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Write doubles with the shortest digits (Żmij), digits in registers
Write doubles with the conversion of Zmij by Victor Zverovich (MIT), ported to C++11 (detail/conversions/zmij.hpp). It finds the shortest decimal that reads back as the same double, and the closest one if there are several. Grisu2, used until now, is fast but not always shortest: it sometimes writes a 17th digit where 16 suffice, or a last digit that is not the closest. The layout is unchanged (1.5, 100.0, 1e+100, -0.0); float keeps Grisu2. Digits are converted eight at a time with the BCD conversion of Xiang JunBo, as in Zmij, and written with one byte swap per eight digits and fixed-size moves instead of per-digit loops. Leading and trailing zeros are counted from those bytes. to_chars() uses a local buffer when the caller's is shorter than the 41 bytes this may write. The powers of ten come from the number-parsing table, adjusted where it holds values rounded up, and extended with Zmij's compressed tables beyond 10^308. write_shortest() converts its 16 digits in one vector register (SSE2 on x86-64, NEON on 64-bit Arm, both baseline) and inserts the decimal point inside the register, avoiding a store-forwarding stall that cost about 25% of the time to write a double. dump() writes floats and integers straight into the serializer's write buffer instead of copying them from a member buffer, and small integers eight digits at a time. read_eight_bytes() and parse_eight_digits() are marked always-inline, which GCC had been calling out of line in the number-parsing loops. Of one million random doubles, about 0.14% are now written with different digits, always to a value that still reads back as the same double. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
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@@ -25,6 +25,7 @@ cc_library(
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"include/nlohmann/detail/conversions/from_json.hpp",
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"include/nlohmann/detail/conversions/to_chars.hpp",
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"include/nlohmann/detail/conversions/to_json.hpp",
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"include/nlohmann/detail/conversions/zmij.hpp",
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"include/nlohmann/detail/exceptions.hpp",
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"include/nlohmann/detail/hash.hpp",
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"include/nlohmann/detail/input/binary_reader.hpp",
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@@ -1394,6 +1394,7 @@ THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR I
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- The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2008-2009 [Björn Hoehrmann](https://bjoern.hoehrmann.de/) <bjoern@hoehrmann.de>
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- 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/)
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- The class contains a port of the shortest double-to-decimal conversion of [Żmij](https://github.com/vitaut/zmij) by Victor Zverovich, which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2025 [Victor Zverovich](https://github.com/vitaut)
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- 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/).
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- 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).
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- 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
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@@ -62,6 +62,9 @@ Linear.
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## Notes
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Floating-point numbers are written with the fewest digits that read back as the same value (for `#!cpp double`; see
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[number handling](../../features/types/number_handling.md#number-serialization)).
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Binary values are serialized as an object containing two keys:
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- "bytes": an array of bytes as integers
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@@ -97,3 +100,5 @@ Binary values are serialized as an object containing two keys:
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- Error handlers added in version 3.4.0.
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- Serialization of binary values added in version 3.8.0.
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- Error handler `keep` added in version 3.13.0.
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- Doubles are written with the shortest digits (Żmij instead of Grisu2) since version 3.13.0; about 0.1% of doubles are
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written differently, most of them with fewer digits.
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@@ -134,9 +134,10 @@ That is, `-0` is stored as a signed integer, but the serialization does not repr
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### Number serialization
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- Integer numbers are serialized as is; that is, no scientific notation is used.
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- Floating-point numbers are serialized as specified by the `#!c %g` printf modifier with
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[`std::numeric_limits<double>::max_digits10`](https://en.cppreference.com/w/cpp/types/numeric_limits/max_digits10)
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significant digits. The rationale is to use the shortest representation while still allowing round-tripping.
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- Floating-point numbers are serialized with the fewest digits that read back as the same value (the closest such
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digits if there are several), in the layout of the `#!c %g` printf modifier: `#!c 1.5`, `#!c 100.0`, `#!c 1e+100`.
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Doubles are converted with the algorithm of [Żmij](https://github.com/vitaut/zmij), floats with Grisu2, which
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can write more digits than necessary.
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!!! hint "Notes regarding precision of floating-point numbers"
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@@ -545,9 +545,10 @@ therefore silently changes parse results rather than raising an error. See
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specifiers, for which the library likewise provides only `#!cpp double` and `#!cpp long double` overloads
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(`#!cpp float` is promoted to `#!cpp double`).
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If `#!cpp std::numeric_limits<NumberFloatType>` describes an IEEE 754 binary32 or binary64 number, `dump` uses the
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Grisu2 algorithm, which produces the shortest representation that round-trips. Otherwise the `snprintf` fallback with
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`max_digits10` digits is used.
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If `#!cpp std::numeric_limits<NumberFloatType>` describes an IEEE 754 binary64 number, `dump` uses the algorithm of
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Żmij, which produces the shortest representation that round-trips. For IEEE 754 binary32 numbers, it uses Grisu2,
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which produces a short representation that round-trips. Otherwise the `snprintf` fallback with `max_digits10` digits is
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used.
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### Required for the binary formats
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@@ -559,7 +560,7 @@ binary32 or binary64 field and have no encoding for `#!cpp long double`.
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| Type | Support |
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|--------------------------|-----------------------------------------------------------------------------------------------------------------------|
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| `#!cpp double` (default) | full; short round-trip output through Grisu2 |
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| `#!cpp double` (default) | full; shortest round-trip output through Żmij |
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| `#!cpp float` | full; short round-trip output through Grisu2 |
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| `#!cpp long double` | `dump` and `parse` only; the binary format writers do not compile, as they only handle IEEE 754 binary32 and binary64 |
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| any other type | not usable |
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@@ -18,6 +18,8 @@ The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed und
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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/)
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The class contains a port of the shortest double-to-decimal conversion of [Żmij](https://github.com/vitaut/zmij) by Victor Zverovich, which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2025 [Victor Zverovich](https://github.com/vitaut)
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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/).
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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
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@@ -86,8 +86,9 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
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}
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/// eight bytes as a little-endian word (compilers fold this into one load on
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/// little-endian targets)
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inline std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
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/// little-endian targets; always inlined, as GCC otherwise calls it in the
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/// number loops)
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JSON_HEDLEY_ALWAYS_INLINE std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
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{
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return static_cast<std::uint64_t>(b[0]) | (static_cast<std::uint64_t>(b[1]) << 8u)
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| (static_cast<std::uint64_t>(b[2]) << 16u) | (static_cast<std::uint64_t>(b[3]) << 24u)
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@@ -96,7 +97,7 @@ inline std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
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}
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/// eight bytes as a little-endian word
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inline std::uint64_t read_eight_bytes(const char* p) noexcept
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JSON_HEDLEY_ALWAYS_INLINE std::uint64_t read_eight_bytes(const char* p) noexcept
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{
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return read_eight_bytes(reinterpret_cast<const unsigned char*>(p)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
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}
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@@ -11,11 +11,32 @@
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#include <array> // array
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#include <cmath> // signbit, isfinite
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#include <cstddef> // size_t
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#include <cstdint> // intN_t, uintN_t
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#include <cstring> // memcpy, memmove
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#include <limits> // numeric_limits
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#include <type_traits> // conditional
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#ifdef _MSC_VER
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#include <cstdlib> // _byteswap_uint64
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#endif
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// SSE2 (every x86-64 CPU) and NEON (every 64-bit Arm CPU) convert the 16
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// digits of a double at once
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#if defined(__x86_64__) || (defined(_M_X64) && !defined(_M_ARM64EC))
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#include <emmintrin.h>
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#define JSON_DTOA_SSE2 1
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#define JSON_DTOA_NEON 0
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#elif (defined(__aarch64__) || defined(_M_ARM64)) && !defined(_M_ARM64EC) && !defined(__ARM_BIG_ENDIAN)
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#include <arm_neon.h>
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#define JSON_DTOA_SSE2 0
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#define JSON_DTOA_NEON 1
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#else
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#define JSON_DTOA_SSE2 0
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#define JSON_DTOA_NEON 0
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#endif
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#include <nlohmann/detail/conversions/zmij.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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NLOHMANN_JSON_NAMESPACE_BEGIN
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@@ -918,6 +939,88 @@ void grisu2(char* buf, int& len, int& decimal_exponent, FloatType value)
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grisu2(buf, len, decimal_exponent, w.minus, w.w, w.plus);
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}
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/*!
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@brief the shortest digits of a positive finite float (other than double): Grisu2
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*/
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template<typename FloatType>
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JSON_HEDLEY_NON_NULL(1)
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void shortest_digits(char* buf, int& len, int& decimal_exponent, FloatType value)
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{
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grisu2(buf, len, decimal_exponent, value);
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}
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/*!
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@brief the shortest digits of a positive finite double: the conversion of
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Zmij (see zmij.hpp), which always finds the shortest digits that read back as
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the same value (Grisu2 does not for about one double in a thousand), and the
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closest of them if there are several
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v = buf * 10^decimal_exponent, as for grisu2()
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*/
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JSON_HEDLEY_NON_NULL(1)
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inline void shortest_digits(char* buf, int& len, int& decimal_exponent, double value)
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{
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static_assert(std::numeric_limits<double>::is_iec559 && std::numeric_limits<double>::digits == 53,
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"internal error: the conversion of Zmij needs IEEE 754 binary64 doubles");
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JSON_ASSERT(std::isfinite(value));
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JSON_ASSERT(value > 0);
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std::uint64_t bits = 0;
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std::memcpy(&bits, &value, sizeof(bits));
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zmij::decimal d = zmij::to_decimal(bits);
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// without trailing zeros (up to 16): 8, 4, 2, 1 at a time
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while (d.significand % 100000000 == 0)
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{
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d.significand /= 100000000;
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d.exponent += 8;
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}
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if (d.significand % 10000 == 0)
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{
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d.significand /= 10000;
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d.exponent += 4;
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}
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if (d.significand % 100 == 0)
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{
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d.significand /= 100;
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d.exponent += 2;
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}
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if (d.significand % 10 == 0)
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{
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d.significand /= 10;
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d.exponent += 1;
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}
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// at most 17 digits, written from the back two at a time
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static constexpr const char* pairs =
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"00010203040506070809101112131415161718192021222324252627282930313233343536373839"
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"40414243444546474849505152535455565758596061626364656667686970717273747576777879"
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"8081828384858687888990919293949596979899";
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std::array<char, 20> digits{};
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std::size_t n = digits.size();
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while (d.significand >= 100)
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{
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const std::uint64_t two_digits = d.significand % 100; // a variable: GCC calls a cast of the remainder useless where std::uint64_t is std::size_t
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const auto i = static_cast<std::size_t>(two_digits) * 2;
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d.significand /= 100;
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n -= 2;
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digits[n] = pairs[i];
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digits[n + 1] = pairs[i + 1];
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}
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if (d.significand >= 10)
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{
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const auto i = static_cast<std::size_t>(d.significand) * 2;
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n -= 2;
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digits[n] = pairs[i];
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digits[n + 1] = pairs[i + 1];
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}
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else
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{
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digits[--n] = static_cast<char>('0' + d.significand);
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}
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len = static_cast<int>(digits.size() - n);
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std::memcpy(buf, digits.data() + n, static_cast<std::size_t>(len));
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decimal_exponent = d.exponent;
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}
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/*!
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@brief appends a decimal representation of e to buf
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@return a pointer to the element following the exponent.
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@@ -1047,6 +1150,374 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
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return append_exponent(buf, n - 1);
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}
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/// eight decimal digits (a value below 10^8) as bytes 0..9, the first digit
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/// in the most significant byte: three steps that divide all lanes at once
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/// by a multiplication (the conversion of Xiang JunBo, as in Zmij)
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inline std::uint64_t eight_digit_bytes(std::uint64_t abcdefgh) noexcept
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{
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const std::uint64_t abcd_efgh = abcdefgh + (((std::uint64_t{1} << 32u) - 10000u) * ((abcdefgh * (((std::uint64_t{1} << 40u) / 10000u) + 1u)) >> 40u));
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const std::uint64_t ab_cd_ef_gh = abcd_efgh + (((std::uint64_t{1} << 16u) - 100u) * (((abcd_efgh * (((std::uint64_t{1} << 19u) / 100u) + 1u)) >> 19u) & 0x7F0000007Fu));
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return ab_cd_ef_gh + (((std::uint64_t{1} << 8u) - 10u) * (((ab_cd_ef_gh * (((std::uint64_t{1} << 10u) / 10u) + 1u)) >> 10u) & 0x000F000F000F000Fu));
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}
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/// store the bytes of v, the most significant one first (one byte swap and
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/// one store where the byte order is known: compilers do not reliably merge
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/// the byte stores once this is inlined)
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inline void store_msb_first(char* p, std::uint64_t v) noexcept
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{
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#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
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v = __builtin_bswap64(v);
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std::memcpy(p, &v, sizeof(v));
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#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
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std::memcpy(p, &v, sizeof(v));
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#elif defined(_MSC_VER) // (little-endian on all its targets)
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v = _byteswap_uint64(v);
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std::memcpy(p, &v, sizeof(v));
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#else
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for (unsigned i = 0; i < 8; ++i)
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{
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p[i] = static_cast<char>(v >> (56u - (8u * i)));
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}
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#endif
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}
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/*!
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@brief digits * 10^exp for a double, in the layout of format_buffer()
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The layout is that of format_buffer() with min_exp -4 and max_exp 15 (the
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digits10 of double). The digits are converted eight at a time and placed
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with fixed-size moves instead of per-digit loops and moves of the buffer.
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@param[in] digits the digits (not 0, at most 17 digits; trailing zeros allowed)
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@param[in] exp the decimal exponent of the last digit
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@return a pointer past the text; up to 41 bytes at @a first are written
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(some beyond the returned end)
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*/
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JSON_HEDLEY_NON_NULL(1)
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JSON_HEDLEY_RETURNS_NON_NULL
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inline char* write_decimal(char* first, std::uint64_t digits, int exp) noexcept
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{
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JSON_ASSERT(digits != 0 && digits < 100000000000000000u);
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const std::uint64_t upper = digits / 100000000u;
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const std::uint64_t b0 = upper / 100000000u; // (one digit: it is its own byte)
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const std::uint64_t b1 = eight_digit_bytes(upper % 100000000u);
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const std::uint64_t b2 = eight_digit_bytes(digits % 100000000u);
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// leading and trailing zero digits: zero bytes, counted without division
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int leading = 16;
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int zeros = 16;
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if (b0 != 0)
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{
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leading = count_leading_zeros(b0) / 8;
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}
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else if (b1 != 0)
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{
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leading = 8 + (count_leading_zeros(b1) / 8);
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}
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else
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||||
{
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||||
leading += count_leading_zeros(b2) / 8;
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||||
}
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||||
if (b2 != 0)
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||||
{
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||||
zeros = count_trailing_zeros(b2) / 8;
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||||
}
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||||
else if (b1 != 0)
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||||
{
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||||
zeros = 8 + (count_trailing_zeros(b1) / 8);
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||||
}
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||||
// (else: 16, b0 is the one digit that is not 0)
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// the digits as text at text + leading, then '0's, so that fixed-size
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||||
// moves need not check how many digits there are
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std::array<char, 64> text; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
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store_msb_first(text.data(), b0 + 0x3030303030303030u);
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store_msb_first(text.data() + 8, b1 + 0x3030303030303030u);
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store_msb_first(text.data() + 16, b2 + 0x3030303030303030u);
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std::memset(text.data() + 24, '0', 40);
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const int k = 24 - leading - zeros; // significant digits
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const int n = k + exp + zeros; // position of the decimal point after the first digit
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const char* const s0 = text.data() + leading;
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||||
if (-4 < n && n <= 15)
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||||
{
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||||
// "0.[000]digits" (n <= 0) is the digits after 1 - n leading '0's
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||||
// with the point after the first; "digits[000].0" (n >= k) and
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||||
// "dig.its" put the point after n characters
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const int pad = n <= 0 ? 1 - n : 0;
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const char* const s = s0 - pad;
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const int len = k + pad;
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const int point = n + pad;
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std::memcpy(first, s, 16);
|
||||
std::memcpy(first + point + 1, s + point, 24);
|
||||
first[point] = '.';
|
||||
return first + (point >= len ? point + 2 : len + 1);
|
||||
}
|
||||
|
||||
// d.igitse+XX, with at least two exponent digits (as append_exponent())
|
||||
std::memcpy(first, s0, 16);
|
||||
std::memcpy(first + 2, s0 + 1, 16);
|
||||
first[1] = '.';
|
||||
char* const end = first + (k == 1 ? 1 : k + 1);
|
||||
const int e = n - 1;
|
||||
const auto ea = static_cast<unsigned>(e < 0 ? -e : e);
|
||||
const bool three = ea >= 100;
|
||||
end[0] = 'e';
|
||||
end[1] = e < 0 ? '-' : '+';
|
||||
end[2] = static_cast<char>('0' + (three ? ea / 100 : (ea / 10) % 10));
|
||||
end[3] = static_cast<char>('0' + (three ? (ea / 10) % 10 : ea % 10));
|
||||
end[4] = static_cast<char>('0' + (ea % 10));
|
||||
return end + (three ? 5 : 4);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief the shortest decimal of a positive double (Zmij), as write_decimal()
|
||||
writes it
|
||||
|
||||
For a normal double, the shorter candidate has 15 or 16 digits: they are
|
||||
converted at once (two halves of eight digits) and followed by the digit
|
||||
after them, if there is one, without the multiplication and division by 10
|
||||
that counting the digits of one number would take. The fixed layouts move
|
||||
the digits after the point by one byte.
|
||||
|
||||
@return a pointer past the text; up to 41 bytes at @a first are written
|
||||
(some beyond the returned end)
|
||||
*/
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_shortest(char* first, const zmij::shortest_decimal d) noexcept
|
||||
{
|
||||
const std::uint64_t sig = d.integral;
|
||||
if (JSON_HEDLEY_UNLIKELY(sig < 100000000000000u || sig >= 10000000000000000u))
|
||||
{
|
||||
// (subnormals)
|
||||
return d.has_digit ? write_decimal(first, (sig * 10) + d.digit, d.exponent) : write_decimal(first, sig, d.exponent + 1);
|
||||
}
|
||||
const bool sixteen = sig >= 1000000000000000u; // (else 15 digits)
|
||||
const int last = d.has_digit ? d.digit : 0;
|
||||
const std::uint64_t upper = sig / 100000000u;
|
||||
#if JSON_DTOA_SSE2
|
||||
// NOLINTBEGIN(portability-simd-intrinsics)
|
||||
// the two halves in the 64-bit lanes, each as abcd * 2^32 + efgh, then as
|
||||
// bytes (as eight_digit_bytes(), one lane each)
|
||||
const __m128i x = _mm_set_epi64x(static_cast<long long>(sig - (upper * 100000000u)), static_cast<long long>(upper));
|
||||
const __m128i abcd = _mm_srli_epi64(_mm_mul_epu32(x, _mm_set1_epi64x(109951163)), 40); // 2^40 / 10000 + 1
|
||||
const __m128i abcd_efgh = _mm_add_epi64(x, _mm_mul_epu32(abcd, _mm_set1_epi64x(4294957296))); // 2^32 - 10000
|
||||
// 32-bit lanes in the order of the text: abcd, efgh of both halves
|
||||
const __m128i fours = _mm_shuffle_epi32(abcd_efgh, _MM_SHUFFLE(2, 3, 0, 1));
|
||||
const __m128i ab = _mm_srli_epi16(_mm_mulhi_epu16(fours, _mm_set1_epi32(5243)), 3);
|
||||
const __m128i ab_cd = _mm_or_si128(_mm_slli_epi32(_mm_sub_epi16(fours, _mm_mullo_epi16(ab, _mm_set1_epi32(100))), 16), ab);
|
||||
// 16-bit lanes ab (< 100) -> bytes a, b: 256 * ab - 2559 * (ab / 10)
|
||||
const __m128i bytes = _mm_sub_epi16(_mm_slli_epi16(ab_cd, 8), _mm_mullo_epi16(_mm_set1_epi16(2559), _mm_mulhi_epu16(ab_cd, _mm_set1_epi16(6554))));
|
||||
// the last digit that is not 0 (sig is not 0)
|
||||
const auto nonzero = static_cast<std::uint64_t>(_mm_movemask_epi8(_mm_cmpgt_epi8(bytes, _mm_setzero_si128())));
|
||||
const int digits = 63 - count_leading_zeros(nonzero) + (sixteen ? 1 : 0); // without trailing zeros
|
||||
const __m128i chars = _mm_add_epi8(bytes, _mm_set1_epi8('0'));
|
||||
// the 16 characters from the first digit
|
||||
const __m128i s = sixteen ? chars : _mm_or_si128(_mm_srli_si128(chars, 1), _mm_slli_si128(_mm_cvtsi32_si128('0' + last), 15));
|
||||
const char s16 = static_cast<char>(sixteen ? '0' + last : '0'); // the 17th
|
||||
const auto store_16 = [&s](char* p) noexcept
|
||||
{
|
||||
std::memcpy(p, &s, 16);
|
||||
};
|
||||
const char first_digit = static_cast<char>(_mm_cvtsi128_si32(s));
|
||||
// NOLINTEND(portability-simd-intrinsics)
|
||||
#elif JSON_DTOA_NEON
|
||||
// as with SSE2: the halves in 32-bit lanes, then abcd, efgh of both
|
||||
const uint32x2_t halves = vcreate_u32(upper | ((sig - (upper * 100000000u)) << 32u));
|
||||
const uint32x2_t abcd = vmovn_u64(vshrq_n_u64(vmull_n_u32(halves, static_cast<std::uint32_t>(((std::uint64_t{1} << 40u) / 10000u) + 1u)), 40));
|
||||
const uint32x2_t efgh = vmls_n_u32(halves, abcd, 10000u);
|
||||
const uint32x4_t fours = vcombine_u32(vzip1_u32(abcd, efgh), vzip2_u32(abcd, efgh));
|
||||
const uint32x4_t ab = vshrq_n_u32(vmulq_n_u32(fours, 5243u), 19);
|
||||
const uint16x8_t ab_cd = vreinterpretq_u16_u32(vorrq_u32(ab, vshlq_n_u32(vmlsq_n_u32(fours, ab, 100u), 16)));
|
||||
const uint16x8_t tens = vshrq_n_u16(vmulq_n_u16(ab_cd, 103u), 10);
|
||||
const uint8x16_t bytes = vreinterpretq_u8_u16(vorrq_u16(tens, vshlq_n_u16(vmlsq_n_u16(ab_cd, tens, 10u), 8)));
|
||||
// the last digit that is not 0 (sig is not 0): a nibble per byte
|
||||
const std::uint64_t nonzero = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(vtstq_u8(bytes, bytes)), 4)), 0);
|
||||
const int digits = ((63 - count_leading_zeros(nonzero)) / 4) + (sixteen ? 1 : 0); // without trailing zeros
|
||||
const uint8x16_t chars = vaddq_u8(bytes, vdupq_n_u8('0'));
|
||||
// the 16 characters from the first digit
|
||||
const uint8x16_t s = sixteen ? chars : vextq_u8(chars, vdupq_n_u8(static_cast<std::uint8_t>('0' + last)), 1);
|
||||
const char s16 = static_cast<char>(sixteen ? '0' + last : '0'); // the 17th
|
||||
const auto store_16 = [&s](char* p) noexcept
|
||||
{
|
||||
vst1q_u8(reinterpret_cast<std::uint8_t*>(p), s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
|
||||
};
|
||||
const auto first_digit = static_cast<char>(vgetq_lane_u8(s, 0));
|
||||
#else
|
||||
const std::uint64_t hi = eight_digit_bytes(upper);
|
||||
const std::uint64_t lo = eight_digit_bytes(sig - (upper * 100000000u));
|
||||
// trailing zero digits: zero bytes (sig is not 0)
|
||||
const int zeros = lo != 0 ? count_trailing_zeros(lo) / 8 : 8 + (count_trailing_zeros(hi) / 8);
|
||||
const int digits = 15 - zeros + (sixteen ? 1 : 0); // without trailing zeros
|
||||
// the 16 characters from the first digit
|
||||
const std::uint64_t s_hi = (sixteen ? hi : (hi << 8u) | (lo >> 56u)) + 0x3030303030303030u;
|
||||
const std::uint64_t s_lo = (sixteen ? lo : (lo << 8u) | static_cast<std::uint64_t>(last)) + 0x3030303030303030u;
|
||||
const char s16 = static_cast<char>(sixteen ? '0' + last : '0'); // the 17th
|
||||
const auto store_16 = [s_hi, s_lo](char* p) noexcept
|
||||
{
|
||||
store_msb_first(p, s_hi);
|
||||
store_msb_first(p + 8, s_lo);
|
||||
};
|
||||
const auto first_digit = static_cast<char>(s_hi >> 56u);
|
||||
#endif
|
||||
const int len = d.has_digit ? 16 + (sixteen ? 1 : 0) : digits; // significant digits
|
||||
const int n = 16 + (sixteen ? 1 : 0) + d.exponent; // digits before the point
|
||||
|
||||
if (JSON_HEDLEY_LIKELY(n >= 1 && n <= 15))
|
||||
{
|
||||
// "dig.its" and "digits[000].0": the digits after the point move by
|
||||
// one byte ('0's follow the digits)
|
||||
#if JSON_DTOA_SSE2
|
||||
// NOLINTBEGIN(portability-simd-intrinsics)
|
||||
// (in the register: reading the digits back from memory right after
|
||||
// storing them waits until the stores are done)
|
||||
const __m128i at = _mm_set1_epi8(static_cast<char>(n));
|
||||
const __m128i index = _mm_setr_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
|
||||
const __m128i before = _mm_cmpgt_epi8(at, index);
|
||||
const __m128i after = _mm_cmpgt_epi8(index, at);
|
||||
const __m128i text = _mm_or_si128(_mm_or_si128(_mm_and_si128(s, before), _mm_and_si128(_mm_slli_si128(s, 1), after)),
|
||||
_mm_andnot_si128(_mm_or_si128(before, after), _mm_set1_epi8('.')));
|
||||
std::memcpy(first, &text, 16);
|
||||
first[16] = static_cast<char>(_mm_extract_epi16(s, 7) >> 8);
|
||||
first[17] = s16;
|
||||
// NOLINTEND(portability-simd-intrinsics)
|
||||
#elif JSON_DTOA_NEON
|
||||
const uint8x16_t index = vcombine_u8(vcreate_u8(0x0706050403020100u), vcreate_u8(0x0F0E0D0C0B0A0908u));
|
||||
const uint8x16_t at = vdupq_n_u8(static_cast<std::uint8_t>(n));
|
||||
const uint8x16_t after_point = vbslq_u8(vcgtq_u8(index, at), vextq_u8(vdupq_n_u8(0), s, 15), vdupq_n_u8('.'));
|
||||
vst1q_u8(reinterpret_cast<std::uint8_t*>(first), vbslq_u8(vcltq_u8(index, at), s, after_point)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
|
||||
first[16] = static_cast<char>(vgetq_lane_u8(s, 15));
|
||||
first[17] = s16;
|
||||
#else
|
||||
store_16(first);
|
||||
first[16] = s16;
|
||||
std::uint64_t after_point[2]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
|
||||
std::memcpy(after_point, first + n, 16);
|
||||
std::memcpy(first + n + 1, after_point, 16);
|
||||
first[n] = '.';
|
||||
#endif
|
||||
return first + (n >= len ? n + 2 : len + 1);
|
||||
}
|
||||
if (n <= 0 && n > -4)
|
||||
{
|
||||
// "0.[000]digits"
|
||||
std::memset(first, '0', 8);
|
||||
first[1] = '.';
|
||||
store_16(first + 2 - n);
|
||||
first[18 - n] = s16;
|
||||
return first + 2 - n + len;
|
||||
}
|
||||
// d.igitse+XX, with at least two exponent digits (as append_exponent())
|
||||
store_16(first + 1);
|
||||
first[17] = s16;
|
||||
first[0] = first_digit;
|
||||
first[1] = '.';
|
||||
char* const end = first + (len == 1 ? 1 : len + 1);
|
||||
const int e = n - 1;
|
||||
const auto ea = static_cast<unsigned>(e < 0 ? -e : e);
|
||||
const bool three = ea >= 100;
|
||||
end[0] = 'e';
|
||||
end[1] = e < 0 ? '-' : '+';
|
||||
end[2] = static_cast<char>('0' + (three ? ea / 100 : (ea / 10) % 10));
|
||||
end[3] = static_cast<char>('0' + (three ? (ea / 10) % 10 : ea % 10));
|
||||
end[4] = static_cast<char>('0' + (ea % 10));
|
||||
return end + (three ? 5 : 4);
|
||||
}
|
||||
|
||||
/// the powers of ten up to 10^16
|
||||
inline const std::array<std::uint64_t, 17>& powers_of_ten_16() noexcept
|
||||
{
|
||||
static const std::array<std::uint64_t, 17> powers =
|
||||
{
|
||||
{
|
||||
1u, 10u, 100u, 1000u, 10000u, 100000u, 1000000u, 10000000u, 100000000u, 1000000000u, 10000000000u,
|
||||
100000000000u, 1000000000000u, 10000000000000u, 100000000000000u, 1000000000000000u, 10000000000000000u
|
||||
}
|
||||
};
|
||||
return powers;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief digits * 10^exp, as write_decimal() writes it, for the digits of a
|
||||
double that need no conversion (count digits, at most 15, the first not 0;
|
||||
trailing zeros allowed): extended to 16 digits and written by write_shortest()
|
||||
|
||||
@return a pointer past the text; up to 41 bytes at @a first are written
|
||||
(some beyond the returned end)
|
||||
*/
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_short_decimal(char* first, std::uint64_t digits, int count, int exp) noexcept
|
||||
{
|
||||
JSON_ASSERT(digits >= powers_of_ten_16()[static_cast<std::size_t>(count - 1)] && count <= 15);
|
||||
const int scale = 16 - count;
|
||||
return write_shortest(first, zmij::shortest_decimal{digits * powers_of_ten_16()[static_cast<std::size_t>(scale)], exp - scale - 1, 0, false});
|
||||
}
|
||||
|
||||
/// as write_short_decimal(), counting the digits (not 0, less than 10^15)
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_short_decimal(char* first, std::uint64_t digits, int exp) noexcept
|
||||
{
|
||||
JSON_ASSERT(digits != 0 && digits < 1000000000000000u);
|
||||
// floor(log10(2^bits)) + 1 digits, or one less
|
||||
const int log2_bound = ((64 - count_leading_zeros(digits)) * 1233) >> 12;
|
||||
const int count = log2_bound + (digits >= powers_of_ten_16()[static_cast<std::size_t>(log2_bound)] ? 1 : 0);
|
||||
return write_short_decimal(first, digits, count, exp);
|
||||
}
|
||||
|
||||
/// a positive finite float (other than double): Grisu2 and format_buffer()
|
||||
template<typename FloatType>
|
||||
JSON_HEDLEY_NON_NULL(1, 2)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
char* write_positive(char* first, const char* last, FloatType value)
|
||||
{
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Compute v = buffer * 10^decimal_exponent.
|
||||
// The decimal digits are stored in the buffer, which needs to be interpreted
|
||||
// as an unsigned decimal integer.
|
||||
// len is the length of the buffer, i.e., the number of decimal digits.
|
||||
int len = 0;
|
||||
int decimal_exponent = 0;
|
||||
shortest_digits(first, len, decimal_exponent, value);
|
||||
|
||||
JSON_ASSERT(len <= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Format the buffer like printf("%.*g", prec, value)
|
||||
constexpr int kMinExp = -4;
|
||||
// Use digits10 here to increase compatibility with version 2.
|
||||
constexpr int kMaxExp = std::numeric_limits<FloatType>::digits10;
|
||||
|
||||
JSON_ASSERT(last - first >= kMaxExp + 2);
|
||||
JSON_ASSERT(last - first >= 2 + (-kMinExp - 1) + std::numeric_limits<FloatType>::max_digits10);
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10 + 6);
|
||||
|
||||
return format_buffer(first, len, decimal_exponent, kMinExp, kMaxExp);
|
||||
}
|
||||
|
||||
/// a positive finite double: the shortest digits (Zmij), laid out by
|
||||
/// write_shortest() (through a local buffer if [first, last) is shorter than
|
||||
/// the 41 bytes it may write)
|
||||
JSON_HEDLEY_NON_NULL(1, 2)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_positive(char* first, const char* last, double value)
|
||||
{
|
||||
static_assert(std::numeric_limits<double>::is_iec559 && std::numeric_limits<double>::digits == 53,
|
||||
"internal error: the conversion of Zmij needs IEEE 754 binary64 doubles");
|
||||
std::uint64_t bits = 0;
|
||||
std::memcpy(&bits, &value, sizeof(bits));
|
||||
const zmij::shortest_decimal d = zmij::to_shortest(bits);
|
||||
if (JSON_HEDLEY_LIKELY(last - first >= 41))
|
||||
{
|
||||
return write_shortest(first, d);
|
||||
}
|
||||
std::array<char, 64> buf; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
|
||||
const auto len = static_cast<std::size_t>(write_shortest(buf.data(), d) - buf.data());
|
||||
JSON_ASSERT(static_cast<std::size_t>(last - first) >= len);
|
||||
std::memcpy(first, buf.data(), len);
|
||||
return first + len;
|
||||
}
|
||||
|
||||
} // namespace dtoa_impl
|
||||
|
||||
/*!
|
||||
@@ -1064,7 +1535,6 @@ JSON_HEDLEY_NON_NULL(1, 2)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
char* to_chars(char* first, const char* last, FloatType value)
|
||||
{
|
||||
static_cast<void>(last); // maybe unused - fix warning
|
||||
JSON_ASSERT(std::isfinite(value));
|
||||
|
||||
// Use signbit(value) instead of (value < 0) since signbit works for -0.
|
||||
@@ -1090,28 +1560,7 @@ char* to_chars(char* first, const char* last, FloatType value)
|
||||
JSON_HEDLEY_DIAGNOSTIC_POP
|
||||
#endif
|
||||
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Compute v = buffer * 10^decimal_exponent.
|
||||
// The decimal digits are stored in the buffer, which needs to be interpreted
|
||||
// as an unsigned decimal integer.
|
||||
// len is the length of the buffer, i.e., the number of decimal digits.
|
||||
int len = 0;
|
||||
int decimal_exponent = 0;
|
||||
dtoa_impl::grisu2(first, len, decimal_exponent, value);
|
||||
|
||||
JSON_ASSERT(len <= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Format the buffer like printf("%.*g", prec, value)
|
||||
constexpr int kMinExp = -4;
|
||||
// Use digits10 here to increase compatibility with version 2.
|
||||
constexpr int kMaxExp = std::numeric_limits<FloatType>::digits10;
|
||||
|
||||
JSON_ASSERT(last - first >= kMaxExp + 2);
|
||||
JSON_ASSERT(last - first >= 2 + (-kMinExp - 1) + std::numeric_limits<FloatType>::max_digits10);
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10 + 6);
|
||||
|
||||
return dtoa_impl::format_buffer(first, len, decimal_exponent, kMinExp, kMaxExp);
|
||||
return dtoa_impl::write_positive(first, last, value);
|
||||
}
|
||||
|
||||
} // namespace detail
|
||||
|
||||
@@ -0,0 +1,238 @@
|
||||
// __ _____ _____ _____
|
||||
// __| | __| | | | JSON for Modern C++
|
||||
// | | |__ | | | | | | version 3.12.0
|
||||
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
|
||||
//
|
||||
// SPDX-FileCopyrightText: 2025 Victor Zverovich <https://github.com/vitaut/zmij>
|
||||
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
|
||||
// SPDX-License-Identifier: MIT
|
||||
|
||||
#pragma once
|
||||
|
||||
#include <array> // array
|
||||
#include <cstddef> // size_t
|
||||
#include <cstdint> // uint32_t, uint64_t
|
||||
|
||||
#include <nlohmann/detail/abi_macros.hpp>
|
||||
#include <nlohmann/detail/bit_ops.hpp>
|
||||
#include <nlohmann/detail/input/pow5_table.hpp>
|
||||
#include <nlohmann/detail/macro_scope.hpp>
|
||||
|
||||
NLOHMANN_JSON_NAMESPACE_BEGIN
|
||||
namespace detail
|
||||
{
|
||||
|
||||
/*!
|
||||
@brief the shortest decimal representation of a double
|
||||
|
||||
A C++11 port of the conversion of Zmij by Victor Zverovich
|
||||
(https://github.com/vitaut/zmij, MIT license): the shortest decimal in the
|
||||
rounding interval of a double, the closest one if there are several. Zmij
|
||||
credits Xiang JunBo (producing the shorter candidate without a division) and
|
||||
Dougall Johnson (the compressed powers of ten). The powers of ten are taken
|
||||
from the table for number parsing (pow5_table.hpp) where it holds them, and
|
||||
computed from the compressed tables of Zmij beyond it.
|
||||
*/
|
||||
namespace zmij
|
||||
{
|
||||
|
||||
/// significand * 10^exponent
|
||||
struct decimal
|
||||
{
|
||||
std::uint64_t significand;
|
||||
int exponent;
|
||||
};
|
||||
|
||||
/// the compressed powers of ten of Zmij
|
||||
inline const std::array<std::uint64_t, 28>& pow10_minor() noexcept
|
||||
{
|
||||
static const std::array<std::uint64_t, 28> table =
|
||||
{
|
||||
{
|
||||
0x8000000000000000u, 0xa000000000000000u, 0xc800000000000000u, 0xfa00000000000000u, 0x9c40000000000000u,
|
||||
0xc350000000000000u, 0xf424000000000000u, 0x9896800000000000u, 0xbebc200000000000u, 0xee6b280000000000u,
|
||||
0x9502f90000000000u, 0xba43b74000000000u, 0xe8d4a51000000000u, 0x9184e72a00000000u, 0xb5e620f480000000u,
|
||||
0xe35fa931a0000000u, 0x8e1bc9bf04000000u, 0xb1a2bc2ec5000000u, 0xde0b6b3a76400000u, 0x8ac7230489e80000u,
|
||||
0xad78ebc5ac620000u, 0xd8d726b7177a8000u, 0x878678326eac9000u, 0xa968163f0a57b400u, 0xd3c21bcecceda100u,
|
||||
0x84595161401484a0u, 0xa56fa5b99019a5c8u, 0xcecb8f27f4200f3au
|
||||
}
|
||||
};
|
||||
return table;
|
||||
}
|
||||
|
||||
/// (high, low) pairs
|
||||
inline const std::array<std::uint64_t, 50>& pow10_major() noexcept
|
||||
{
|
||||
static const std::array<std::uint64_t, 50> table =
|
||||
{
|
||||
{
|
||||
0xaddcb9e83c6b1793u, 0xdf4abe242a1bbf3eu, 0xaf8e5410288e1b6fu, 0x07ecf0ae5ee44ddau, 0xb1442798f49ffb4au, 0x99cd11cfdf41779du,
|
||||
0xb2fe3f0b8599ef07u, 0x861fa7e6dcb4aa15u, 0xb4bca50b065abe63u, 0x0fed077a756b53aau, 0xb67f6455292cbf08u, 0x1a3bc84c17b1d543u,
|
||||
0xb84687c269ef3bfbu, 0x3d5d514f40eea742u, 0xba121a4650e4ddebu, 0x92f34d62616ce413u, 0xbbe226efb628afeau, 0x890489f70a55368cu,
|
||||
0xbdb6b8e905cb600fu, 0x5400e987bbc1c921u, 0xbf8fdb78849a5f96u, 0xde98520472bdd034u, 0xc16d9a0095928a27u, 0x75b7053c0f178294u,
|
||||
0xc350000000000000u, 0x0000000000000000u, 0xc5371912364ce305u, 0x6c28000000000000u, 0xc722f0ef9d80aad6u, 0x424d3ad2b7b97ef6u,
|
||||
0xc913936dd571c84cu, 0x03bc3a19cd1e38eau, 0xcb090c8001ab551cu, 0x5cadf5bfd3072cc6u, 0xcd036837130890a1u, 0x36dba887c37a8c10u,
|
||||
0xcf02b2c21207ef2eu, 0x94f967e45e03f4bcu, 0xd106f86e69d785c7u, 0xe13336d701beba52u, 0xd31045a8341ca07cu, 0x1ede48111209a051u,
|
||||
0xd51ea6fa85785631u, 0x552a74227f3ea566u, 0xd732290fbacaf133u, 0xa97c177947ad4096u, 0xd94ad8b1c7380874u, 0x18375281ae7822bdu,
|
||||
0xdb68c2ca82ed2a05u, 0xa67398db9f6820e1u
|
||||
}
|
||||
};
|
||||
return table;
|
||||
}
|
||||
|
||||
/// one bit per power: whether the computed value is one unit too large
|
||||
inline const std::array<std::uint32_t, 21>& pow10_fixups() noexcept
|
||||
{
|
||||
static const std::array<std::uint32_t, 21> table =
|
||||
{
|
||||
{
|
||||
0x8d8fc810u, 0x06100293u, 0x19000000u, 0x00100000u, 0x00000908u, 0x00000000u, 0x04e00300u, 0x3807e0b2u, 0x3d83d793u, 0x0006f5ccu,
|
||||
0x00000000u, 0xffff0000u, 0x8076337du, 0x4ff45ba0u, 0x09405033u, 0x034376d9u, 0x09000000u, 0x4e100501u, 0x076d14dcu, 0xf964f45eu,
|
||||
0x0000003du
|
||||
}
|
||||
};
|
||||
return table;
|
||||
}
|
||||
|
||||
/// the 128-bit significand of 10^k, rounded down, for k in [-307, 341]
|
||||
/// (compute_pow10 of Zmij)
|
||||
inline uint128_parts compute_pow10(int k) noexcept
|
||||
{
|
||||
const auto i = static_cast<unsigned>(k + 307);
|
||||
const std::uint64_t m = pow10_minor()[(i + 24) % 28];
|
||||
const std::size_t j = 2 * static_cast<std::size_t>((i + 24) / 28);
|
||||
const std::uint64_t h_hi = pow10_major()[j];
|
||||
const std::uint64_t h_lo = pow10_major()[j + 1];
|
||||
const std::uint64_t h1 = full_multiplication(h_lo, m).high;
|
||||
const std::uint64_t c0 = h_lo * m;
|
||||
const std::uint64_t c1 = h1 + (h_hi * m);
|
||||
const std::uint64_t c2 = (c1 < h1 ? 1u : 0u) + full_multiplication(h_hi, m).high;
|
||||
uint128_parts r{};
|
||||
if ((c2 >> 63u) != 0)
|
||||
{
|
||||
r.high = c2;
|
||||
r.low = c1;
|
||||
}
|
||||
else
|
||||
{
|
||||
r.high = (c2 << 1u) | (c1 >> 63u);
|
||||
r.low = (c1 << 1u) | (c0 >> 63u);
|
||||
}
|
||||
r.low -= (pow10_fixups()[i >> 5u] >> (i & 31u)) & 1u;
|
||||
return r;
|
||||
}
|
||||
|
||||
/// The 128-bit significand of 10^k, rounded down, for k in [-342, 341].
|
||||
/// Up to 10^308, the table for number parsing holds the same significands
|
||||
/// (those of 5^k), except for k in [-27, -1], where it holds them one unit
|
||||
/// larger (as the Eisel-Lemire algorithm needs them).
|
||||
inline uint128_parts pow10(int k) noexcept
|
||||
{
|
||||
if (k > pow5_128_largest_power)
|
||||
{
|
||||
return compute_pow10(k); // (only for the smallest doubles)
|
||||
}
|
||||
const auto i = 2 * static_cast<std::size_t>(k - pow5_128_smallest_power);
|
||||
uint128_parts r{pow5_128()[i + 1], pow5_128()[i]};
|
||||
const std::uint64_t adjust = static_cast<unsigned>(k + 27) < 27u ? 1u : 0u;
|
||||
r.high -= r.low < adjust ? 1u : 0u;
|
||||
r.low -= adjust;
|
||||
return r;
|
||||
}
|
||||
|
||||
/// (x_hi * 2^64 + x_lo) * y >> 64, as 128 bits
|
||||
inline uint128_parts umul192_hi128(std::uint64_t x_hi, std::uint64_t x_lo, std::uint64_t y) noexcept
|
||||
{
|
||||
const uint128_parts p = full_multiplication(x_hi, y);
|
||||
uint128_parts r{};
|
||||
r.low = p.low + full_multiplication(x_lo, y).high;
|
||||
r.high = p.high + (r.low < p.low ? 1u : 0u);
|
||||
return r;
|
||||
}
|
||||
|
||||
/// (x * y + c) >> 64
|
||||
inline std::uint64_t umul128_add_hi64(std::uint64_t x, std::uint64_t y, std::uint64_t c) noexcept
|
||||
{
|
||||
const uint128_parts p = full_multiplication(x, y);
|
||||
return p.high + (p.low + c < p.low ? 1u : 0u);
|
||||
}
|
||||
|
||||
/// the result of Zmij: the shorter candidate and, if that is outside the
|
||||
/// rounding interval, the digit after it (16 bytes: returned in registers)
|
||||
struct shortest_decimal
|
||||
{
|
||||
std::uint64_t integral; ///< the shorter candidate (15 or 16 digits for normal doubles)
|
||||
int exponent; ///< the decimal exponent of the digit after it
|
||||
unsigned char digit; ///< the digit after it (if has_digit)
|
||||
bool has_digit; ///< whether the shortest decimal is integral * 10 + digit
|
||||
};
|
||||
|
||||
/// The shortest decimal in the rounding interval of a positive finite double
|
||||
/// given by its bits, the closest one if there are several (to_decimal of
|
||||
/// Zmij, which keeps the last digit apart: the 15 or 16 digits before it can be
|
||||
/// converted without a multiplication by 10 first). Always inlined: GCC
|
||||
/// otherwise calls it, and its result goes through memory.
|
||||
JSON_HEDLEY_ALWAYS_INLINE shortest_decimal to_shortest(std::uint64_t bits) noexcept
|
||||
{
|
||||
constexpr int extra_shift = 9;
|
||||
const auto raw_exp = static_cast<int>((bits >> 52u) & 0x7FFu);
|
||||
std::uint64_t bin_sig = bits & ((std::uint64_t{1} << 52u) - 1);
|
||||
// a power of two has a narrower interval below (except the smallest normal)
|
||||
const bool regular = bin_sig != 0 || raw_exp <= 1;
|
||||
const int bin_exp = (raw_exp == 0 ? 1 : raw_exp) - 1075;
|
||||
if (raw_exp != 0)
|
||||
{
|
||||
bin_sig |= std::uint64_t{1} << 52u;
|
||||
}
|
||||
// floor(log10(2^bin_exp)), or floor(log10(3/4 * 2^bin_exp)) for the irregular case
|
||||
const int dec_exp = ((bin_exp * 315653) - (regular ? 0 : 131072)) >> 20;
|
||||
// scaled by 10^(-dec_exp - 1): the integral part is the shorter candidate
|
||||
const int shift = bin_exp + ((-(dec_exp + 1) * 217707) >> 16) + 1 + extra_shift;
|
||||
const uint128_parts p10 = pow10(-dec_exp - 1);
|
||||
const uint128_parts p = umul192_hi128(p10.high, p10.low, bin_sig << static_cast<unsigned>(shift));
|
||||
std::uint64_t integral = p.high >> static_cast<unsigned>(extra_shift);
|
||||
const std::uint64_t fractional = (p.high << static_cast<unsigned>(64 - extra_shift)) | (p.low >> static_cast<unsigned>(extra_shift));
|
||||
std::uint64_t digit = 0;
|
||||
bool round_up = false;
|
||||
bool round_down = false;
|
||||
if (JSON_HEDLEY_LIKELY(regular))
|
||||
{
|
||||
const std::uint64_t half_ulp = (p10.high >> static_cast<unsigned>(extra_shift + 1 - shift)) + (1 - (bin_sig & 1u));
|
||||
round_up = fractional + half_ulp < fractional;
|
||||
round_down = half_ulp > fractional;
|
||||
// the last digit of the longer candidate, rounded to nearest
|
||||
digit = umul128_add_hi64(fractional, 10, (std::uint64_t{1} << 63u) + 6);
|
||||
if (fractional == (std::uint64_t{1} << 62u))
|
||||
{
|
||||
digit = 2; // 2.5 rounds to 2
|
||||
}
|
||||
}
|
||||
else
|
||||
{
|
||||
const std::uint64_t half_ulp = p10.high >> static_cast<unsigned>(extra_shift + 1 - shift);
|
||||
round_up = half_ulp > ~std::uint64_t{0} - fractional;
|
||||
round_down = (half_ulp >> 1u) > fractional;
|
||||
digit = umul128_add_hi64(fractional, 10, (std::uint64_t{1} << 63u) - 1);
|
||||
const std::uint64_t lowest = umul128_add_hi64(fractional - (half_ulp >> 1u), 10, ~std::uint64_t{0});
|
||||
digit = digit < lowest ? lowest : digit;
|
||||
}
|
||||
integral += round_up ? 1u : 0u;
|
||||
// if the shorter candidate is outside the rounding interval: one digit more
|
||||
return shortest_decimal{integral, dec_exp, static_cast<unsigned char>(digit), !round_up && !round_down};
|
||||
}
|
||||
|
||||
/// The shortest decimal in the rounding interval of a positive finite double
|
||||
/// given by its bits, as one number. The significand can end in zeros.
|
||||
inline decimal to_decimal(std::uint64_t bits) noexcept
|
||||
{
|
||||
const shortest_decimal d = to_shortest(bits);
|
||||
if (d.has_digit)
|
||||
{
|
||||
return decimal{(d.integral * 10) + d.digit, d.exponent};
|
||||
}
|
||||
return decimal{d.integral, d.exponent + 1};
|
||||
}
|
||||
|
||||
} // namespace zmij
|
||||
} // namespace detail
|
||||
NLOHMANN_JSON_NAMESPACE_END
|
||||
@@ -249,8 +249,9 @@ template<typename FloatType>
|
||||
using native_float_t = typename std::conditional<std::numeric_limits<FloatType>::digits == 24, float, double>::type;
|
||||
|
||||
/// the value of the eight ASCII digits in @a v (see read_eight_bytes()), three
|
||||
/// multiplications instead of eight (after simdjson and fast_float)
|
||||
inline std::uint32_t parse_eight_digits(std::uint64_t v) noexcept
|
||||
/// multiplications instead of eight (after simdjson and fast_float); always
|
||||
/// inlined, as GCC otherwise calls it in the number loops
|
||||
JSON_HEDLEY_ALWAYS_INLINE std::uint32_t parse_eight_digits(std::uint64_t v) noexcept
|
||||
{
|
||||
v = ((v & 0x0F0F0F0F0F0F0F0Fu) * 2561u) >> 8u;
|
||||
v = ((v & 0x00FF00FF00FF00FFu) * 6553601u) >> 16u;
|
||||
|
||||
@@ -21,6 +21,8 @@
|
||||
#undef JSON_NO_UNIQUE_ADDRESS
|
||||
#undef JSON_DISABLE_ENUM_SERIALIZATION
|
||||
#undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
|
||||
#undef JSON_DTOA_SSE2
|
||||
#undef JSON_DTOA_NEON
|
||||
|
||||
#ifndef JSON_TEST_KEEP_MACROS
|
||||
#undef JSON_CATCH
|
||||
|
||||
@@ -1366,8 +1366,9 @@ class serializer
|
||||
/*!
|
||||
@brief dump an integer
|
||||
|
||||
Dump a given integer, appending it to @ref write_buffer. Works internally with
|
||||
@a number_buffer.
|
||||
Dump a given integer, appending it to @ref write_buffer (directly: copying
|
||||
the digits from another buffer right after writing them waits until the
|
||||
stores are done).
|
||||
|
||||
@param[in] x integer number (signed or unsigned) to dump
|
||||
@tparam NumberType either @a number_integer_t or @a number_unsigned_t
|
||||
@@ -1402,33 +1403,57 @@ class serializer
|
||||
return;
|
||||
}
|
||||
|
||||
// use a pointer to fill the buffer
|
||||
auto buffer_ptr = number_buffer.begin(); // NOLINT(llvm-qualified-auto,readability-qualified-auto)
|
||||
// use a pointer to fill the buffer (room for as much as number_buffer holds)
|
||||
if (JSON_HEDLEY_UNLIKELY(write_buffer_pos + number_buffer.size() > write_buffer.size()))
|
||||
{
|
||||
flush();
|
||||
}
|
||||
auto* buffer_ptr = write_buffer.data() + write_buffer_pos;
|
||||
|
||||
number_unsigned_t abs_value;
|
||||
|
||||
unsigned int n_chars{};
|
||||
// one byte for the minus sign
|
||||
unsigned int n_chars = 0;
|
||||
|
||||
if (is_negative_number(x))
|
||||
{
|
||||
*buffer_ptr = '-';
|
||||
abs_value = remove_sign(static_cast<number_integer_t>(x));
|
||||
|
||||
// account one more byte for the minus sign
|
||||
n_chars = 1 + count_digits(abs_value);
|
||||
n_chars = 1;
|
||||
}
|
||||
else
|
||||
{
|
||||
abs_value = static_cast<number_unsigned_t>(x);
|
||||
n_chars = count_digits(abs_value);
|
||||
}
|
||||
|
||||
// up to 16 digits: eight at a time (as the digits of floats), written
|
||||
// without leading zeros
|
||||
if (abs_value < 10000000000000000u)
|
||||
{
|
||||
const std::uint64_t value = abs_value;
|
||||
const std::uint64_t upper = value / 100000000u;
|
||||
const std::uint64_t first = dtoa_impl::eight_digit_bytes(upper != 0 ? upper : value);
|
||||
const auto leading = static_cast<unsigned>(count_leading_zeros(first) / 8); // (first is not 0)
|
||||
char* const p = buffer_ptr + n_chars;
|
||||
dtoa_impl::store_msb_first(p, (first << (8 * leading)) + 0x3030303030303030u);
|
||||
n_chars += 8 - leading;
|
||||
if (upper != 0)
|
||||
{
|
||||
dtoa_impl::store_msb_first(p + 8 - leading, dtoa_impl::eight_digit_bytes(value - (upper * 100000000u)) + 0x3030303030303030u);
|
||||
n_chars += 8;
|
||||
}
|
||||
write_buffer_pos += n_chars;
|
||||
return;
|
||||
}
|
||||
|
||||
n_chars += count_digits(abs_value);
|
||||
|
||||
// spare 1 byte for '\0'
|
||||
JSON_ASSERT(n_chars < number_buffer.size() - 1);
|
||||
|
||||
// jump to the end to generate the string from backward,
|
||||
// so we later avoid reversing the result
|
||||
buffer_ptr += static_cast<typename decltype(number_buffer)::difference_type>(n_chars);
|
||||
buffer_ptr += n_chars;
|
||||
|
||||
// Fast int2ascii implementation inspired by "Fastware" talk by Andrei Alexandrescu
|
||||
// See: https://www.youtube.com/watch?v=o4-CwDo2zpg
|
||||
@@ -1451,14 +1476,13 @@ class serializer
|
||||
*(--buffer_ptr) = static_cast<char>('0' + abs_value);
|
||||
}
|
||||
|
||||
put_buffer(number_buffer, n_chars);
|
||||
write_buffer_pos += n_chars;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief dump a floating-point number
|
||||
|
||||
Dump a given floating-point number, appending it to @ref write_buffer. Works internally
|
||||
with @a number_buffer.
|
||||
Dump a given floating-point number, appending it to @ref write_buffer.
|
||||
|
||||
@param[in] x floating-point number to dump
|
||||
*/
|
||||
@@ -1485,10 +1509,15 @@ class serializer
|
||||
|
||||
void dump_float(number_float_t x, std::true_type /*is_ieee_single_or_double*/)
|
||||
{
|
||||
auto* begin = number_buffer.data();
|
||||
// directly into the write buffer: copying the text from number_buffer
|
||||
// right after to_chars() wrote it waits until its stores are done
|
||||
if (JSON_HEDLEY_UNLIKELY(write_buffer_pos + number_buffer.size() > write_buffer.size()))
|
||||
{
|
||||
flush();
|
||||
}
|
||||
auto* begin = write_buffer.data() + write_buffer_pos;
|
||||
auto* end = ::nlohmann::detail::to_chars(begin, begin + number_buffer.size(), x);
|
||||
|
||||
put_buffer(number_buffer, static_cast<std::size_t>(end - begin));
|
||||
write_buffer_pos += static_cast<std::size_t>(end - begin);
|
||||
}
|
||||
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
|
||||
@@ -8868,8 +8868,9 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
|
||||
}
|
||||
|
||||
/// eight bytes as a little-endian word (compilers fold this into one load on
|
||||
/// little-endian targets)
|
||||
inline std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
|
||||
/// little-endian targets; always inlined, as GCC otherwise calls it in the
|
||||
/// number loops)
|
||||
JSON_HEDLEY_ALWAYS_INLINE std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
|
||||
{
|
||||
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)
|
||||
@@ -8878,7 +8879,7 @@ inline std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
|
||||
}
|
||||
|
||||
/// eight bytes as a little-endian word
|
||||
inline std::uint64_t read_eight_bytes(const char* p) noexcept
|
||||
JSON_HEDLEY_ALWAYS_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)
|
||||
}
|
||||
@@ -9487,8 +9488,9 @@ template<typename FloatType>
|
||||
using native_float_t = typename std::conditional<std::numeric_limits<FloatType>::digits == 24, float, double>::type;
|
||||
|
||||
/// the value of the eight ASCII digits in @a v (see read_eight_bytes()), three
|
||||
/// multiplications instead of eight (after simdjson and fast_float)
|
||||
inline std::uint32_t parse_eight_digits(std::uint64_t v) noexcept
|
||||
/// multiplications instead of eight (after simdjson and fast_float); always
|
||||
/// inlined, as GCC otherwise calls it in the number loops
|
||||
JSON_HEDLEY_ALWAYS_INLINE std::uint32_t parse_eight_digits(std::uint64_t v) noexcept
|
||||
{
|
||||
v = ((v & 0x0F0F0F0F0F0F0F0Fu) * 2561u) >> 8u;
|
||||
v = ((v & 0x00FF00FF00FF00FFu) * 6553601u) >> 16u;
|
||||
@@ -24589,11 +24591,275 @@ NLOHMANN_JSON_NAMESPACE_END
|
||||
|
||||
#include <array> // array
|
||||
#include <cmath> // signbit, isfinite
|
||||
#include <cstddef> // size_t
|
||||
#include <cstdint> // intN_t, uintN_t
|
||||
#include <cstring> // memcpy, memmove
|
||||
#include <limits> // numeric_limits
|
||||
#include <type_traits> // conditional
|
||||
|
||||
#ifdef _MSC_VER
|
||||
#include <cstdlib> // _byteswap_uint64
|
||||
#endif
|
||||
|
||||
// SSE2 (every x86-64 CPU) and NEON (every 64-bit Arm CPU) convert the 16
|
||||
// digits of a double at once
|
||||
#if defined(__x86_64__) || (defined(_M_X64) && !defined(_M_ARM64EC))
|
||||
#include <emmintrin.h>
|
||||
#define JSON_DTOA_SSE2 1
|
||||
#define JSON_DTOA_NEON 0
|
||||
#elif (defined(__aarch64__) || defined(_M_ARM64)) && !defined(_M_ARM64EC) && !defined(__ARM_BIG_ENDIAN)
|
||||
#include <arm_neon.h>
|
||||
#define JSON_DTOA_SSE2 0
|
||||
#define JSON_DTOA_NEON 1
|
||||
#else
|
||||
#define JSON_DTOA_SSE2 0
|
||||
#define JSON_DTOA_NEON 0
|
||||
#endif
|
||||
|
||||
// #include <nlohmann/detail/conversions/zmij.hpp>
|
||||
// __ _____ _____ _____
|
||||
// __| | __| | | | JSON for Modern C++
|
||||
// | | |__ | | | | | | version 3.12.0
|
||||
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
|
||||
//
|
||||
// SPDX-FileCopyrightText: 2025 Victor Zverovich <https://github.com/vitaut/zmij>
|
||||
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
|
||||
// SPDX-License-Identifier: MIT
|
||||
|
||||
|
||||
|
||||
#include <array> // array
|
||||
#include <cstddef> // size_t
|
||||
#include <cstdint> // uint32_t, uint64_t
|
||||
|
||||
// #include <nlohmann/detail/abi_macros.hpp>
|
||||
|
||||
// #include <nlohmann/detail/bit_ops.hpp>
|
||||
|
||||
// #include <nlohmann/detail/input/pow5_table.hpp>
|
||||
|
||||
// #include <nlohmann/detail/macro_scope.hpp>
|
||||
|
||||
|
||||
NLOHMANN_JSON_NAMESPACE_BEGIN
|
||||
namespace detail
|
||||
{
|
||||
|
||||
/*!
|
||||
@brief the shortest decimal representation of a double
|
||||
|
||||
A C++11 port of the conversion of Zmij by Victor Zverovich
|
||||
(https://github.com/vitaut/zmij, MIT license): the shortest decimal in the
|
||||
rounding interval of a double, the closest one if there are several. Zmij
|
||||
credits Xiang JunBo (producing the shorter candidate without a division) and
|
||||
Dougall Johnson (the compressed powers of ten). The powers of ten are taken
|
||||
from the table for number parsing (pow5_table.hpp) where it holds them, and
|
||||
computed from the compressed tables of Zmij beyond it.
|
||||
*/
|
||||
namespace zmij
|
||||
{
|
||||
|
||||
/// significand * 10^exponent
|
||||
struct decimal
|
||||
{
|
||||
std::uint64_t significand;
|
||||
int exponent;
|
||||
};
|
||||
|
||||
/// the compressed powers of ten of Zmij
|
||||
inline const std::array<std::uint64_t, 28>& pow10_minor() noexcept
|
||||
{
|
||||
static const std::array<std::uint64_t, 28> table =
|
||||
{
|
||||
{
|
||||
0x8000000000000000u, 0xa000000000000000u, 0xc800000000000000u, 0xfa00000000000000u, 0x9c40000000000000u,
|
||||
0xc350000000000000u, 0xf424000000000000u, 0x9896800000000000u, 0xbebc200000000000u, 0xee6b280000000000u,
|
||||
0x9502f90000000000u, 0xba43b74000000000u, 0xe8d4a51000000000u, 0x9184e72a00000000u, 0xb5e620f480000000u,
|
||||
0xe35fa931a0000000u, 0x8e1bc9bf04000000u, 0xb1a2bc2ec5000000u, 0xde0b6b3a76400000u, 0x8ac7230489e80000u,
|
||||
0xad78ebc5ac620000u, 0xd8d726b7177a8000u, 0x878678326eac9000u, 0xa968163f0a57b400u, 0xd3c21bcecceda100u,
|
||||
0x84595161401484a0u, 0xa56fa5b99019a5c8u, 0xcecb8f27f4200f3au
|
||||
}
|
||||
};
|
||||
return table;
|
||||
}
|
||||
|
||||
/// (high, low) pairs
|
||||
inline const std::array<std::uint64_t, 50>& pow10_major() noexcept
|
||||
{
|
||||
static const std::array<std::uint64_t, 50> table =
|
||||
{
|
||||
{
|
||||
0xaddcb9e83c6b1793u, 0xdf4abe242a1bbf3eu, 0xaf8e5410288e1b6fu, 0x07ecf0ae5ee44ddau, 0xb1442798f49ffb4au, 0x99cd11cfdf41779du,
|
||||
0xb2fe3f0b8599ef07u, 0x861fa7e6dcb4aa15u, 0xb4bca50b065abe63u, 0x0fed077a756b53aau, 0xb67f6455292cbf08u, 0x1a3bc84c17b1d543u,
|
||||
0xb84687c269ef3bfbu, 0x3d5d514f40eea742u, 0xba121a4650e4ddebu, 0x92f34d62616ce413u, 0xbbe226efb628afeau, 0x890489f70a55368cu,
|
||||
0xbdb6b8e905cb600fu, 0x5400e987bbc1c921u, 0xbf8fdb78849a5f96u, 0xde98520472bdd034u, 0xc16d9a0095928a27u, 0x75b7053c0f178294u,
|
||||
0xc350000000000000u, 0x0000000000000000u, 0xc5371912364ce305u, 0x6c28000000000000u, 0xc722f0ef9d80aad6u, 0x424d3ad2b7b97ef6u,
|
||||
0xc913936dd571c84cu, 0x03bc3a19cd1e38eau, 0xcb090c8001ab551cu, 0x5cadf5bfd3072cc6u, 0xcd036837130890a1u, 0x36dba887c37a8c10u,
|
||||
0xcf02b2c21207ef2eu, 0x94f967e45e03f4bcu, 0xd106f86e69d785c7u, 0xe13336d701beba52u, 0xd31045a8341ca07cu, 0x1ede48111209a051u,
|
||||
0xd51ea6fa85785631u, 0x552a74227f3ea566u, 0xd732290fbacaf133u, 0xa97c177947ad4096u, 0xd94ad8b1c7380874u, 0x18375281ae7822bdu,
|
||||
0xdb68c2ca82ed2a05u, 0xa67398db9f6820e1u
|
||||
}
|
||||
};
|
||||
return table;
|
||||
}
|
||||
|
||||
/// one bit per power: whether the computed value is one unit too large
|
||||
inline const std::array<std::uint32_t, 21>& pow10_fixups() noexcept
|
||||
{
|
||||
static const std::array<std::uint32_t, 21> table =
|
||||
{
|
||||
{
|
||||
0x8d8fc810u, 0x06100293u, 0x19000000u, 0x00100000u, 0x00000908u, 0x00000000u, 0x04e00300u, 0x3807e0b2u, 0x3d83d793u, 0x0006f5ccu,
|
||||
0x00000000u, 0xffff0000u, 0x8076337du, 0x4ff45ba0u, 0x09405033u, 0x034376d9u, 0x09000000u, 0x4e100501u, 0x076d14dcu, 0xf964f45eu,
|
||||
0x0000003du
|
||||
}
|
||||
};
|
||||
return table;
|
||||
}
|
||||
|
||||
/// the 128-bit significand of 10^k, rounded down, for k in [-307, 341]
|
||||
/// (compute_pow10 of Zmij)
|
||||
inline uint128_parts compute_pow10(int k) noexcept
|
||||
{
|
||||
const auto i = static_cast<unsigned>(k + 307);
|
||||
const std::uint64_t m = pow10_minor()[(i + 24) % 28];
|
||||
const std::size_t j = 2 * static_cast<std::size_t>((i + 24) / 28);
|
||||
const std::uint64_t h_hi = pow10_major()[j];
|
||||
const std::uint64_t h_lo = pow10_major()[j + 1];
|
||||
const std::uint64_t h1 = full_multiplication(h_lo, m).high;
|
||||
const std::uint64_t c0 = h_lo * m;
|
||||
const std::uint64_t c1 = h1 + (h_hi * m);
|
||||
const std::uint64_t c2 = (c1 < h1 ? 1u : 0u) + full_multiplication(h_hi, m).high;
|
||||
uint128_parts r{};
|
||||
if ((c2 >> 63u) != 0)
|
||||
{
|
||||
r.high = c2;
|
||||
r.low = c1;
|
||||
}
|
||||
else
|
||||
{
|
||||
r.high = (c2 << 1u) | (c1 >> 63u);
|
||||
r.low = (c1 << 1u) | (c0 >> 63u);
|
||||
}
|
||||
r.low -= (pow10_fixups()[i >> 5u] >> (i & 31u)) & 1u;
|
||||
return r;
|
||||
}
|
||||
|
||||
/// The 128-bit significand of 10^k, rounded down, for k in [-342, 341].
|
||||
/// Up to 10^308, the table for number parsing holds the same significands
|
||||
/// (those of 5^k), except for k in [-27, -1], where it holds them one unit
|
||||
/// larger (as the Eisel-Lemire algorithm needs them).
|
||||
inline uint128_parts pow10(int k) noexcept
|
||||
{
|
||||
if (k > pow5_128_largest_power)
|
||||
{
|
||||
return compute_pow10(k); // (only for the smallest doubles)
|
||||
}
|
||||
const auto i = 2 * static_cast<std::size_t>(k - pow5_128_smallest_power);
|
||||
uint128_parts r{pow5_128()[i + 1], pow5_128()[i]};
|
||||
const std::uint64_t adjust = static_cast<unsigned>(k + 27) < 27u ? 1u : 0u;
|
||||
r.high -= r.low < adjust ? 1u : 0u;
|
||||
r.low -= adjust;
|
||||
return r;
|
||||
}
|
||||
|
||||
/// (x_hi * 2^64 + x_lo) * y >> 64, as 128 bits
|
||||
inline uint128_parts umul192_hi128(std::uint64_t x_hi, std::uint64_t x_lo, std::uint64_t y) noexcept
|
||||
{
|
||||
const uint128_parts p = full_multiplication(x_hi, y);
|
||||
uint128_parts r{};
|
||||
r.low = p.low + full_multiplication(x_lo, y).high;
|
||||
r.high = p.high + (r.low < p.low ? 1u : 0u);
|
||||
return r;
|
||||
}
|
||||
|
||||
/// (x * y + c) >> 64
|
||||
inline std::uint64_t umul128_add_hi64(std::uint64_t x, std::uint64_t y, std::uint64_t c) noexcept
|
||||
{
|
||||
const uint128_parts p = full_multiplication(x, y);
|
||||
return p.high + (p.low + c < p.low ? 1u : 0u);
|
||||
}
|
||||
|
||||
/// the result of Zmij: the shorter candidate and, if that is outside the
|
||||
/// rounding interval, the digit after it (16 bytes: returned in registers)
|
||||
struct shortest_decimal
|
||||
{
|
||||
std::uint64_t integral; ///< the shorter candidate (15 or 16 digits for normal doubles)
|
||||
int exponent; ///< the decimal exponent of the digit after it
|
||||
unsigned char digit; ///< the digit after it (if has_digit)
|
||||
bool has_digit; ///< whether the shortest decimal is integral * 10 + digit
|
||||
};
|
||||
|
||||
/// The shortest decimal in the rounding interval of a positive finite double
|
||||
/// given by its bits, the closest one if there are several (to_decimal of
|
||||
/// Zmij, which keeps the last digit apart: the 15 or 16 digits before it can be
|
||||
/// converted without a multiplication by 10 first). Always inlined: GCC
|
||||
/// otherwise calls it, and its result goes through memory.
|
||||
JSON_HEDLEY_ALWAYS_INLINE shortest_decimal to_shortest(std::uint64_t bits) noexcept
|
||||
{
|
||||
constexpr int extra_shift = 9;
|
||||
const auto raw_exp = static_cast<int>((bits >> 52u) & 0x7FFu);
|
||||
std::uint64_t bin_sig = bits & ((std::uint64_t{1} << 52u) - 1);
|
||||
// a power of two has a narrower interval below (except the smallest normal)
|
||||
const bool regular = bin_sig != 0 || raw_exp <= 1;
|
||||
const int bin_exp = (raw_exp == 0 ? 1 : raw_exp) - 1075;
|
||||
if (raw_exp != 0)
|
||||
{
|
||||
bin_sig |= std::uint64_t{1} << 52u;
|
||||
}
|
||||
// floor(log10(2^bin_exp)), or floor(log10(3/4 * 2^bin_exp)) for the irregular case
|
||||
const int dec_exp = ((bin_exp * 315653) - (regular ? 0 : 131072)) >> 20;
|
||||
// scaled by 10^(-dec_exp - 1): the integral part is the shorter candidate
|
||||
const int shift = bin_exp + ((-(dec_exp + 1) * 217707) >> 16) + 1 + extra_shift;
|
||||
const uint128_parts p10 = pow10(-dec_exp - 1);
|
||||
const uint128_parts p = umul192_hi128(p10.high, p10.low, bin_sig << static_cast<unsigned>(shift));
|
||||
std::uint64_t integral = p.high >> static_cast<unsigned>(extra_shift);
|
||||
const std::uint64_t fractional = (p.high << static_cast<unsigned>(64 - extra_shift)) | (p.low >> static_cast<unsigned>(extra_shift));
|
||||
std::uint64_t digit = 0;
|
||||
bool round_up = false;
|
||||
bool round_down = false;
|
||||
if (JSON_HEDLEY_LIKELY(regular))
|
||||
{
|
||||
const std::uint64_t half_ulp = (p10.high >> static_cast<unsigned>(extra_shift + 1 - shift)) + (1 - (bin_sig & 1u));
|
||||
round_up = fractional + half_ulp < fractional;
|
||||
round_down = half_ulp > fractional;
|
||||
// the last digit of the longer candidate, rounded to nearest
|
||||
digit = umul128_add_hi64(fractional, 10, (std::uint64_t{1} << 63u) + 6);
|
||||
if (fractional == (std::uint64_t{1} << 62u))
|
||||
{
|
||||
digit = 2; // 2.5 rounds to 2
|
||||
}
|
||||
}
|
||||
else
|
||||
{
|
||||
const std::uint64_t half_ulp = p10.high >> static_cast<unsigned>(extra_shift + 1 - shift);
|
||||
round_up = half_ulp > ~std::uint64_t{0} - fractional;
|
||||
round_down = (half_ulp >> 1u) > fractional;
|
||||
digit = umul128_add_hi64(fractional, 10, (std::uint64_t{1} << 63u) - 1);
|
||||
const std::uint64_t lowest = umul128_add_hi64(fractional - (half_ulp >> 1u), 10, ~std::uint64_t{0});
|
||||
digit = digit < lowest ? lowest : digit;
|
||||
}
|
||||
integral += round_up ? 1u : 0u;
|
||||
// if the shorter candidate is outside the rounding interval: one digit more
|
||||
return shortest_decimal{integral, dec_exp, static_cast<unsigned char>(digit), !round_up && !round_down};
|
||||
}
|
||||
|
||||
/// The shortest decimal in the rounding interval of a positive finite double
|
||||
/// given by its bits, as one number. The significand can end in zeros.
|
||||
inline decimal to_decimal(std::uint64_t bits) noexcept
|
||||
{
|
||||
const shortest_decimal d = to_shortest(bits);
|
||||
if (d.has_digit)
|
||||
{
|
||||
return decimal{(d.integral * 10) + d.digit, d.exponent};
|
||||
}
|
||||
return decimal{d.integral, d.exponent + 1};
|
||||
}
|
||||
|
||||
} // namespace zmij
|
||||
} // namespace detail
|
||||
NLOHMANN_JSON_NAMESPACE_END
|
||||
|
||||
// #include <nlohmann/detail/macro_scope.hpp>
|
||||
|
||||
|
||||
@@ -25497,6 +25763,88 @@ void grisu2(char* buf, int& len, int& decimal_exponent, FloatType value)
|
||||
grisu2(buf, len, decimal_exponent, w.minus, w.w, w.plus);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief the shortest digits of a positive finite float (other than double): Grisu2
|
||||
*/
|
||||
template<typename FloatType>
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
void shortest_digits(char* buf, int& len, int& decimal_exponent, FloatType value)
|
||||
{
|
||||
grisu2(buf, len, decimal_exponent, value);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief the shortest digits of a positive finite double: the conversion of
|
||||
Zmij (see zmij.hpp), which always finds the shortest digits that read back as
|
||||
the same value (Grisu2 does not for about one double in a thousand), and the
|
||||
closest of them if there are several
|
||||
|
||||
v = buf * 10^decimal_exponent, as for grisu2()
|
||||
*/
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
inline void shortest_digits(char* buf, int& len, int& decimal_exponent, double value)
|
||||
{
|
||||
static_assert(std::numeric_limits<double>::is_iec559 && std::numeric_limits<double>::digits == 53,
|
||||
"internal error: the conversion of Zmij needs IEEE 754 binary64 doubles");
|
||||
JSON_ASSERT(std::isfinite(value));
|
||||
JSON_ASSERT(value > 0);
|
||||
|
||||
std::uint64_t bits = 0;
|
||||
std::memcpy(&bits, &value, sizeof(bits));
|
||||
zmij::decimal d = zmij::to_decimal(bits);
|
||||
// without trailing zeros (up to 16): 8, 4, 2, 1 at a time
|
||||
while (d.significand % 100000000 == 0)
|
||||
{
|
||||
d.significand /= 100000000;
|
||||
d.exponent += 8;
|
||||
}
|
||||
if (d.significand % 10000 == 0)
|
||||
{
|
||||
d.significand /= 10000;
|
||||
d.exponent += 4;
|
||||
}
|
||||
if (d.significand % 100 == 0)
|
||||
{
|
||||
d.significand /= 100;
|
||||
d.exponent += 2;
|
||||
}
|
||||
if (d.significand % 10 == 0)
|
||||
{
|
||||
d.significand /= 10;
|
||||
d.exponent += 1;
|
||||
}
|
||||
// at most 17 digits, written from the back two at a time
|
||||
static constexpr const char* pairs =
|
||||
"00010203040506070809101112131415161718192021222324252627282930313233343536373839"
|
||||
"40414243444546474849505152535455565758596061626364656667686970717273747576777879"
|
||||
"8081828384858687888990919293949596979899";
|
||||
std::array<char, 20> digits{};
|
||||
std::size_t n = digits.size();
|
||||
while (d.significand >= 100)
|
||||
{
|
||||
const std::uint64_t two_digits = d.significand % 100; // a variable: GCC calls a cast of the remainder useless where std::uint64_t is std::size_t
|
||||
const auto i = static_cast<std::size_t>(two_digits) * 2;
|
||||
d.significand /= 100;
|
||||
n -= 2;
|
||||
digits[n] = pairs[i];
|
||||
digits[n + 1] = pairs[i + 1];
|
||||
}
|
||||
if (d.significand >= 10)
|
||||
{
|
||||
const auto i = static_cast<std::size_t>(d.significand) * 2;
|
||||
n -= 2;
|
||||
digits[n] = pairs[i];
|
||||
digits[n + 1] = pairs[i + 1];
|
||||
}
|
||||
else
|
||||
{
|
||||
digits[--n] = static_cast<char>('0' + d.significand);
|
||||
}
|
||||
len = static_cast<int>(digits.size() - n);
|
||||
std::memcpy(buf, digits.data() + n, static_cast<std::size_t>(len));
|
||||
decimal_exponent = d.exponent;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief appends a decimal representation of e to buf
|
||||
@return a pointer to the element following the exponent.
|
||||
@@ -25626,6 +25974,374 @@ inline char* format_buffer(char* buf, int len, int decimal_exponent,
|
||||
return append_exponent(buf, n - 1);
|
||||
}
|
||||
|
||||
/// eight decimal digits (a value below 10^8) as bytes 0..9, the first digit
|
||||
/// in the most significant byte: three steps that divide all lanes at once
|
||||
/// by a multiplication (the conversion of Xiang JunBo, as in Zmij)
|
||||
inline std::uint64_t eight_digit_bytes(std::uint64_t abcdefgh) noexcept
|
||||
{
|
||||
const std::uint64_t abcd_efgh = abcdefgh + (((std::uint64_t{1} << 32u) - 10000u) * ((abcdefgh * (((std::uint64_t{1} << 40u) / 10000u) + 1u)) >> 40u));
|
||||
const std::uint64_t ab_cd_ef_gh = abcd_efgh + (((std::uint64_t{1} << 16u) - 100u) * (((abcd_efgh * (((std::uint64_t{1} << 19u) / 100u) + 1u)) >> 19u) & 0x7F0000007Fu));
|
||||
return ab_cd_ef_gh + (((std::uint64_t{1} << 8u) - 10u) * (((ab_cd_ef_gh * (((std::uint64_t{1} << 10u) / 10u) + 1u)) >> 10u) & 0x000F000F000F000Fu));
|
||||
}
|
||||
|
||||
/// store the bytes of v, the most significant one first (one byte swap and
|
||||
/// one store where the byte order is known: compilers do not reliably merge
|
||||
/// the byte stores once this is inlined)
|
||||
inline void store_msb_first(char* p, std::uint64_t v) noexcept
|
||||
{
|
||||
#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
|
||||
v = __builtin_bswap64(v);
|
||||
std::memcpy(p, &v, sizeof(v));
|
||||
#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
|
||||
std::memcpy(p, &v, sizeof(v));
|
||||
#elif defined(_MSC_VER) // (little-endian on all its targets)
|
||||
v = _byteswap_uint64(v);
|
||||
std::memcpy(p, &v, sizeof(v));
|
||||
#else
|
||||
for (unsigned i = 0; i < 8; ++i)
|
||||
{
|
||||
p[i] = static_cast<char>(v >> (56u - (8u * i)));
|
||||
}
|
||||
#endif
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief digits * 10^exp for a double, in the layout of format_buffer()
|
||||
|
||||
The layout is that of format_buffer() with min_exp -4 and max_exp 15 (the
|
||||
digits10 of double). The digits are converted eight at a time and placed
|
||||
with fixed-size moves instead of per-digit loops and moves of the buffer.
|
||||
|
||||
@param[in] digits the digits (not 0, at most 17 digits; trailing zeros allowed)
|
||||
@param[in] exp the decimal exponent of the last digit
|
||||
@return a pointer past the text; up to 41 bytes at @a first are written
|
||||
(some beyond the returned end)
|
||||
*/
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_decimal(char* first, std::uint64_t digits, int exp) noexcept
|
||||
{
|
||||
JSON_ASSERT(digits != 0 && digits < 100000000000000000u);
|
||||
const std::uint64_t upper = digits / 100000000u;
|
||||
const std::uint64_t b0 = upper / 100000000u; // (one digit: it is its own byte)
|
||||
const std::uint64_t b1 = eight_digit_bytes(upper % 100000000u);
|
||||
const std::uint64_t b2 = eight_digit_bytes(digits % 100000000u);
|
||||
// leading and trailing zero digits: zero bytes, counted without division
|
||||
int leading = 16;
|
||||
int zeros = 16;
|
||||
if (b0 != 0)
|
||||
{
|
||||
leading = count_leading_zeros(b0) / 8;
|
||||
}
|
||||
else if (b1 != 0)
|
||||
{
|
||||
leading = 8 + (count_leading_zeros(b1) / 8);
|
||||
}
|
||||
else
|
||||
{
|
||||
leading += count_leading_zeros(b2) / 8;
|
||||
}
|
||||
if (b2 != 0)
|
||||
{
|
||||
zeros = count_trailing_zeros(b2) / 8;
|
||||
}
|
||||
else if (b1 != 0)
|
||||
{
|
||||
zeros = 8 + (count_trailing_zeros(b1) / 8);
|
||||
}
|
||||
// (else: 16, b0 is the one digit that is not 0)
|
||||
// the digits as text at text + leading, then '0's, so that fixed-size
|
||||
// moves need not check how many digits there are
|
||||
std::array<char, 64> text; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
|
||||
store_msb_first(text.data(), b0 + 0x3030303030303030u);
|
||||
store_msb_first(text.data() + 8, b1 + 0x3030303030303030u);
|
||||
store_msb_first(text.data() + 16, b2 + 0x3030303030303030u);
|
||||
std::memset(text.data() + 24, '0', 40);
|
||||
const int k = 24 - leading - zeros; // significant digits
|
||||
const int n = k + exp + zeros; // position of the decimal point after the first digit
|
||||
const char* const s0 = text.data() + leading;
|
||||
|
||||
if (-4 < n && n <= 15)
|
||||
{
|
||||
// "0.[000]digits" (n <= 0) is the digits after 1 - n leading '0's
|
||||
// with the point after the first; "digits[000].0" (n >= k) and
|
||||
// "dig.its" put the point after n characters
|
||||
const int pad = n <= 0 ? 1 - n : 0;
|
||||
const char* const s = s0 - pad;
|
||||
const int len = k + pad;
|
||||
const int point = n + pad;
|
||||
std::memcpy(first, s, 16);
|
||||
std::memcpy(first + point + 1, s + point, 24);
|
||||
first[point] = '.';
|
||||
return first + (point >= len ? point + 2 : len + 1);
|
||||
}
|
||||
|
||||
// d.igitse+XX, with at least two exponent digits (as append_exponent())
|
||||
std::memcpy(first, s0, 16);
|
||||
std::memcpy(first + 2, s0 + 1, 16);
|
||||
first[1] = '.';
|
||||
char* const end = first + (k == 1 ? 1 : k + 1);
|
||||
const int e = n - 1;
|
||||
const auto ea = static_cast<unsigned>(e < 0 ? -e : e);
|
||||
const bool three = ea >= 100;
|
||||
end[0] = 'e';
|
||||
end[1] = e < 0 ? '-' : '+';
|
||||
end[2] = static_cast<char>('0' + (three ? ea / 100 : (ea / 10) % 10));
|
||||
end[3] = static_cast<char>('0' + (three ? (ea / 10) % 10 : ea % 10));
|
||||
end[4] = static_cast<char>('0' + (ea % 10));
|
||||
return end + (three ? 5 : 4);
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief the shortest decimal of a positive double (Zmij), as write_decimal()
|
||||
writes it
|
||||
|
||||
For a normal double, the shorter candidate has 15 or 16 digits: they are
|
||||
converted at once (two halves of eight digits) and followed by the digit
|
||||
after them, if there is one, without the multiplication and division by 10
|
||||
that counting the digits of one number would take. The fixed layouts move
|
||||
the digits after the point by one byte.
|
||||
|
||||
@return a pointer past the text; up to 41 bytes at @a first are written
|
||||
(some beyond the returned end)
|
||||
*/
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_shortest(char* first, const zmij::shortest_decimal d) noexcept
|
||||
{
|
||||
const std::uint64_t sig = d.integral;
|
||||
if (JSON_HEDLEY_UNLIKELY(sig < 100000000000000u || sig >= 10000000000000000u))
|
||||
{
|
||||
// (subnormals)
|
||||
return d.has_digit ? write_decimal(first, (sig * 10) + d.digit, d.exponent) : write_decimal(first, sig, d.exponent + 1);
|
||||
}
|
||||
const bool sixteen = sig >= 1000000000000000u; // (else 15 digits)
|
||||
const int last = d.has_digit ? d.digit : 0;
|
||||
const std::uint64_t upper = sig / 100000000u;
|
||||
#if JSON_DTOA_SSE2
|
||||
// NOLINTBEGIN(portability-simd-intrinsics)
|
||||
// the two halves in the 64-bit lanes, each as abcd * 2^32 + efgh, then as
|
||||
// bytes (as eight_digit_bytes(), one lane each)
|
||||
const __m128i x = _mm_set_epi64x(static_cast<long long>(sig - (upper * 100000000u)), static_cast<long long>(upper));
|
||||
const __m128i abcd = _mm_srli_epi64(_mm_mul_epu32(x, _mm_set1_epi64x(109951163)), 40); // 2^40 / 10000 + 1
|
||||
const __m128i abcd_efgh = _mm_add_epi64(x, _mm_mul_epu32(abcd, _mm_set1_epi64x(4294957296))); // 2^32 - 10000
|
||||
// 32-bit lanes in the order of the text: abcd, efgh of both halves
|
||||
const __m128i fours = _mm_shuffle_epi32(abcd_efgh, _MM_SHUFFLE(2, 3, 0, 1));
|
||||
const __m128i ab = _mm_srli_epi16(_mm_mulhi_epu16(fours, _mm_set1_epi32(5243)), 3);
|
||||
const __m128i ab_cd = _mm_or_si128(_mm_slli_epi32(_mm_sub_epi16(fours, _mm_mullo_epi16(ab, _mm_set1_epi32(100))), 16), ab);
|
||||
// 16-bit lanes ab (< 100) -> bytes a, b: 256 * ab - 2559 * (ab / 10)
|
||||
const __m128i bytes = _mm_sub_epi16(_mm_slli_epi16(ab_cd, 8), _mm_mullo_epi16(_mm_set1_epi16(2559), _mm_mulhi_epu16(ab_cd, _mm_set1_epi16(6554))));
|
||||
// the last digit that is not 0 (sig is not 0)
|
||||
const auto nonzero = static_cast<std::uint64_t>(_mm_movemask_epi8(_mm_cmpgt_epi8(bytes, _mm_setzero_si128())));
|
||||
const int digits = 63 - count_leading_zeros(nonzero) + (sixteen ? 1 : 0); // without trailing zeros
|
||||
const __m128i chars = _mm_add_epi8(bytes, _mm_set1_epi8('0'));
|
||||
// the 16 characters from the first digit
|
||||
const __m128i s = sixteen ? chars : _mm_or_si128(_mm_srli_si128(chars, 1), _mm_slli_si128(_mm_cvtsi32_si128('0' + last), 15));
|
||||
const char s16 = static_cast<char>(sixteen ? '0' + last : '0'); // the 17th
|
||||
const auto store_16 = [&s](char* p) noexcept
|
||||
{
|
||||
std::memcpy(p, &s, 16);
|
||||
};
|
||||
const char first_digit = static_cast<char>(_mm_cvtsi128_si32(s));
|
||||
// NOLINTEND(portability-simd-intrinsics)
|
||||
#elif JSON_DTOA_NEON
|
||||
// as with SSE2: the halves in 32-bit lanes, then abcd, efgh of both
|
||||
const uint32x2_t halves = vcreate_u32(upper | ((sig - (upper * 100000000u)) << 32u));
|
||||
const uint32x2_t abcd = vmovn_u64(vshrq_n_u64(vmull_n_u32(halves, static_cast<std::uint32_t>(((std::uint64_t{1} << 40u) / 10000u) + 1u)), 40));
|
||||
const uint32x2_t efgh = vmls_n_u32(halves, abcd, 10000u);
|
||||
const uint32x4_t fours = vcombine_u32(vzip1_u32(abcd, efgh), vzip2_u32(abcd, efgh));
|
||||
const uint32x4_t ab = vshrq_n_u32(vmulq_n_u32(fours, 5243u), 19);
|
||||
const uint16x8_t ab_cd = vreinterpretq_u16_u32(vorrq_u32(ab, vshlq_n_u32(vmlsq_n_u32(fours, ab, 100u), 16)));
|
||||
const uint16x8_t tens = vshrq_n_u16(vmulq_n_u16(ab_cd, 103u), 10);
|
||||
const uint8x16_t bytes = vreinterpretq_u8_u16(vorrq_u16(tens, vshlq_n_u16(vmlsq_n_u16(ab_cd, tens, 10u), 8)));
|
||||
// the last digit that is not 0 (sig is not 0): a nibble per byte
|
||||
const std::uint64_t nonzero = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(vtstq_u8(bytes, bytes)), 4)), 0);
|
||||
const int digits = ((63 - count_leading_zeros(nonzero)) / 4) + (sixteen ? 1 : 0); // without trailing zeros
|
||||
const uint8x16_t chars = vaddq_u8(bytes, vdupq_n_u8('0'));
|
||||
// the 16 characters from the first digit
|
||||
const uint8x16_t s = sixteen ? chars : vextq_u8(chars, vdupq_n_u8(static_cast<std::uint8_t>('0' + last)), 1);
|
||||
const char s16 = static_cast<char>(sixteen ? '0' + last : '0'); // the 17th
|
||||
const auto store_16 = [&s](char* p) noexcept
|
||||
{
|
||||
vst1q_u8(reinterpret_cast<std::uint8_t*>(p), s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
|
||||
};
|
||||
const auto first_digit = static_cast<char>(vgetq_lane_u8(s, 0));
|
||||
#else
|
||||
const std::uint64_t hi = eight_digit_bytes(upper);
|
||||
const std::uint64_t lo = eight_digit_bytes(sig - (upper * 100000000u));
|
||||
// trailing zero digits: zero bytes (sig is not 0)
|
||||
const int zeros = lo != 0 ? count_trailing_zeros(lo) / 8 : 8 + (count_trailing_zeros(hi) / 8);
|
||||
const int digits = 15 - zeros + (sixteen ? 1 : 0); // without trailing zeros
|
||||
// the 16 characters from the first digit
|
||||
const std::uint64_t s_hi = (sixteen ? hi : (hi << 8u) | (lo >> 56u)) + 0x3030303030303030u;
|
||||
const std::uint64_t s_lo = (sixteen ? lo : (lo << 8u) | static_cast<std::uint64_t>(last)) + 0x3030303030303030u;
|
||||
const char s16 = static_cast<char>(sixteen ? '0' + last : '0'); // the 17th
|
||||
const auto store_16 = [s_hi, s_lo](char* p) noexcept
|
||||
{
|
||||
store_msb_first(p, s_hi);
|
||||
store_msb_first(p + 8, s_lo);
|
||||
};
|
||||
const auto first_digit = static_cast<char>(s_hi >> 56u);
|
||||
#endif
|
||||
const int len = d.has_digit ? 16 + (sixteen ? 1 : 0) : digits; // significant digits
|
||||
const int n = 16 + (sixteen ? 1 : 0) + d.exponent; // digits before the point
|
||||
|
||||
if (JSON_HEDLEY_LIKELY(n >= 1 && n <= 15))
|
||||
{
|
||||
// "dig.its" and "digits[000].0": the digits after the point move by
|
||||
// one byte ('0's follow the digits)
|
||||
#if JSON_DTOA_SSE2
|
||||
// NOLINTBEGIN(portability-simd-intrinsics)
|
||||
// (in the register: reading the digits back from memory right after
|
||||
// storing them waits until the stores are done)
|
||||
const __m128i at = _mm_set1_epi8(static_cast<char>(n));
|
||||
const __m128i index = _mm_setr_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
|
||||
const __m128i before = _mm_cmpgt_epi8(at, index);
|
||||
const __m128i after = _mm_cmpgt_epi8(index, at);
|
||||
const __m128i text = _mm_or_si128(_mm_or_si128(_mm_and_si128(s, before), _mm_and_si128(_mm_slli_si128(s, 1), after)),
|
||||
_mm_andnot_si128(_mm_or_si128(before, after), _mm_set1_epi8('.')));
|
||||
std::memcpy(first, &text, 16);
|
||||
first[16] = static_cast<char>(_mm_extract_epi16(s, 7) >> 8);
|
||||
first[17] = s16;
|
||||
// NOLINTEND(portability-simd-intrinsics)
|
||||
#elif JSON_DTOA_NEON
|
||||
const uint8x16_t index = vcombine_u8(vcreate_u8(0x0706050403020100u), vcreate_u8(0x0F0E0D0C0B0A0908u));
|
||||
const uint8x16_t at = vdupq_n_u8(static_cast<std::uint8_t>(n));
|
||||
const uint8x16_t after_point = vbslq_u8(vcgtq_u8(index, at), vextq_u8(vdupq_n_u8(0), s, 15), vdupq_n_u8('.'));
|
||||
vst1q_u8(reinterpret_cast<std::uint8_t*>(first), vbslq_u8(vcltq_u8(index, at), s, after_point)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
|
||||
first[16] = static_cast<char>(vgetq_lane_u8(s, 15));
|
||||
first[17] = s16;
|
||||
#else
|
||||
store_16(first);
|
||||
first[16] = s16;
|
||||
std::uint64_t after_point[2]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
|
||||
std::memcpy(after_point, first + n, 16);
|
||||
std::memcpy(first + n + 1, after_point, 16);
|
||||
first[n] = '.';
|
||||
#endif
|
||||
return first + (n >= len ? n + 2 : len + 1);
|
||||
}
|
||||
if (n <= 0 && n > -4)
|
||||
{
|
||||
// "0.[000]digits"
|
||||
std::memset(first, '0', 8);
|
||||
first[1] = '.';
|
||||
store_16(first + 2 - n);
|
||||
first[18 - n] = s16;
|
||||
return first + 2 - n + len;
|
||||
}
|
||||
// d.igitse+XX, with at least two exponent digits (as append_exponent())
|
||||
store_16(first + 1);
|
||||
first[17] = s16;
|
||||
first[0] = first_digit;
|
||||
first[1] = '.';
|
||||
char* const end = first + (len == 1 ? 1 : len + 1);
|
||||
const int e = n - 1;
|
||||
const auto ea = static_cast<unsigned>(e < 0 ? -e : e);
|
||||
const bool three = ea >= 100;
|
||||
end[0] = 'e';
|
||||
end[1] = e < 0 ? '-' : '+';
|
||||
end[2] = static_cast<char>('0' + (three ? ea / 100 : (ea / 10) % 10));
|
||||
end[3] = static_cast<char>('0' + (three ? (ea / 10) % 10 : ea % 10));
|
||||
end[4] = static_cast<char>('0' + (ea % 10));
|
||||
return end + (three ? 5 : 4);
|
||||
}
|
||||
|
||||
/// the powers of ten up to 10^16
|
||||
inline const std::array<std::uint64_t, 17>& powers_of_ten_16() noexcept
|
||||
{
|
||||
static const std::array<std::uint64_t, 17> powers =
|
||||
{
|
||||
{
|
||||
1u, 10u, 100u, 1000u, 10000u, 100000u, 1000000u, 10000000u, 100000000u, 1000000000u, 10000000000u,
|
||||
100000000000u, 1000000000000u, 10000000000000u, 100000000000000u, 1000000000000000u, 10000000000000000u
|
||||
}
|
||||
};
|
||||
return powers;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief digits * 10^exp, as write_decimal() writes it, for the digits of a
|
||||
double that need no conversion (count digits, at most 15, the first not 0;
|
||||
trailing zeros allowed): extended to 16 digits and written by write_shortest()
|
||||
|
||||
@return a pointer past the text; up to 41 bytes at @a first are written
|
||||
(some beyond the returned end)
|
||||
*/
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_short_decimal(char* first, std::uint64_t digits, int count, int exp) noexcept
|
||||
{
|
||||
JSON_ASSERT(digits >= powers_of_ten_16()[static_cast<std::size_t>(count - 1)] && count <= 15);
|
||||
const int scale = 16 - count;
|
||||
return write_shortest(first, zmij::shortest_decimal{digits * powers_of_ten_16()[static_cast<std::size_t>(scale)], exp - scale - 1, 0, false});
|
||||
}
|
||||
|
||||
/// as write_short_decimal(), counting the digits (not 0, less than 10^15)
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_short_decimal(char* first, std::uint64_t digits, int exp) noexcept
|
||||
{
|
||||
JSON_ASSERT(digits != 0 && digits < 1000000000000000u);
|
||||
// floor(log10(2^bits)) + 1 digits, or one less
|
||||
const int log2_bound = ((64 - count_leading_zeros(digits)) * 1233) >> 12;
|
||||
const int count = log2_bound + (digits >= powers_of_ten_16()[static_cast<std::size_t>(log2_bound)] ? 1 : 0);
|
||||
return write_short_decimal(first, digits, count, exp);
|
||||
}
|
||||
|
||||
/// a positive finite float (other than double): Grisu2 and format_buffer()
|
||||
template<typename FloatType>
|
||||
JSON_HEDLEY_NON_NULL(1, 2)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
char* write_positive(char* first, const char* last, FloatType value)
|
||||
{
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Compute v = buffer * 10^decimal_exponent.
|
||||
// The decimal digits are stored in the buffer, which needs to be interpreted
|
||||
// as an unsigned decimal integer.
|
||||
// len is the length of the buffer, i.e., the number of decimal digits.
|
||||
int len = 0;
|
||||
int decimal_exponent = 0;
|
||||
shortest_digits(first, len, decimal_exponent, value);
|
||||
|
||||
JSON_ASSERT(len <= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Format the buffer like printf("%.*g", prec, value)
|
||||
constexpr int kMinExp = -4;
|
||||
// Use digits10 here to increase compatibility with version 2.
|
||||
constexpr int kMaxExp = std::numeric_limits<FloatType>::digits10;
|
||||
|
||||
JSON_ASSERT(last - first >= kMaxExp + 2);
|
||||
JSON_ASSERT(last - first >= 2 + (-kMinExp - 1) + std::numeric_limits<FloatType>::max_digits10);
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10 + 6);
|
||||
|
||||
return format_buffer(first, len, decimal_exponent, kMinExp, kMaxExp);
|
||||
}
|
||||
|
||||
/// a positive finite double: the shortest digits (Zmij), laid out by
|
||||
/// write_shortest() (through a local buffer if [first, last) is shorter than
|
||||
/// the 41 bytes it may write)
|
||||
JSON_HEDLEY_NON_NULL(1, 2)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
inline char* write_positive(char* first, const char* last, double value)
|
||||
{
|
||||
static_assert(std::numeric_limits<double>::is_iec559 && std::numeric_limits<double>::digits == 53,
|
||||
"internal error: the conversion of Zmij needs IEEE 754 binary64 doubles");
|
||||
std::uint64_t bits = 0;
|
||||
std::memcpy(&bits, &value, sizeof(bits));
|
||||
const zmij::shortest_decimal d = zmij::to_shortest(bits);
|
||||
if (JSON_HEDLEY_LIKELY(last - first >= 41))
|
||||
{
|
||||
return write_shortest(first, d);
|
||||
}
|
||||
std::array<char, 64> buf; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
|
||||
const auto len = static_cast<std::size_t>(write_shortest(buf.data(), d) - buf.data());
|
||||
JSON_ASSERT(static_cast<std::size_t>(last - first) >= len);
|
||||
std::memcpy(first, buf.data(), len);
|
||||
return first + len;
|
||||
}
|
||||
|
||||
} // namespace dtoa_impl
|
||||
|
||||
/*!
|
||||
@@ -25643,7 +26359,6 @@ JSON_HEDLEY_NON_NULL(1, 2)
|
||||
JSON_HEDLEY_RETURNS_NON_NULL
|
||||
char* to_chars(char* first, const char* last, FloatType value)
|
||||
{
|
||||
static_cast<void>(last); // maybe unused - fix warning
|
||||
JSON_ASSERT(std::isfinite(value));
|
||||
|
||||
// Use signbit(value) instead of (value < 0) since signbit works for -0.
|
||||
@@ -25669,28 +26384,7 @@ char* to_chars(char* first, const char* last, FloatType value)
|
||||
JSON_HEDLEY_DIAGNOSTIC_POP
|
||||
#endif
|
||||
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Compute v = buffer * 10^decimal_exponent.
|
||||
// The decimal digits are stored in the buffer, which needs to be interpreted
|
||||
// as an unsigned decimal integer.
|
||||
// len is the length of the buffer, i.e., the number of decimal digits.
|
||||
int len = 0;
|
||||
int decimal_exponent = 0;
|
||||
dtoa_impl::grisu2(first, len, decimal_exponent, value);
|
||||
|
||||
JSON_ASSERT(len <= std::numeric_limits<FloatType>::max_digits10);
|
||||
|
||||
// Format the buffer like printf("%.*g", prec, value)
|
||||
constexpr int kMinExp = -4;
|
||||
// Use digits10 here to increase compatibility with version 2.
|
||||
constexpr int kMaxExp = std::numeric_limits<FloatType>::digits10;
|
||||
|
||||
JSON_ASSERT(last - first >= kMaxExp + 2);
|
||||
JSON_ASSERT(last - first >= 2 + (-kMinExp - 1) + std::numeric_limits<FloatType>::max_digits10);
|
||||
JSON_ASSERT(last - first >= std::numeric_limits<FloatType>::max_digits10 + 6);
|
||||
|
||||
return dtoa_impl::format_buffer(first, len, decimal_exponent, kMinExp, kMaxExp);
|
||||
return dtoa_impl::write_positive(first, last, value);
|
||||
}
|
||||
|
||||
} // namespace detail
|
||||
@@ -27049,8 +27743,9 @@ class serializer
|
||||
/*!
|
||||
@brief dump an integer
|
||||
|
||||
Dump a given integer, appending it to @ref write_buffer. Works internally with
|
||||
@a number_buffer.
|
||||
Dump a given integer, appending it to @ref write_buffer (directly: copying
|
||||
the digits from another buffer right after writing them waits until the
|
||||
stores are done).
|
||||
|
||||
@param[in] x integer number (signed or unsigned) to dump
|
||||
@tparam NumberType either @a number_integer_t or @a number_unsigned_t
|
||||
@@ -27085,33 +27780,57 @@ class serializer
|
||||
return;
|
||||
}
|
||||
|
||||
// use a pointer to fill the buffer
|
||||
auto buffer_ptr = number_buffer.begin(); // NOLINT(llvm-qualified-auto,readability-qualified-auto)
|
||||
// use a pointer to fill the buffer (room for as much as number_buffer holds)
|
||||
if (JSON_HEDLEY_UNLIKELY(write_buffer_pos + number_buffer.size() > write_buffer.size()))
|
||||
{
|
||||
flush();
|
||||
}
|
||||
auto* buffer_ptr = write_buffer.data() + write_buffer_pos;
|
||||
|
||||
number_unsigned_t abs_value;
|
||||
|
||||
unsigned int n_chars{};
|
||||
// one byte for the minus sign
|
||||
unsigned int n_chars = 0;
|
||||
|
||||
if (is_negative_number(x))
|
||||
{
|
||||
*buffer_ptr = '-';
|
||||
abs_value = remove_sign(static_cast<number_integer_t>(x));
|
||||
|
||||
// account one more byte for the minus sign
|
||||
n_chars = 1 + count_digits(abs_value);
|
||||
n_chars = 1;
|
||||
}
|
||||
else
|
||||
{
|
||||
abs_value = static_cast<number_unsigned_t>(x);
|
||||
n_chars = count_digits(abs_value);
|
||||
}
|
||||
|
||||
// up to 16 digits: eight at a time (as the digits of floats), written
|
||||
// without leading zeros
|
||||
if (abs_value < 10000000000000000u)
|
||||
{
|
||||
const std::uint64_t value = abs_value;
|
||||
const std::uint64_t upper = value / 100000000u;
|
||||
const std::uint64_t first = dtoa_impl::eight_digit_bytes(upper != 0 ? upper : value);
|
||||
const auto leading = static_cast<unsigned>(count_leading_zeros(first) / 8); // (first is not 0)
|
||||
char* const p = buffer_ptr + n_chars;
|
||||
dtoa_impl::store_msb_first(p, (first << (8 * leading)) + 0x3030303030303030u);
|
||||
n_chars += 8 - leading;
|
||||
if (upper != 0)
|
||||
{
|
||||
dtoa_impl::store_msb_first(p + 8 - leading, dtoa_impl::eight_digit_bytes(value - (upper * 100000000u)) + 0x3030303030303030u);
|
||||
n_chars += 8;
|
||||
}
|
||||
write_buffer_pos += n_chars;
|
||||
return;
|
||||
}
|
||||
|
||||
n_chars += count_digits(abs_value);
|
||||
|
||||
// spare 1 byte for '\0'
|
||||
JSON_ASSERT(n_chars < number_buffer.size() - 1);
|
||||
|
||||
// jump to the end to generate the string from backward,
|
||||
// so we later avoid reversing the result
|
||||
buffer_ptr += static_cast<typename decltype(number_buffer)::difference_type>(n_chars);
|
||||
buffer_ptr += n_chars;
|
||||
|
||||
// Fast int2ascii implementation inspired by "Fastware" talk by Andrei Alexandrescu
|
||||
// See: https://www.youtube.com/watch?v=o4-CwDo2zpg
|
||||
@@ -27134,14 +27853,13 @@ class serializer
|
||||
*(--buffer_ptr) = static_cast<char>('0' + abs_value);
|
||||
}
|
||||
|
||||
put_buffer(number_buffer, n_chars);
|
||||
write_buffer_pos += n_chars;
|
||||
}
|
||||
|
||||
/*!
|
||||
@brief dump a floating-point number
|
||||
|
||||
Dump a given floating-point number, appending it to @ref write_buffer. Works internally
|
||||
with @a number_buffer.
|
||||
Dump a given floating-point number, appending it to @ref write_buffer.
|
||||
|
||||
@param[in] x floating-point number to dump
|
||||
*/
|
||||
@@ -27168,10 +27886,15 @@ class serializer
|
||||
|
||||
void dump_float(number_float_t x, std::true_type /*is_ieee_single_or_double*/)
|
||||
{
|
||||
auto* begin = number_buffer.data();
|
||||
// directly into the write buffer: copying the text from number_buffer
|
||||
// right after to_chars() wrote it waits until its stores are done
|
||||
if (JSON_HEDLEY_UNLIKELY(write_buffer_pos + number_buffer.size() > write_buffer.size()))
|
||||
{
|
||||
flush();
|
||||
}
|
||||
auto* begin = write_buffer.data() + write_buffer_pos;
|
||||
auto* end = ::nlohmann::detail::to_chars(begin, begin + number_buffer.size(), x);
|
||||
|
||||
put_buffer(number_buffer, static_cast<std::size_t>(end - begin));
|
||||
write_buffer_pos += static_cast<std::size_t>(end - begin);
|
||||
}
|
||||
|
||||
JSON_HEDLEY_NON_NULL(1)
|
||||
@@ -35253,6 +35976,8 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
|
||||
#undef JSON_NO_UNIQUE_ADDRESS
|
||||
#undef JSON_DISABLE_ENUM_SERIALIZATION
|
||||
#undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
|
||||
#undef JSON_DTOA_SSE2
|
||||
#undef JSON_DTOA_NEON
|
||||
|
||||
#ifndef JSON_TEST_KEEP_MACROS
|
||||
#undef JSON_CATCH
|
||||
|
||||
@@ -38,7 +38,7 @@ TEST_CASE("Binary Formats")
|
||||
const auto ubjson_2_size = json::to_ubjson(j, true).size();
|
||||
const auto ubjson_3_size = json::to_ubjson(j, true, true).size();
|
||||
|
||||
CHECK(json_size == 2090303);
|
||||
CHECK(json_size == 2090234);
|
||||
CHECK(bjdata_1_size == 1112030);
|
||||
CHECK(bjdata_2_size == 1224148);
|
||||
CHECK(bjdata_3_size == 1224148);
|
||||
@@ -51,16 +51,16 @@ TEST_CASE("Binary Formats")
|
||||
CHECK(ubjson_3_size == 1169069);
|
||||
|
||||
CHECK((100.0 * double(json_size) / double(json_size)) == Approx(100.0));
|
||||
CHECK((100.0 * double(bjdata_1_size) / double(json_size)) == Approx(53.199));
|
||||
CHECK((100.0 * double(bjdata_2_size) / double(json_size)) == Approx(58.563));
|
||||
CHECK((100.0 * double(bjdata_3_size) / double(json_size)) == Approx(58.563));
|
||||
CHECK((100.0 * double(bon8_size) / double(json_size)) == Approx(50.509));
|
||||
CHECK((100.0 * double(bson_size) / double(json_size)) == Approx(85.849));
|
||||
CHECK((100.0 * double(cbor_size) / double(json_size)) == Approx(50.497));
|
||||
CHECK((100.0 * double(msgpack_size) / double(json_size)) == Approx(50.526));
|
||||
CHECK((100.0 * double(ubjson_1_size) / double(json_size)) == Approx(53.199));
|
||||
CHECK((100.0 * double(ubjson_2_size) / double(json_size)) == Approx(58.563));
|
||||
CHECK((100.0 * double(ubjson_3_size) / double(json_size)) == Approx(55.928));
|
||||
CHECK((100.0 * double(bjdata_1_size) / double(json_size)) == Approx(53.201));
|
||||
CHECK((100.0 * double(bjdata_2_size) / double(json_size)) == Approx(58.565));
|
||||
CHECK((100.0 * double(bjdata_3_size) / double(json_size)) == Approx(58.565));
|
||||
CHECK((100.0 * double(bon8_size) / double(json_size)) == Approx(50.511));
|
||||
CHECK((100.0 * double(bson_size) / double(json_size)) == Approx(85.853));
|
||||
CHECK((100.0 * double(cbor_size) / double(json_size)) == Approx(50.499));
|
||||
CHECK((100.0 * double(msgpack_size) / double(json_size)) == Approx(50.528));
|
||||
CHECK((100.0 * double(ubjson_1_size) / double(json_size)) == Approx(53.201));
|
||||
CHECK((100.0 * double(ubjson_2_size) / double(json_size)) == Approx(58.565));
|
||||
CHECK((100.0 * double(ubjson_3_size) / double(json_size)) == Approx(55.930));
|
||||
}
|
||||
|
||||
SECTION("twitter.json")
|
||||
|
||||
+261
-1
@@ -15,6 +15,23 @@
|
||||
#include <nlohmann/json.hpp>
|
||||
using nlohmann::detail::dtoa_impl::reinterpret_bits;
|
||||
|
||||
#include <array>
|
||||
#include <cmath>
|
||||
#include <cstdint>
|
||||
#include <cstdio>
|
||||
#include <cstdlib>
|
||||
#include <iomanip>
|
||||
#include <limits>
|
||||
#include <locale>
|
||||
#include <random>
|
||||
#include <sstream>
|
||||
#include <string>
|
||||
#include <utility>
|
||||
#include <vector>
|
||||
#if defined(JSON_HAS_CPP_17)
|
||||
#include <charconv>
|
||||
#endif
|
||||
|
||||
namespace
|
||||
{
|
||||
float make_float(uint32_t sign_bit, uint32_t biased_exponent, uint32_t significand)
|
||||
@@ -450,7 +467,7 @@ TEST_CASE("formatting")
|
||||
check_double( 1.2345e+18, "1.2345e+18" ); // 1.2345e+18 1.2345e+18 1.2345e18
|
||||
check_double( 1.2345e+19, "1.2345e+19" ); // 1.2345e+19 1.2345e+19 1.2345e19
|
||||
check_double( 1.2345e+20, "1.2345e+20" ); // 1.2345e+20 1.2345e+20 1.2345e20
|
||||
check_double( 1.2345e+21, "1.2344999999999999e+21" ); // 1.2345e+21 1.2344999999999999e+21 1.2345e21
|
||||
check_double( 1.2345e+21, "1.2345e+21" ); // 1.2345e+21 1.2344999999999999e+21 1.2345e21
|
||||
check_double( 1.2345e+22, "1.2345e+22" ); // 1.2345e+22 1.2345e+22 1.2345e22
|
||||
}
|
||||
|
||||
@@ -514,3 +531,246 @@ TEST_CASE("formatting")
|
||||
check_integer(1000000000000000000LL, "1000000000000000000");
|
||||
}
|
||||
}
|
||||
|
||||
namespace
|
||||
{
|
||||
// a small unsigned big integer (32-bit limbs, least significant first), to
|
||||
// recompute the powers of ten of the shortest double conversion
|
||||
using big = std::vector<std::uint32_t>;
|
||||
|
||||
void big_mul_small(big& x, std::uint32_t m)
|
||||
{
|
||||
std::uint64_t carry = 0;
|
||||
for (auto& limb : x)
|
||||
{
|
||||
const std::uint64_t v = (static_cast<std::uint64_t>(limb) * m) + carry;
|
||||
limb = static_cast<std::uint32_t>(v);
|
||||
carry = v >> 32u;
|
||||
}
|
||||
if (carry != 0)
|
||||
{
|
||||
x.push_back(static_cast<std::uint32_t>(carry));
|
||||
}
|
||||
}
|
||||
|
||||
void big_div_small(big& x, std::uint32_t d)
|
||||
{
|
||||
std::uint64_t rest = 0;
|
||||
for (std::size_t i = x.size(); i-- > 0;)
|
||||
{
|
||||
const std::uint64_t v = (rest << 32u) | x[i];
|
||||
x[i] = static_cast<std::uint32_t>(v / d);
|
||||
rest = v % d;
|
||||
}
|
||||
while (!x.empty() && x.back() == 0)
|
||||
{
|
||||
x.pop_back();
|
||||
}
|
||||
}
|
||||
|
||||
std::size_t big_bit_length(const big& x)
|
||||
{
|
||||
std::size_t n = 32 * x.size();
|
||||
for (std::uint32_t top = x.back(); (top & 0x80000000u) == 0; top <<= 1u)
|
||||
{
|
||||
--n;
|
||||
}
|
||||
return n;
|
||||
}
|
||||
|
||||
bool big_bit(const big& x, std::size_t i)
|
||||
{
|
||||
return ((x[i / 32] >> (i % 32)) & 1u) != 0;
|
||||
}
|
||||
|
||||
/// the 128 most significant bits of x (floor), shifted left if x has fewer bits
|
||||
std::pair<std::uint64_t, std::uint64_t> big_top128(const big& x)
|
||||
{
|
||||
const std::size_t n = big_bit_length(x);
|
||||
std::uint64_t high = 0;
|
||||
std::uint64_t low = 0;
|
||||
for (std::size_t k = 0; k < 128; ++k)
|
||||
{
|
||||
const bool bit = k < n && big_bit(x, n - 1 - k);
|
||||
if (k < 64)
|
||||
{
|
||||
high = (high << 1u) | (bit ? 1u : 0u);
|
||||
}
|
||||
else
|
||||
{
|
||||
low = (low << 1u) | (bit ? 1u : 0u);
|
||||
}
|
||||
}
|
||||
return {high, low};
|
||||
}
|
||||
|
||||
/// the digits (without trailing zeros) and the decimal exponent of a
|
||||
/// representation "[-]d[.ddd][e[+-]x]"
|
||||
std::pair<std::string, int> digits_and_exponent(const std::string& s)
|
||||
{
|
||||
std::string digits;
|
||||
int point = -1;
|
||||
int exponent = 0;
|
||||
for (std::size_t i = 0; i < s.size(); ++i)
|
||||
{
|
||||
const char c = s[i];
|
||||
if (c >= '0' && c <= '9')
|
||||
{
|
||||
digits += c;
|
||||
}
|
||||
else if (c == '.')
|
||||
{
|
||||
point = static_cast<int>(digits.size());
|
||||
}
|
||||
else if (c == 'e' || c == 'E')
|
||||
{
|
||||
exponent = std::stoi(s.substr(i + 1));
|
||||
break;
|
||||
}
|
||||
}
|
||||
int e = exponent + (point < 0 ? static_cast<int>(digits.size()) : point) - static_cast<int>(digits.size());
|
||||
const std::size_t first = digits.find_first_not_of('0');
|
||||
digits = first == std::string::npos ? "0" : digits.substr(first);
|
||||
while (digits.size() > 1 && digits.back() == '0')
|
||||
{
|
||||
digits.pop_back();
|
||||
++e;
|
||||
}
|
||||
return {digits, e};
|
||||
}
|
||||
|
||||
/// whether the decimal digits * 10^e reads back as v
|
||||
bool reads_back(const std::string& digits, int e, double v)
|
||||
{
|
||||
const std::string text = digits + "e" + std::to_string(e);
|
||||
// (compared bit for bit: v is positive and finite, and -Wfloat-equal)
|
||||
return reinterpret_bits<std::uint64_t>(std::strtod(text.c_str(), nullptr)) == reinterpret_bits<std::uint64_t>(v);
|
||||
}
|
||||
|
||||
/// Check the representation of a positive finite double: it reads back as
|
||||
/// the same value, and no representation with fewer digits does.
|
||||
void check_shortest(double v)
|
||||
{
|
||||
std::array<char, 33> buf{};
|
||||
char* end = nlohmann::detail::to_chars(buf.data(), buf.data() + 32, v);
|
||||
const std::string text(buf.data(), end);
|
||||
CAPTURE(text)
|
||||
CHECK(std::strtod(text.c_str(), nullptr) == v);
|
||||
// the layout is that of format_buffer() for the same digits
|
||||
std::array<char, 64> reference{};
|
||||
int len = 0;
|
||||
int exponent = 0;
|
||||
nlohmann::detail::dtoa_impl::shortest_digits(reference.data(), len, exponent, v);
|
||||
const char* const reference_end = nlohmann::detail::dtoa_impl::format_buffer(reference.data(), len, exponent, -4, 15);
|
||||
CHECK(text == std::string(reference.data(), static_cast<std::size_t>(reference_end - reference.data())));
|
||||
const auto de = digits_and_exponent(text);
|
||||
const std::string& digits = de.first;
|
||||
if (digits.size() > 1)
|
||||
{
|
||||
// the decimals of one digit fewer next to the value
|
||||
// (a stream rather than snprintf("%.*e"), whose output GCC cannot bound)
|
||||
std::ostringstream shorter;
|
||||
shorter.imbue(std::locale::classic());
|
||||
shorter << std::scientific << std::setprecision(static_cast<int>(digits.size()) - 2) << v;
|
||||
const auto near = digits_and_exponent(shorter.str());
|
||||
// as an integer with digits.size() - 1 digits
|
||||
std::string m = near.first;
|
||||
int e = near.second;
|
||||
while (m.size() < digits.size() - 1)
|
||||
{
|
||||
m += '0';
|
||||
--e;
|
||||
}
|
||||
const std::uint64_t mid = std::stoull(m);
|
||||
for (const std::uint64_t candidate :
|
||||
{
|
||||
mid - 1, mid, mid + 1
|
||||
})
|
||||
{
|
||||
CAPTURE(candidate)
|
||||
CHECK(!reads_back(std::to_string(candidate), e, v));
|
||||
}
|
||||
}
|
||||
#if defined(JSON_HAS_CPP_17) && defined(__cpp_lib_to_chars)
|
||||
// the closest of the shortest representations, as std::to_chars finds it
|
||||
std::array<char, 64> std_text{};
|
||||
const auto r = std::to_chars(std_text.data(), std_text.data() + std_text.size(), v, std::chars_format::scientific);
|
||||
CHECK(digits_and_exponent(std::string(std_text.data(), r.ptr)) == de);
|
||||
#endif
|
||||
}
|
||||
} // namespace
|
||||
|
||||
TEST_CASE("shortest digits of doubles")
|
||||
{
|
||||
SECTION("powers of ten")
|
||||
{
|
||||
// the 128-bit significands of 10^k, rounded down, recomputed
|
||||
for (int k = -342; k <= 341; ++k)
|
||||
{
|
||||
CAPTURE(k)
|
||||
big x{1};
|
||||
if (k >= 0)
|
||||
{
|
||||
for (int i = 0; i < k; ++i)
|
||||
{
|
||||
big_mul_small(x, 10);
|
||||
}
|
||||
}
|
||||
else
|
||||
{
|
||||
// floor(2^b / 10^-k) for a b that leaves more than 128 bits
|
||||
const int b = 128 + 64 + (4 * -k);
|
||||
x.assign(static_cast<std::size_t>(b / 32) + 1, 0);
|
||||
x.back() = 1u << (b % 32);
|
||||
for (int i = 0; i < -k; ++i)
|
||||
{
|
||||
big_div_small(x, 10);
|
||||
}
|
||||
}
|
||||
const auto expected = big_top128(x);
|
||||
const auto actual = nlohmann::detail::zmij::pow10(k);
|
||||
CHECK(actual.high == expected.first);
|
||||
CHECK(actual.low == expected.second);
|
||||
}
|
||||
}
|
||||
|
||||
SECTION("boundary values")
|
||||
{
|
||||
for (const double v :
|
||||
{
|
||||
std::numeric_limits<double>::min(), std::numeric_limits<double>::max(), std::numeric_limits<double>::denorm_min(),
|
||||
std::nextafter(std::numeric_limits<double>::min(), 0.0), 1.0, 2.0, 0.1, 0.3, 1e21, 1e22, 1e23, 5e-324, 9007199254740993.0,
|
||||
1.2345e+21, 2.2250738585072014e-308, 1.7976931348623157e308, 4.9406564584124654e-324, 123456789012345680.0
|
||||
})
|
||||
{
|
||||
check_shortest(v);
|
||||
}
|
||||
// all powers of two (their rounding interval is narrower below)
|
||||
for (int e = -1074; e <= 1023; ++e)
|
||||
{
|
||||
check_shortest(std::ldexp(1.0, e));
|
||||
}
|
||||
// powers of ten and their neighbors
|
||||
for (int e = -323; e <= 308; ++e)
|
||||
{
|
||||
const double p = std::strtod(("1e" + std::to_string(e)).c_str(), nullptr);
|
||||
check_shortest(p);
|
||||
check_shortest(std::nextafter(p, 0.0));
|
||||
check_shortest(std::nextafter(p, std::numeric_limits<double>::infinity()));
|
||||
}
|
||||
}
|
||||
|
||||
SECTION("random doubles")
|
||||
{
|
||||
std::mt19937_64 rng(5295); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed): reproducible
|
||||
for (int i = 0; i < 100000; ++i)
|
||||
{
|
||||
const std::uint64_t bits = rng() & 0x7FFFFFFFFFFFFFFFu;
|
||||
const auto v = reinterpret_bits<double>(bits);
|
||||
if (std::isfinite(v) && bits != 0)
|
||||
{
|
||||
check_shortest(v);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
Reference in new issue
Block a user