Merge branch 'json-view/11-view-access' into json-view/13-view-dump

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

single_include/nlohmann/json_view.hpp

@@ -16,7 +16,7 @@
  * the read-only part of the basic_json interface; materialize() turns a     *
  * subtree into the basic_json value that parse() would produce.             *
  *                                                                           *
- * The source text must outlive a document that borrows it (lvalue byte     *
+ * The source text must outlive a document that borrows it (lvalue byte      *
  * containers, C strings); rvalue strings, streams, and other inputs are     *
  * owned by the document.                                                    *
 \****************************************************************************/
@@ -59,7 +59,7 @@
 
 
 
-#include <algorithm> // find, find_if, max
+#include <algorithm> // find, find_if, max, min
 #include <array> // array
 #include <cstddef> // size_t, ptrdiff_t
 #include <cstdint> // int64_t, uint8_t, uint16_t, uint32_t, uint64_t
@@ -83,7 +83,8 @@
 #include <array> // array
 #include <cstddef> // size_t
 #include <cstring> // memcpy
-#include <new> // operator new, placement new
+#include <limits> // numeric_limits
+#include <new> // bad_alloc, operator new, placement new
 #include <string> // string
 
 // #include <nlohmann/json.hpp>
@@ -193,6 +194,11 @@ static_assert(static_cast<std::uint8_t>(value_t::null) == 0 && static_cast<std::
               && static_cast<std::uint8_t>(value_t::number_unsigned) == 6 && static_cast<std::uint8_t>(value_t::number_float) == 7,
               "the node format depends on the numbering of value_t");
 
+/// The largest input a document accepts, in bytes. Offsets and node counts are
+/// 32 bits wide; the limit keeps 16 bytes (the width of the scanner's steps)
+/// below 2^32, so that a position one step past the end of the text fits.
+static constexpr std::size_t max_input_size = 0xFFFFFFEFu;
+
 /// node flags
 struct node_flags
 {
@@ -221,17 +227,27 @@ NLOHMANN_VIEW_ALWAYS_INLINE bool is_container(const node& n) noexcept
     return static_cast<unsigned>(n.kind) - 1u <= 1u;
 }
 
-/// the converted value of an integer node (stored in len/next)
+/// the converted value of an integer node: len is its low half, next its high
+/// half (on little-endian targets the two words are the value in memory)
 NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t integer_bits(const node& n) noexcept
 {
+#if NLOHMANN_VIEW_LITTLE_ENDIAN
     std::uint64_t v = 0;
     std::memcpy(&v, reinterpret_cast<const unsigned char*>(&n) + 8, 8); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
     return v;
+#else
+    return static_cast<std::uint64_t>(n.len) | (static_cast<std::uint64_t>(n.next) << 32);
+#endif
 }
 
 NLOHMANN_VIEW_ALWAYS_INLINE void set_integer_bits(node& n, std::uint64_t v) noexcept
 {
+#if NLOHMANN_VIEW_LITTLE_ENDIAN
     std::memcpy(reinterpret_cast<unsigned char*>(&n) + 8, &v, 8); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+#else
+    n.len = static_cast<std::uint32_t>(v);
+    n.next = static_cast<std::uint32_t>(v >> 32);
+#endif
 }
 
 /// token length of a number node
@@ -327,13 +343,30 @@ struct document_data
         tape_cap = inline_cap;
     }
 
-    /// make room for n nodes; keeps the first tape_size nodes
+    /// the largest node count whose size in bytes fits a std::size_t
+    static constexpr std::size_t max_nodes() noexcept
+    {
+        return (std::numeric_limits<std::size_t>::max)() / sizeof(node);
+    }
+
+    [[noreturn]] NLOHMANN_VIEW_NOINLINE static void throw_bad_alloc()
+    {
+        NLOHMANN_VIEW_THROW(std::bad_alloc());
+    }
+
+    /// make room for n nodes; keeps the first tape_size nodes (throws
+    /// std::bad_alloc for a count that does not fit the address space,
+    /// instead of wrapping around in n * sizeof(node))
     void reserve(std::size_t n)
     {
         if (n <= tape_cap)
         {
             return;
         }
+        if (NLOHMANN_VIEW_UNLIKELY(n > max_nodes()))
+        {
+            throw_bad_alloc();
+        }
         node* fresh = static_cast<node*>(::operator new (n * sizeof(node)));
         if (tape_size != 0)
         {
@@ -740,8 +773,18 @@ class builder
         const std::uint64_t done = static_cast<std::uint64_t>(at - b) + 1;
         const std::uint64_t guess = static_cast<std::uint64_t>(n) * static_cast<std::uint64_t>(e - b + 1) / done;
         const std::uint64_t grown = guess + (guess / 4) + 64; // a variable: GCC calls a cast of the sum useless where std::uint64_t is std::size_t
+        // (n is below 2^32: the input is smaller than 4 GiB; the sum cannot wrap)
+        const std::uint64_t wanted = (std::max)(grown, static_cast<std::uint64_t>(n) + (n / 2) + 64);
+        const std::uint64_t limit = document_data::max_nodes();
         doc.tape_size = n;
-        doc.reserve((std::max)(static_cast<std::size_t>(grown), n + (n / 2) + 64));
+        // LCOV_EXCL_START (a node array that fills the address space)
+        if (NLOHMANN_VIEW_UNLIKELY(n >= limit))
+        {
+            document_data::throw_bad_alloc(); // no room for another node
+        }
+        // LCOV_EXCL_STOP
+        // (a count beyond the limit is cut: the index does not grow beyond what can be addressed)
+        doc.reserve(static_cast<std::size_t>((std::min)(wanted, limit)));
         return doc.tape;
     }
 
@@ -1346,7 +1389,10 @@ indent_done:
             n->flags = flags;
             n->extra = extra;
             n->off = static_cast<std::uint32_t>(off);
-            set_integer_bits(*n, second);
+            // len is the low half of the second word, next the high half
+            // (not a native word over both, which swaps them on big-endian)
+            n->len = static_cast<std::uint32_t>(second);
+            n->next = static_cast<std::uint32_t>(second >> 32);
 #endif
             return n;
         }
@@ -1967,9 +2013,8 @@ template<typename BasicJsonType>
 {
     if (f.code == error_code::input_too_large)
     {
-        // LCOV_EXCL_START (4 GiB)
-        NLOHMANN_VIEW_THROW(out_of_range::create(416, "input of 4 GiB or more is not supported by json_document", nullptr));
-        // LCOV_EXCL_STOP
+        // (the limit is detail::view::max_input_size: 4 GiB minus 16 bytes)
+        NLOHMANN_VIEW_THROW(out_of_range::create(416, "input of 4294967280 bytes or more is not supported by json_document", nullptr));
     }
     const BasicJsonType accepted = BasicJsonType::parse(src, src + size, nullptr, true, ignore_comments, ignore_trailing_commas);
     // LCOV_EXCL_START (only if parse() accepts what the view rejects: a bug)
@@ -2008,7 +2053,7 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 #include <string> // basic_string, char_traits, string
-#include <type_traits> // decay, integral_constant, is_array, is_lvalue_reference, is_pointer, is_same, remove_reference
+#include <type_traits> // decay, integral_constant, is_array, is_const, is_integral, is_lvalue_reference, is_pointer, is_same, remove_reference
 #include <utility> // forward
 
 // #include <nlohmann/json.hpp>
@@ -2028,12 +2073,12 @@ namespace view
 /// how a document takes its input
 enum class input_kind
 {
-    move_string,  ///< rvalue std::string: owned without a copy
+    move_string,  ///< non-const rvalue std::string: owned without a copy
     c_string,     ///< const char* (NUL-terminated): borrowed
     char_array,   ///< char array (e.g. a string literal): borrowed
     borrow_range, ///< lvalue contiguous byte container, or std::string_view: borrowed
-    copy_range,   ///< rvalue contiguous byte container: copied
-    adapter,      ///< anything else parse() accepts (streams, wide strings, ...): read into a buffer
+    copy_range,   ///< rvalue contiguous byte container (a const rvalue std::string too): copied
+    adapter,      ///< streams, wide strings, and the rest of what the library's input adapter reads: read into a buffer
 };
 
 template<typename InputType>
@@ -2052,13 +2097,20 @@ struct classify_input
     static constexpr input_kind value =
         std::is_array<R>::value ? input_kind::char_array
         : std::is_pointer<D>::value ? input_kind::c_string
-        : (is_rvalue && std::is_same<D, std::string>::value) ? input_kind::move_string
+        : (is_rvalue && !std::is_const<R>::value && std::is_same<D, std::string>::value) ? input_kind::move_string
         : (is_bytes && (!is_rvalue || is_string_view)) ? input_kind::borrow_range
         : is_bytes ? input_kind::copy_range
         : input_kind::adapter;
     // NOLINTEND(readability-avoid-nested-conditional-operator)
 };
 
+/// an integer type other than bool: a length passed where a flag is expected
+template<typename T>
+struct is_integer_not_bool : std::is_integral<T> {};
+
+template<>
+struct is_integer_not_bool<bool> : std::false_type {};
+
 /// std::basic_string guarantees a NUL at data()[size()] (the parser's sentinel)
 template<typename T>
 struct is_std_string : std::false_type {};
@@ -2370,6 +2422,8 @@ NLOHMANN_JSON_NAMESPACE_END
 #include <cstddef> // size_t
 #include <cstdint> // uint16_t, uint32_t, uint64_t
 #include <cstring> // memcmp, memcpy
+#include <limits> // numeric_limits
+#include <type_traits> // integral_constant, is_integral, is_same
 
 // #include <nlohmann/json.hpp>
 // #include <nlohmann/detail/view/document_data.hpp>
@@ -2443,12 +2497,14 @@ class short_key
     std::uint64_t m_b = 0;
 };
 
-/// the key node of the first member of an object with the given key, or
-/// nullptr; most keys are rejected by their length, from the index alone
+/// the key node of the last member of an object with the given key, or
+/// nullptr (the last one, as materialize() and parse() keep it); most keys are
+/// rejected by their length, from the index alone
 inline const node* find_member(const document_data& d, const node* object, const char* key, std::size_t n) noexcept
 {
     const node* const end = document_data::child_end(object);
     const auto* const k = reinterpret_cast<const unsigned char*>(key); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    const node* last = nullptr;
     if (NLOHMANN_VIEW_LIKELY(n <= 16))
     {
         const short_key probe(k, n);
@@ -2456,19 +2512,37 @@ inline const node* find_member(const document_data& d, const node* object, const
         {
             if (m->len == n && probe.matches(reinterpret_cast<const unsigned char*>(d.str(*m)))) // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
             {
-                return m;
+                last = m;
             }
         }
-        return nullptr;
+        return last;
     }
     for (const node* m = document_data::first_child(object); m != end; m = document_data::after(m + 1))
     {
         if (m->len == n && std::memcmp(d.str(*m), key, n) == 0)
         {
-            return m;
+            last = m;
         }
     }
-    return nullptr;
+    return last;
+}
+
+/// whether an integer type is accepted as an array index by the view's
+/// operator[] and at(): every integer type but bool and size_t, which has its
+/// own overload
+template<typename T>
+struct is_index_type : std::integral_constant < bool,
+    std::is_integral<T>::value && !std::is_same<T, bool>::value && !std::is_same<T, std::size_t>::value >
+{};
+
+/// an integer as an index: negative values, and values that do not fit a
+/// size_t, map to the largest size_t (out of range for every array)
+template<typename SizeType, typename IntegerType>
+SizeType to_index(IntegerType idx) noexcept
+{
+    const IntegerType zero = 0;
+    const auto result = static_cast<SizeType>(idx);
+    return (idx < zero || static_cast<IntegerType>(result) != idx) ? (std::numeric_limits<SizeType>::max)() : result;
 }
 
 /// the element of an array at an index below its size
@@ -3757,12 +3831,6 @@ class basic_json_view
         return type() == value_t::discarded;
     }
 
-    /// false for discarded views
-    explicit operator bool() const noexcept
-    {
-        return m_node != nullptr;
-    }
-
     /// the name of the type, as basic_json::type_name()
     const char* type_name() const noexcept
     {
@@ -3822,13 +3890,18 @@ class basic_json_view
     // element access //
     ////////////////////
 
-    /// the value of the member with this key (the first one, should the key
-    /// occur more than once); a discarded view if there is none. Throws
-    /// type_error.305 if this is not an object.
+    /// the value of the member with this key (the last one, should the key
+    /// occur more than once); a discarded view if there is none, or if this
+    /// is a discarded view (so that v["a"]["b"] is safe). Throws type_error.305
+    /// if this is any other value but an object.
     NLOHMANN_VIEW_ALWAYS_INLINE basic_json_view operator[](string_view_t key) const
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
         {
+            if (is_discarded())
+            {
+                return basic_json_view();
+            }
             detail::view::throw_type_error(305, "cannot use operator[] with a string argument with ", type_name());
         }
         return lookup(key);
@@ -3845,31 +3918,43 @@ class basic_json_view
     }
 
     /// the element at this index; a discarded view if the index is out of
-    /// range. Throws type_error.305 if this is not an array.
+    /// range, or if this is a discarded view. Throws type_error.305 if this is
+    /// any other value but an array.
     basic_json_view operator[](size_type idx) const
     {
         if (NLOHMANN_VIEW_UNLIKELY(!is_array()))
         {
+            if (is_discarded())
+            {
+                return basic_json_view();
+            }
             detail::view::throw_type_error(305, "cannot use operator[] with a numeric argument with ", type_name());
         }
         return idx < m_node->len ? basic_json_view(m_doc, detail::view::element_at(m_node, idx)) : basic_json_view();
     }
 
-    /// (an int argument would be ambiguous between size_type and const char*)
-    basic_json_view operator[](int idx) const
+    /// any other integer type (int, unsigned, long, std::int64_t, ...; a
+    /// single overload for size_type alone would be ambiguous for all of them
+    /// and for const char*); negative values are out of range
+    template < typename IntegerType, typename std::enable_if < detail::view::is_index_type<IntegerType>::value, int >::type = 0 >
+    basic_json_view operator[](IntegerType idx) const
     {
-        return operator[](static_cast<size_type>(idx));
+        return operator[](detail::view::to_index<size_type>(idx));
     }
 
     /// the value a JSON pointer refers to; a discarded view if a key is
-    /// missing or an index is out of range. Other errors throw what const
-    /// basic_json::operator[] throws.
+    /// missing or an index is out of range, or if this is a discarded view.
+    /// Other errors throw what const basic_json::operator[] throws.
     basic_json_view operator[](const json_pointer& ptr) const
     {
+        if (NLOHMANN_VIEW_UNLIKELY(is_discarded()))
+        {
+            return basic_json_view();
+        }
         return detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::unchecked);
     }
 
-    /// the value of the member with this key (the first one, should the key
+    /// the value of the member with this key (the last one, should the key
     /// occur more than once). Throws type_error.304 if this is not an object,
     /// and out_of_range.403 if there is no such member.
     basic_json_view at(string_view_t key) const
@@ -3879,7 +3964,7 @@ class basic_json_view
             detail::view::throw_type_error(304, "cannot use at() with ", type_name());
         }
         const basic_json_view r = lookup(key);
-        if (NLOHMANN_VIEW_UNLIKELY(!r))
+        if (NLOHMANN_VIEW_UNLIKELY(r.is_discarded()))
         {
             detail::view::throw_out_of_range(403, detail::concat("key '", std::string(key.data(), key.size()), "' not found"));
         }
@@ -3911,9 +3996,12 @@ class basic_json_view
         return basic_json_view(m_doc, detail::view::element_at(m_node, idx));
     }
 
-    basic_json_view at(int idx) const
+    /// any other integer type, see operator[]; negative values are out of
+    /// range
+    template < typename IntegerType, typename std::enable_if < detail::view::is_index_type<IntegerType>::value, int >::type = 0 >
+    basic_json_view at(IntegerType idx) const
     {
-        return at(static_cast<size_type>(idx));
+        return at(detail::view::to_index<size_type>(idx));
     }
 
     /// the value a JSON pointer refers to; throws what basic_json::at()
@@ -3924,7 +4012,7 @@ class basic_json_view
     }
 
     /// the member with this key converted to T, or the default value if there
-    /// is no such member (the first one, should the key occur more than
+    /// is no such member (the last one, should the key occur more than
     /// once). Throws type_error.306 if this is not an object.
     template < typename T, typename std::enable_if < !std::is_same<typename std::decay<T>::type, const char*>::value, int >::type = 0 >
     T value(string_view_t key, const T& default_value) const
@@ -3934,7 +4022,7 @@ class basic_json_view
             detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = lookup(key);
-        return r ? r.template get<T>() : default_value;
+        return r.is_discarded() ? default_value : r.template get<T>();
     }
 
     string_t value(string_view_t key, const char* default_value) const
@@ -3953,7 +4041,7 @@ class basic_json_view
             detail::view::throw_type_error(306, "cannot use value() with ", type_name());
         }
         const basic_json_view r = detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::value);
-        return r ? r.template get<T>() : default_value;
+        return r.is_discarded() ? default_value : r.template get<T>();
     }
 
     string_t value(const json_pointer& ptr, const char* default_value) const
@@ -3989,7 +4077,7 @@ class basic_json_view
     // lookup //
     ////////////
 
-    /// an iterator to the member with this key (the first one, should the
+    /// an iterator to the member with this key (the last one, should the
     /// key occur more than once), or end(); end() also for non-objects
     iterator find(string_view_t key) const
     {
@@ -4031,7 +4119,7 @@ class basic_json_view
     /// basic_json::contains())
     bool contains(const json_pointer& ptr) const
     {
-        return static_cast<bool>(detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::contains));
+        return !detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::contains).is_discarded();
     }
 
     /// 1 if this is an object with a member with this key, else 0 (duplicate
@@ -4294,7 +4382,7 @@ class basic_json_view
         return (std::min)(m_doc->size - m_node->off, static_cast<std::size_t>(1024) + nodes * 16);
     }
 
-    /// the value of the first member with this key, or a discarded view
+    /// the value of the last member with this key, or a discarded view
     /// (object required)
     NLOHMANN_VIEW_ALWAYS_INLINE basic_json_view lookup(string_view_t key) const noexcept
     {
@@ -4428,6 +4516,13 @@ class basic_json_document
         return d;
     }
 
+    /// parse(ptr, len) does not compile: len would convert to allow_exceptions
+    /// and ptr be read as a C string (as for the overloads of parse_copy,
+    /// accept, and read below)
+    template<typename InputType, typename IntegerType, typename... Flags>
+    static typename std::enable_if<detail::view::is_integer_not_bool<IntegerType>::value, basic_json_document>::type
+    parse(InputType&& input, IntegerType value, Flags&&... flags) = delete;
+
     /// parse [first, last)
     template<typename IteratorType, typename std::enable_if<
                  std::is_base_of<std::input_iterator_tag, typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
@@ -4455,6 +4550,10 @@ class basic_json_document
         return d;
     }
 
+    template<typename InputType, typename IntegerType, typename... Flags>
+    static typename std::enable_if<detail::view::is_integer_not_bool<IntegerType>::value, basic_json_document>::type
+    parse_copy(InputType&& input, IntegerType value, Flags&&... flags) = delete;
+
     /// check whether the input is valid JSON (the result of basic_json::accept)
     template<typename InputType>
     static bool accept(InputType&& input, const bool ignore_comments = false, const bool ignore_trailing_commas = false)
@@ -4464,6 +4563,10 @@ class basic_json_document
         return !d.is_discarded();
     }
 
+    template<typename InputType, typename IntegerType, typename... Flags>
+    static typename std::enable_if<detail::view::is_integer_not_bool<IntegerType>::value, bool>::type
+    accept(InputType&& input, IntegerType value, Flags&&... flags) = delete;
+
     /// parse into this document, reusing its memory
     template<typename InputType>
     // flawfinder: ignore (a member function, not POSIX read())
@@ -4476,12 +4579,17 @@ class basic_json_document
                   std::integral_constant<detail::view::input_kind, detail::view::classify_input<InputType>::value> {});
     }
 
+    template<typename InputType, typename IntegerType, typename... Flags>
+    // flawfinder: ignore (a member function, not POSIX read())
+    typename std::enable_if<detail::view::is_integer_not_bool<IntegerType>::value, void>::type
+    read(InputType&& input, IntegerType value, Flags&&... flags) = delete;
+
     ////////////
     // access //
     ////////////
 
     /// the root value (discarded if parsing failed without exceptions)
-    view_type root() const noexcept
+    view_type root() const& noexcept
     {
         if (!m_data || m_data->discarded)
         {
@@ -4490,6 +4598,9 @@ class basic_json_document
         return view_type(m_data.get(), m_data->tape);
     }
 
+    /// deleted: the view of a temporary document would dangle
+    view_type root() const&& = delete;
+
     bool is_discarded() const noexcept
     {
         return !m_data || m_data->discarded;
@@ -4595,9 +4706,9 @@ class basic_json_document
         d.discarded = true;
         detail::view::parse_failure failure;
         bool ok = false;
-        if (NLOHMANN_VIEW_UNLIKELY(size >= 0xFFFFFFF0u))
+        if (NLOHMANN_VIEW_UNLIKELY(size > detail::view::max_input_size))
         {
-            failure.code = detail::view::error_code::input_too_large; // LCOV_EXCL_LINE (4 GiB)
+            failure.code = detail::view::error_code::input_too_large;
         }
         else
         {