_t::npos;
-                pos = reference_string.find_first_of('~', pos + 1))
-        {
-            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));
-            }
-        }
-
-        // compare token by token, unescaping the string on the fly
-        std::size_t pos = 0; // the slash in front of the next token
-        for (const auto& reference_token : reference_tokens)
-        {
-            if (pos >= size)
-            {
-                return false;
-            }
-
-            std::size_t i = pos + 1;
-            std::size_t j = 0;
-            const std::size_t token_size = reference_token.size();
-            while (i < size && reference_string[i] != '/')
-            {
-                char c = reference_string[i++];
-                if (c == '~')
-                {
-                    c = (reference_string[i++] == '0') ? '~' : '/';
-                }
-                if (j == token_size || reference_token[j] != c)
-                {
-                    return false;
-                }
-                ++j;
-            }
-            if (j != token_size)
-            {
-                return false;
-            }
-            pos = i;
-        }
-        return pos == size;
-    }
-
-    /// @brief object member access with a key that is only copied if it is inserted
-    template<typename BasicJsonType>
-    static BasicJsonType& object_member(BasicJsonType& object, const string_t& key)
-    {
-        auto& members = *object.m_data.m_value.object;
-        const auto it = members.find(key);
-        if (it != members.end())
-        {
-            return it->second;
-        }
-        return object.operator[](key);
-    }
-
   JSON_PRIVATE_UNLESS_TESTED:
     json_pointer top() const
     {
@@ -498,141 +384,84 @@ class json_pointer
     the result independent of the order in which the flattened object is
     iterated, which is unspecified for some object types.
 
-    The prefixes form a tree and are numbered (number 0 is the empty prefix),
-    so each of them is stored only once (as a node) rather than as a copy of
-    all of its reference tokens. The tree does not own the reference tokens:
-    it refers to the tokens of the parsed keys, which must outlive it.
+    The prefixes form a tree and are numbered, so each of them is stored only
+    once (as a node) rather than as a copy of all of its reference tokens.
     */
     struct prefix_tree
     {
-        // open-addressing hash table from (parent, last reference token) to
-        // the number of the node; empty slots have token == nullptr
-        struct slot
-        {
-            std::size_t hash;
-            std::size_t parent;
-            const string_t* token;
-            std::size_t id;
-
-            slot() noexcept
-                : hash(0), parent(0), token(nullptr), id(0)
-            {}
-
-            slot(std::size_t h, std::size_t p, const string_t* t, std::size_t i) noexcept
-                : hash(h), parent(p), token(t), id(i)
-            {}
-        };
-
-        std::vector<slot> slots;
-        std::size_t used = 0;
-
-        static std::size_t hash_of(std::size_t parent, const string_t& token) noexcept
-        {
-            std::size_t h = parent * static_cast<std::size_t>(0x9E3779B97F4A7C15ULL);
-            for (std::size_t i = 0; i < token.size(); ++i)
-            {
-                h = (h ^ static_cast<unsigned char>(token[i])) * static_cast<std::size_t>(0x100000001B3ULL);
-            }
-            return h ^ (h >> 29u);
-        }
-
-        void grow()
-        {
-            std::vector<slot> old(slots.size() * 2);
-            old.swap(slots);
-            const std::size_t mask = slots.size() - 1;
-            for (const auto& s : old)
-            {
-                if (s.token != nullptr)
-                {
-                    std::size_t i = s.hash & mask;
-                    while (slots[i].token != nullptr)
-                    {
-                        i = (i + 1) & mask;
-                    }
-                    slots[i] = s;
-                }
-            }
-        }
-
-        // parent[id] is the number of the prefix without its last token
-        std::vector<std::size_t> parent;
+        // children[id] maps a reference token to the number of the prefix
+        // extended by that token; number 0 is the empty prefix
+        std::vector<std::map<string_t, std::size_t>> children;
         // is_array[id] is true iff some flattened key has the reference token
         // 0 directly below the prefix with number id
         std::vector<bool> is_array;
 
         // start with the empty prefix only
         prefix_tree()
-            : slots(16)
-            , parent(1, 0)
+            : children(1)
             , is_array(1, false)
         {}
 
         // return the number of the prefix with number id extended by
         // reference_token, adding it if it is new
-        std::size_t add_child(std::size_t id, const string_t& reference_token)
+        std::size_t add_child(std::size_t id, string_t&& reference_token)
         {
-            const std::size_t hash = hash_of(id, reference_token);
-            const std::size_t mask = slots.size() - 1;
-            std::size_t i = hash & mask;
-            while (slots[i].token != nullptr)
-            {
-                if (slots[i].hash == hash && slots[i].parent == id && *slots[i].token == reference_token)
-                {
-                    return slots[i].id;
-                }
-                i = (i + 1) & mask;
-            }
-
-            // new prefix
-            const std::size_t child = parent.size();
-            slots[i] = slot(hash, id, &reference_token, child);
             if (reference_token == "0")
             {
                 is_array[id] = true;
             }
-            parent.push_back(id);
-            is_array.push_back(false);
 
-            // keep the load factor below 1/2
-            if (++used * 2 > slots.size())
+            // read the number before the emplace_back below, which may
+            // reallocate children and invalidate the iterator
+            const std::size_t next = children.size();
+            const auto inserted = children[id].emplace(std::move(reference_token), next);
+            const std::size_t child = inserted.first->second;
+            if (inserted.second)
             {
-                grow();
+                children.emplace_back();
+                is_array.push_back(false);
             }
             return child;
         }
+
+        // return the number of the prefix with number id extended by
+        // reference_token, which must have been added before
+        std::size_t find_child(std::size_t id, const string_t& reference_token) const
+        {
+            const auto it = children[id].find(reference_token);
+            JSON_ASSERT(it != children[id].end());
+            return it->second;
+        }
     };
 
     /*!
     @brief create and return a reference to the pointed to value
 
-    @param[in] j  the value to create the pointed to value in
-    @param[in] tokens  the reference tokens of the pointer
-    @param[in] prefixes  prefixes[i] is the number in @a tree of the prefix
-                         consisting of the first i reference tokens
-
-    Complexity: Linear in the number of reference tokens.
+    Complexity: Linear in the number of reference tokens (times the logarithm
+    of the number of siblings for the prefix lookup).
 
     @throw parse_error.106 if an array index begins with '0'
     @throw parse_error.109 if array index is not a number
     @throw type_error.313 if value cannot be unflattened
     */
     template<typename BasicJsonType>
-    static BasicJsonType& get_and_create(BasicJsonType& j, const std::vector<string_t>& tokens,
-                                         const std::vector<std::size_t>& prefixes, const prefix_tree& tree)
+    BasicJsonType& get_and_create(BasicJsonType& j, const prefix_tree& tree) const
     {
         auto* result = &j;
 
+        // the number of the prefix consumed so far; used to look up whether
+        // the value to be created below is an array or an object
+        std::size_t id = 0;
+
         // in case no reference tokens exist, return a reference to the JSON value
         // j which will be overwritten by a primitive value
-        for (std::size_t i = 0; i < tokens.size(); ++i)
+        for (const auto& reference_token : reference_tokens)
         {
-            const auto& reference_token = tokens[i];
             switch (result->type())
             {
                 case detail::value_t::null:
                 {
-                    if (tree.is_array[prefixes[i]])
+                    if (tree.is_array[id])
                     {
                         // some reference token below this position is 0, so the
                         // value is an array
@@ -649,7 +478,7 @@ class json_pointer
                 case detail::value_t::object:
                 {
                     // create an entry in the object
-                    result = &object_member(*result, reference_token);
+                    result = &result->operator[](reference_token);
                     break;
                 }
 
@@ -676,6 +505,8 @@ class json_pointer
                 default:
                     JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_invalid_value, "invalid value to unflatten", &j));
             }
+
+            id = tree.find_child(id, reference_token);
         }
 
         return *result;
@@ -727,7 +558,7 @@ class json_pointer
                 case detail::value_t::object:
                 {
                     // use unchecked object access
-                    ptr = &object_member(*ptr, reference_token);
+                    ptr = &ptr->operator[](reference_token);
                     break;
                 }
 
@@ -777,13 +608,8 @@ class json_pointer
             {
                 case detail::value_t::object:
                 {
-                    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;
+                    // note: at performs range check
+                    ptr = &ptr->at(reference_token);
                     break;
                 }
 
@@ -804,7 +630,7 @@ class json_pointer
                         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];
+                    ptr = &ptr->operator[](idx);
                     break;
                 }
 
@@ -852,9 +678,7 @@ class json_pointer
                 {
                     // 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;
+                    ptr = &ptr->operator[](reference_token);
                     break;
                 }
 
@@ -868,9 +692,7 @@ class json_pointer
 
                     // 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];
+                    ptr = &ptr->operator[](array_index<BasicJsonType>(reference_token));
                     break;
                 }
 
@@ -911,12 +733,12 @@ class json_pointer
             {
                 case detail::value_t::object:
                 {
-                    const auto it = ptr->m_data.m_value.object->find(reference_token);
-                    if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                    const auto it = ptr->find(reference_token);
+                    if (JSON_HEDLEY_UNLIKELY(it == ptr->end()))
                     {
                         return nullptr;
                     }
-                    ptr = &it->second;
+                    ptr = &*it;
                     break;
                 }
 
@@ -953,7 +775,7 @@ class json_pointer
                     {
                         return nullptr;
                     }
-                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    ptr = &ptr->operator[](idx);
                     break;
                 }
 
@@ -986,14 +808,13 @@ class json_pointer
             {
                 case detail::value_t::object:
                 {
-                    const auto it = ptr->m_data.m_value.object->find(reference_token);
-                    if (it == ptr->m_data.m_value.object->end())
+                    if (!ptr->contains(reference_token))
                     {
                         // we did not find the key in the object
                         return false;
                     }
 
-                    ptr = &it->second;
+                    ptr = &ptr->operator[](reference_token);
                     break;
                 }
 
@@ -1015,13 +836,13 @@ class json_pointer
                         return false;
                     }
 
-                    if (idx >= ptr->m_data.m_value.array->size())
+                    if (idx >= ptr->size())
                     {
                         // index out of range
                         return false;
                     }
 
-                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    ptr = &ptr->operator[](idx);
                     break;
                 }
 
@@ -1071,15 +892,6 @@ class json_pointer
             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();
-        std::size_t token_count = 0;
-        for (std::size_t i = 0; i < size; ++i)
-        {
-            token_count += (reference_string[i] == '/') ? 1 : 0;
-        }
-        result.reserve(token_count);
-
         // extract the reference tokens:
         // - slash: position of the last read slash (or end of string)
         // - start: position after the previous slash
@@ -1101,52 +913,31 @@ class json_pointer
             const auto count = (slash == string_t::npos ? reference_string.size() : slash) - start;
             auto reference_token = string_t(reference_string.data() + start, count);
 
-            // check reference tokens are properly escaped; a token without
-            // a '~' (the common case) needs neither check nor unescaping
-            std::size_t pos = reference_token.find_first_of('~');
-            if (pos != string_t::npos)
+            // check reference tokens are properly escaped
+            for (std::size_t pos = reference_token.find_first_of('~');
+                    pos != string_t::npos;
+                    pos = reference_token.find_first_of('~', pos + 1))
             {
-                for (; pos != string_t::npos; pos = reference_token.find_first_of('~', pos + 1))
+                JSON_ASSERT(reference_token[pos] == '~');
+
+                // ~ must be followed by 0 or 1
+                if (JSON_HEDLEY_UNLIKELY(pos == reference_token.size() - 1 ||
+                                         (reference_token[pos + 1] != '0' &&
+                                          reference_token[pos + 1] != '1')))
                 {
-                    JSON_ASSERT(reference_token[pos] == '~');
-
-                    // ~ must be followed by 0 or 1
-                    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));
-                    }
+                    JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_invalid_escape, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
                 }
-
-                detail::unescape(reference_token);
             }
 
             // finally, store the reference token
-            result.push_back(std::move(reference_token));
+            detail::unescape(reference_token);
+            result.push_back(reference_token);
         }
 
         return result;
     }
 
   private:
-    // Add the entry (key, v) to the object `obj`. Flattened paths are pairwise
-    // distinct, so objects that can append a key known to be absent
-    // (ordered_map) skip the lookup, which is linear and would make flatten
-    // quadratic; all other object types use operator[].
-    template<typename ObjectType, typename ValueType>
-    static auto add_flattened(ObjectType& obj, const string_t& key, ValueType&& v, int /*unused*/)
-    -> decltype(obj.emplace_new_key(key, std::forward<ValueType>(v)), void())
-    {
-        obj.emplace_new_key(key, std::forward<ValueType>(v));
-    }
-
-    template<typename ObjectType, typename ValueType>
-    static void add_flattened(ObjectType& obj, const string_t& key, ValueType&& v, ...)
-    {
-        obj[key] = std::forward<ValueType>(v);
-    }
-
     /*!
     @param[in] reference_string  the reference string to the current value
     @param[in] value             the value to consider
@@ -1191,8 +982,7 @@ class json_pointer
 
         // flatten `v`, whose path is `path`: primitives and empty containers
         // are added to the result right away; other containers get a frame
-        auto& object = *result.m_data.m_value.object;
-        const auto enter = [&stack, &path, &object](const BasicJsonType & v)
+        const auto enter = [&stack, &path, &result](const BasicJsonType & v)
         {
             switch (v.type())
             {
@@ -1201,7 +991,7 @@ class json_pointer
                     if (v.m_data.m_value.array->empty())
                     {
                         // flatten empty array as null
-                        add_flattened(object, path, nullptr, 0);
+                        result[path] = nullptr;
                     }
                     else
                     {
@@ -1215,7 +1005,7 @@ class json_pointer
                     if (v.m_data.m_value.object->empty())
                     {
                         // flatten empty object as null
-                        add_flattened(object, path, nullptr, 0);
+                        result[path] = nullptr;
                     }
                     else
                     {
@@ -1235,7 +1025,7 @@ class json_pointer
                 default:
                 {
                     // add a primitive value with its reference string
-                    add_flattened(object, path, v, 0);
+                    result[path] = v;
                     return;
                 }
             }
@@ -1281,10 +1071,6 @@ class json_pointer
                 enter(it->second);
             }
         }
-
-        // the entries were added without going through basic_json, so the
-        // parent pointers (JSON_DIAGNOSTICS) have to be set now
-        result.set_parents();
     }
 
     /*!
@@ -1308,53 +1094,21 @@ class json_pointer
 
         BasicJsonType result;
 
-        // parse every key once; the reference tokens are kept for the second
-        // pass (the vectors are never resized, so the tree may refer to them)
-        std::vector<std::vector<string_t>> keys;
-        keys.reserve(value.m_data.m_value.object->size());
-        for (const auto& element : *value.m_data.m_value.object)
-        {
-            json_pointer ptr(element.first);
-            keys.push_back(std::move(ptr.reference_tokens));
-        }
-
         // collect the pointer prefixes that have a reference token 0 among
         // their children; the values below them are arrays, all others are
         // objects (see prefix_tree)
         prefix_tree tree;
-        // the number of the prefix with i + 1 tokens of the previous key; keys
-        // are often sorted, so most of the prefix is the same as for the
-        // previous key and need not be looked up again
-        std::vector<std::size_t> path;
-        const std::vector<string_t>* previous = nullptr;
-        // the number of the complete prefix (i.e., the key) of each key
-        std::vector<std::size_t> leaves;
-        leaves.reserve(keys.size());
-        for (const auto& tokens : keys)
+        for (const auto& element : *value.m_data.m_value.object)
         {
-            std::size_t common = 0;
-            if (previous != nullptr)
+            json_pointer ptr(element.first);
+            std::size_t id = 0;
+            for (auto& reference_token : ptr.reference_tokens)
             {
-                const std::size_t limit = (std::min)(tokens.size(), previous->size());
-                while (common < limit && tokens[common] == (*previous)[common])
-                {
-                    ++common;
-                }
+                id = tree.add_child(id, std::move(reference_token));
             }
-            path.resize(common);
-            std::size_t id = common == 0 ? 0 : path[common - 1];
-            for (std::size_t i = common; i < tokens.size(); ++i)
-            {
-                id = tree.add_child(id, tokens[i]);
-                path.push_back(id);
-            }
-            leaves.push_back(id);
-            previous = &tokens;
         }
 
         // iterate the JSON object values
-        std::vector<std::size_t> prefixes;
-        std::size_t key_index = 0;
         for (const auto& element : *value.m_data.m_value.object)
         {
             if (JSON_HEDLEY_UNLIKELY(!element.second.is_primitive()))
@@ -1362,21 +1116,11 @@ class json_pointer
                 JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_value_not_primitive, "values in object must be primitive", &element.second));
             }
 
-            const auto& tokens = keys[key_index];
-            // number the prefixes of this key from its last one to the first
-            prefixes.resize(tokens.size());
-            for (std::size_t i = tokens.size(), id = leaves[key_index]; i > 0; --i)
-            {
-                id = tree.parent[id];
-                prefixes[i - 1] = id;
-            }
-            ++key_index;
-
             // Assign the value to the reference pointed to by JSON pointer. Note
             // that if the JSON pointer is "" (i.e., points to the whole value),
             // function get_and_create returns a reference to the result itself.
             // An assignment will then create a primitive value.
-            get_and_create(result, tokens, prefixes, tree) = element.second;
+            json_pointer(element.first).get_and_create(result, tree) = element.second;
         }
 
         return result;
@@ -1415,7 +1159,7 @@ class json_pointer
         = delete;
 #else
     {
-        return equals_string(rhs);
+        return *this == json_pointer(rhs);
     }
 #endif
 
@@ -1499,7 +1243,7 @@ inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
     = delete;
 #else
 {
-    return lhs.equals_string(rhs);
+    return lhs == json_pointer<RefStringTypeLhs>(rhs);
 }
 #endif
 
@@ -1512,7 +1256,7 @@ inline bool operator==(const StringType& lhs,
     = delete;
 #else
 {
-    return rhs.equals_string(lhs);
+    return json_pointer<RefStringTypeRhs>(lhs) == rhs;
 }
 #endif
 

include/nlohmann/detail/string_escape.hpp

@@ -9,7 +9,6 @@
 #pragma once
 
 #include <cstddef> // size_t
-#include <utility> // move
 
 #include <nlohmann/detail/abi_macros.hpp>
 
@@ -25,46 +24,39 @@ namespace detail
  * Note the order of escaping "~" to "~0" and "/" to "~1" is important.
  *
  * The string is rebuilt in a single pass, appending whole runs between the
- * characters that need escaping, while repeated replace() calls would move
- * the tail of the string once per escaped character. @ref escape_into appends
- * the escaped string to an existing one.
+ * characters that need escaping. Scanning with find_first_of() keeps the
+ * common case -- nothing to escape -- as fast as a single search, while
+ * repeated replace() calls would move the tail of the string once per
+ * escaped character.
  */
-template<typename StringType>
-inline void escape_into(StringType& out, const StringType& s)
-{
-    const std::size_t size = s.size();
-    std::size_t run = 0;
-    for (std::size_t i = 0; i < size; ++i)
-    {
-        const char c = s[i];
-        if (c == '~' || c == '/')
-        {
-            out.append(s.data() + run, i - run);
-            out.append(c == '~' ? "~0" : "~1", 2);
-            run = i + 1;
-        }
-    }
-    out.append(s.data() + run, size - run);
-}
-
 template<typename StringType>
 inline StringType escape(const StringType& s)
 {
-    // a single scan for both special characters; nothing to escape is the common case
-    const std::size_t size = s.size();
-    std::size_t i = 0;
-    while (i < size && s[i] != '~' && s[i] != '/')
+    auto next_special = [&s](std::size_t from)
     {
-        ++i;
-    }
-    if (i == size)
+        const auto tilde = s.find_first_of('~', from);
+        const auto slash = s.find_first_of('/', from);
+        return tilde < slash ? tilde : slash; // npos is the largest value
+    };
+
+    auto pos = next_special(0);
+    if (pos == StringType::npos)
     {
         return s;
     }
 
     StringType result;
-    result.reserve(size + 2);
-    escape_into(result, s);
+    result.reserve(s.size() + 2);
+
+    std::size_t run = 0;
+    while (pos != StringType::npos)
+    {
+        result.append(s.data() + run, pos - run);
+        result.append(s[pos] == '~' ? "~0" : "~1", 2);
+        run = pos + 1;
+        pos = next_special(run);
+    }
+    result.append(s.data() + run, s.size() - run);
     return result;
 }
 
@@ -109,7 +101,7 @@ inline void unescape(StringType& s)
         pos = s.find_first_of('~', run);
     }
     result.append(s.data() + run, s.size() - run);
-    s = std::move(result);
+    s = result;
 }
 
 }  // namespace detail

include/nlohmann/json.hpp

@@ -6562,18 +6562,24 @@ public:
         };
 
         // wrapper for "add" operation; add value at ptr
-        const auto operation_add = [&result](json_pointer & ptr, basic_json val)
+        const auto operation_add = [&result](json_pointer & ptr, const basic_json & val)
         {
             // adding to the root of the target document means replacing it
             if (ptr.empty())
             {
-                result = std::move(val);
+                result = val;
                 return;
             }
 
-            // get reference to the parent of the JSON pointer ptr; a missing
-            // parent (or one of its ancestors) is reported by at()
-            auto last_path = std::move(ptr.reference_tokens.back());
+            // make sure the top element of the pointer exists
+            json_pointer const top_pointer = ptr.top();
+            if (top_pointer != ptr)
+            {
+                result.at(top_pointer);
+            }
+
+            // get reference to the parent of the JSON pointer ptr
+            const auto last_path = ptr.back();
             ptr.pop_back();
             // parent must exist when performing patch add per RFC6902 specs
             basic_json& parent = result.at(ptr);
@@ -6584,7 +6590,7 @@ public:
                 case value_t::object:
                 {
                     // use operator[] to add value
-                    parent[std::move(last_path)] = std::move(val);
+                    parent[last_path] = val;
                     break;
                 }
 
@@ -6593,7 +6599,7 @@ public:
                     if (last_path == "-")
                     {
                         // special case: append to back
-                        parent.push_back(std::move(val));
+                        parent.push_back(val);
                     }
                     else
                     {
@@ -6605,7 +6611,7 @@ public:
                         }
 
                         // default case: insert add offset
-                        parent.insert(parent.begin() + static_cast<difference_type>(idx), std::move(val));
+                        parent.insert(parent.begin() + static_cast<difference_type>(idx), val);
                     }
                     break;
                 }
@@ -6628,8 +6634,7 @@ public:
         const auto operation_remove = [this, & result](json_pointer & ptr)
         {
             // get reference to the parent of the JSON pointer ptr
-            static_cast<void>(ptr.back()); // throws out_of_range.405 if ptr is the root
-            const auto last_path = std::move(ptr.reference_tokens.back());
+            const auto last_path = ptr.back();
             ptr.pop_back();
             basic_json& parent = result.at(ptr);
 
@@ -6729,8 +6734,8 @@ public:
             }
 
             // collect mandatory members
-            const string_t& op = *get_value("op", "op", true).m_data.m_value.string;
-            const string_t& path = *get_value(op, "path", true).m_data.m_value.string;
+            const auto op = get_value("op", "op", true).template get<string_t>();
+            const auto path = get_value(op, "path", true).template get<string_t>();
             json_pointer ptr(path);
 
             switch (get_op(op))
@@ -6756,7 +6761,7 @@ public:
 
                 case patch_operations::move:
                 {
-                    const string_t& from_path = *get_value("move", "from", true).m_data.m_value.string;
+                    const auto from_path = get_value("move", "from", true).template get<string_t>();
                     json_pointer from_ptr(from_path);
 
                     if (JSON_HEDLEY_UNLIKELY(is_proper_prefix(from_ptr, ptr)))
@@ -6765,28 +6770,29 @@ public:
                     }
 
                     // the "from" location must exist - use at()
-                    // a root "from" is rejected by operation_remove below, which must leave result intact
-                    basic_json v = from_ptr.empty() ? basic_json(result) : std::move(result.at(from_ptr));
+                    basic_json const v = result.at(from_ptr);
 
                     // The move operation is functionally identical to a
                     // "remove" operation on the "from" location, followed
                     // immediately by an "add" operation at the target
                     // location with the value that was just removed.
                     operation_remove(from_ptr);
-                    operation_add(ptr, std::move(v));
+                    operation_add(ptr, v);
                     break;
                 }
 
                 case patch_operations::copy:
                 {
-                    const string_t& from_path = *get_value("copy", "from", true).m_data.m_value.string;
+                    const auto from_path = get_value("copy", "from", true).template get<string_t>();
                     const json_pointer from_ptr(from_path);
 
+                    // the "from" location must exist - use at()
+                    basic_json const v = result.at(from_ptr);
+
                     // The copy is functionally identical to an "add"
                     // operation at the target location using the value
-                    // specified in the "from" member; the "from" location
-                    // must exist - use at()
-                    operation_add(ptr, result.at(from_ptr));
+                    // specified in the "from" member.
+                    operation_add(ptr, v);
                     break;
                 }
 

include/nlohmann/ordered_map.hpp

@@ -143,17 +143,6 @@ public:
         return {std::prev(this->end()), true};
     }
 
-    /// @brief add an element at the end without checking whether the key exists
-    /// @note The caller must guarantee that @a key is not yet contained, otherwise
-    ///       the container holds duplicate keys. This avoids the linear search of
-    ///       emplace() and operator[] when many keys known to be new are added.
-    template<class V, detail::enable_if_t<
-                 detail::is_constructible<T, V>::value, int> = 0>
-    void emplace_new_key(const key_type& key, V && t)
-    {
-        append(key, std::forward<V>(t));
-    }
-
     T& operator[](const key_type& key)
     {
         return emplace(key, T{}).first->second;

single_include/nlohmann/json.hpp

@@ -3415,7 +3415,6 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 #include <cstddef> // size_t
-#include <utility> // move
 
 // #include <nlohmann/detail/abi_macros.hpp>
 
@@ -3432,46 +3431,39 @@ namespace detail
  * Note the order of escaping "~" to "~0" and "/" to "~1" is important.
  *
  * The string is rebuilt in a single pass, appending whole runs between the
- * characters that need escaping, while repeated replace() calls would move
- * the tail of the string once per escaped character. @ref escape_into appends
- * the escaped string to an existing one.
+ * characters that need escaping. Scanning with find_first_of() keeps the
+ * common case -- nothing to escape -- as fast as a single search, while
+ * repeated replace() calls would move the tail of the string once per
+ * escaped character.
  */
-template<typename StringType>
-inline void escape_into(StringType& out, const StringType& s)
-{
-    const std::size_t size = s.size();
-    std::size_t run = 0;
-    for (std::size_t i = 0; i < size; ++i)
-    {
-        const char c = s[i];
-        if (c == '~' || c == '/')
-        {
-            out.append(s.data() + run, i - run);
-            out.append(c == '~' ? "~0" : "~1", 2);
-            run = i + 1;
-        }
-    }
-    out.append(s.data() + run, size - run);
-}
-
 template<typename StringType>
 inline StringType escape(const StringType& s)
 {
-    // a single scan for both special characters; nothing to escape is the common case
-    const std::size_t size = s.size();
-    std::size_t i = 0;
-    while (i < size && s[i] != '~' && s[i] != '/')
+    auto next_special = [&s](std::size_t from)
     {
-        ++i;
-    }
-    if (i == size)
+        const auto tilde = s.find_first_of('~', from);
+        const auto slash = s.find_first_of('/', from);
+        return tilde < slash ? tilde : slash; // npos is the largest value
+    };
+
+    auto pos = next_special(0);
+    if (pos == StringType::npos)
     {
         return s;
     }
 
     StringType result;
-    result.reserve(size + 2);
-    escape_into(result, s);
+    result.reserve(s.size() + 2);
+
+    std::size_t run = 0;
+    while (pos != StringType::npos)
+    {
+        result.append(s.data() + run, pos - run);
+        result.append(s[pos] == '~' ? "~0" : "~1", 2);
+        run = pos + 1;
+        pos = next_special(run);
+    }
+    result.append(s.data() + run, s.size() - run);
     return result;
 }
 
@@ -3516,7 +3508,7 @@ inline void unescape(StringType& s)
         pos = s.find_first_of('~', run);
     }
     result.append(s.data() + run, s.size() - run);
-    s = std::move(result);
+    s = result;
 }
 
 }  // namespace detail
@@ -10159,7 +10151,7 @@ inline void float_from_bits(std::uint64_t bits, float& value) noexcept
 {
     static_assert(sizeof(float) == sizeof(std::uint32_t), "float must have 32 bits");
     const auto bits32 = static_cast<std::uint32_t>(bits);
-    std::memcpy(&value, &bits32, sizeof(value));
+    std::memcpy(&value, &bits32, sizeof(bits32));
 }
 
 /// the powers of ten that are exact in binary64 (up to 10^22)
@@ -13858,19 +13850,16 @@ class json_sax_dom_callback_parser
         if (keep && ref_stack.back())
         {
             auto& obj = *ref_stack.back()->m_data.m_value.object;
-            // a single lookup: insert the placeholder, or find the existing member
-            const auto inserted = obj.emplace(val, discarded);
-            const auto it = inserted.first;
-            if (!inserted.second)
+            const auto it = obj.find(val);
+            if (it != obj.end())
             {
                 // this is a duplicate key (legal in JSON); remember its
                 // current value so it can be restored later if the new
                 // value is rejected by the callback, instead of being
                 // erased together with the discarded placeholder
                 duplicate_key_stash.emplace_back(&(it->second), it->second);
-                it->second = discarded;
             }
-            object_element = &(it->second);
+            object_element = &(obj[val] = discarded);
         }
 
         return true;
@@ -20642,6 +20631,8 @@ NLOHMANN_JSON_NAMESPACE_END
     #include <iosfwd> // ostream
 #endif  // JSON_NO_IO
 #include <limits> // max
+#include <map> // map
+#include <numeric> // accumulate
 #include <string> // string
 #include <utility> // move
 #include <vector> // vector
@@ -20699,21 +20690,12 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/to_string/
     string_t to_string() const
     {
-        // one buffer: every token adds its escaped form (at least its length) and a slash
-        std::size_t length = 0;
-        for (const auto& reference_token : reference_tokens)
+        return std::accumulate(reference_tokens.begin(), reference_tokens.end(),
+                               string_t{},
+                               [](const string_t& a, const string_t& b)
         {
-            length += reference_token.size() + 1;
-        }
-
-        string_t result;
-        result.reserve(length);
-        for (const auto& reference_token : reference_tokens)
-        {
-            result.append("/", 1);
-            detail::escape_into(result, reference_token);
-        }
-        return result;
+            return detail::concat<string_t>(a, '/', detail::escape(b));
+        });
     }
 
     /// @brief return a string representation of the JSON pointer
@@ -20768,29 +20750,21 @@ class json_pointer
     friend json_pointer operator/(const json_pointer& lhs,
                                   const json_pointer& rhs)
     {
-        json_pointer result;
-        result.reference_tokens.reserve(lhs.reference_tokens.size() + rhs.reference_tokens.size());
-        result.reference_tokens.insert(result.reference_tokens.end(), lhs.reference_tokens.begin(), lhs.reference_tokens.end());
-        result.reference_tokens.insert(result.reference_tokens.end(), rhs.reference_tokens.begin(), rhs.reference_tokens.end());
-        return result;
+        return json_pointer(lhs) /= rhs;
     }
 
     /// @brief create a new JSON pointer by appending the unescaped token at the end of the JSON pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slash/
     friend json_pointer operator/(const json_pointer& lhs, string_t token) // NOLINT(performance-unnecessary-value-param)
     {
-        json_pointer result;
-        result.reference_tokens.reserve(lhs.reference_tokens.size() + 1);
-        result.reference_tokens.insert(result.reference_tokens.end(), lhs.reference_tokens.begin(), lhs.reference_tokens.end());
-        result.reference_tokens.push_back(std::move(token));
-        return result;
+        return json_pointer(lhs) /= std::move(token);
     }
 
     /// @brief create a new JSON pointer by appending the array-index-token at the end of the JSON pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slash/
     friend json_pointer operator/(const json_pointer& lhs, std::size_t array_idx)
     {
-        return lhs / detail::to_string<string_t>(array_idx);
+        return json_pointer(lhs) /= array_idx;
     }
 
     /// @brief returns the parent of this JSON pointer
@@ -20802,8 +20776,8 @@ class json_pointer
             return *this;
         }
 
-        json_pointer res;
-        res.reference_tokens = std::vector<string_t>(reference_tokens.begin(), reference_tokens.end() - 1);
+        json_pointer res = *this;
+        res.pop_back();
         return res;
     }
 
@@ -20892,14 +20866,14 @@ class json_pointer
 
   private:
     /// @throw out_of_range.405 always
-    JSON_HEDLEY_NEVER_INLINE JSON_HEDLEY_NO_RETURN static void throw_no_parent()
+    JSON_HEDLEY_NO_RETURN static void throw_no_parent()
     {
         JSON_THROW(detail::out_of_range::create(detail::exception_id::patch_on_root, "JSON pointer has no parent", nullptr));
     }
 
     /// @throw out_of_range.404 always
     template<typename BasicJsonContext>
-    JSON_HEDLEY_NEVER_INLINE JSON_HEDLEY_NO_RETURN static void throw_unresolved(const string_t& reference_token, BasicJsonContext context)
+    JSON_HEDLEY_NO_RETURN static void throw_unresolved(const string_t& reference_token, BasicJsonContext context)
     {
         static_cast<void>(reference_token); // unused when JSON_NOEXCEPTION is defined
         static_cast<void>(context);
@@ -20952,28 +20926,6 @@ class json_pointer
             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
@@ -21030,83 +20982,6 @@ class json_pointer
         return idx;
     }
 
-    /*!
-    @brief compare with a JSON pointer string without splitting it into tokens
-
-    @throw parse_error.107  if the string is not empty or begins with '/'
-    @throw parse_error.108  if character '~' is not followed by '0' or '1'
-    */
-    bool equals_string(const string_t& reference_string) const
-    {
-        if (reference_string.empty())
-        {
-            return reference_tokens.empty();
-        }
-
-        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();
-        for (std::size_t pos = reference_string.find_first_of('~');
-                pos != string_t::npos;
-                pos = reference_string.find_first_of('~', pos + 1))
-        {
-            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));
-            }
-        }
-
-        // compare token by token, unescaping the string on the fly
-        std::size_t pos = 0; // the slash in front of the next token
-        for (const auto& reference_token : reference_tokens)
-        {
-            if (pos >= size)
-            {
-                return false;
-            }
-
-            std::size_t i = pos + 1;
-            std::size_t j = 0;
-            const std::size_t token_size = reference_token.size();
-            while (i < size && reference_string[i] != '/')
-            {
-                char c = reference_string[i++];
-                if (c == '~')
-                {
-                    c = (reference_string[i++] == '0') ? '~' : '/';
-                }
-                if (j == token_size || reference_token[j] != c)
-                {
-                    return false;
-                }
-                ++j;
-            }
-            if (j != token_size)
-            {
-                return false;
-            }
-            pos = i;
-        }
-        return pos == size;
-    }
-
-    /// @brief object member access with a key that is only copied if it is inserted
-    template<typename BasicJsonType>
-    static BasicJsonType& object_member(BasicJsonType& object, const string_t& key)
-    {
-        auto& members = *object.m_data.m_value.object;
-        const auto it = members.find(key);
-        if (it != members.end())
-        {
-            return it->second;
-        }
-        return object.operator[](key);
-    }
-
   JSON_PRIVATE_UNLESS_TESTED:
     json_pointer top() const
     {
@@ -21130,141 +21005,84 @@ class json_pointer
     the result independent of the order in which the flattened object is
     iterated, which is unspecified for some object types.
 
-    The prefixes form a tree and are numbered (number 0 is the empty prefix),
-    so each of them is stored only once (as a node) rather than as a copy of
-    all of its reference tokens. The tree does not own the reference tokens:
-    it refers to the tokens of the parsed keys, which must outlive it.
+    The prefixes form a tree and are numbered, so each of them is stored only
+    once (as a node) rather than as a copy of all of its reference tokens.
     */
     struct prefix_tree
     {
-        // open-addressing hash table from (parent, last reference token) to
-        // the number of the node; empty slots have token == nullptr
-        struct slot
-        {
-            std::size_t hash;
-            std::size_t parent;
-            const string_t* token;
-            std::size_t id;
-
-            slot() noexcept
-                : hash(0), parent(0), token(nullptr), id(0)
-            {}
-
-            slot(std::size_t h, std::size_t p, const string_t* t, std::size_t i) noexcept
-                : hash(h), parent(p), token(t), id(i)
-            {}
-        };
-
-        std::vector<slot> slots;
-        std::size_t used = 0;
-
-        static std::size_t hash_of(std::size_t parent, const string_t& token) noexcept
-        {
-            std::size_t h = parent * static_cast<std::size_t>(0x9E3779B97F4A7C15ULL);
-            for (std::size_t i = 0; i < token.size(); ++i)
-            {
-                h = (h ^ static_cast<unsigned char>(token[i])) * static_cast<std::size_t>(0x100000001B3ULL);
-            }
-            return h ^ (h >> 29u);
-        }
-
-        void grow()
-        {
-            std::vector<slot> old(slots.size() * 2);
-            old.swap(slots);
-            const std::size_t mask = slots.size() - 1;
-            for (const auto& s : old)
-            {
-                if (s.token != nullptr)
-                {
-                    std::size_t i = s.hash & mask;
-                    while (slots[i].token != nullptr)
-                    {
-                        i = (i + 1) & mask;
-                    }
-                    slots[i] = s;
-                }
-            }
-        }
-
-        // parent[id] is the number of the prefix without its last token
-        std::vector<std::size_t> parent;
+        // children[id] maps a reference token to the number of the prefix
+        // extended by that token; number 0 is the empty prefix
+        std::vector<std::map<string_t, std::size_t>> children;
         // is_array[id] is true iff some flattened key has the reference token
         // 0 directly below the prefix with number id
         std::vector<bool> is_array;
 
         // start with the empty prefix only
         prefix_tree()
-            : slots(16)
-            , parent(1, 0)
+            : children(1)
             , is_array(1, false)
         {}
 
         // return the number of the prefix with number id extended by
         // reference_token, adding it if it is new
-        std::size_t add_child(std::size_t id, const string_t& reference_token)
+        std::size_t add_child(std::size_t id, string_t&& reference_token)
         {
-            const std::size_t hash = hash_of(id, reference_token);
-            const std::size_t mask = slots.size() - 1;
-            std::size_t i = hash & mask;
-            while (slots[i].token != nullptr)
-            {
-                if (slots[i].hash == hash && slots[i].parent == id && *slots[i].token == reference_token)
-                {
-                    return slots[i].id;
-                }
-                i = (i + 1) & mask;
-            }
-
-            // new prefix
-            const std::size_t child = parent.size();
-            slots[i] = slot(hash, id, &reference_token, child);
             if (reference_token == "0")
             {
                 is_array[id] = true;
             }
-            parent.push_back(id);
-            is_array.push_back(false);
 
-            // keep the load factor below 1/2
-            if (++used * 2 > slots.size())
+            // read the number before the emplace_back below, which may
+            // reallocate children and invalidate the iterator
+            const std::size_t next = children.size();
+            const auto inserted = children[id].emplace(std::move(reference_token), next);
+            const std::size_t child = inserted.first->second;
+            if (inserted.second)
             {
-                grow();
+                children.emplace_back();
+                is_array.push_back(false);
             }
             return child;
         }
+
+        // return the number of the prefix with number id extended by
+        // reference_token, which must have been added before
+        std::size_t find_child(std::size_t id, const string_t& reference_token) const
+        {
+            const auto it = children[id].find(reference_token);
+            JSON_ASSERT(it != children[id].end());
+            return it->second;
+        }
     };
 
     /*!
     @brief create and return a reference to the pointed to value
 
-    @param[in] j  the value to create the pointed to value in
-    @param[in] tokens  the reference tokens of the pointer
-    @param[in] prefixes  prefixes[i] is the number in @a tree of the prefix
-                         consisting of the first i reference tokens
-
-    Complexity: Linear in the number of reference tokens.
+    Complexity: Linear in the number of reference tokens (times the logarithm
+    of the number of siblings for the prefix lookup).
 
     @throw parse_error.106 if an array index begins with '0'
     @throw parse_error.109 if array index is not a number
     @throw type_error.313 if value cannot be unflattened
     */
     template<typename BasicJsonType>
-    static BasicJsonType& get_and_create(BasicJsonType& j, const std::vector<string_t>& tokens,
-                                         const std::vector<std::size_t>& prefixes, const prefix_tree& tree)
+    BasicJsonType& get_and_create(BasicJsonType& j, const prefix_tree& tree) const
     {
         auto* result = &j;
 
+        // the number of the prefix consumed so far; used to look up whether
+        // the value to be created below is an array or an object
+        std::size_t id = 0;
+
         // in case no reference tokens exist, return a reference to the JSON value
         // j which will be overwritten by a primitive value
-        for (std::size_t i = 0; i < tokens.size(); ++i)
+        for (const auto& reference_token : reference_tokens)
         {
-            const auto& reference_token = tokens[i];
             switch (result->type())
             {
                 case detail::value_t::null:
                 {
-                    if (tree.is_array[prefixes[i]])
+                    if (tree.is_array[id])
                     {
                         // some reference token below this position is 0, so the
                         // value is an array
@@ -21281,7 +21099,7 @@ class json_pointer
                 case detail::value_t::object:
                 {
                     // create an entry in the object
-                    result = &object_member(*result, reference_token);
+                    result = &result->operator[](reference_token);
                     break;
                 }
 
@@ -21308,6 +21126,8 @@ class json_pointer
                 default:
                     JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_invalid_value, "invalid value to unflatten", &j));
             }
+
+            id = tree.find_child(id, reference_token);
         }
 
         return *result;
@@ -21359,7 +21179,7 @@ class json_pointer
                 case detail::value_t::object:
                 {
                     // use unchecked object access
-                    ptr = &object_member(*ptr, reference_token);
+                    ptr = &ptr->operator[](reference_token);
                     break;
                 }
 
@@ -21409,13 +21229,8 @@ class json_pointer
             {
                 case detail::value_t::object:
                 {
-                    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;
+                    // note: at performs range check
+                    ptr = &ptr->at(reference_token);
                     break;
                 }
 
@@ -21436,7 +21251,7 @@ class json_pointer
                         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];
+                    ptr = &ptr->operator[](idx);
                     break;
                 }
 
@@ -21484,9 +21299,7 @@ class json_pointer
                 {
                     // 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;
+                    ptr = &ptr->operator[](reference_token);
                     break;
                 }
 
@@ -21500,9 +21313,7 @@ class json_pointer
 
                     // 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];
+                    ptr = &ptr->operator[](array_index<BasicJsonType>(reference_token));
                     break;
                 }
 
@@ -21543,12 +21354,12 @@ class json_pointer
             {
                 case detail::value_t::object:
                 {
-                    const auto it = ptr->m_data.m_value.object->find(reference_token);
-                    if (JSON_HEDLEY_UNLIKELY(it == ptr->m_data.m_value.object->end()))
+                    const auto it = ptr->find(reference_token);
+                    if (JSON_HEDLEY_UNLIKELY(it == ptr->end()))
                     {
                         return nullptr;
                     }
-                    ptr = &it->second;
+                    ptr = &*it;
                     break;
                 }
 
@@ -21585,7 +21396,7 @@ class json_pointer
                     {
                         return nullptr;
                     }
-                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    ptr = &ptr->operator[](idx);
                     break;
                 }
 
@@ -21618,14 +21429,13 @@ class json_pointer
             {
                 case detail::value_t::object:
                 {
-                    const auto it = ptr->m_data.m_value.object->find(reference_token);
-                    if (it == ptr->m_data.m_value.object->end())
+                    if (!ptr->contains(reference_token))
                     {
                         // we did not find the key in the object
                         return false;
                     }
 
-                    ptr = &it->second;
+                    ptr = &ptr->operator[](reference_token);
                     break;
                 }
 
@@ -21647,13 +21457,13 @@ class json_pointer
                         return false;
                     }
 
-                    if (idx >= ptr->m_data.m_value.array->size())
+                    if (idx >= ptr->size())
                     {
                         // index out of range
                         return false;
                     }
 
-                    ptr = &(*ptr->m_data.m_value.array)[idx];
+                    ptr = &ptr->operator[](idx);
                     break;
                 }
 
@@ -21703,15 +21513,6 @@ class json_pointer
             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();
-        std::size_t token_count = 0;
-        for (std::size_t i = 0; i < size; ++i)
-        {
-            token_count += (reference_string[i] == '/') ? 1 : 0;
-        }
-        result.reserve(token_count);
-
         // extract the reference tokens:
         // - slash: position of the last read slash (or end of string)
         // - start: position after the previous slash
@@ -21733,52 +21534,31 @@ class json_pointer
             const auto count = (slash == string_t::npos ? reference_string.size() : slash) - start;
             auto reference_token = string_t(reference_string.data() + start, count);
 
-            // check reference tokens are properly escaped; a token without
-            // a '~' (the common case) needs neither check nor unescaping
-            std::size_t pos = reference_token.find_first_of('~');
-            if (pos != string_t::npos)
+            // check reference tokens are properly escaped
+            for (std::size_t pos = reference_token.find_first_of('~');
+                    pos != string_t::npos;
+                    pos = reference_token.find_first_of('~', pos + 1))
             {
-                for (; pos != string_t::npos; pos = reference_token.find_first_of('~', pos + 1))
+                JSON_ASSERT(reference_token[pos] == '~');
+
+                // ~ must be followed by 0 or 1
+                if (JSON_HEDLEY_UNLIKELY(pos == reference_token.size() - 1 ||
+                                         (reference_token[pos + 1] != '0' &&
+                                          reference_token[pos + 1] != '1')))
                 {
-                    JSON_ASSERT(reference_token[pos] == '~');
-
-                    // ~ must be followed by 0 or 1
-                    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));
-                    }
+                    JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_invalid_escape, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
                 }
-
-                detail::unescape(reference_token);
             }
 
             // finally, store the reference token
-            result.push_back(std::move(reference_token));
+            detail::unescape(reference_token);
+            result.push_back(reference_token);
         }
 
         return result;
     }
 
   private:
-    // Add the entry (key, v) to the object `obj`. Flattened paths are pairwise
-    // distinct, so objects that can append a key known to be absent
-    // (ordered_map) skip the lookup, which is linear and would make flatten
-    // quadratic; all other object types use operator[].
-    template<typename ObjectType, typename ValueType>
-    static auto add_flattened(ObjectType& obj, const string_t& key, ValueType&& v, int /*unused*/)
-    -> decltype(obj.emplace_new_key(key, std::forward<ValueType>(v)), void())
-    {
-        obj.emplace_new_key(key, std::forward<ValueType>(v));
-    }
-
-    template<typename ObjectType, typename ValueType>
-    static void add_flattened(ObjectType& obj, const string_t& key, ValueType&& v, ...)
-    {
-        obj[key] = std::forward<ValueType>(v);
-    }
-
     /*!
     @param[in] reference_string  the reference string to the current value
     @param[in] value             the value to consider
@@ -21823,8 +21603,7 @@ class json_pointer
 
         // flatten `v`, whose path is `path`: primitives and empty containers
         // are added to the result right away; other containers get a frame
-        auto& object = *result.m_data.m_value.object;
-        const auto enter = [&stack, &path, &object](const BasicJsonType & v)
+        const auto enter = [&stack, &path, &result](const BasicJsonType & v)
         {
             switch (v.type())
             {
@@ -21833,7 +21612,7 @@ class json_pointer
                     if (v.m_data.m_value.array->empty())
                     {
                         // flatten empty array as null
-                        add_flattened(object, path, nullptr, 0);
+                        result[path] = nullptr;
                     }
                     else
                     {
@@ -21847,7 +21626,7 @@ class json_pointer
                     if (v.m_data.m_value.object->empty())
                     {
                         // flatten empty object as null
-                        add_flattened(object, path, nullptr, 0);
+                        result[path] = nullptr;
                     }
                     else
                     {
@@ -21867,7 +21646,7 @@ class json_pointer
                 default:
                 {
                     // add a primitive value with its reference string
-                    add_flattened(object, path, v, 0);
+                    result[path] = v;
                     return;
                 }
             }
@@ -21913,10 +21692,6 @@ class json_pointer
                 enter(it->second);
             }
         }
-
-        // the entries were added without going through basic_json, so the
-        // parent pointers (JSON_DIAGNOSTICS) have to be set now
-        result.set_parents();
     }
 
     /*!
@@ -21940,53 +21715,21 @@ class json_pointer
 
         BasicJsonType result;
 
-        // parse every key once; the reference tokens are kept for the second
-        // pass (the vectors are never resized, so the tree may refer to them)
-        std::vector<std::vector<string_t>> keys;
-        keys.reserve(value.m_data.m_value.object->size());
-        for (const auto& element : *value.m_data.m_value.object)
-        {
-            json_pointer ptr(element.first);
-            keys.push_back(std::move(ptr.reference_tokens));
-        }
-
         // collect the pointer prefixes that have a reference token 0 among
         // their children; the values below them are arrays, all others are
         // objects (see prefix_tree)
         prefix_tree tree;
-        // the number of the prefix with i + 1 tokens of the previous key; keys
-        // are often sorted, so most of the prefix is the same as for the
-        // previous key and need not be looked up again
-        std::vector<std::size_t> path;
-        const std::vector<string_t>* previous = nullptr;
-        // the number of the complete prefix (i.e., the key) of each key
-        std::vector<std::size_t> leaves;
-        leaves.reserve(keys.size());
-        for (const auto& tokens : keys)
+        for (const auto& element : *value.m_data.m_value.object)
         {
-            std::size_t common = 0;
-            if (previous != nullptr)
+            json_pointer ptr(element.first);
+            std::size_t id = 0;
+            for (auto& reference_token : ptr.reference_tokens)
             {
-                const std::size_t limit = (std::min)(tokens.size(), previous->size());
-                while (common < limit && tokens[common] == (*previous)[common])
-                {
-                    ++common;
-                }
+                id = tree.add_child(id, std::move(reference_token));
             }
-            path.resize(common);
-            std::size_t id = common == 0 ? 0 : path[common - 1];
-            for (std::size_t i = common; i < tokens.size(); ++i)
-            {
-                id = tree.add_child(id, tokens[i]);
-                path.push_back(id);
-            }
-            leaves.push_back(id);
-            previous = &tokens;
         }
 
         // iterate the JSON object values
-        std::vector<std::size_t> prefixes;
-        std::size_t key_index = 0;
         for (const auto& element : *value.m_data.m_value.object)
         {
             if (JSON_HEDLEY_UNLIKELY(!element.second.is_primitive()))
@@ -21994,21 +21737,11 @@ class json_pointer
                 JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_value_not_primitive, "values in object must be primitive", &element.second));
             }
 
-            const auto& tokens = keys[key_index];
-            // number the prefixes of this key from its last one to the first
-            prefixes.resize(tokens.size());
-            for (std::size_t i = tokens.size(), id = leaves[key_index]; i > 0; --i)
-            {
-                id = tree.parent[id];
-                prefixes[i - 1] = id;
-            }
-            ++key_index;
-
             // Assign the value to the reference pointed to by JSON pointer. Note
             // that if the JSON pointer is "" (i.e., points to the whole value),
             // function get_and_create returns a reference to the result itself.
             // An assignment will then create a primitive value.
-            get_and_create(result, tokens, prefixes, tree) = element.second;
+            json_pointer(element.first).get_and_create(result, tree) = element.second;
         }
 
         return result;
@@ -22047,7 +21780,7 @@ class json_pointer
         = delete;
 #else
     {
-        return equals_string(rhs);
+        return *this == json_pointer(rhs);
     }
 #endif
 
@@ -22131,7 +21864,7 @@ inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
     = delete;
 #else
 {
-    return lhs.equals_string(rhs);
+    return lhs == json_pointer<RefStringTypeLhs>(rhs);
 }
 #endif
 
@@ -22144,7 +21877,7 @@ inline bool operator==(const StringType& lhs,
     = delete;
 #else
 {
-    return rhs.equals_string(lhs);
+    return json_pointer<RefStringTypeRhs>(lhs) == rhs;
 }
 #endif
 
@@ -29425,17 +29158,6 @@ public:
         return {std::prev(this->end()), true};
     }
 
-    /// @brief add an element at the end without checking whether the key exists
-    /// @note The caller must guarantee that @a key is not yet contained, otherwise
-    ///       the container holds duplicate keys. This avoids the linear search of
-    ///       emplace() and operator[] when many keys known to be new are added.
-    template<class V, detail::enable_if_t<
-                 detail::is_constructible<T, V>::value, int> = 0>
-    void emplace_new_key(const key_type& key, V && t)
-    {
-        append(key, std::forward<V>(t));
-    }
-
     T& operator[](const key_type& key)
     {
         return emplace(key, T{}).first->second;
@@ -36188,18 +35910,24 @@ public:
         };
 
         // wrapper for "add" operation; add value at ptr
-        const auto operation_add = [&result](json_pointer & ptr, basic_json val)
+        const auto operation_add = [&result](json_pointer & ptr, const basic_json & val)
         {
             // adding to the root of the target document means replacing it
             if (ptr.empty())
             {
-                result = std::move(val);
+                result = val;
                 return;
             }
 
-            // get reference to the parent of the JSON pointer ptr; a missing
-            // parent (or one of its ancestors) is reported by at()
-            auto last_path = std::move(ptr.reference_tokens.back());
+            // make sure the top element of the pointer exists
+            json_pointer const top_pointer = ptr.top();
+            if (top_pointer != ptr)
+            {
+                result.at(top_pointer);
+            }
+
+            // get reference to the parent of the JSON pointer ptr
+            const auto last_path = ptr.back();
             ptr.pop_back();
             // parent must exist when performing patch add per RFC6902 specs
             basic_json& parent = result.at(ptr);
@@ -36210,7 +35938,7 @@ public:
                 case value_t::object:
                 {
                     // use operator[] to add value
-                    parent[std::move(last_path)] = std::move(val);
+                    parent[last_path] = val;
                     break;
                 }
 
@@ -36219,7 +35947,7 @@ public:
                     if (last_path == "-")
                     {
                         // special case: append to back
-                        parent.push_back(std::move(val));
+                        parent.push_back(val);
                     }
                     else
                     {
@@ -36231,7 +35959,7 @@ public:
                         }
 
                         // default case: insert add offset
-                        parent.insert(parent.begin() + static_cast<difference_type>(idx), std::move(val));
+                        parent.insert(parent.begin() + static_cast<difference_type>(idx), val);
                     }
                     break;
                 }
@@ -36254,8 +35982,7 @@ public:
         const auto operation_remove = [this, & result](json_pointer & ptr)
         {
             // get reference to the parent of the JSON pointer ptr
-            static_cast<void>(ptr.back()); // throws out_of_range.405 if ptr is the root
-            const auto last_path = std::move(ptr.reference_tokens.back());
+            const auto last_path = ptr.back();
             ptr.pop_back();
             basic_json& parent = result.at(ptr);
 
@@ -36355,8 +36082,8 @@ public:
             }
 
             // collect mandatory members
-            const string_t& op = *get_value("op", "op", true).m_data.m_value.string;
-            const string_t& path = *get_value(op, "path", true).m_data.m_value.string;
+            const auto op = get_value("op", "op", true).template get<string_t>();
+            const auto path = get_value(op, "path", true).template get<string_t>();
             json_pointer ptr(path);
 
             switch (get_op(op))
@@ -36382,7 +36109,7 @@ public:
 
                 case patch_operations::move:
                 {
-                    const string_t& from_path = *get_value("move", "from", true).m_data.m_value.string;
+                    const auto from_path = get_value("move", "from", true).template get<string_t>();
                     json_pointer from_ptr(from_path);
 
                     if (JSON_HEDLEY_UNLIKELY(is_proper_prefix(from_ptr, ptr)))
@@ -36391,28 +36118,29 @@ public:
                     }
 
                     // the "from" location must exist - use at()
-                    // a root "from" is rejected by operation_remove below, which must leave result intact
-                    basic_json v = from_ptr.empty() ? basic_json(result) : std::move(result.at(from_ptr));
+                    basic_json const v = result.at(from_ptr);
 
                     // The move operation is functionally identical to a
                     // "remove" operation on the "from" location, followed
                     // immediately by an "add" operation at the target
                     // location with the value that was just removed.
                     operation_remove(from_ptr);
-                    operation_add(ptr, std::move(v));
+                    operation_add(ptr, v);
                     break;
                 }
 
                 case patch_operations::copy:
                 {
-                    const string_t& from_path = *get_value("copy", "from", true).m_data.m_value.string;
+                    const auto from_path = get_value("copy", "from", true).template get<string_t>();
                     const json_pointer from_ptr(from_path);
 
+                    // the "from" location must exist - use at()
+                    basic_json const v = result.at(from_ptr);
+
                     // The copy is functionally identical to an "add"
                     // operation at the target location using the value
-                    // specified in the "from" member; the "from" location
-                    // must exist - use at()
-                    operation_add(ptr, result.at(from_ptr));
+                    // specified in the "from" member.
+                    operation_add(ptr, v);
                     break;
                 }
 

tests/src/unit-algorithms.cpp

@@ -9,7 +9,6 @@
 #include "doctest_compatibility.h"
 
 #include <algorithm>
-#include <numeric>
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 

tests/src/unit-json_pointer.cpp

@@ -23,14 +23,8 @@ using nlohmann::json;
     using namespace nlohmann::literals; // NOLINT(google-build-using-namespace)
 #endif
 
-#include <cerrno>
-#include <cstdlib>
-#include <limits>
 #include <map>
-#include <random>
 #include <sstream>
-#include <string>
-#include <vector>
 
 TEST_CASE("JSON pointers")
 {
@@ -1077,242 +1071,3 @@ TEST_CASE("flatten of structured values")
               R"({"/z":"s","/a~1b/~0":1,"/a~1b/k":null,"/a/0":1,"/a/1/c":null,"/a/1/b":null,"/a/2/0/x~0~1/0":true,"/a/2/0/x~0~1/1":null,"/a/2/0/w":2})");
     }
 }
-
-TEST_CASE("flatten of ordered_json")
-{
-    using nlohmann::ordered_json;
-
-    SECTION("keeps the document order of the leaves")
-    {
-        const ordered_json j = ordered_json::parse(R"({
-            "z": 1, "a": {"y": [true, null, {}], "b": "x", "": []},
-            "m~n": 2.5, "o/p": {"k": {}}, "0": [[1], [2, 3]]
-        })");
-
-        const ordered_json flat = j.flatten();
-        std::vector<std::string> keys;
-        for (const auto& el : flat.items())
-        {
-            keys.push_back(el.key());
-        }
-        const std::vector<std::string> expected =
-        {
-            "/z", "/a/y/0", "/a/y/1", "/a/y/2", "/a/b", "/a/", "/m~0n", "/o~1p/k", "/0/0/0", "/0/1/0", "/0/1/1"
-        };
-        CHECK(keys == expected);
-        CHECK(flat.size() == expected.size());
-        CHECK(flat["/m~0n"] == 2.5);
-        CHECK(flat["/a/y/2"].is_null());
-    }
-
-    SECTION("round-trips and agrees with json")
-    {
-        ordered_json j;
-        for (int i = 0; i < 200; ++i)
-        {
-            j["k" + std::to_string(i)] = {{"v", i}, {"l", {i, i + 1, "s"}}};
-        }
-        const ordered_json flat = j.flatten();
-        CHECK(flat.size() == 800);
-        CHECK(flat.unflatten() == j);
-
-        // same entries as for a sorted object
-        const nlohmann::json plain = nlohmann::json::parse(j.dump());
-        CHECK(nlohmann::json::parse(flat.dump()) == plain.flatten());
-    }
-
-    SECTION("primitive and empty root")
-    {
-        CHECK(ordered_json(1).flatten() == ordered_json({{"", 1}}));
-        CHECK(ordered_json::array().flatten() == ordered_json({{"", nullptr}}));
-    }
-}
-namespace
-{
-// reference implementation of the array index rules (RFC 6901, Sect. 4) based on strtoull
-enum class index_class
-{
-    ok,
-    leading_zero,
-    not_a_number,
-    unresolved,
-    exceeds_size_type
-};
-
-index_class classify_index(const std::string& s, std::size_t& idx)
-{
-    if (s.size() > 1 && s[0] == '0')
-    {
-        return index_class::leading_zero;
-    }
-    if (!s.empty() && s != "-" && !(s[0] >= '0' && s[0] <= '9'))
-    {
-        return index_class::not_a_number;
-    }
-    char* end = nullptr;
-    errno = 0;
-    const unsigned long long res = std::strtoull(s.c_str(), &end, 10); // NOLINT(runtime/int)
-    if (end == s.c_str() || errno == ERANGE || static_cast<std::size_t>(end - s.c_str()) != s.size())
-    {
-        return index_class::unresolved;
-    }
-    if (res >= static_cast<unsigned long long>((std::numeric_limits<std::size_t>::max)())) // NOLINT(runtime/int)
-    {
-        return index_class::exceeds_size_type;
-    }
-    idx = static_cast<std::size_t>(res);
-    return index_class::ok;
-}
-
-// the observable behavior of json_pointer::at() and contains() for an array index token
-void check_index_token(const std::string& token)
-{
-    const json array = {10, 20, 30};
-    const json::json_pointer ptr("/" + token);
-
-    std::size_t idx = 0;
-    const auto cls = classify_index(token, idx);
-    const bool exists = cls == index_class::ok && idx < array.size();
-
-    CAPTURE(token)
-    CHECK(array.contains(ptr) == (exists && token != "-"));
-
-    if (token == "-")
-    {
-        CHECK_THROWS_AS(array.at(ptr), json::out_of_range&);
-        return;
-    }
-
-    switch (cls)
-    {
-        case index_class::leading_zero:
-            CHECK_THROWS_AS(array.at(ptr), json::parse_error&);
-            break;
-        case index_class::not_a_number:
-            CHECK_THROWS_AS(array.at(ptr), json::parse_error&);
-            break;
-        case index_class::unresolved:
-        case index_class::exceeds_size_type:
-            CHECK_THROWS_AS(array.at(ptr), json::out_of_range&);
-            break;
-        case index_class::ok:
-        default:
-            if (exists)
-            {
-                CHECK(array.at(ptr) == array[idx]);
-            }
-            else
-            {
-                CHECK_THROWS_AS(array.at(ptr), json::out_of_range&);
-            }
-            break;
-    }
-}
-} // namespace
-
-TEST_CASE("JSON pointer array index tokens match strtoull semantics")
-{
-    SECTION("boundary values")
-    {
-        const std::string max_digits = std::to_string((std::numeric_limits<std::size_t>::max)());
-        const std::vector<std::string> tokens =
-        {
-            "", "-", "0", "1", "2", "3", "00", "01", "007", "+1", "-1", " 1", "1 ", "1a", "a1", "0x1", "1e1", "1.0",
-            "999999999", "1000000000", "99999999999999999", "999999999999999999", "1000000000000000000",
-            "9999999999999999999", "18446744073709551614", max_digits, "18446744073709551616",
-            "99999999999999999999999", "000000000000000000000"
-        };
-        for (const auto& token : tokens)
-        {
-            check_index_token(token);
-        }
-    }
-
-    SECTION("random tokens")
-    {
-        std::mt19937 gen(42);
-        const std::string alphabet = "0123456789012345678901234567890123456789-+ ex";
-        for (int i = 0; i < 5000; ++i)
-        {
-            std::string token(static_cast<std::size_t>(gen() % 23), '0');
-            for (auto& c : token)
-            {
-                c = alphabet[gen() % alphabet.size()];
-            }
-            check_index_token(token);
-        }
-    }
-}
-
-TEST_CASE("JSON pointer operations on pointers with escaped tokens")
-{
-    const std::vector<std::string> strings =
-    {
-        "", "/", "//", "/a", "/a/b", "/a~1b", "/~0", "/~01", "/~10", "/a~0~1/b/", "/0/1/2", "/ ", "/a/", "/~1/~0"
-    };
-
-    for (const auto& str : strings)
-    {
-        CAPTURE(str)
-        const json::json_pointer ptr(str);
-        CHECK(ptr.to_string() == str);
-        CHECK(ptr / "x" / "y" / std::size_t{3} == json::json_pointer(str + "/x/y/3"));
-        CHECK(ptr.parent_pointer() == (str.empty() ? ptr : json::json_pointer(str.substr(0, str.rfind('/')))));
-
-        // comparison with a string, in place, and with every other pointer
-#if !defined(JSON_TEST_DEPRECATED_FUNCTIONS_DELETED)
-        for (const auto& other : strings)
-        {
-            CAPTURE(other)
-            CHECK((ptr == other) == (str == other));
-            CHECK((other == ptr) == (str == other));
-            CHECK((ptr != other) == (str != other));
-        }
-        CHECK_THROWS_AS(ptr == "x", json::parse_error&);
-        CHECK_THROWS_AS(ptr == "/~", json::parse_error&);
-        CHECK_THROWS_AS(ptr == "/b/~2", json::parse_error&);
-#endif
-    }
-}
-
-TEST_CASE("JSON pointer lookups")
-{
-    json j = {{"a", {{"b", {1, 2, 3}}}}, {"", 7}, {"~/", {{"x", nullptr}}}};
-    const json& cj = j;
-
-    CHECK(cj[json::json_pointer("/a/b/2")] == 3);
-    CHECK(cj.at(json::json_pointer("/a/b/1")) == 2);
-    CHECK(cj.at(json::json_pointer("/")) == 7);
-    CHECK(cj.contains(json::json_pointer("/~0~1/x")));
-    CHECK(!cj.contains(json::json_pointer("/a/c")));
-    CHECK(cj.value(json::json_pointer("/a/b/0"), 5) == 1);
-    CHECK(cj.value(json::json_pointer("/a/b/3"), 5) == 5);
-    CHECK(cj.value(json::json_pointer("/a/zz"), 5) == 5);
-
-    CHECK_THROWS_AS(cj.at(json::json_pointer("/a/c")), json::out_of_range&);
-    CHECK_THROWS_AS(cj.at(json::json_pointer("/a/b/3")), json::out_of_range&);
-
-    // non-const access reuses existing entries and creates missing ones
-    j[json::json_pointer("/a/b/1")] = 20;
-    j[json::json_pointer("/n/m")] = 1;
-    CHECK(j["a"]["b"] == json({1, 20, 3}));
-    CHECK(j["n"]["m"] == 1);
-}
-
-TEST_CASE("JSON patch with moves and copies")
-{
-    json doc = {{"a", {{"b", {1, 2, 3}}}}, {"c", {{"d", "x"}}}};
-
-    CHECK(doc.patch(json::parse(R"([{"op":"move","from":"/a/b","path":"/c/e"}])")) ==
-          json::parse(R"({"a":{},"c":{"d":"x","e":[1,2,3]}})"));
-    CHECK(doc.patch(json::parse(R"([{"op":"copy","from":"/a/b","path":"/c/e"}])")) ==
-          json::parse(R"({"a":{"b":[1,2,3]},"c":{"d":"x","e":[1,2,3]}})"));
-    CHECK(doc.patch(json::parse(R"([{"op":"move","from":"/a/b/0","path":"/a/b/2"}])")) ==
-          json::parse(R"({"a":{"b":[2,3,1]},"c":{"d":"x"}})"));
-
-    // a failing move leaves a copy-patched document untouched
-    CHECK_THROWS_AS(doc.patch(json::parse(R"([{"op":"move","from":"","path":""}])")), json::out_of_range&);
-    json inplace = doc;
-    CHECK_THROWS_AS(inplace.patch_inplace(json::parse(R"([{"op":"move","from":"","path":""}])")), json::out_of_range&);
-    CHECK(inplace == doc);
-}