Regenerate the amalgamated headers

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

README.md

@@ -1387,7 +1387,7 @@ THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR I
 - The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2009 [Florian Loitsch](https://florian.loitsch.com/)
 - The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
 - The class contains parts of [Google Abseil](https://github.com/abseil/abseil-cpp) which is licensed under the [Apache 2.0 License](https://opensource.org/licenses/Apache-2.0).
-- The class contains an adapted version of the Eisel-Lemire algorithm and its table of powers of five from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
+- The class contains an adapted version of the Eisel-Lemire algorithm, its table of powers of five, and its digit comparison for long numbers from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
 
 <img align="right" src="https://git.fsfe.org/reuse/reuse-ci/raw/branch/master/reuse-horizontal.png" alt="REUSE Software">
 

docs/mkdocs/docs/api/basic_json/diff.md

@@ -59,7 +59,6 @@ Currently, only `remove`, `add`, and `replace` operations are generated.
 - [patch](patch.md) applies a JSON Patch
 - [patch_inplace](patch_inplace.md) applies a JSON Patch in place
 - [merge_patch](merge_patch.md) applies a JSON Merge Patch
-- [merge_diff](merge_diff.md) creates a diff as a JSON Merge Patch
 
 ## Version history
 

docs/mkdocs/docs/api/basic_json/index.md

@@ -285,7 +285,6 @@ Access to the JSON value
 ### JSON Merge Patch functions
 
 - [**merge_patch**](merge_patch.md) - applies a JSON Merge Patch
-- [**merge_diff**](merge_diff.md) (_static_) - creates a diff as a JSON Merge Patch
 
 ## Static functions
 

docs/mkdocs/docs/api/basic_json/merge_diff.md

@@ -1,79 +0,0 @@
-# <small>nlohmann::basic_json::</small>merge_diff
-
-```cpp
-static basic_json merge_diff(const basic_json& source,
-                             const basic_json& target);
-```
-
-Creates a [JSON Merge Patch](https://tools.ietf.org/html/rfc7396) so that value `source` can be changed into the value
-`target` by calling the [`merge_patch`](merge_patch.md) function. The patch contains only what differs: changed and
-added members with their new values, and removed members with the value `#!json null`. Nested objects are compared
-member by member; any other value that differs, including an array, is replaced as a whole.
-
-For two JSON values `source` and `target`, where `target` contains no object member whose value is `#!json null`, the
-following code always yields `#!cpp true`:
-```cpp
-basic_json patched = source;
-patched.merge_patch(merge_diff(source, target));
-patched == target;
-```
-
-## Parameters
-
-`source` (in)
-:   JSON value to compare from
-
-`target` (in)
-:   JSON value to compare against
-
-## Return value
-
-a JSON Merge Patch to convert the `source` to `target`
-
-## Exception safety
-
-Strong guarantee: `source` and `target` are never modified.
-
-## Complexity
-
-Linear in the total number of values (including nested ones) in `source` and `target`, times the cost of a key-based
-object operation (looking up a key, or adding one to the patch): logarithmic for [`json`](../json.md), and linear for
-[`ordered_json`](../ordered_json.md) (see [`ordered_map` complexity](../ordered_map.md#complexity)). For
-`ordered_json`, diffing two objects with `n` and `m` members therefore takes O((n+m)²).
-
-## Notes
-
-- A merge patch uses `#!json null` to remove a member, so it cannot set a member to `#!json null`. As in RFC 7396, a
-  `#!json null` member of `target` is treated as absent: the patch removes the member from `source` instead of setting
-  it to `#!json null`. A member that is `#!json null` in both `source` and `target` is unchanged and left out of the
-  patch, so `source` keeps it.
-- A merge patch cannot reorder object members, and [`merge_patch`](merge_patch.md) appends added members at the end.
-  For [`ordered_json`](../ordered_json.md), the patched value therefore has the same members as `target`, but not
-  necessarily in the same order, and may compare unequal to it. The patch lists changed and removed members in the
-  order of `source`, followed by added members in the order of `target`.
-
-## Examples
-
-??? example
-
-    The following code shows how a JSON Merge Patch is created as a diff for two JSON values.
-
-    ```cpp
-    --8<-- "examples/merge_diff.cpp"
-    ```
-
-    Output:
-
-    ```json
-    --8<-- "examples/merge_diff.output"
-    ```
-
-## See also
-
-- [RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396)
-- [merge_patch](merge_patch.md) applies a JSON Merge Patch
-- [diff](diff.md) creates a diff as a JSON Patch
-
-## Version history
-
-- Added in version 3.13.0.

docs/mkdocs/docs/api/basic_json/merge_patch.md

@@ -67,7 +67,6 @@ returned by `#!cpp (*this)[key]`); it is read as it was when `merge_patch()` was
 
 - [RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396)
 - [patch](patch.md) apply a JSON patch
-- [merge_diff](merge_diff.md) creates a diff as a JSON Merge Patch
 
 ## Version history
 

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

@@ -23,9 +23,10 @@ type to use.
 ## Template parameters
 
 `NumberFloatType`
-:   the type to store floating-point numbers. Parsing and serialization are implemented in terms of
+:   the type to store floating-point numbers. The type must be `#!cpp float`, `#!cpp double`, or
-    `#!cpp std::strtof`/`#!cpp std::strtod`/`#!cpp std::strtold` and `#!cpp std::snprintf`, so the type must be
+    `#!cpp long double`. The parser converts `#!cpp float`, `#!cpp double`, and a `#!cpp long double` that is IEEE 754
-    `#!cpp float`, `#!cpp double`, or `#!cpp long double`. The
+    binary64 itself. It converts other `#!cpp long double` formats with `#!cpp std::from_chars` where available, or
+    with `#!cpp std::strtold` otherwise. Serialization falls back to `#!cpp std::snprintf`. The
     [binary formats](../../features/binary_formats/index.md) additionally require `#!cpp float` or `#!cpp double`,
     because they have no encoding for `#!cpp long double`. See
     [Template Parameter Requirements](../../features/types/template_parameters.md#numberfloattype).

docs/mkdocs/docs/examples/merge_diff.cpp

@@ -1,51 +0,0 @@
-#include <iostream>
-#include <iomanip>
-#include <nlohmann/json.hpp>
-
-using json = nlohmann::json;
-using namespace nlohmann::literals;
-
-int main()
-{
-    // the source document
-    json source = R"(
-        {
-            "title": "Goodbye!",
-            "author": {
-                "givenName": "John",
-                "familyName": "Doe"
-            },
-            "tags": [
-                "example",
-                "sample"
-            ],
-            "content": "This will be unchanged"
-        }
-    )"_json;
-
-    // the target document
-    json target = R"(
-        {
-            "title": "Hello!",
-            "author": {
-                "givenName": "John"
-            },
-            "tags": [
-                "example"
-            ],
-            "content": "This will be unchanged",
-            "phoneNumber": "+01-123-456-7890"
-        }
-    )"_json;
-
-    // create the patch
-    json patch = json::merge_diff(source, target);
-
-    // roundtrip
-    json patched_source = source;
-    patched_source.merge_patch(patch);
-
-    // output patch and roundtrip result
-    std::cout << std::setw(4) << patch << "\n\n"
-              << std::setw(4) << patched_source << std::endl;
-}

docs/mkdocs/docs/examples/merge_diff.output

@@ -1,22 +0,0 @@
-{
-    "author": {
-        "familyName": null
-    },
-    "phoneNumber": "+01-123-456-7890",
-    "tags": [
-        "example"
-    ],
-    "title": "Hello!"
-}
-
-{
-    "author": {
-        "givenName": "John"
-    },
-    "content": "This will be unchanged",
-    "phoneNumber": "+01-123-456-7890",
-    "tags": [
-        "example"
-    ],
-    "title": "Hello!"
-}

docs/mkdocs/docs/features/merge_patch.md

@@ -9,9 +9,6 @@ syntax that closely mimics the document being modified. Unlike [JSON Patch](json
 express every kind of change (e.g., it cannot reorder array elements or remove a specific array element), but it is
 easier to read and write for object-shaped documents.
 
-The function [`merge_diff`](../api/basic_json/merge_diff.md) creates a merge patch that changes one JSON value into
-another.
-
 !!! tip "Not a general deep merge"
 
     A merge patch is not a general deep merge: a `#!json null` value in the patch deletes the key from the target.
@@ -38,5 +35,4 @@ another.
 - [JSON Patch and Diff](json_patch.md) - a more expressive alternative that describes a sequence of operations
 - [JSON Pointer](json_pointer.md) - the addressing scheme used by JSON Patch
 - Function [`merge_patch`](../api/basic_json/merge_patch.md)
-- Function [`merge_diff`](../api/basic_json/merge_diff.md)
 - Function [`update`](../api/basic_json/update.md) - merge objects, optionally recursively

docs/mkdocs/docs/features/types/number_handling.md

@@ -82,12 +82,13 @@ flowchart TD
 
     - Numbers with a decimal digit or scientific notation are always stored as `#!c double`.
     - The number types can be changed, see [Template number types](#template-number-types). 
-    - Integers are converted by the library's own digit parser. Floating-point numbers are converted with
+    - The library converts integers and floating-point numbers itself, independent of the locale. Floating-point
-      [`std::from_chars`](https://en.cppreference.com/w/cpp/utility/from_chars) if the library is compiled with C++17
+      numbers are correctly rounded (to nearest, ties to even). Only a `#!c long double` that is not IEEE 754 binary64
-      and the standard library supports it, then with an exact fast path for `#!c double` values with few significant
+      (e.g., the 80-bit x87 format) is converted with `#!cpp std::from_chars` where available, or else with
-      digits, and otherwise with the locale-aware
+      [`std::strtold`](https://en.cppreference.com/w/cpp/string/byte/strtof). For that call, the library temporarily
-      [`std::strtod`](https://en.cppreference.com/w/cpp/string/byte/strtof) (`std::strtof`/`std::strtold` for the
+      replaces the `.` with the decimal point of the current locale (which may be longer than one byte, e.g., in
-      other floating-point types). Before version 3.13.0, the conversion was realized by
+      `fa_IR.UTF-8`), so the result does not depend on the locale either. Changing the locale in another thread during
+      parsing is undefined behavior of the C library, though. Before version 3.13.0, the conversion was realized by
       [`std::strtoull`](https://en.cppreference.com/w/cpp/string/byte/strtoul),
       [`std::strtoll`](https://en.cppreference.com/w/cpp/string/byte/strtol), and `std::strtod`, respectively.
 
@@ -100,10 +101,10 @@ flowchart TD
 ### Number limits
 
 - Any 64-bit signed or unsigned integer can be stored without loss of precision.
-- Numbers exceeding the limits of `#!c double` (i.e., numbers that after conversion via
+- Numbers exceeding the limits of `#!c double` (i.e., numbers whose rounded value is not satisfying
-[`std::strtod`](https://en.cppreference.com/w/cpp/string/byte/strtof) are not satisfying
 [`std::isfinite`](https://en.cppreference.com/w/cpp/numeric/math/isfinite) such as `#!c 1E400`) will throw exception
-[`json.exception.out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406) during parsing.
+[`json.exception.out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406) during parsing. Numbers too
+small for `#!c double` (such as `#!c 1E-400`) become zero, with the sign of the number.
 - Floating-point numbers are rounded to the next number representable as `double`. For instance
 `#!c 3.141592653589793238462643383279` is stored as [`0x400921fb54442d18`](https://float.exposed/0x400921fb54442d18).
 This is the same behavior as the code `#!c double x = 3.141592653589793238462643383279;`.

docs/mkdocs/docs/features/types/template_parameters.md

@@ -30,9 +30,9 @@ Requirements are split into two groups:
     diagnosed with dedicated error messages, and violating most of them results in a compiler error somewhere inside
     the library. Four violations are not caught at compile time at all:
 
-    - A [`StringType`](#stringtype) whose `data()` is not null-terminated compiles and can silently misparse
+    - A [`StringType`](#stringtype) whose `data()` is not null-terminated compiles and silently misparses numbers
-      floating-point numbers, because the lexer may hand the buffer to `#!cpp std::strtod`, which reads up to the
+      stored as a `#!cpp long double` that is not IEEE 754 binary64 (e.g., the 80-bit x87 format), because the lexer
-      terminating null character.
+      hands the buffer to `#!cpp std::strtold`.
     - A stateful [`AllocatorType`](#allocatortype) compiles and silently ignores its state: allocation, deallocation,
       and [`get_allocator()`](../../api/basic_json/get_allocator.md) each use a different default-constructed instance.
     - The two [cross-specialization conversions](#cross-specialization-conversions) below. These abort on an assertion
@@ -353,16 +353,21 @@ using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
 ### Always required
 
 - A member type `value_type` that is one byte wide and `char`-compatible. The library stores and processes UTF-8
-  encoded `char` data and passes `data()` to functions that take a `#!cpp const char*`, such as `#!cpp std::strtod`.
+  encoded `char` data and passes `data()` to functions that take a `#!cpp const char*`, such as `#!cpp std::strtold`
+  (only used to parse a `#!cpp long double` that is not IEEE 754 binary64, see
+  [`NumberFloatType`](#numberfloattype)).
   `#!cpp std::wstring`, `#!cpp std::u16string`, and `#!cpp std::u32string` are **not** valid choices; see the FAQ on
   [wide string handling](../../home/faq.md#wide-string-handling).
 - Constructors: default, copy, move, from `#!cpp const char*` (which must not be `#!cpp explicit`), from
   `#!cpp (const char*, size_type)`, and from `#!cpp (size_type, char)`; and copy or move assignment.
 - Member functions `size()`, `clear()`, `resize(n, c)`, `data()`, `push_back(char)`, and `operator[]`
   (const and non-const, returning references). `c_str()` and `back()` are **not** required.
-- `data()` must return a pointer to a contiguous, **null-terminated** buffer -- the parser may hand it to
+- `data()` must return a pointer to a contiguous, **null-terminated** buffer. `#!cpp float`, `#!cpp double`, and a
-  `#!cpp std::strtod`, which reads up to the null character. A type whose `data()` is not null-terminated does not
+  `#!cpp long double` that is IEEE 754 binary64 are converted by the library itself and do not depend on this. For any
-  fail to compile; it can silently misparse floating-point numbers.
+  other `NumberFloatType` (a `#!cpp long double` of another format), the parser falls back to `#!cpp std::strtold` when
+  `#!cpp std::from_chars` is not available or declines the token, and `std::strtold` reads up to the null character. A type whose `data()`
+  is not null-terminated does not fail to compile; with such a `NumberFloatType` it can silently misparse
+  floating-point numbers.
 - `append(const char*, size_type)`, used by [`dump`](../../api/basic_json/dump.md), and `append(const StringType&)`,
   used by the CBOR reader for indefinite-length strings. The library's internal string concatenation additionally has
   to append a `#!cpp char` and a `#!cpp const char*`; for each it selects between `append(arg)`, `#!cpp operator+=`,
@@ -541,9 +546,10 @@ therefore silently changes parse results rather than raising an error. See
 
 `NumberFloatType` must be one of `#!cpp float`, `#!cpp double`, or `#!cpp long double`:
 
-- The [parser](../parsing/index.md) converts number literals with `#!cpp std::from_chars` or, as a fallback, with
+- The [parser](../parsing/index.md) converts number literals to `#!cpp float`, `#!cpp double`, and a
-  `#!cpp std::strtof`, `#!cpp std::strtod`, or `#!cpp std::strtold`; the library provides overloads for exactly these
+  `#!cpp long double` that is IEEE 754 binary64 itself; other `#!cpp long double` formats are converted with
-  three types.
+  `#!cpp std::from_chars` where available, or with `#!cpp std::strtold`. The library provides overloads for exactly
+  these three types.
 - [`dump`](../../api/basic_json/dump.md) falls back to `#!cpp std::snprintf` with the `%g` and `%Lg` conversion
   specifiers, for which the library likewise provides only `#!cpp double` and `#!cpp long double` overloads
   (`#!cpp float` is promoted to `#!cpp double`).

docs/mkdocs/docs/home/architecture.md

@@ -185,11 +185,9 @@ The lexer detects two optional extensions at compile time. Only `iterator_input_
 random-access input of single-byte characters:
 
 - `supports_seek`, `get_consumed_count()`, and `copy_consumed_range()` let the lexer reconstruct already consumed input
-  for error messages instead of copying every character it reads. With `get_read_count()` and
+  for error messages instead of copying every character it reads.
-  `count_consumed_lines()`, the lexer also derives the read position from the adapter and counts lines only when an
-  error needs them, instead of counting characters and lines on every read.
 - `supports_bulk_scan`, `bulk_data()`, `bulk_remaining()`, and `bulk_skip()` let the lexer scan strings directly in
-  contiguous memory, several bytes at a time, and skip the spaces that indent a line in 8-byte steps.
+  contiguous memory, several bytes at a time.
 
 The function `input_adapter` picks the right adapter for the argument passed to `parse`, `accept`, `sax_parse`, or the
 `from_*` functions:

docs/mkdocs/docs/home/license.md

@@ -20,4 +20,4 @@ The class contains a slightly modified version of the Grisu2 algorithm from Flor
 
 The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
 
-The class contains an adapted version of the Eisel-Lemire algorithm and its table of powers of five from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
+The class contains an adapted version of the Eisel-Lemire algorithm, its table of powers of five, and its digit comparison for long numbers from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors

docs/mkdocs/mkdocs.yml

@@ -182,7 +182,6 @@ nav:
           - 'json_serializer': api/basic_json/json_serializer.md
           - 'max_size': api/basic_json/max_size.md
           - 'meta': api/basic_json/meta.md
-          - 'merge_diff': api/basic_json/merge_diff.md
           - 'merge_patch': api/basic_json/merge_patch.md
           - 'number_float_t': api/basic_json/number_float_t.md
           - 'number_integer_t': api/basic_json/number_integer_t.md

include/nlohmann/detail/bit_ops.hpp

@@ -9,8 +9,9 @@
 #pragma once
 
 #include <cstdint> // uint64_t
-#if !defined(__SIZEOF_INT128__) && defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+#include <cstring> // memcpy
-    #include <intrin0.h> // __umulh, _umul128
+#if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64)) && (!defined(__SIZEOF_INT128__) || (!defined(__GNUC__) && !defined(__clang__)))
+    #include <intrin0.h> // __umulh, _umul128, _BitScanForward64, _BitScanReverse64
 #endif
 
 #include <nlohmann/detail/abi_macros.hpp>
@@ -28,6 +29,10 @@ inline int count_leading_zeros(std::uint64_t x) noexcept
 {
 #if defined(__GNUC__) || defined(__clang__)
     return __builtin_clzll(x);
+#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    unsigned long index = 0; // NOLINT(runtime/int): the type _BitScan*64 takes
+    _BitScanReverse64(&index, x);
+    return 63 - static_cast<int>(index);
 #else
     int n = 0;
     for (int shift = 32; shift != 0; shift >>= 1)
@@ -47,6 +52,10 @@ inline int count_trailing_zeros(std::uint64_t x) noexcept
 {
 #if defined(__GNUC__) || defined(__clang__)
     return __builtin_ctzll(x);
+#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    unsigned long index = 0; // NOLINT(runtime/int): the type _BitScan*64 takes
+    _BitScanForward64(&index, x);
+    return static_cast<int>(index);
 #else
     int n = 0;
     for (int shift = 32; shift != 0; shift >>= 1)
@@ -94,15 +103,26 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
 #endif
 }
 
-/// eight bytes as a little-endian word (compilers fold this into one load on
+/// eight bytes as a little-endian word (a single load on little-endian targets)
-/// little-endian targets)
+inline std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
-inline std::uint64_t read_eight_bytes(const char* p) noexcept
 {
-    const auto* b = reinterpret_cast<const unsigned char*>(p); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+#if defined(_MSC_VER) || defined(__x86_64__) || defined(__i386__) || (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+    // the byte order already matches (all MSVC targets are little-endian)
+    std::uint64_t result = 0;
+    std::memcpy(&result, b, sizeof(result));
+    return result;
+#else
     return static_cast<std::uint64_t>(b[0]) | (static_cast<std::uint64_t>(b[1]) << 8u)
            | (static_cast<std::uint64_t>(b[2]) << 16u) | (static_cast<std::uint64_t>(b[3]) << 24u)
            | (static_cast<std::uint64_t>(b[4]) << 32u) | (static_cast<std::uint64_t>(b[5]) << 40u)
            | (static_cast<std::uint64_t>(b[6]) << 48u) | (static_cast<std::uint64_t>(b[7]) << 56u);
+#endif
+}
+
+/// eight bytes as a little-endian word
+inline std::uint64_t read_eight_bytes(const char* p) noexcept
+{
+    return read_eight_bytes(reinterpret_cast<const unsigned char*>(p)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
 }
 
 }  // namespace detail

include/nlohmann/detail/input/input_adapters.hpp

@@ -8,12 +8,12 @@
 
 #pragma once
 
-#include <algorithm> // count, find, min
+#include <algorithm> // min
 #include <array> // array
 #include <cstddef> // size_t
 #include <cstdint> // uint32_t
 #include <cstring> // strlen
-#include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next, reverse_iterator
+#include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next
 #include <streambuf> // streambuf
 #include <string> // string, char_traits
 #include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
@@ -297,7 +297,6 @@ class iterator_input_adapter
             return result;
         }
 
-        ++eof_reads;
         return char_traits<char_type>::eof();
     }
 
@@ -307,26 +306,6 @@ class iterator_input_adapter
         return static_cast<std::size_t>(std::distance(begin, current));
     }
 
-    // number of get_character() calls so far, including those that returned
-    // EOF; the lexer derives its position from it (see lexer::lazy_position)
-    std::size_t get_read_count() const
-    {
-        return get_consumed_count() + eof_reads;
-    }
-
-    // number of newlines in the consumed range [0, last_index); @a line_start
-    // is set to the index after the last of them (0 if there is none); only
-    // valid when supports_seek
-    std::size_t count_consumed_lines(std::size_t last_index, std::size_t& line_start) const
-    {
-        const auto to = std::next(begin, static_cast<typename std::iterator_traits<IteratorType>::difference_type>(last_index));
-        const auto newline = char_traits<char_type>::to_char_type('\n');
-        using reverse_it = std::reverse_iterator<IteratorType>;
-        const auto last_newline = std::find(reverse_it(to), reverse_it(begin), newline);
-        line_start = static_cast<std::size_t>(std::distance(begin, last_newline.base()));
-        return static_cast<std::size_t>(std::count(begin, last_newline.base(), newline));
-    }
-
     // append the already-consumed characters in the half-open range
     // [first_index, last_index) to @a out; only valid when supports_seek
     template<typename ContainerType>
@@ -443,8 +422,6 @@ class iterator_input_adapter
     IteratorType begin;
     IteratorType current;
     SentinelType end;
-    /// number of get_character() calls that returned EOF
-    std::size_t eof_reads = 0;
 
     template<typename BaseInputAdapter, size_t T>
     friend struct wide_string_input_helper;

include/nlohmann/detail/input/json_sax.hpp

@@ -217,7 +217,7 @@ struct diagnostic_positions
         {
             // Lexer has read the first character of the container, so
             // subtract 1 from the position to get the correct start position.
-            v.start_position = lexer->get_chars_read_total() - 1;
+            v.start_position = lexer->get_position() - 1;
         }
     }
 
@@ -231,7 +231,7 @@ struct diagnostic_positions
         if (lexer)
         {
             // Lexer's position is past the closing brace or bracket, so set that as the end position.
-            v.end_position = lexer->get_chars_read_total();
+            v.end_position = lexer->get_position();
         }
     }
 
@@ -247,7 +247,7 @@ struct diagnostic_positions
             // Lexer has read past the current field value, so set the end position to the current position.
             // The start position will be set below based on the length of the string representation
             // of the value.
-            v.end_position = lexer->get_chars_read_total();
+            v.end_position = lexer->get_position();
 
             switch (v.type())
             {

include/nlohmann/detail/input/lexer.hpp

@@ -17,7 +17,6 @@
 #include <utility> // move
 #include <vector> // vector
 
-#include <nlohmann/detail/bit_ops.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
 #include <nlohmann/detail/input/number_parse.hpp>
 #include <nlohmann/detail/input/position_t.hpp>
@@ -187,15 +186,6 @@ class lexer : public lexer_base<BasicJsonType>
     static constexpr bool lazy_token_string =
         input_adapter_supports_seek<InputAdapterType>(is_detected<detect_supports_seek, InputAdapterType> {});
 
-    /// whether the read position is derived from the input adapter on demand
-    /// instead of being counted on every scanned character. Seekable adapters
-    /// know how much input they consumed and can revisit it, so
-    /// chars_read_total is the adapter's read count (minus a pending unget),
-    /// and line and column are recomputed from the consumed input only when
-    /// get_position() is called (errors). Counting per character kept two
-    /// increments and a newline check in the hot path of every get().
-    static constexpr bool lazy_position = lazy_token_string;
-
     /// whether a simulated unget can be passed on to the input adapter, which
     /// then leaves the character in the input; see
     /// input_adapter_supports_lookahead
@@ -205,9 +195,7 @@ class lexer : public lexer_base<BasicJsonType>
     /// whether string scanning may bulk-consume runs of ordinary characters
     /// directly from a contiguous input buffer (SWAR fast path). This requires
     /// the token to be reconstructible lazily (lazy_token_string), so bypassing
-    /// the per-character capture in get() cannot lose error diagnostics. It
+    /// the per-character capture in get() cannot lose error diagnostics.
-    /// also implies lazy_position, so the bulk paths need not advance the
-    /// position counters.
     static constexpr bool bulk_scan =
         lazy_token_string
         && input_adapter_supports_bulk_scan<InputAdapterType>(is_detected<detect_supports_bulk_scan, InputAdapterType> {});
@@ -233,6 +221,44 @@ class lexer : public lexer_base<BasicJsonType>
     // scan functions
     /////////////////////
 
+    /// contiguous input: try to decode the 4 hex digits following `\\u`
+    /// directly from the input buffer via hex_codepoint(), instead of 4 calls
+    /// to get(). On success, advances the adapter and the position counters
+    /// exactly as those 4 get() calls would (a hex digit is never '\n', so
+    /// only the flat counters move) and leaves @a current holding the last of
+    /// the 4 digits, just as the last such get() would; the codepoint is
+    /// written to @a out. Makes no state change and returns false - for a
+    /// pending unget, fewer than 4 remaining bytes, or any of the 4 bytes not
+    /// being a hex digit - so the caller falls back unchanged to the
+    /// per-character loop, which then reports the same diagnostic (stopping
+    /// at the first invalid digit) as before this optimization.
+    bool get_codepoint_bulk(std::true_type /*bulk*/, int& out)
+    {
+        if (next_unget || ia.bulk_remaining() < 4)
+        {
+            return false;
+        }
+        const char_type* const raw = ia.bulk_data();
+        const int codepoint = hex_codepoint(reinterpret_cast<const unsigned char*>(raw));
+        if (codepoint < 0)
+        {
+            return false;
+        }
+        ia.bulk_skip(4);
+        // a hex digit is never a newline, so only the flat counters advance
+        position.chars_read_total += 4;
+        position.chars_read_current_line += 4;
+        current = char_traits<char_type>::to_int_type(raw[3]);
+        out = codepoint;
+        return true;
+    }
+
+    /// streaming input: no bulk fast path
+    bool get_codepoint_bulk(std::false_type /*bulk*/, int& /*out*/) const noexcept
+    {
+        return false;
+    }
+
     /*!
     @brief get codepoint from 4 hex characters following `\\u`
 
@@ -252,6 +278,14 @@ class lexer : public lexer_base<BasicJsonType>
     {
         // this function only makes sense after reading `\u`
         JSON_ASSERT(current == 'u');
+
+        // contiguous input: decode all 4 hex digits directly from the buffer
+        int fast_codepoint = 0;
+        if (get_codepoint_bulk(std::integral_constant<bool, bulk_scan> {}, fast_codepoint))
+        {
+            return fast_codepoint;
+        }
+
         int codepoint = 0;
 
         const auto factors = { 12u, 8u, 4u, 0u };
@@ -343,6 +377,10 @@ class lexer : public lexer_base<BasicJsonType>
         }
         token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), pos);
         ia.bulk_skip(pos);
+        // the run contains no newline (all bytes < 0x20 are treated as special),
+        // so only the flat character counters advance
+        position.chars_read_total += pos;
+        position.chars_read_current_line += pos;
     }
 
     /// streaming input: no bulk fast path
@@ -1052,9 +1090,11 @@ class lexer : public lexer_base<BasicJsonType>
             token_type::parse_error otherwise
 
     @note The scanner is independent of the current locale: token_buffer
-          always holds `.`. Only the std::strtod fallback of convert_number()
+          always holds `.`. The conversion of float and double does not use
-          depends on the locale, and it looks up the decimal point right
+          the locale either. Only the std::strtold fallback of
-          before converting (see detail::convert_float_locale_aware()).
+          convert_number() for long double formats other than binary64
+          depends on it, and it looks up the decimal point right before
+          converting (see detail::convert_float_locale_aware()).
     */
     token_type scan_number()  // lgtm [cpp/use-of-goto] `goto` is used in this function to implement the number-parsing state machine described above. By design, any finite input will eventually reach the "done" state or return token_type::parse_error. In each intermediate state, 1 byte of the input is appended to the token_buffer vector, and only the already initialized variables token_buffer, number_type, and error_message are manipulated.
     {
@@ -1067,7 +1107,7 @@ class lexer : public lexer_base<BasicJsonType>
 
         // offset just past the last mantissa byte in token_buffer (i.e. the
         // index of 'e'/'E', or the whole token when there is no exponent).
-        // convert_number() uses it to count significant digits; npos means
+        // convert_number() uses it to split the token; npos means
         // "not seen an exponent yet" and is resolved at scan_number_done
         std::size_t mantissa_end = std::string::npos;
 
@@ -1397,8 +1437,8 @@ scan_number_done:
     @param[in] mantissa_end  offset just past the last mantissa byte in
                              token_buffer (the index of 'e'/'E', or
                              token_buffer.size() when there is no exponent);
-                             used to skip Clinger's fast path when it cannot
+                             with decimal_point_position, it locates the parts
-                             possibly succeed - see detail::mantissa_fits_clinger()
+                             of a float token without scanning it again
     */
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
@@ -1452,10 +1492,11 @@ scan_number_done:
         }
 
         // this code is reached if we parse a floating-point number or if an
-        // integer conversion above overflowed. Prefer std::from_chars
+        // integer conversion above overflowed. float and double (and long
-        // (Eisel-Lemire, locale-independent, correctly rounded) when available;
+        // double where it is binary64) are converted by the library itself,
-        // otherwise the exact Clinger fast path (double only); otherwise the
+        // correctly rounded and independent of the locale; other long double
-        // locale-aware strtof/strtod/strtold.
+        // formats use std::from_chars when available, otherwise the
+        // locale-aware strtold.
         if (convert_float_fast(num_begin, num_end, decimal_point_position, mantissa_end, value_float))
         {
             return token_type::value_float;
@@ -1575,6 +1616,8 @@ scan_number_done:
             if (JSON_HEDLEY_LIKELY(integer_result != token_type::uninitialized))
             {
                 ia.bulk_skip(len - 1);
+                position.chars_read_total += (len - 1);
+                position.chars_read_current_line += (len - 1);
                 return integer_result;
             }
             // The value does not fit an integer, so this token converts as a
@@ -1591,6 +1634,8 @@ scan_number_done:
         decimal_point_position = dot_index;
 
         ia.bulk_skip(len - 1);
+        position.chars_read_total += (len - 1);
+        position.chars_read_current_line += (len - 1);
 
         return convert_number(number_type, mantissa_end);
     }
@@ -1641,7 +1686,7 @@ scan_number_done:
 
 #if JSON_DIAGNOSTIC_POSITIONS
         // the first character of the token has already been read, hence the -1
-        token_start_position = get_chars_read_total() - 1;
+        token_start_position = position.chars_read_total - 1;
 #endif
 
         note_token_start(std::integral_constant<bool, lazy_token_string> {});
@@ -1694,15 +1739,6 @@ scan_number_done:
     /// per-character position counters (line-count-on-'\n' bookkeeping is
     /// handled afterwards, in track_after_read(), once `current` is known)
     void advance_position() noexcept
-    {
-        advance_position_impl(std::integral_constant<bool, lazy_position> {});
-    }
-
-    /// seekable adapter: the position is derived from the adapter on demand
-    void advance_position_impl(std::true_type /*lazy*/) const noexcept {}
-
-    /// streaming adapter: count the character
-    void advance_position_impl(std::false_type /*lazy*/) noexcept
     {
         ++position.chars_read_total;
         ++position.chars_read_current_line;
@@ -1716,16 +1752,7 @@ scan_number_done:
         // seekable adapters reconstruct the token lazily on error (see
         // get_token_string), so the eager per-character copy is skipped
         capture_char(std::integral_constant<bool, lazy_token_string> {});
-        track_newline(std::integral_constant<bool, lazy_position> {});
-        return current;
-    }
 
-    /// seekable adapter: lines are counted on demand in get_position()
-    void track_newline(std::true_type /*lazy*/) const noexcept {}
-
-    /// streaming adapter: start a new line after reading a newline
-    void track_newline(std::false_type /*lazy*/) noexcept
-    {
         if (current == '\n')
         {
             ++position.lines_read;
@@ -1734,6 +1761,8 @@ scan_number_done:
             chars_read_before_newline = position.chars_read_current_line;
             position.chars_read_current_line = 0;
         }
+
+        return current;
     }
 
     /*!
@@ -1777,22 +1806,12 @@ scan_number_done:
     We implement unget by setting variable next_unget to true. The input is not
     changed - we just simulate ungetting by modifying chars_read_total,
     chars_read_current_line, and token_string. The next call to get() will
-    behave as if the unget character is read again. With lazy_position, the
+    behave as if the unget character is read again.
-    pending next_unget is all get_chars_read_total() needs.
     */
     void unget()
     {
         next_unget = true;
-        unget_position(std::integral_constant<bool, lazy_position> {});
-        uncapture_char(std::integral_constant<bool, lazy_token_string> {});
-    }
 
-    /// seekable adapter: get_chars_read_total() accounts for next_unget
-    void unget_position(std::true_type /*lazy*/) const noexcept {}
-
-    /// streaming adapter: step the counters back over the ungotten character
-    void unget_position(std::false_type /*lazy*/) noexcept
-    {
         --position.chars_read_total;
 
         // in case we "unget" a newline, we have to also decrement the lines_read
@@ -1815,6 +1834,8 @@ scan_number_done:
         {
             --position.chars_read_current_line;
         }
+
+        uncapture_char(std::integral_constant<bool, lazy_token_string> {});
     }
 
     /// adapter without lookahead: nothing to do (see release_lookahead)
@@ -1885,21 +1906,10 @@ scan_number_done:
     // diagnostics
     /////////////////////
 
-    /*!
-    @brief return the number of characters read so far
-
-    Unlike get_position(), this is O(1) for all adapters, so it may be called
-    for every value (JSON_DIAGNOSTIC_POSITIONS).
-    */
-    std::size_t get_chars_read_total() const noexcept
-    {
-        return get_chars_read_total_impl(std::integral_constant<bool, lazy_position> {});
-    }
-
     /// return position of last read token
-    position_t get_position() const
+    constexpr position_t get_position() const noexcept
     {
-        return get_position_impl(std::integral_constant<bool, lazy_position> {});
+        return position;
     }
 
     /*!
@@ -1936,43 +1946,6 @@ scan_number_done:
     }
 #endif
 
-  private:
-    /// seekable adapter: every get() either read from the adapter (including
-    /// reads at EOF, which get() counts as characters as well) or replayed an
-    /// ungotten character, so the count is the adapter's read count minus a
-    /// still pending unget
-    std::size_t get_chars_read_total_impl(std::true_type /*lazy*/) const noexcept
-    {
-        return ia.get_read_count() - (next_unget ? 1u : 0u);
-    }
-
-    /// streaming adapter: the counter is maintained by get() and unget()
-    std::size_t get_chars_read_total_impl(std::false_type /*lazy*/) const noexcept
-    {
-        return position.chars_read_total;
-    }
-
-    /// seekable adapter: count the lines in the consumed input; O(input read
-    /// so far), but only called on errors
-    position_t get_position_impl(std::true_type /*lazy*/) const
-    {
-        position_t result;
-        result.chars_read_total = get_chars_read_total();
-        // reads at EOF count as characters but are not part of the input
-        const std::size_t consumed = (std::min)(result.chars_read_total, ia.get_consumed_count());
-        std::size_t line_start = 0;
-        result.lines_read = ia.count_consumed_lines(consumed, line_start);
-        result.chars_read_current_line = result.chars_read_total - line_start;
-        return result;
-    }
-
-    /// streaming adapter: the position is maintained by get() and unget()
-    position_t get_position_impl(std::false_type /*lazy*/) const noexcept
-    {
-        return position;
-    }
-
-  public:
     /// seekable adapter: rebuild the last read token from the input on demand
     const std::vector<char_type>& collect_token_chars(std::vector<char_type>& out, std::true_type /*lazy*/) const
     {
@@ -2080,57 +2053,15 @@ scan_number_done:
         // into one that reloads the pointer from memory every character
         do
         {
-            if (current == '\n')
-            {
-                skip_indentation(std::integral_constant<bool, bulk_scan> {});
-            }
             get_ignoring_pending_unget();
         }
         while (current_is_whitespace());
     }
 
-    /*!
-    @brief contiguous input: skip the space indentation that follows a newline
-           8 bytes at a time
-
-    Pretty-printed JSON indents every line with a run of spaces, which the loop
-    in skip_whitespace() would otherwise read one character at a time. The
-    spaces are skipped 8 bytes at a time; the last 7 bytes of the input and any
-    other whitespace are left to that loop. Skipping bypasses get(), which is
-    fine because bulk_scan implies lazy_position: the position is derived from
-    the adapter, not counted per character.
-    */
-    void skip_indentation(std::true_type /*bulk*/)
-    {
-        JSON_ASSERT(!next_unget);
-        const std::size_t remaining = ia.bulk_remaining();
-        if (remaining < 8)
-        {
-            return;
-        }
-        const char* const data = reinterpret_cast<const char*>(ia.bulk_data());
-        std::size_t pos = 0;
-        for (; pos + 8 <= remaining; pos += 8)
-        {
-            // little-endian, so the first byte is the lowest
-            const std::uint64_t non_space = read_eight_bytes(data + pos) ^ 0x2020202020202020ull;
-            if (non_space != 0)
-            {
-                // skip the spaces before the first other byte of this word
-                pos += static_cast<std::size_t>(count_trailing_zeros(non_space)) / 8;
-                break;
-            }
-        }
-        ia.bulk_skip(pos);
-    }
-
-    /// streaming input: no bulk fast path
-    void skip_indentation(std::false_type /*bulk*/) const noexcept {}
-
     token_type scan()
     {
         // initially, skip the BOM
-        if (get_chars_read_total() == 0 && !skip_bom())
+        if (position.chars_read_total == 0 && !skip_bom())
         {
             error_message = "invalid BOM; must be 0xEF 0xBB 0xBF if given";
             return token_type::parse_error;
@@ -2157,7 +2088,7 @@ scan_number_done:
     token_type scan_expecting(token_type expected_type)
     {
         JSON_ASSERT(expected_type == token_type::name_separator || expected_type == token_type::value_separator);
-        JSON_ASSERT(get_chars_read_total() > 0);
+        JSON_ASSERT(position.chars_read_total > 0);
         const char_int_type expected_char = static_cast<unsigned char>((expected_type == token_type::name_separator) ? ':' : ',');
         skip_whitespace();
         if (JSON_HEDLEY_LIKELY(current == expected_char))

include/nlohmann/detail/input/parser.hpp

@@ -370,7 +370,7 @@ class parser
                     }
                     case token_type::end_of_input:
                     {
-                        if (JSON_HEDLEY_UNLIKELY(m_lexer.get_chars_read_total() == 1))
+                        if (JSON_HEDLEY_UNLIKELY(m_lexer.get_position().chars_read_total == 1))
                         {
                             return syntax_error(*sax, "attempting to parse an empty input; check that your input string or stream contains the expected JSON");
                         }
@@ -520,10 +520,8 @@ class parser
     {
         // MSVC 2015 reports C4100 (unreferenced parameter) when SAX::parse_error is static
         static_cast<void>(sax);
-        // computing the position is O(input read so far) for seekable input
+        return sax.parse_error(m_lexer.get_position(), m_lexer.get_token_string(),
-        const position_t position = m_lexer.get_position();
+                               parse_error::create(exception_id::syntax_error, m_lexer.get_position(), message, nullptr));
-        return sax.parse_error(position, m_lexer.get_token_string(),
-                               parse_error::create(exception_id::syntax_error, position, message, nullptr));
     }
 
     std::string exception_message(const token_type expected, const std::string& context)

include/nlohmann/detail/input/pow5_table.hpp

@@ -22,6 +22,10 @@ namespace detail
 constexpr std::int64_t pow5_128_smallest_power = -342;
 constexpr std::int64_t pow5_128_largest_power = 308;
 
+// every entry of pow5_128() holds two 64-bit halves of 5^q, one per covered power of 5
+static_assert((pow5_128_largest_power - pow5_128_smallest_power + 1) * 2 == 1302,
+              "pow5_128_smallest_power/pow5_128_largest_power must match the size of the pow5_128() table");
+
 /*!
 @brief 128-bit approximations of 5^q for q in [-342, 308]
 

include/nlohmann/detail/input/string_scan.hpp

@@ -8,10 +8,12 @@
 
 #pragma once
 
+#include <array> // array
 #include <cstddef> // size_t
-#include <cstdint> // uint64_t
+#include <cstdint> // uint64_t, uint8_t
 #include <cstring> // memcpy
 
+#include <nlohmann/detail/bit_ops.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 
 // Optional SIMD backend for bulk UTF-8 validation. This is an opt-in external
@@ -69,18 +71,12 @@ inline std::size_t find_string_special(const unsigned char* data, std::size_t n)
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
     {
-        std::uint64_t word = 0;
+        const std::uint64_t special = swar_string_special(read_eight_bytes(data + i));
-        std::memcpy(&word, data + i, sizeof(word));
+        if (special != 0)
-        if (swar_string_special(word) != 0)
         {
-            // a special byte is in this word; locate it (endian-agnostic)
+            // the lowest flagged byte is the first special one: the borrows of
-            for (std::size_t j = 0; j < 8; ++j)
+            // the subtractions can only flag bytes above a true hit
-            {
+            return i + (static_cast<std::size_t>(count_trailing_zeros(special)) / 8);
-                if (is_string_special(data[i + j]))
-                {
-                    return i + j;
-                }
-            }
         }
     }
     for (; i < n; ++i)
@@ -114,8 +110,7 @@ inline std::size_t find_ascii_copyable_run(const unsigned char* data, std::size_
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
     {
-        std::uint64_t v = 0;
+        const std::uint64_t v = read_eight_bytes(data + i);
-        std::memcpy(&v, data + i, sizeof(v));
         const std::uint64_t q = v ^ 0x2222222222222222ull; // '"'  (0x22)
         const std::uint64_t b = v ^ 0x5C5C5C5C5C5C5C5Cull; // '\\' (0x5C)
         const std::uint64_t d = v ^ 0x7F7F7F7F7F7F7F7Full; // DEL  (0x7F)
@@ -126,7 +121,9 @@ inline std::size_t find_ascii_copyable_run(const unsigned char* data, std::size_
                                    | (v & high);               // >= 0x80
         if (stop != 0)
         {
-            break;
+            // the lowest flagged byte is the first one to stop at (see
+            // find_string_special())
+            return i + (static_cast<std::size_t>(count_trailing_zeros(stop)) / 8);
         }
     }
     for (; i < n; ++i)
@@ -253,13 +250,19 @@ inline std::size_t scalar_string_bulk_run(const unsigned char* data, std::size_t
         {
             break; // end of buffer, or a quote/escape/control byte
         }
+        // a run of multi-byte sequences (e.g. CJK text) is validated sequence
+        // by sequence without searching for the next special byte in between
+        do
+        {
             const std::size_t seq = validate_one_utf8(data + pos, n - pos);
             if (seq == 0)
             {
-            break; // ill-formed or truncated: let the byte path diagnose it
+                return pos; // ill-formed or truncated: let the byte path diagnose it
             }
             pos += seq;
         }
+        while (pos < n && data[pos] >= 0x80u);
+    }
     return pos;
 }
 
@@ -273,8 +276,7 @@ inline std::size_t find_string_delimiter(const unsigned char* data, std::size_t
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
     {
-        std::uint64_t v = 0;
+        const std::uint64_t v = read_eight_bytes(data + i);
-        std::memcpy(&v, data + i, sizeof(v));
         const std::uint64_t q = v ^ 0x2222222222222222ull;
         const std::uint64_t b = v ^ 0x5C5C5C5C5C5C5C5Cull;
         const std::uint64_t hit = ((q - ones) & ~q & high)
@@ -282,14 +284,8 @@ inline std::size_t find_string_delimiter(const unsigned char* data, std::size_t
                                   | ((v - 0x2020202020202020ull) & ~v & high);
         if (hit != 0)
         {
-            for (std::size_t j = 0; j < 8; ++j)
+            // the lowest flagged byte is the first delimiter (see find_string_special())
-            {
+            return i + (static_cast<std::size_t>(count_trailing_zeros(hit)) / 8);
-                const unsigned char c = data[i + j];
-                if (c == '\"' || c == '\\' || c < 0x20u)
-                {
-                    return i + j;
-                }
-            }
         }
     }
     for (; i < n; ++i)
@@ -320,5 +316,50 @@ inline std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noe
     return scalar_string_bulk_run(data, n);
 }
 
+// Decode the 4 hex digits at [data, data+4) - the digits following a `\u`
+// escape - into a codepoint 0x0000..0xFFFF via one table lookup per byte
+// (after yyjson's read_hex_u16), or return -1 if any of the 4 bytes is not a
+// hex digit ('0'..'9', 'A'..'F', 'a'..'f'). The caller must already have
+// checked that 4 bytes are available; used by lexer::get_codepoint()'s
+// contiguous fast path. On -1 it falls back to the byte-at-a-time loop, which
+// stops at the first invalid digit, so the reported error and position are
+// unaffected by this fast path.
+inline int hex_codepoint(const unsigned char* data) noexcept
+{
+    static const std::array<std::uint8_t, 256> hex_digit_table = // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+    {
+        {
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 00..0F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 10..1F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 20..2F
+            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 30..3F ('0'..'9')
+            0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 40..4F ('A'..'F')
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 50..5F
+            0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 60..6F ('a'..'f')
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 70..7F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 80..8F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 90..9F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // A0..AF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // B0..BF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // C0..CF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // D0..DF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // E0..EF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF  // F0..FF
+        }
+    };
+
+    const std::uint8_t d0 = hex_digit_table[data[0]];
+    const std::uint8_t d1 = hex_digit_table[data[1]];
+    const std::uint8_t d2 = hex_digit_table[data[2]];
+    const std::uint8_t d3 = hex_digit_table[data[3]];
+    // every valid digit is <= 0xF; the combined OR only exceeds it if at
+    // least one of the four bytes was not a hex digit (looked up as 0xFF)
+    if ((d0 | d1 | d2 | d3) > 0x0F)
+    {
+        return -1;
+    }
+    return (d0 << 12) | (d1 << 8) | (d2 << 4) | d3;
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/json.hpp

@@ -7449,176 +7449,6 @@ public:
     }
 
   public:
-    /// @brief creates a diff as a JSON Merge Patch
-    /// @sa https://json.nlohmann.me/api/basic_json/merge_diff/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
-    static basic_json merge_diff(const basic_json& source, const basic_json& target)
-    {
-        // unless both are objects, the patch is the target itself
-        if (!source.is_object() || !target.is_object())
-        {
-            return target;
-        }
-
-        return merge_diff_recursively(source, target, 0);
-    }
-
-  private:
-    /// @brief two objects @ref merge_diff_iteratively is diffing
-    struct merge_diff_frame
-    {
-        merge_diff_frame(const basic_json* source_, const basic_json* target_)
-            : source(source_), target(target_), member(source_->cbegin()), patch(value_t::object)
-        {}
-
-        // declared for GCC's -Weffc++, as in diff_frame
-        merge_diff_frame(const merge_diff_frame&) = default;
-        merge_diff_frame(merge_diff_frame&&) = default;
-        merge_diff_frame& operator=(const merge_diff_frame&) = default;
-        merge_diff_frame& operator=(merge_diff_frame&&) = default;
-        ~merge_diff_frame() = default;
-
-        /// the objects being diffed
-        const basic_json* source;
-        const basic_json* target;
-        /// the member of source being diffed; advanced once it is done
-        const_iterator member;
-        /// the patch for the members of source diffed so far
-        basic_json patch;
-    };
-
-    /// @brief add the members of object @a target that @a source does not
-    ///        have to the merge patch @a result
-    static void merge_diff_added_members(basic_json& result, const basic_json& source, const basic_json& target)
-    {
-        for (auto it = target.begin(); it != target.end(); ++it)
-        {
-            auto itf = source.find(it.key());
-            if (itf == source.end())
-            {
-                result[it.key()] = it.value();
-            }
-        }
-    }
-
-    /*!
-    @brief @ref merge_diff of two objects at nesting level @a depth
-
-    Diffing two nested objects calls this function again, once per nesting
-    level, so values nested deeply enough would exhaust the call stack and
-    terminate the process. The descent is bounded here: once @ref
-    detail::recursion_depth_limit levels have been entered, @ref
-    merge_diff_iteratively diffs what is left without the call stack.
-    */
-    static basic_json merge_diff_recursively(const basic_json& source, const basic_json& target, const std::size_t depth)
-    {
-        JSON_ASSERT(source.is_object() && target.is_object());
-
-        if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
-        {
-            return merge_diff_iteratively(source, target);
-        }
-
-        basic_json result(value_t::object);
-
-        for (auto it = source.begin(); it != source.end(); ++it)
-        {
-            auto itf = target.find(it.key());
-            if (itf != target.end())
-            {
-                if (it.value().is_object() && itf.value().is_object())
-                {
-                    auto diff = merge_diff_recursively(it.value(), itf.value(), depth + 1);
-                    if (!diff.empty())
-                    {
-                        result[it.key()] = std::move(diff);
-                    }
-                }
-                else if (it.value() != itf.value())
-                {
-                    result[it.key()] = itf.value();
-                }
-            }
-            else
-            {
-                result[it.key()] = value_t::null;
-            }
-        }
-
-        merge_diff_added_members(result, source, target);
-        return result;
-    }
-
-    /*!
-    @brief @ref merge_diff of two objects without the call stack
-
-    Produces the same patch as @ref merge_diff_recursively, keeping the objects
-    being diffed on an explicit stack instead of descending into them. Two
-    nested objects are still diffed completely before the next member, so the
-    patch has its members in the same order as in the recursive version. Only
-    reached for objects nested more deeply than @ref
-    detail::recursion_depth_limit.
-    */
-    static basic_json merge_diff_iteratively(const basic_json& source, const basic_json& target)
-    {
-        // the patch of source and target, set once their frame is popped
-        basic_json result;
-        std::vector<merge_diff_frame> stack;
-        stack.emplace_back(&source, &target);
-        while (!stack.empty())
-        {
-            // the frame's members are copied out and it is changed through
-            // stack.back(): pushing a frame for nested objects or popping
-            // this one would invalidate a reference to it
-            const basic_json* const s = stack.back().source;
-            const basic_json* const t = stack.back().target;
-            const const_iterator it = stack.back().member;
-
-            if (it != s->cend())
-            {
-                const const_iterator itf = t->find(it.key());
-                if (itf != t->cend())
-                {
-                    if (it.value().is_object() && itf.value().is_object())
-                    {
-                        // member is advanced once their patch is under its key
-                        stack.emplace_back(&it.value(), &itf.value());
-                        continue;
-                    }
-                    if (it.value() != itf.value())
-                    {
-                        stack.back().patch[it.key()] = itf.value();
-                    }
-                }
-                else
-                {
-                    stack.back().patch[it.key()] = value_t::null;
-                }
-                ++stack.back().member;
-                continue;
-            }
-
-            merge_diff_added_members(stack.back().patch, *s, *t);
-
-            // these objects are done: continue with the ones they are in
-            basic_json patch = std::move(stack.back().patch);
-            stack.pop_back();
-            if (stack.empty())
-            {
-                result = std::move(patch);
-            }
-            else
-            {
-                if (!patch.empty())
-                {
-                    stack.back().patch[stack.back().member.key()] = std::move(patch);
-                }
-                ++stack.back().member;
-            }
-        }
-        return result;
-    }
-
     /// @}
 };
 

tests/src/float_hard_cases.hpp

@@ -0,0 +1,599 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <array> // array
+#include <cstdint> // uint32_t, uint64_t
+
+// Number tokens that are hard to round correctly, with the IEEE-754 binary64
+// and binary32 bits of their correctly rounded values (ties to even; infinity
+// for an overflow, a signed zero for an underflow).
+//
+// For doubles and floats around 0, the smallest normal number, 1, 2^24, 2^53,
+// 0.1, and the largest finite number, and for random ones, the exact midpoint
+// m to the next number gives: m, m with one unit more and less in the last
+// digit, m with "01" and "0...01" appended, m with trailing zeros, and m cut
+// after 17 to 30 digits (rounded down and up, so that the rounding is decided
+// after the 19th digit), in fixed and exponent notation, 30% of them negative.
+// Tokens longer than 80 characters are left out, except for four of 700 digits
+// and more. Zeros, underflow, overflow, huge exponents, and integers beyond 64
+// bits complete the set. Of the 508 tokens, 134 (as double) and 150 (as
+// float) need the exact comparison with the midpoint (detail::digit_comparison()).
+//
+// The expected bits were computed with exact rational arithmetic in Python
+// (fractions.Fraction) and cross-checked with Python's float(); strtod_l and
+// strtof_l of Apple's libc and of glibc agree. Generated by
+// compact_hard_cases.py 5 (with hard_cases.py), see the pull request that
+// added this file.
+
+namespace float_hard_cases
+{
+
+struct hard_case
+{
+    const char* token;
+    std::uint64_t bits64;
+    std::uint32_t bits32;
+};
+
+inline const std::array<hard_case, 508>& cases()
+{
+    static const std::array<hard_case, 508> table =
+    {
+        {
+            {"-2.4703282292062327e-324", 0x8000000000000000u, 0x80000000u},
+            {"24703282292062328e-340", 0x0000000000000001u, 0x00000000u},
+            {"247032822920623272e-341", 0x0000000000000000u, 0x00000000u},
+            {"-0.2470328229206232721e-323", 0x8000000000000001u, 0x80000000u},
+            {"-0.24703282292062327208e-323", 0x8000000000000000u, 0x80000000u},
+            {"-2.4703282292062327209e-324", 0x8000000000000001u, 0x80000000u},
+            {"2.47032822920623272088e-324", 0x0000000000000000u, 0x00000000u},
+            {"247032822920623272089e-344", 0x0000000000000001u, 0x00000000u},
+            {"-247032822920623272088284396434e-353", 0x8000000000000000u, 0x80000000u},
+            {"0.247032822920623272088284396435e-323", 0x0000000000000001u, 0x00000000u},
+            {"-74109846876186981e-340", 0x8000000000000001u, 0x80000000u},
+            {"0.74109846876186982e-323", 0x0000000000000002u, 0x00000000u},
+            {"-0.7410984687618698162e-323", 0x8000000000000001u, 0x80000000u},
+            {"-7.410984687618698163e-324", 0x8000000000000002u, 0x80000000u},
+            {"7.4109846876186981626e-324", 0x0000000000000001u, 0x00000000u},
+            {"-74109846876186981627e-343", 0x8000000000000002u, 0x80000000u},
+            {"-741098468761869816264e-344", 0x8000000000000001u, 0x80000000u},
+            {"0.741098468761869816265e-323", 0x0000000000000002u, 0x00000000u},
+            {"0.741098468761869816264853189302e-323", 0x0000000000000001u, 0x00000000u},
+            {"-7.41098468761869816264853189303e-324", 0x8000000000000002u, 0x80000000u},
+            {"0.22250738585072006e-307", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"2.2250738585072007e-308", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"2.225073858507200641e-308", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"-2225073858507200642e-326", 0x800FFFFFFFFFFFFFu, 0x80000000u},
+            {"22250738585072006419e-327", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"0.2225073858507200642e-307", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"0.222507385850720064199e-307", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"2.225073858507200642e-308", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"-2.22507385850720064199176395546e-308", 0x800FFFFFFFFFFFFEu, 0x80000000u},
+            {"222507385850720064199176395547e-337", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"-2.2250738585072011e-308", 0x800FFFFFFFFFFFFFu, 0x80000000u},
+            {"-22250738585072012e-324", 0x8010000000000000u, 0x80000000u},
+            {"-2225073858507201136e-326", 0x800FFFFFFFFFFFFFu, 0x80000000u},
+            {"0.2225073858507201137e-307", 0x0010000000000000u, 0x00000000u},
+            {"0.2225073858507201136e-307", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"-2.2250738585072011361e-308", 0x8010000000000000u, 0x80000000u},
+            {"2.22507385850720113605e-308", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"222507385850720113606e-328", 0x0010000000000000u, 0x00000000u},
+            {"22250738585072011360574097967e-336", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"0.222507385850720113605740979671e-307", 0x0010000000000000u, 0x00000000u},
+            {"22250738585072016e-324", 0x0010000000000000u, 0x00000000u},
+            {"0.22250738585072017e-307", 0x0010000000000001u, 0x00000000u},
+            {"0.222507385850720163e-307", 0x0010000000000000u, 0x00000000u},
+            {"2.225073858507201631e-308", 0x0010000000000001u, 0x00000000u},
+            {"-2.2250738585072016301e-308", 0x8010000000000000u, 0x80000000u},
+            {"22250738585072016302e-327", 0x0010000000000001u, 0x00000000u},
+            {"-222507385850720163012e-328", 0x8010000000000000u, 0x80000000u},
+            {"0.222507385850720163013e-307", 0x0010000000000001u, 0x00000000u},
+            {"0.222507385850720163012305563795e-307", 0x0010000000000000u, 0x00000000u},
+            {"-2.22507385850720163012305563796e-308", 0x8010000000000001u, 0x80000000u},
+            {"0.17976931348623156E+309", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"1.7976931348623157e308", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"1.797693134862315608e308", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"-1797693134862315609e290", 0xFFEFFFFFFFFFFFFFu, 0xFF800000u},
+            {"-17976931348623156083e289", 0xFFEFFFFFFFFFFFFEu, 0xFF800000u},
+            {"-0.17976931348623156084E+309", 0xFFEFFFFFFFFFFFFFu, 0xFF800000u},
+            {"0.179769313486231560835E+309", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"-1.79769313486231560836e308", 0xFFEFFFFFFFFFFFFFu, 0xFF800000u},
+            {"1.79769313486231560835325876058e308", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"179769313486231560835325876059e279", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"1.7976931348623158e308", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"17976931348623159e292", 0x7FF0000000000000u, 0x7F800000u},
+            {"1797693134862315807e290", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"0.1797693134862315808E+309", 0x7FF0000000000000u, 0x7F800000u},
+            {"0.17976931348623158079E+309", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"-1.797693134862315808e308", 0xFFF0000000000000u, 0xFF800000u},
+            {"1.79769313486231580793e308", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"179769313486231580794e288", 0x7FF0000000000000u, 0x7F800000u},
+            {"179769313486231580793728971405e279", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"-0.179769313486231580793728971406E+309", 0xFFF0000000000000u, 0xFF800000u},
+            {"100000000000000011102230246251565404236316680908203125e-53", 0x3FF0000000000000u, 0x3F800000u},
+            {"-1.00000000000000011102230246251565404236316680908203126", 0xBFF0000000000001u, 0xBF800000u},
+            {"1.00000000000000011102230246251565404236316680908203124e0", 0x3FF0000000000000u, 0x3F800000u},
+            {"10000000000000001110223024625156540423631668090820312501e-55", 0x3FF0000000000001u, 0x3F800000u},
+            {"1.00000000000000011102230246251565404236316680908203125000000000000000000001", 0x3FF0000000000001u, 0x3F800000u},
+            {"10000000000000001e-16", 0x3FF0000000000000u, 0x3F800000u},
+            {"1.0000000000000002", 0x3FF0000000000001u, 0x3F800000u},
+            {"1.000000000000000111", 0x3FF0000000000000u, 0x3F800000u},
+            {"1.000000000000000112e0", 0x3FF0000000000001u, 0x3F800000u},
+            {"1.000000000000000111e0", 0x3FF0000000000000u, 0x3F800000u},
+            {"-10000000000000001111e-19", 0xBFF0000000000001u, 0xBF800000u},
+            {"-100000000000000011102e-20", 0xBFF0000000000000u, 0xBF800000u},
+            {"-1.00000000000000011103", 0xBFF0000000000001u, 0xBF800000u},
+            {"1.00000000000000011102230246251", 0x3FF0000000000000u, 0x3F800000u},
+            {"1.00000000000000011102230246252e0", 0x3FF0000000000001u, 0x3F800000u},
+            {"-0.999999999999999944488848768742172978818416595458984375", 0xBFF0000000000000u, 0xBF800000u},
+            {"-9.99999999999999944488848768742172978818416595458984376e-1", 0xBFF0000000000000u, 0xBF800000u},
+            {"999999999999999944488848768742172978818416595458984374e-54", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"0.99999999999999994448884876874217297881841659545898437501", 0x3FF0000000000000u, 0x3F800000u},
+            {"9.99999999999999944488848768742172978818416595458984375000000000000000000001e-1", 0x3FF0000000000000u, 0x3F800000u},
+            {"-0.99999999999999994", 0xBFEFFFFFFFFFFFFFu, 0xBF800000u},
+            {"9.9999999999999995e-1", 0x3FF0000000000000u, 0x3F800000u},
+            {"9.999999999999999444e-1", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"9999999999999999445e-19", 0x3FF0000000000000u, 0x3F800000u},
+            {"99999999999999994448e-20", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"-0.99999999999999994449", 0xBFF0000000000000u, 0xBF800000u},
+            {"0.999999999999999944488", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"-9.99999999999999944489e-1", 0xBFF0000000000000u, 0xBF800000u},
+            {"9.99999999999999944488848768742e-1", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"999999999999999944488848768743e-30", 0x3FF0000000000000u, 0x3F800000u},
+            {"-9.007199254740993e15", 0xC340000000000000u, 0xDA000000u},
+            {"9007199254740994e0", 0x4340000000000001u, 0x5A000000u},
+            {"9007199254740992", 0x4340000000000000u, 0x5A000000u},
+            {"9.00719925474099301e15", 0x4340000000000001u, 0x5A000000u},
+            {"9007199254740993000000000000000000001e-21", 0x4340000000000001u, 0x5A000000u},
+            {"-9007199254740993.000000000000000000000000000000", 0xC340000000000000u, 0xDA000000u},
+            {"90071992547409915e-1", 0x4340000000000000u, 0x5A000000u},
+            {"-9007199254740991.6", 0xC340000000000000u, 0xDA000000u},
+            {"9.0071992547409914e15", 0x433FFFFFFFFFFFFFu, 0x5A000000u},
+            {"-9007199254740991501e-3", 0xC340000000000000u, 0xDA000000u},
+            {"9007199254740991.5000000000000000000001", 0x4340000000000000u, 0x5A000000u},
+            {"9.0071992547409915000000000000000000000000000000e15", 0x4340000000000000u, 0x5A000000u},
+            {"0.100000000000000012490009027033011079765856266021728515625", 0x3FB999999999999Au, 0x3DCCCCCDu},
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+            {"-1.0000000596046447754", 0xBFF0000010000000u, 0xBF800001u},
+            {"0.9999999701976776123046875", 0x3FEFFFFFF0000000u, 0x3F800000u},
+            {"9.999999701976776123046876e-1", 0x3FEFFFFFF0000000u, 0x3F800000u},
+            {"9999999701976776123046874e-25", 0x3FEFFFFFF0000000u, 0x3F7FFFFFu},
+            {"0.999999970197677612304687501", 0x3FEFFFFFF0000000u, 0x3F800000u},
+            {"-9.999999701976776123046875000000000000000000001e-1", 0xBFEFFFFFF0000000u, 0xBF800000u},
+            {"-9999999701976776123046875000000000000000000000000000000e-55", 0xBFEFFFFFF0000000u, 0xBF800000u},
+            {"0.99999997019767761", 0x3FEFFFFFF0000000u, 0x3F7FFFFFu},
+            {"-9.9999997019767762e-1", 0xBFEFFFFFF0000000u, 0xBF800000u},
+            {"-9.999999701976776123e-1", 0xBFEFFFFFF0000000u, 0xBF7FFFFFu},
+            {"9999999701976776124e-19", 0x3FEFFFFFF0000000u, 0x3F800000u},
+            {"9999999701976776123e-19", 0x3FEFFFFFF0000000u, 0x3F7FFFFFu},
+            {"0.99999997019767761231", 0x3FEFFFFFF0000000u, 0x3F800000u},
+            {"-0.999999970197677612304", 0xBFEFFFFFF0000000u, 0xBF7FFFFFu},
+            {"9.99999970197677612305e-1", 0x3FEFFFFFF0000000u, 0x3F800000u},
+            {"-1.6777217e7", 0xC170000010000000u, 0xCB800000u},
+            {"16777218e0", 0x4170000020000000u, 0x4B800001u},
+            {"16777216", 0x4170000000000000u, 0x4B800000u},
+            {"-1.677721701e7", 0xC17000001028F5C3u, 0xCB800001u},
+            {"-16777217000000000000000000001e-21", 0xC170000010000000u, 0xCB800001u},
+            {"16777217.000000000000000000000000000000", 0x4170000010000000u, 0x4B800000u},
+            {"167772155e-1", 0x416FFFFFF0000000u, 0x4B800000u},
+            {"16777215.6", 0x416FFFFFF3333333u, 0x4B800000u},
+            {"1.67772154e7", 0x416FFFFFECCCCCCDu, 0x4B7FFFFFu},
+            {"16777215501e-3", 0x416FFFFFF0083127u, 0x4B800000u},
+            {"-16777215.5000000000000000000001", 0xC16FFFFFF0000000u, 0xCB800000u},
+            {"-1.67772155000000000000000000000000000000e7", 0xC16FFFFFF0000000u, 0xCB800000u},
+            {"0.1000000052154064178466796875", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"1.000000052154064178466796876e-1", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"-1000000052154064178466796874e-28", 0xBFB99999B0000000u, 0xBDCCCCCDu},
+            {"0.100000005215406417846679687501", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"1.000000052154064178466796875000000000000000000001e-1", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"-1000000052154064178466796875000000000000000000000000000000e-58", 0xBFB99999B0000000u, 0xBDCCCCCEu},
+            {"-0.10000000521540641", 0xBFB99999AFFFFFFFu, 0xBDCCCCCDu},
+            {"-1.0000000521540642e-1", 0xBFB99999B0000000u, 0xBDCCCCCEu},
+            {"1.000000052154064178e-1", 0x3FB99999B0000000u, 0x3DCCCCCDu},
+            {"-1000000052154064179e-19", 0xBFB99999B0000000u, 0xBDCCCCCEu},
+            {"10000000521540641784e-20", 0x3FB99999B0000000u, 0x3DCCCCCDu},
+            {"0.10000000521540641785", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"0.100000005215406417846", 0x3FB99999B0000000u, 0x3DCCCCCDu},
+            {"1.00000005215406417847e-1", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"5.429001220703125e3", 0x40B5350050000000u, 0x45A9A802u},
+            {"-5429001220703126e-12", 0xC0B5350050000001u, 0xC5A9A803u},
+            {"-5429.001220703124", 0xC0B535004FFFFFFFu, 0xC5A9A802u},
+            {"5.42900122070312501e3", 0x40B5350050000000u, 0x45A9A803u},
+            {"5429001220703125000000000000000000001e-33", 0x40B5350050000000u, 0x45A9A803u},
+            {"-5429.001220703125000000000000000000000000000000", 0xC0B5350050000000u, 0xC5A9A802u},
+            {"503719056e0", 0x41BE062490000000u, 0x4DF03124u},
+            {"503719057", 0x41BE062491000000u, 0x4DF03125u},
+            {"5.03719055e8", 0x41BE06248F000000u, 0x4DF03124u},
+            {"50371905601e-2", 0x41BE062490028F5Cu, 0x4DF03125u},
+            {"503719056.000000000000000000001", 0x41BE062490000000u, 0x4DF03125u},
+            {"5.03719056000000000000000000000000000000e8", 0x41BE062490000000u, 0x4DF03124u},
+            {"-92331620", 0xC196037990000000u, 0xCCB01BCCu},
+            {"9.233163e7", 0x41960379B8000000u, 0x4CB01BCEu},
+            {"9233161e1", 0x4196037968000000u, 0x4CB01BCBu},
+            {"92331620.1", 0x4196037990666666u, 0x4CB01BCDu},
+            {"9.233162000000000000000000001e7", 0x4196037990000000u, 0x4CB01BCDu},
+            {"9233162000000000000000000000000000000e-29", 0x4196037990000000u, 0x4CB01BCCu},
+            {"3.002458625e6", 0x4146E82D50000000u, 0x4A37416Au},
+            {"3002458626e-3", 0x4146E82D5020C49Cu, 0x4A37416Bu},
+            {"3002458.624", 0x4146E82D4FDF3B64u, 0x4A37416Au},
+            {"-3.00245862501e6", 0xC146E82D500053E3u, 0xCA37416Bu},
+            {"3002458625000000000000000000001e-24", 0x4146E82D50000000u, 0x4A37416Bu},
+            {"3002458.625000000000000000000000000000000", 0x4146E82D50000000u, 0x4A37416Au},
+            {"-1095485584696182596504479582065262592e1", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"10954855846961825965044795820652625930", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"1.095485584696182596504479582065262591e37", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"109548558469618259650447958206526259201e-1", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"-10954855846961825965044795820652625920.00000000000000000001", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"1.095485584696182596504479582065262592000000000000000000000000000000e37", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"10954855846961825e21", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"10954855846961826000000000000000000000", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"10954855846961825960000000000000000000", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"1.095485584696182597e37", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"1.0954855846961825965e37", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"-10954855846961825966e18", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"10954855846961825965e18", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"10954855846961825965100000000000000000", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"10954855846961825965044795820600000000", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"-1.09548558469618259650447958207e37", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"1.6449216019182103706535606608388384863861375606575165875256061553955078126e-21", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"-16449216019182103706535606608388384863861375606575165875256061553955078124e-94", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"-0.0000000000000000000016449216019182103", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"-1.6449216019182104e-21", 0xBB9F125A50000000u, 0x9CF892D3u},
+            {"-1.64492160191821037e-21", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"-1644921601918210371e-39", 0xBB9F125A50000000u, 0x9CF892D3u},
+            {"-16449216019182103706e-40", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"0.0000000000000000000016449216019182103707", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"0.00000000000000000000164492160191821037065", 0x3B9F125A50000000u, 0x1CF892D2u},
+            {"1.64492160191821037066e-21", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"1.64492160191821037065356066083e-21", 0x3B9F125A50000000u, 0x1CF892D2u},
+            {"164492160191821037065356066084e-50", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"6.565061509609222412109375e-1", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"6565061509609222412109376e-25", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"0.6565061509609222412109374", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"6.56506150960922241210937501e-1", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"6565061509609222412109375000000000000000000001e-46", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"-0.6565061509609222412109375000000000000000000000000000000", 0xBFE5021930000000u, 0xBF2810CAu},
+            {"6.5650615096092224e-1", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"-65650615096092225e-17", 0xBFE5021930000000u, 0xBF2810CAu},
+            {"6565061509609222412e-19", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"0.6565061509609222413", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"0.65650615096092224121", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"6.5650615096092224122e-1", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"-6.5650615096092224121e-1", 0xBFE5021930000000u, 0xBF2810C9u},
+            {"656506150960922241211e-21", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"18014627239033005156980393746124491372029297053813934326171875e-77", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"0.00000000000000018014627239033005156980393746124491372029297053813934326171876", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"-1.8014627239033005156980393746124491372029297053813934326171874e-16", 0xBCA9F63970000000u, 0xA54FB1CBu},
+            {"1801462723903300515698039374612449137202929705381393432617187501e-79", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"18014627239033005e-32", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"0.00000000000000018014627239033006", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"0.0000000000000001801462723903300515", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"-1.801462723903300516e-16", 0xBCA9F63970000000u, 0xA54FB1CCu},
+            {"-1.8014627239033005156e-16", 0xBCA9F63970000000u, 0xA54FB1CBu},
+            {"18014627239033005157e-35", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"180146272390330051569e-36", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"-0.00000000000000018014627239033005157", 0xBCA9F63970000000u, 0xA54FB1CCu},
+            {"0.000000000000000180146272390330051569803937461", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"1.80146272390330051569803937462e-16", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"0.05534819327294826507568359375", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"-5.534819327294826507568359376e-2", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"5534819327294826507568359374e-29", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"-0.0553481932729482650756835937501", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"5.534819327294826507568359375000000000000000000001e-2", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"5534819327294826507568359375000000000000000000000000000000e-59", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"0.055348193272948265", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"5.5348193272948266e-2", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"5.534819327294826507e-2", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"5534819327294826508e-20", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"55348193272948265075e-21", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"-0.055348193272948265076", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"0.0553481932729482650756", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"-5.53481932729482650757e-2", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"5.179692133247783258005389047985340416e36", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"5179692133247783258005389047985340417e0", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"5179692133247783258005389047985340415", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"-5.17969213324778325800538904798534041601e36", 0xC78F2C9450000000u, 0xFC7964A3u},
+            {"-5179692133247783258005389047985340416000000000000000000001e-21", 0xC78F2C9450000000u, 0xFC7964A3u},
+            {"-5179692133247783258005389047985340416.000000000000000000000000000000", 0xC78F2C9450000000u, 0xFC7964A2u},
+            {"5.1796921332477832e36", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"51796921332477833e20", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"-5179692133247783258e18", 0xC78F2C9450000000u, 0xFC7964A2u},
+            {"5179692133247783259000000000000000000", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"5179692133247783258000000000000000000", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"5.1796921332477832581e36", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"-5.179692133247783258e36", 0xC78F2C9450000000u, 0xFC7964A2u},
+            {"-517969213324778325801e16", 0xC78F2C9450000000u, 0xFC7964A3u},
+            {"517969213324778325800538904798e7", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"5179692133247783258005389047990000000", 0x478F2C9450000000u, 0x7C7964A3u},
+            {
+                "0.22250738585072011360574097967091319759348195463516456480234261097248222220210769455165295239081350"
+                "8791414915891303962110687008643869459464552765720740782062174337998814106326732925355228688137214901"
+                "2981122451451889849057222307285255133155755015914397476397983411801999323962548289017107081850690630"
+                "6666559949382757725720157630626906633326475653000092458883164330377797918696120494973903778297049050"
+                "5108060994073026293712895895000358379996720725430436028407889577179615094551674824347103070260914462"
+                "1572289880258182545180325707018860872113128079512233426288368622321503775666622503982534335974568884"
+                "4239002654981983854879482922068947216898310996983658468140228542433306603398508864458040010349339704"
+                "2756718644338377048603786162277173854562306587467901408672332763671875e-307", 0x0010000000000000u, 0x00000000u
+            },
+            {
+                "2.22507385850720113605740979670913197593481954635164564802342610972482222202107694551652952390813508"
+                "7914149158913039621106870086438694594645527657207407820621743379988141063267329253552286881372149012"
+                "9811224514518898490572223072852551331557550159143974763979834118019993239625482890171070818506906306"
+                "6665599493827577257201576306269066333264756530000924588831643303777979186961204949739037782970490505"
+                "1080609940730262937128958950003583799967207254304360284078895771796150945516748243471030702609144621"
+                "5722898802581825451803257070188608721131280795122334262883686223215037756666225039825343359745688844"
+                "2390026549819838548794829220689472168983109969836584681402285424333066033985088644580400103493397042"
+                "756718644338377048603786162277173854562306587467901408672332763671875000000000000000000001e-308", 0x0010000000000000u, 0x00000000u
+            },
+            {
+                "0.11754942807573642917278829910357665133228589927589904276829631184250030649651730385585324256680905"
+                "8189392089843750000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "00000000000000000000000000000000000000000000000000000000000000000e-37", 0x380FFFFFE0000000u, 0x00800000u
+            },
+            {
+                "1175494280757364291727882991035766513322858992758990427682963118425003064965173038558532425668090581"
+                "8939208984375000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "00000000000001e-751", 0x380FFFFFE0000000u, 0x00800000u
+            },
+            {"0", 0x0000000000000000u, 0x00000000u},
+            {"-0", 0x8000000000000000u, 0x80000000u},
+            {"0.0", 0x0000000000000000u, 0x00000000u},
+            {"-0.0", 0x8000000000000000u, 0x80000000u},
+            {"0e999999999999999999999", 0x0000000000000000u, 0x00000000u},
+            {"-0.000e-99999", 0x8000000000000000u, 0x80000000u},
+            {"1e-400", 0x0000000000000000u, 0x00000000u},
+            {"-1e-400", 0x8000000000000000u, 0x80000000u},
+            {"1e400", 0x7FF0000000000000u, 0x7F800000u},
+            {"-1e400", 0xFFF0000000000000u, 0xFF800000u},
+            {"1e-50", 0x358DEE7A4AD4B81Fu, 0x00000000u},
+            {"-1e-50", 0xB58DEE7A4AD4B81Fu, 0x80000000u},
+            {"1e39", 0x48078287F49C4A1Du, 0x7F800000u},
+            {"-1e39", 0xC8078287F49C4A1Du, 0xFF800000u},
+            {"1e99999999999999999999999999", 0x7FF0000000000000u, 0x7F800000u},
+            {"1e-99999999999999999999999999", 0x0000000000000000u, 0x00000000u},
+            {"1e0000000000000000000000000000000000000000308", 0x7FE1CCF385EBC8A0u, 0x7F800000u},
+            {"123456789012345678901234567890e-30", 0x3FBF9ADD3746F65Fu, 0x3DFCD6EAu},
+            {"18446744073709551615", 0x43F0000000000000u, 0x5F800000u},
+            {"18446744073709551616", 0x43F0000000000000u, 0x5F800000u},
+            {"-9223372036854775808", 0xC3E0000000000000u, 0xDF000000u},
+            {"-9223372036854775809", 0xC3E0000000000000u, 0xDF000000u},
+        }
+    };
+    return table;
+}
+
+} // namespace float_hard_cases

tests/src/unit-class_lexer.cpp

@@ -13,16 +13,20 @@
 using nlohmann::json;
 
 #include <array> // array
-#include <cfloat> // FLT_EVAL_METHOD
 #include <cstdint> // uint32_t, uint64_t
+#include <cstdio> // snprintf
 #include <cstdlib> // strtod
 #include <cstring> // memcpy
 #include <limits> // numeric_limits
+#include <map> // map
+#include <random> // mt19937
 #include <sstream> // stringstream
 #include <string> // string
 #include <utility> // pair
 #include <vector> // vector
 
+#include "float_hard_cases.hpp"
+
 namespace
 {
 // shortcut to scan a string literal
@@ -258,7 +262,7 @@ TEST_CASE("lexer number fast path")
             "123456789012345678901234567890",  // huge -> float
             "0.30000000000000004", "2.2250738585072014e-308", "1e308",
             // high-precision / wide-exponent values that exercise the
-            // std::from_chars (Eisel-Lemire) path beyond the Clinger subset
+            // Eisel-Lemire path beyond the Clinger subset
             "1.7976931348623157e308", "1.2345678901234567e-250",
             "9007199254740993", "5e-324", "1e-320"
         };
@@ -280,20 +284,18 @@ TEST_CASE("lexer number fast path")
         }
     }
 
-    SECTION("significant-digit gate for the Clinger fast path")
+    SECTION("significant digits around Clinger's fast path")
     {
-        // Clinger's fast path needs a significand below 2^53, so it cannot
+        // Clinger's fast path needs a significand of at most 2^53, which
-        // succeed once the mantissa has 17 or more significant digits (the
+        // tokens with 17 or more significant digits exceed. The conversion
-        // significand would be at least 10^16). The lexer skips the attempt
+        // splits the token at the positions the scanners recorded, so leading
-        // there. That is only allowed to save work: every value must still come
+        // zeros must not count as digits - "0.1234567890123456" has 16
-        // out bit-exactly, and both scanners must agree. In particular the gate
+        // significant digits, not 17 - and both scanners must agree.
-        // must not fire for tokens whose leading zeros merely look like extra
-        // digits - "0.1234567890123456" has 16 significant digits, not 17.
         const std::vector<std::string> numbers =
         {
             "1234567890123456",                  // 16 significant digits
-            "12345678901234567",                 // 17 -> attempt skipped
+            "12345678901234567",                 // 17
-            "123456789012345678",                // 18 -> attempt skipped
+            "123456789012345678",                // 18
             "0.1234567890123456",                // 16: the leading "0" is not significant
             "0.12345678901234567",               // 17
             "0.00000000000000001",               // 1, in a long token
@@ -664,46 +666,323 @@ TEST_CASE("lexer string fast path")
     }
 }
 
-TEST_CASE("parse_float_fast declines what it cannot convert exactly")
+TEST_CASE("lexer escape fast path")
 {
-    // The lexer only hands well-formed numbers to parse_float_fast, so the
+    // json::accept() never throws, so this section stays covered without
-    // malformed ones below can only be passed to it directly. Declining is
+    // exceptions; it pins which of the cases below are valid/invalid and
-    // always safe: the caller then falls back to a slower, exact conversion.
+    // checks the contiguous and streaming paths agree on that classification.
-    const auto fast = [](const std::string & s, double & out)
+    SECTION("accept() parity")
     {
-        return nlohmann::detail::parse_float_fast(s.data(), s.data() + s.size(), out);
+        const std::vector<std::pair<std::string, bool>> cases =
+        {
+            {"\\u0041", true}, {"\\u00e4", true}, {"\\u00E4", true},
+            {"\\uD83D\\uDE00", true},
+            {"\\u12", false}, {"\\u12G4", false}, {"\\uXYZW", false},
+            {"\\uD800", false}, {"\\uD800A", false}, {"\\uD800\\u0041", false},
+            {"\\uDC00", false}, {"\\u", false}
         };
-    double out = 0;
 
-#if defined(FLT_EVAL_METHOD) && FLT_EVAL_METHOD != 0
+        for (const auto& c : cases)
-    // without true double precision, the fast path declines everything
+        {
-    CHECK_FALSE(fast("1.5", out));
+            for (const std::size_t offset :
-#else
+                    {
-    CHECK(fast("1.5", out));
+                        std::size_t{0}, std::size_t{9}
-    CHECK(out == 1.5);
+                    })
-    CHECK(fast("+2.5e1", out));
+            {
-    CHECK(out == 25.0);
+                const std::string doc = "[\"" + std::string(offset, 'a') + c.first + "\"]";
-    CHECK(fast("-25E-1", out));
+                CAPTURE(doc)
-    CHECK(out == -2.5);
+                CHECK(json::accept(doc) == c.second);
-    CHECK(fast("1e", out));
+                std::stringstream ss(doc);
-    CHECK(out == 1.0);
+                CHECK(json::accept(ss) == c.second);
+            }
+        }
+    }
+
+#if !defined(JSON_NOEXCEPTION)
+    // the full outcome of parsing @a doc: the parsed value, or the exact
+    // error message, so a mismatch in either is caught
+    const auto outcome = [](const std::string & doc, bool streaming) -> std::string
+    {
+        try
+        {
+            if (streaming)
+            {
+                std::stringstream ss(doc);
+                const json j = json::parse(ss);
+                return j.dump();
+            }
+            const json j = json::parse(doc);
+            return j.dump();
+        }
+        catch (const json::exception& e)
+        {
+            return {e.what()};
+        }
+    };
+
+    SECTION("contiguous vs streaming parity")
+    {
+        const std::vector<std::string> escapes =
+        {
+            "\\u0041",             // "A"
+            "\\u00e4",             // "ä" (lowercase hex)
+            "\\u00E4",             // "ä" (uppercase hex)
+            "\\uD83D\\uDE00",      // valid surrogate pair (an emoji)
+            "\\u12",               // truncated: only 2 hex digits before the closing quote
+            "\\u12G4",             // invalid hex digit at the 3rd position
+            "\\uXYZW",             // all 4 bytes invalid
+            "\\uD800",             // lone high surrogate, string ends right after
+            "\\uD800A",            // high surrogate not followed by another \u escape
+            "\\uD800\\u0041",      // high surrogate followed by \u, but not a low surrogate
+            "\\uDC00",             // lone low surrogate
+            "\\u",                 // '\u' with nothing after (closing quote right away)
+        };
+
+        // once at the start of the string and once past the first 8-byte SWAR
+        // word of the outer string_bulk_run, so the escape is reached both
+        // right after the opening quote and mid-run
+        for (const auto& escape : escapes)
+        {
+            for (const std::size_t offset :
+                    {
+                        std::size_t{0}, std::size_t{9}
+                    })
+            {
+                const std::string doc = "[\"" + std::string(offset, 'a') + escape + "\"]";
+                CAPTURE(doc)
+                CHECK(outcome(doc, false) == outcome(doc, true));
+            }
+
+            // the escape is the last thing before end of input: no closing
+            // quote at all
+            const std::string truncated_doc = "[\"" + escape;
+            CAPTURE(truncated_doc)
+            CHECK(outcome(truncated_doc, false) == outcome(truncated_doc, true));
+        }
+    }
+
+    SECTION("truncated \\u escape at every distance from the end of input")
+    {
+        // ia.bulk_remaining() must correctly report fewer than 4 bytes for
+        // every possible count of trailing hex-looking bytes (0, 1, 2, or 3)
+        // before end of input, so the fast path declines and the byte path
+        // alone reports the "must be followed by 4 hex digits" error, at the
+        // same position, in every case
+        for (const std::string& tail :
+                {
+                    std::string{}, std::string("1"), std::string("12"), std::string("123")
+                })
+        {
+            const std::string doc = "[\"\\u" + tail;
+            CAPTURE(doc)
+            CHECK(outcome(doc, false) == outcome(doc, true));
+            CHECK(outcome(doc, false).find("must be followed by 4 hex digits") != std::string::npos);
+        }
+    }
+
+    SECTION("invalid hex digit at every position of the 4")
+    {
+        // the fast path must decline for *any* invalid byte among the 4, not
+        // just the first, and the byte path must then stop at exactly that
+        // position - same as it always has
+        for (std::size_t bad_pos = 0; bad_pos < 4; ++bad_pos)
+        {
+            std::string digits = "1234";
+            digits[bad_pos] = 'g'; // not a hex digit
+            const std::string doc = "[\"\\u" + digits + "\"]";
+            CAPTURE(doc)
+            CHECK(outcome(doc, false) == outcome(doc, true));
+            CHECK(outcome(doc, false).find("must be followed by 4 hex digits") != std::string::npos);
+        }
+    }
+
+    SECTION("random escapes")
+    {
+        // A seeded PRNG builds the 4 bytes following `\u` from a mix of hex
+        // digits and non-hex bytes, at varying distances from the start of
+        // the string, to compare the two scanners on many more shapes than
+        // are practical to enumerate by hand.
+        std::mt19937 gen(7654321); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
+        const std::string hex_alphabet = "0123456789AaBbCcDdEeFf";
+        std::uniform_int_distribution<std::size_t> pick_hex(0, hex_alphabet.size() - 1);
+        std::uniform_int_distribution<int> pick_byte(1, 255); // never NUL
+        std::uniform_int_distribution<int> pick_is_hex(0, 4); // 4-in-5 chance of a hex digit
+        std::uniform_int_distribution<std::size_t> pick_offset(0, 12);
+
+        std::vector<std::string> mismatches;
+        for (int iter = 0; iter < 3000; ++iter)
+        {
+            std::string digits;
+            for (int i = 0; i < 4; ++i)
+            {
+                if (pick_is_hex(gen) != 0)
+                {
+                    digits += hex_alphabet[pick_hex(gen)];
+                }
+                else
+                {
+                    char c = static_cast<char>(pick_byte(gen));
+                    if (c == '"' || c == '\\')
+                    {
+                        // keep the string well-formed apart from the escape
+                        // itself, so any mismatch is attributable to the \u
+                        // handling and not to an unrelated quote/escape
+                        c = 'z';
+                    }
+                    digits += c;
+                }
+            }
+            const std::string doc = "[\"" + std::string(pick_offset(gen), 'a') + "\\u" + digits + "\"]";
+            if (outcome(doc, false) != outcome(doc, true))
+            {
+                mismatches.push_back(doc);
+            }
+        }
+        CAPTURE(mismatches)
+        CHECK(mismatches.empty());
+    }
 #endif
+}
 
-    // not a number
+namespace
-    CHECK_FALSE(fast("", out));
+{
-    CHECK_FALSE(fast("-", out));
+// the index of the decimal point (or npos) and of the end of the mantissa of a
-    CHECK_FALSE(fast(".", out));
+// number token, which the lexer records while scanning it
-    CHECK_FALSE(fast("1.2.3", out));
+std::pair<std::size_t, std::size_t> float_token_layout(const std::string& s)
-    CHECK_FALSE(fast("1x", out));
+{
-    CHECK_FALSE(fast("1e+", out));
+    std::size_t dot = std::string::npos;
-    CHECK_FALSE(fast("1e1x", out));
+    std::size_t mantissa_end = s.size();
+    for (std::size_t i = 0; i < s.size(); ++i)
+    {
+        if (s[i] == '.')
+        {
+            dot = i;
+        }
+        else if (s[i] == 'e' || s[i] == 'E')
+        {
+            mantissa_end = i;
+            break;
+        }
+    }
+    return {dot, mantissa_end};
+}
 
-    // numbers that are not represented exactly on the fast path
+template<typename FloatType>
-    CHECK_FALSE(fast("12345678901234567890", out));
+FloatType parse_native(const std::string& s)
-    CHECK_FALSE(fast("1e10000", out));
+{
-    CHECK_FALSE(fast("9007199254740993", out));
+    const auto layout = float_token_layout(s);
-    CHECK_FALSE(fast("1e23", out));
+    return nlohmann::detail::parse_float_native<FloatType>(s.data(), s.data() + s.size(), layout.first, layout.second);
-    CHECK_FALSE(fast("1e-23", out));
+}
+
+std::uint64_t bits_of(double d)
+{
+    std::uint64_t b = 0;
+    std::memcpy(&b, &d, sizeof(b));
+    return b;
+}
+
+std::uint32_t bits_of(float f)
+{
+    std::uint32_t b = 0;
+    std::memcpy(&b, &f, sizeof(b));
+    return b;
+}
+
+std::uint64_t native_bits64(const std::string& s)
+{
+    return bits_of(parse_native<double>(s));
+}
+
+std::uint32_t native_bits32(const std::string& s)
+{
+    return bits_of(parse_native<float>(s));
+}
+} // namespace
+
+TEST_CASE("parse_float_native rounds correctly")
+{
+    SECTION("double")
+    {
+        CHECK(native_bits64("1.5") == 0x3FF8000000000000u);
+        CHECK(native_bits64("0.1") == 0x3FB999999999999Au);
+        CHECK(native_bits64("-0.0") == 0x8000000000000000u);
+        CHECK(native_bits64("0e999999999999999999999") == 0u);
+        // 2^53 + 1 is exactly between two doubles: ties to even, unless more digits follow
+        CHECK(native_bits64("9007199254740993") == 0x4340000000000000u);
+        CHECK(native_bits64("9007199254740993.0000000000000000001") == 0x4340000000000001u);
+        CHECK(native_bits64("9007199254740992.9999999999999999999") == 0x4340000000000000u);
+        // 1 + 2^-53 exactly (a tie), and one unit in the 55th digit around it
+        CHECK(native_bits64("1.00000000000000011102230246251565404236316680908203125") == 0x3FF0000000000000u);
+        CHECK(native_bits64("1.00000000000000011102230246251565404236316680908203126") == 0x3FF0000000000001u);
+        CHECK(native_bits64("1.00000000000000011102230246251565404236316680908203124") == 0x3FF0000000000000u);
+        // subnormal and overflow boundaries
+        CHECK(native_bits64("2.4703282292062327e-324") == 0u);
+        CHECK(native_bits64("2.4703282292062328e-324") == 1u);
+        CHECK(native_bits64("2.2250738585072011e-308") == 0x000FFFFFFFFFFFFFu);
+        CHECK(native_bits64("2.2250738585072012e-308") == 0x0010000000000000u);
+        CHECK(native_bits64("1.7976931348623157e308") == 0x7FEFFFFFFFFFFFFFu);
+        CHECK(native_bits64("1.7976931348623159e308") == 0x7FF0000000000000u);
+        CHECK(native_bits64("-1e400") == 0xFFF0000000000000u);
+        CHECK(native_bits64("-1e-400") == 0x8000000000000000u);
+        // exponents and zeros far beyond the range cancel out
+        CHECK(native_bits64("0." + std::string(1000, '0') + "1e1001") == 0x3FF0000000000000u);
+        CHECK(native_bits64("1" + std::string(1000, '0') + "e-1000") == 0x3FF0000000000000u);
+        CHECK(native_bits64("1e-99999999999999999999999") == 0u);
+        CHECK(native_bits64("1E+99999999999999999999999") == 0x7FF0000000000000u);
+        // more digits than any midpoint has (769): only whether a nonzero digit follows matters
+        const std::string tie = "1.00000000000000011102230246251565404236316680908203125";
+        CHECK(native_bits64(tie + std::string(800, '0')) == 0x3FF0000000000000u);
+        CHECK(native_bits64(tie + std::string(800, '0') + "1") == 0x3FF0000000000001u);
+    }
+
+    SECTION("float")
+    {
+        CHECK(native_bits32("1.5") == 0x3FC00000u);
+        CHECK(native_bits32("0.1") == 0x3DCCCCCDu);
+        CHECK(native_bits32("-0.0") == 0x80000000u);
+        // 2^24 + 1 is exactly between two floats
+        CHECK(native_bits32("16777217") == 0x4B800000u);
+        CHECK(native_bits32("16777217.000000000000000000001") == 0x4B800001u);
+        CHECK(native_bits32("16777218.999999999999999999999") == 0x4B800001u);
+        CHECK(native_bits32("16777219") == 0x4B800002u);
+        // subnormal and overflow boundaries
+        CHECK(native_bits32("3.4028235677973366e38") == 0x7F7FFFFFu);
+        CHECK(native_bits32("3.4028235677973367e38") == 0x7F800000u);
+        CHECK(native_bits32("7.006492321624085e-46") == 0u);
+        CHECK(native_bits32("7.006492321624086e-46") == 1u);
+        CHECK(native_bits32("1.1754942e-38") == 0x007FFFFFu);
+        CHECK(native_bits32("-1.17549435e-38") == 0x80800000u);
+        CHECK(native_bits32("1e39") == 0x7F800000u);
+        CHECK(native_bits32("-1e-50") == 0x80000000u);
+        // not rounded through double: its double would round to another float
+        CHECK(native_bits32("1.00000005960464477539062500000000001") == 0x3F800001u);
+        CHECK(native_bits32("9007199254740993") == 0x5A000000u);
+    }
+
+    SECTION("the conversion shared with other parsers")
+    {
+        // convert_float() gives the lexer's results, for every type
+        const std::vector<std::string> tokens =
+        {
+            "0", "-0.0", "1.5", "0.1", "1e-400", "-2.5E+3", "123456789012345678901234567890",
+            "9007199254740993.0000000000000000001", "4.9406564584124654e-324"
+        };
+        using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
+        using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+        for (const auto& t : tokens)
+        {
+            CAPTURE(t)
+            const auto layout = float_token_layout(t);
+            const char* const first = t.data();
+            const char* const last = first + t.size();
+            const auto d = nlohmann::detail::convert_float<double>(first, last, layout.first, layout.second);
+            const auto f = nlohmann::detail::convert_float<float>(first, last, layout.first, layout.second);
+            const auto ld = nlohmann::detail::convert_float<long double>(first, last, layout.first, layout.second);
+            CHECK(bits_of(d) == bits_of(json::parse(t).get<double>()));
+            CHECK(bits_of(f) == bits_of(float_json::parse(t).get<float>()));
+            CHECK(ld == long_double_json::parse(t).get<long double>());
+        }
+    }
 }
 
 namespace
@@ -807,40 +1086,6 @@ std::size_t big_bit_length(const big_uint& a)
     }
     return n;
 }
-
-std::uint64_t bits_of(double d)
-{
-    std::uint64_t b = 0;
-    std::memcpy(&b, &d, sizeof(b));
-    return b;
-}
-
-bool eisel_lemire(const std::string& s, double& out)
-{
-    return nlohmann::detail::parse_float_eisel_lemire(s.data(), s.data() + s.size(), out);
-}
-
-// significant digits of a token, without trailing zeros
-std::size_t significant_digits(const std::string& s)
-{
-    std::string digits;
-    for (const char c : s)
-    {
-        if (c == 'e' || c == 'E')
-        {
-            break;
-        }
-        if (c >= '0' && c <= '9' && !(digits.empty() && c == '0'))
-        {
-            digits += c;
-        }
-    }
-    while (!digits.empty() && digits.back() == '0')
-    {
-        digits.pop_back();
-    }
-    return digits.size();
-}
 } // namespace
 
 TEST_CASE("Eisel-Lemire float conversion")
@@ -938,10 +1183,6 @@ TEST_CASE("Eisel-Lemire float conversion")
             const int k = i % 64;
             const std::uint64_t x = (std::uint64_t{1} << k) | (a & ((std::uint64_t{1} << k) - 1));
             CHECK(nlohmann::detail::count_leading_zeros(x) == 63 - k);
-
-            // the mirror image: bit k set, arbitrary bits above it
-            const std::uint64_t y = (std::uint64_t{1} << k) | (k == 63 ? 0 : (a << (k + 1)));
-            CHECK(nlohmann::detail::count_trailing_zeros(y) == k);
         }
     }
 
@@ -1272,26 +1513,33 @@ TEST_CASE("Eisel-Lemire float conversion")
         for (const auto& c : known)
         {
             CAPTURE(c.first)
-            double out = 0;
+            CHECK(native_bits64(c.first) == c.second);
-            if (eisel_lemire(c.first, out))
+        }
+    }
+
+    SECTION("binary32")
     {
-                CHECK(bits_of(out) == c.second);
+        using binary32 = nlohmann::detail::ieee_binary_format<24>;
-            }
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(0, 1) == 0x3F800000u);
-            else
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-1, 1) == 0x3DCCCCCDu);
-            {
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-1, 15) == 0x3FC00000u);
-                // only tokens with more than 19 significant digits are left to
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(0, 16777217) == 0x4B800000u); // tie, to even
-                // strtod: those whose value lies too close to a tie
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(0, 16777219) == 0x4B800002u); // tie, to even
-                CHECK(significant_digits(c.first) > 19);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-45, 1) == 0x00000001u);
-            }
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-46, 7) == 0x00000000u);
-        }
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-46, 8) == 0x00000001u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-65, 9999999999999999999u) == 0x00000000u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(20, 3402823466385288598u) == 0x7F7FFFFFu);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(20, 3402823669209384635u) == 0x7F800000u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(39, 1) == 0x7F800000u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-5, 0) == 0x00000000u);
     }
 
     SECTION("round trip")
     {
-        // every double written by to_chars and read back, also with trailing
+        // every double written by to_chars and read back, and its 17-digit
-        // digits that make the token longer than 19 digits
+        // form with trailing digits that make the token longer than 19 digits
         std::uint64_t state = 5295;
-        std::size_t declined = 0;
         for (int i = 0; i < 200000; ++i)
         {
             state ^= state << 13u;
@@ -1313,30 +1561,51 @@ TEST_CASE("Eisel-Lemire float conversion")
             const char* end = nlohmann::detail::to_chars(buffer.data(), buffer.data() + buffer.size(), d);
             const std::string token(buffer.data(), static_cast<std::size_t>(end - buffer.data()));
             CAPTURE(token)
-            double out = 0;
+            CHECK(native_bits64(token) == b);
-            REQUIRE(eisel_lemire(token, out));
-            CHECK(bits_of(out) == b);
 
-            // insert digits before the exponent: the value moves by far less
+            // insert digits before the exponent of the 17-digit form: that
-            // than the distance to the rounding boundary, so it must not change
+            // form lies strictly inside the rounding interval of the double
-            std::string longer = token;
+            // (the shortest one may lie on its boundary), and the digits move
+            // it by far less than the distance to the boundary, so the value
+            // must not change
+            std::array<char, 64> digits17{};
+            static_cast<void>(std::snprintf(digits17.data(), digits17.size(), "%.17g", d)); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            std::string longer = digits17.data();
             const std::size_t e = longer.find('e');
             const std::size_t dot = longer.find('.');
             const std::string extra = dot == std::string::npos ? ".000000000000000000001" : "000000000000000000001";
             longer.insert(e == std::string::npos ? longer.size() : e, extra);
             CAPTURE(longer)
-            if (eisel_lemire(longer, out))
+            CHECK(native_bits64(longer) == b);
+        }
+    }
+
+    SECTION("round trip, binary32")
     {
-                CHECK(bits_of(out) == b);
+        std::uint32_t state = 5295;
-            }
+        for (int i = 0; i < 100000; ++i)
-            else
         {
-                // w and w + 1 round differently: only when the value is very
+            state ^= state << 13u;
-                // close to a rounding boundary
+            state ^= state >> 17u;
-                ++declined;
+            state ^= state << 5u;
+            std::uint32_t b = state;
+            if ((b & 0x7F800000u) == 0x7F800000u)
+            {
+                continue; // infinity or NaN
             }
+            if (i % 4 == 0)
+            {
+                b &= 0x807FFFFFu; // subnormals
+            }
+            float f = 0;
+            std::memcpy(&f, &b, sizeof(f));
+
+            std::array<char, 64> buffer{};
+            const char* end = nlohmann::detail::to_chars(buffer.data(), buffer.data() + buffer.size(), f);
+            const std::string token(buffer.data(), static_cast<std::size_t>(end - buffer.data()));
+            CAPTURE(token)
+            CHECK(native_bits32(token) == b);
         }
-        CHECK(declined < 1000); // 107 of the 200,000
     }
 
     SECTION("used by the lexer")
@@ -1350,3 +1619,184 @@ TEST_CASE("Eisel-Lemire float conversion")
                              "[json.exception.out_of_range.406] number overflow parsing '1.7976931348623159e308'", json::out_of_range&);
     }
 }
+
+namespace
+{
+using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
+
+// the bits of the float that parse() gives for a token, via both scanners;
+// the value must be the same for both
+template<typename Json, typename Bits>
+void check_parse(const std::string& token, Bits expected, Bits infinity)
+{
+    std::stringstream stream(token);
+    if ((expected & ~(Bits{1} << ((8 * sizeof(Bits)) - 1))) == infinity)
+    {
+        Json _;
+        CHECK_THROWS_WITH_AS(_ = Json::parse(token), ("[json.exception.out_of_range.406] number overflow parsing '" + token + "'").c_str(), typename Json::out_of_range&);
+        CHECK_THROWS_WITH_AS(_ = Json::parse(stream), ("[json.exception.out_of_range.406] number overflow parsing '" + token + "'").c_str(), typename Json::out_of_range&);
+        return;
+    }
+    const Json contiguous = Json::parse(token);
+    const Json streamed = Json::parse(stream);
+    if (contiguous.is_number_float()) // not an integer that fits
+    {
+        CHECK(bits_of(contiguous.template get<typename Json::number_float_t>()) == expected);
+        CHECK(bits_of(streamed.template get<typename Json::number_float_t>()) == expected);
+    }
+    else
+    {
+        CHECK(streamed.is_number_integer());
+    }
+}
+} // namespace
+
+TEST_CASE("float conversion of hard cases")
+{
+    // see float_hard_cases.hpp
+    for (const auto& c : float_hard_cases::cases())
+    {
+        const std::string token = c.token;
+        CAPTURE(token)
+        CHECK(native_bits64(token) == c.bits64);
+        CHECK(native_bits32(token) == c.bits32);
+        check_parse<json>(token, c.bits64, std::uint64_t{0x7FF0000000000000u});
+        check_parse<float_json>(token, c.bits32, std::uint32_t{0x7F800000u});
+    }
+}
+
+TEST_CASE("float overflow and underflow in the parser")
+{
+    SECTION("double")
+    {
+        check_parse<json>("1.7976931348623157e308", std::uint64_t{0x7FEFFFFFFFFFFFFFu}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("1.7976931348623159e308", std::uint64_t{0x7FF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("-1e309", std::uint64_t{0xFFF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("1" + std::string(400, '0'), std::uint64_t{0x7FF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("1e99999999999999999999", std::uint64_t{0x7FF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        // an underflow gives a zero with the sign of the token
+        check_parse<json>("1e-400", std::uint64_t{0}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("-1e-400", std::uint64_t{0x8000000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("-2.4703282292062327e-324", std::uint64_t{0x8000000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("0." + std::string(400, '0') + "1", std::uint64_t{0}, std::uint64_t{0x7FF0000000000000u});
+    }
+
+    SECTION("float")
+    {
+        check_parse<float_json>("3.4028234e38", std::uint32_t{0x7F7FFFFFu}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("3.4028236e38", std::uint32_t{0x7F800000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-1e39", std::uint32_t{0xFF800000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("1e-46", std::uint32_t{0}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-1e-46", std::uint32_t{0x80000000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-7.006492321624085e-46", std::uint32_t{0x80000000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-7.006492321624086e-46", std::uint32_t{0x80000001u}, std::uint32_t{0x7F800000u});
+    }
+}
+
+TEST_CASE("string scanning kernels")
+{
+    // the word-at-a-time kernels must stop exactly where a byte-by-byte scan
+    // stops, for any content, length, and alignment
+    const auto reference_special = [](const unsigned char* data, std::size_t n)
+    {
+        std::size_t i = 0;
+        while (i < n && !nlohmann::detail::is_string_special(data[i]))
+        {
+            ++i;
+        }
+        return i;
+    };
+    const auto reference_copyable = [](const unsigned char* data, std::size_t n)
+    {
+        std::size_t i = 0;
+        while (i < n && nlohmann::detail::is_ascii_copyable(data[i]))
+        {
+            ++i;
+        }
+        return i;
+    };
+    const auto reference_bulk_run = [](const unsigned char* data, std::size_t n)
+    {
+        std::size_t i = 0;
+        while (i < n)
+        {
+            if (data[i] < 0x80u)
+            {
+                if (nlohmann::detail::is_string_special(data[i]))
+                {
+                    break;
+                }
+                ++i;
+                continue;
+            }
+            const std::size_t seq = nlohmann::detail::validate_one_utf8(data + i, n - i);
+            if (seq == 0)
+            {
+                break;
+            }
+            i += seq;
+        }
+        return i;
+    };
+
+    // pieces: ordinary ASCII, stops, DEL, well-formed sequences of every
+    // length, and ill-formed or truncated ones
+    const std::vector<std::string> pieces =
+    {
+        "a", "Z", " ", "~", "0123456789", "\"", "\\", std::string(1, '\0'), "\n", "\x1F", "\x7F",
+        "\xC3\xA4", "\xE2\x82\xAC", "\xE6\x97\xA5\xE6\x9C\xAC", "\xF0\x9F\x98\x80", "\xED\x9F\xBF",
+        "\x80", "\xC0\x80", "\xC3", "\xE2\x82", "\xED\xA0\x80", "\xF4\x90\x80\x80", "\xFF",
+    };
+    std::uint64_t state = 5295;
+    const auto next = [&state]()
+    {
+        state ^= state << 13u;
+        state ^= state >> 7u;
+        state ^= state << 17u;
+        return state;
+    };
+    // the upper half as a 32-bit value: converts to std::size_t implicitly on
+    // every platform (a cast of std::uint64_t is useless where both are the
+    // same type, and required where std::size_t is 32 bits wide)
+    const auto next_small = [&next]()
+    {
+        return static_cast<std::uint32_t>(next() >> 32u);
+    };
+    for (int round = 0; round < 100000; ++round)
+    {
+        // mostly ordinary text, so that runs span several words
+        std::string text(next_small() % 8u, '.');
+        const std::size_t count = next_small() % 12u;
+        for (std::size_t k = 0; k < count; ++k)
+        {
+            const std::size_t p = (next() % 4 == 0) ? next_small() % pieces.size() : 0;
+            text += pieces[p];
+            text += std::string(next_small() % 10u, 'x');
+        }
+        const auto* data = reinterpret_cast<const unsigned char*>(text.data()); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+        for (std::size_t offset = 0; offset < 3 && offset <= text.size(); ++offset)
+        {
+            const std::size_t n = text.size() - offset;
+            CAPTURE(text)
+            CAPTURE(offset)
+            CHECK(nlohmann::detail::find_string_special(data + offset, n) == reference_special(data + offset, n));
+            CHECK(nlohmann::detail::find_ascii_copyable_run(data + offset, n) == reference_copyable(data + offset, n));
+            CHECK(nlohmann::detail::scalar_string_bulk_run(data + offset, n) == reference_bulk_run(data + offset, n));
+        }
+    }
+
+    // the trailing-zero count, whichever implementation the compiler gets
+    for (int k = 0; k < 64; ++k)
+    {
+        const std::uint64_t bit = std::uint64_t{1} << k;
+        CHECK(nlohmann::detail::count_trailing_zeros(bit) == k);
+        CHECK(nlohmann::detail::count_trailing_zeros(bit | (bit << 1u) | 0x8000000000000000u) == k);
+    }
+
+    // eight bytes as a little-endian word, at any alignment
+    const std::array<unsigned char, 16> bytes = {{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF}};
+    CHECK(nlohmann::detail::read_eight_bytes(bytes.data()) == 0x0807060504030201u);
+    CHECK(nlohmann::detail::read_eight_bytes(bytes.data() + 1) == 0x0908070605040302u);
+    CHECK(nlohmann::detail::read_eight_bytes(bytes.data() + 8) == 0xFF0F0E0D0C0B0A09u);
+    CHECK(nlohmann::detail::read_eight_bytes(reinterpret_cast<const char*>(bytes.data()) + 3) == 0x0B0A090807060504u);
+}

tests/src/unit-custom-binary-type.cpp

@@ -8,13 +8,6 @@
 
 #include "doctest_compatibility.h"
 
-// capture whether JSON_DISABLE_ENUM_SERIALIZATION was enabled on the command
-// line before including json.hpp, which #undefs it; std::byte is an enum, so
-// converting std::vector<std::byte> needs enum serialization
-#if defined(JSON_DISABLE_ENUM_SERIALIZATION) && (JSON_DISABLE_ENUM_SERIALIZATION == 1)
-    #define SKIP_TESTS_FOR_ENUM_SERIALIZATION
-#endif
-
 #include <nlohmann/json.hpp>
 
 #include <cstdint>
@@ -92,53 +85,3 @@ TEST_CASE("binary type whose value type is not std::uint8_t")
     }
 #endif
 }
-
-#ifdef JSON_HAS_CPP_17
-// moved from unit-regression3.cpp, so that file does not instantiate a second
-// basic_json specialization (MinGW section limit, see windows.yml)
-TEST_CASE("std::vector<std::byte> as binary type")
-{
-    SECTION("issue #4804: from_cbor incompatible with std::vector<std::byte> as binary_t")
-    {
-        const std::vector<std::uint8_t> data = {0x80};
-        const auto decoded = byte_binary_json::from_cbor(data);
-        CHECK((decoded == byte_binary_json::array()));
-    }
-
-#ifndef SKIP_TESTS_FOR_ENUM_SERIALIZATION
-    SECTION("discussion #4209 - custom BinaryType direct assignment and round-tripping")
-    {
-        // Test that assigning a custom BinaryType directly creates a binary value, not an array
-        const std::vector<std::byte> original{std::byte{1}, std::byte{2}, std::byte{3}};
-        const byte_binary_json j = original;
-        CHECK(j.is_binary());
-        CHECK(!j.is_array());
-
-        // Test round-tripping: extracting the binary value back as the custom container type
-        const auto extracted = j.get<std::vector<std::byte>>();
-        CHECK(extracted == original);
-
-        // Test that the default json alias behavior is unchanged: std::vector<uint8_t> -> array
-        const nlohmann::json default_json = std::vector<std::uint8_t> {1, 2, 3};
-        CHECK(default_json.is_array());
-        CHECK(!default_json.is_binary());
-    }
-
-    SECTION("discussion #4209 - custom BinaryType extraction from parsed array")
-    {
-        // Test that extracting a custom BinaryType from a parsed JSON array still works
-        // (not just from a binary-typed node)
-        const auto j = byte_binary_json::parse("[1,2,3]");
-        CHECK(j.is_array());
-        CHECK(!j.is_binary());
-
-        // Extracting as custom BinaryType should work from arrays
-        const auto extracted = j.get<std::vector<std::byte>>();
-        CHECK(extracted.size() == 3);
-        CHECK(extracted[0] == std::byte{1});
-        CHECK(extracted[1] == std::byte{2});
-        CHECK(extracted[2] == std::byte{3});
-    }
-#endif
-}
-#endif

tests/src/unit-deserialization.cpp

@@ -35,7 +35,6 @@ using nlohmann::json;
 #include <sstream>
 #include <string>
 #include <valarray>
-#include <vector>
 
 #include "sax_event_loggers.hpp"
 
@@ -1251,139 +1250,3 @@ TEST_CASE_TEMPLATE("deserialization of different character types (UTF-32)", T, c
     CHECK(json::sax_parse(v, &l));
     CHECK(l.events.size() == 1);
 }
-
-namespace
-{
-// records the position and message of a parse error; reporting the error via
-// SAX does not throw, so the test also runs with JSON_NOEXCEPTION
-struct SaxErrorRecorder : public SaxEventLogger
-{
-    bool parse_error(std::size_t position, const std::string& /*last_token*/, const json::exception& ex) override
-    {
-        error = std::to_string(position) + " " + ex.what();
-        return false;
-    }
-
-    std::string error {}; // NOLINT(readability-redundant-member-init)
-};
-} // namespace
-
-TEST_CASE("parse error positions are the same for contiguous and stream input")
-{
-    // contiguous input derives the position from the input on error, stream
-    // input counts it while reading (see lexer::lazy_position); the cases
-    // cover newlines before the error, ungetting a newline after a number,
-    // newlines inside a string, a comment, and reads at the end of input
-    struct test_case
-    {
-        std::string input;
-        std::size_t byte;
-        std::string message;
-    };
-    const std::vector<test_case> cases =
-    {
-        {"[\n  1,\n  2\n", 12, "[json.exception.parse_error.101] parse error at line 4, column 1: syntax error while parsing array - unexpected end of input; expected ']'"},
-        {"[1\n,2,\n]", 8, "[json.exception.parse_error.101] parse error at line 3, column 1: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal"},
-        {"[1\n x]", 5, "[json.exception.parse_error.101] parse error at line 2, column 2: syntax error while parsing array - invalid literal; last read: '1<U+000A> x'; expected ']'"},
-        {"1\n2", 3, "[json.exception.parse_error.101] parse error at line 2, column 1: syntax error while parsing value - unexpected number literal; expected end of input"},
-        {
-            "{\"a\":\n\"b\nc\"}", 9, R"([json.exception.parse_error.101] parse error at line 3, column 0: syntax error while parsing value - invalid string: control character U+000A (LF) must be escaped to \u000A or \n; last read: '"b<U+000A>')"
-        },
-        {"/* a\n b */\n x", 13, "[json.exception.parse_error.101] parse error at line 3, column 2: syntax error while parsing value - invalid literal; last read: '/* a<U+000A> b */<U+000A> x'"},
-        {"\n\n", 3, "[json.exception.parse_error.101] parse error at line 3, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal"},
-        {"[\"a\",\n 1e\n]", 10, "[json.exception.parse_error.101] parse error at line 3, column 0: syntax error while parsing value - invalid number; expected '+', '-', or digit after exponent; last read: '1e<U+000A>'"},
-        {"[tru\n]", 5, "[json.exception.parse_error.101] parse error at line 2, column 0: syntax error while parsing value - invalid literal; last read: '[tru<U+000A>'"},
-    };
-
-    for (const auto& c : cases)
-    {
-        CAPTURE(c.input)
-        const std::string expected = std::to_string(c.byte) + " " + c.message;
-
-        SaxErrorRecorder string_sax;
-        CHECK_FALSE(json::sax_parse(c.input, &string_sax, json::input_format_t::json, true, true));
-        CHECK(string_sax.error == expected);
-
-        SaxErrorRecorder pointer_sax;
-        CHECK_FALSE(json::sax_parse(c.input.data(), c.input.data() + c.input.size(), &pointer_sax, json::input_format_t::json, true, true));
-        CHECK(pointer_sax.error == expected);
-
-        std::istringstream is(c.input);
-        SaxErrorRecorder stream_sax;
-        CHECK_FALSE(json::sax_parse(is, &stream_sax, json::input_format_t::json, true, true));
-        CHECK(stream_sax.error == expected);
-    }
-}
-
-#if !defined(JSON_NOEXCEPTION)
-TEST_CASE("indentation runs of every length around the 8-byte skip")
-{
-    // contiguous input skips the spaces after a newline 8 bytes at a time (see
-    // lexer::skip_indentation), stream input reads them one by one; results,
-    // byte offsets, and messages must be the same for runs that end anywhere
-    // relative to a word boundary, including at the end of the input
-    const auto parse_result = [](const std::string & input, bool contiguous)
-    {
-        try
-        {
-            if (contiguous)
-            {
-                return json::parse(input.data(), input.data() + input.size(), nullptr, true, true).dump();
-            }
-            std::istringstream is(input);
-            return json::parse(is, nullptr, true, true).dump();
-        }
-        catch (const json::parse_error& e)
-        {
-            return std::to_string(e.byte).append(" ").append(e.what());
-        }
-    };
-
-    // replace every '~' in a pattern by an indentation run
-    const auto indented = [](const std::string & pattern, const std::string & indent)
-    {
-        std::string result;
-        for (const char c : pattern)
-        {
-            if (c == '~')
-            {
-                result += indent;
-            }
-            else
-            {
-                result += c;
-            }
-        }
-        return result;
-    };
-
-    const std::vector<std::string> patterns =
-    {
-        "[\n~1,\n~2\n]",
-        "[\n~1,\n~x]",
-        "[\n~1,\n~",
-        "1\n~",
-        "[\n~\t1,\n~\r\n~2]",
-        "[\n~/* c */ 1]",
-        "[\n~1\n~2]",
-    };
-
-    for (std::size_t n = 0; n <= 33; ++n)
-    {
-        const std::string indent(n, ' ');
-        for (const auto& pattern : patterns)
-        {
-            const std::string input = indented(pattern, indent);
-            CAPTURE(n)
-            CAPTURE(input)
-            const std::string expected = parse_result(input, false);
-            CHECK(parse_result(input, true) == expected);
-            CHECK(json::accept(input.data(), input.data() + input.size(), true) == json::accept(input, true));
-        }
-    }
-
-    // and against fixed expectations, in case both paths broke the same way
-    CHECK(parse_result(indented("[\n~x]", std::string(16, ' ')), true) == "19 [json.exception.parse_error.101] parse error at line 2, column 17: syntax error while parsing value - invalid literal; last read: '[<U+000A>                x'");
-    CHECK(parse_result(indented("[\n~1]", std::string(17, ' ')), true) == "[1]");
-}
-#endif

tests/src/unit-diagnostics.cpp

@@ -567,9 +567,9 @@ TEST_CASE("Regression tests for extended diagnostics")
     }
 }
 
-TEST_CASE("Better diagnostics past the descent bound of update(), merge_patch() and merge_diff()")
+TEST_CASE("Better diagnostics past the descent bound of update() and merge_patch()")
 {
-    // All three handle objects nested more than detail::recursion_depth_limit()
+    // Both merge objects nested more than detail::recursion_depth_limit()
     // (128) levels deep without recursing; the values they add or replace
     // there must still know their parents.
     // The values are built rather than parsed, so that the expected messages
@@ -615,19 +615,4 @@ TEST_CASE("Better diagnostics past the descent bound of update(), merge_patch()
         CHECK_THROWS_WITH_AS(p->at("x").at(0), expected_x.c_str(), json::type_error);
         CHECK_THROWS_WITH_AS(p->at("y").at(0), expected_y.c_str(), json::type_error);
     }
-
-    SECTION("merge_diff()")
-    {
-        // target and patch differ only in their innermost members, so the
-        // diff of the two is nested as deeply: {"a": ... {"x": null, "y": 2}}
-        const json diff = json::merge_diff(target, patch); // NOLINT(readability-suspicious-call-argument)
-
-        const json* p = &diff;
-        for (std::size_t i = 0; i < depth; ++i)
-        {
-            p = &p->at("a");
-        }
-        CHECK(p->at("x").is_null());
-        CHECK_THROWS_WITH_AS(p->at("y").at(0), expected_y.c_str(), json::type_error);
-    }
 }

tests/src/unit-locale-cpp.cpp

@@ -260,10 +260,11 @@ struct LocaleSwitchingSax final: public nlohmann::json_sax<json>
 
 TEST_CASE("locale changes between lexer construction and number conversion (#5198)")
 {
-    // The numbers are chosen so that the conversion also takes the strtod
+    // float and double are converted without the locale. A long double that
-    // fallback, which honors the locale that is current at conversion time:
+    // is not binary64 can take the strtold fallback, which honors the locale
-    // too many significant digits for Clinger's fast path, an underflow that
+    // that is current at conversion time. The numbers are chosen so that it
-    // std::from_chars rejects, and a plain value.
+    // does: too many significant digits for Clinger's fast path, an underflow
+    // that std::from_chars rejects, and a plain value.
     const std::vector<std::string> numbers = {"3.14159265358979323846", "1.5e-400", "12.34", "-0.000123456789012345678"};
     std::string text = "[";
     for (const auto& n : numbers)
@@ -327,7 +328,8 @@ TEST_CASE("locale changes between lexer construction and number conversion (#519
             }
         }
 
-        // a long double goes through std::strtold unless std::from_chars supports it
+        // a long double goes through std::strtold unless it is binary64 or
+        // std::from_chars supports it
         {
             bool switched = false;
             const auto cb = [&](int /*depth*/, long_double_json::parse_event_t event, long_double_json& /*parsed*/) noexcept
@@ -353,8 +355,15 @@ TEST_CASE("locale with a multi-byte decimal point")
 {
     // Some locales use a decimal point that is not a single character, e.g.
     // U+066B ARABIC DECIMAL SEPARATOR (two bytes in UTF-8). It cannot be
-    // substituted in place for '.', so the strtod fallback stops early. The
+    // substituted in place for '.', so the strtold fallback (only for long
-    // conversion must still terminate rather than retry forever.
+    // double formats other than binary64) converts a copy of the token with
+    // the whole decimal point instead (#5660). The values must be those of the
+    // "C" locale.
+    using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+    const char* const long_double_numbers = "[3.14159265358979323846, 1.5e-400, -0.000123456789012345678]";
+    REQUIRE(std::setlocale(LC_NUMERIC, "C") != nullptr);
+    const long_double_json expected_long_double = long_double_json::parse(long_double_numbers);
+
     const std::array<const char*, 6> names = {{"ar_EG.UTF-8", "ar_SA.UTF-8", "fa_IR.UTF-8", "ps_AF.UTF-8", "ar_EG", "fa_IR"}};
     bool tested = false;
     for (const char* name : names)
@@ -372,12 +381,20 @@ TEST_CASE("locale with a multi-byte decimal point")
         tested = true;
 
         // too many significant digits for Clinger's fast path, and an underflow
-        // that std::from_chars rejects: both reach the strtod fallback
+        // that std::from_chars rejects: double does not depend on the locale
         json j;
         CHECK_NOTHROW(j = json::parse("[3.14159265358979323846, 1.5e-400, -0.000123456789012345678]"));
         CHECK(j.is_array());
+        CHECK(j[0] == 3.14159265358979323846);
+        CHECK(j[1] == 0.0);
+        CHECK(j[2] == -0.000123456789012345678);
         CHECK(json::accept("3.14159265358979323846"));
 
+        // a long double that reaches the strtold fallback is not truncated
+        long_double_json ld;
+        CHECK_NOTHROW(ld = long_double_json::parse(long_double_numbers));
+        CHECK(ld == expected_long_double);
+
         // a value the locale-independent paths convert is not affected
         CHECK(json::parse("12.5") == 12.5);
     }

tests/src/unit-regression3.cpp

@@ -58,6 +58,11 @@ using ordered_json = nlohmann::ordered_json;
         #include <optional>
     #elif __has_include(<experimental/optional>)
     #endif
+
+    /////////////////////////////////////////////////////////////////////
+    // for #4804
+    /////////////////////////////////////////////////////////////////////
+    using json_4804 = nlohmann::json::with_binary_t<std::vector<std::byte>>;
 #endif
 
 #ifdef JSON_HAS_CPP_20
@@ -453,6 +458,49 @@ TEST_CASE("regression tests 3")
 #endif
 
 #ifdef JSON_HAS_CPP_17
+    SECTION("issue #4804: from_cbor incompatible with std::vector<std::byte> as binary_t")
+    {
+        const std::vector<std::uint8_t> data = {0x80};
+        const auto decoded = json_4804::from_cbor(data);
+        CHECK((decoded == json_4804::array()));
+    }
+
+#ifndef SKIP_TESTS_FOR_ENUM_SERIALIZATION
+    SECTION("discussion #4209 - custom BinaryType direct assignment and round-tripping")
+    {
+        // Test that assigning a custom BinaryType directly creates a binary value, not an array
+        const std::vector<std::byte> original{std::byte{1}, std::byte{2}, std::byte{3}};
+        const json_4804 j = original;
+        CHECK(j.is_binary());
+        CHECK(!j.is_array());
+
+        // Test round-tripping: extracting the binary value back as the custom container type
+        const auto extracted = j.get<std::vector<std::byte>>();
+        CHECK(extracted == original);
+
+        // Test that the default json alias behavior is unchanged: std::vector<uint8_t> -> array
+        const json default_json = std::vector<std::uint8_t> {1, 2, 3};
+        CHECK(default_json.is_array());
+        CHECK(!default_json.is_binary());
+    }
+
+    SECTION("discussion #4209 - custom BinaryType extraction from parsed array")
+    {
+        // Test that extracting a custom BinaryType from a parsed JSON array still works
+        // (not just from a binary-typed node)
+        const auto j = json_4804::parse("[1,2,3]");
+        CHECK(j.is_array());
+        CHECK(!j.is_binary());
+
+        // Extracting as custom BinaryType should work from arrays
+        const auto extracted = j.get<std::vector<std::byte>>();
+        CHECK(extracted.size() == 3);
+        CHECK(extracted[0] == std::byte{1});
+        CHECK(extracted[1] == std::byte{2});
+        CHECK(extracted[2] == std::byte{3});
+    }
+#endif
+
     SECTION("issue #5046 - implicit conversion of return json to std::optional no longer implicit")
     {
         const json jval{};