libcxx/src/include/ryu/ryu.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 // Copyright (c) Microsoft Corporation.
  11 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  12
  13 // Copyright 2018 Ulf Adams
  14 // Copyright (c) Microsoft Corporation. All rights reserved.
  15
  16 // Boost Software License - Version 1.0 - August 17th, 2003
  17
  18 // Permission is hereby granted, free of charge, to any person or organization
  19 // obtaining a copy of the software and accompanying documentation covered by
  20 // this license (the "Software") to use, reproduce, display, distribute,
  21 // execute, and transmit the Software, and to prepare derivative works of the
  22 // Software, and to permit third-parties to whom the Software is furnished to
  23 // do so, all subject to the following:
  24
  25 // The copyright notices in the Software and this entire statement, including
  26 // the above license grant, this restriction and the following disclaimer,
  27 // must be included in all copies of the Software, in whole or in part, and
  28 // all derivative works of the Software, unless such copies or derivative
  29 // works are solely in the form of machine-executable object code generated by
  30 // a source language processor.
  31
  32 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  33 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  34 // FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
  35 // SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
  36 // FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
  37 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  38 // DEALINGS IN THE SOFTWARE.
  39
  40 #ifndef _LIBCPP_SRC_INCLUDE_RYU_RYU_H
  41 #define _LIBCPP_SRC_INCLUDE_RYU_RYU_H
  42
  43 // Avoid formatting to keep the changes with the original code minimal.
  44 // clang-format off
  45
  46 #include <__charconv/chars_format.h>
  47 #include <__charconv/to_chars_result.h>
  48 #include <__config>
  49 #include <__system_error/errc.h>
  50 #include <cstdint>
  51 #include <cstring>
  52 #include <type_traits>
  53
  54 #include "include/ryu/f2s.h"
  55 #include "include/ryu/d2s.h"
  56 #include "include/ryu/d2fixed.h"
  57
  58 #if defined(_MSC_VER)
  59 #include <intrin.h> // for _umul128(), __shiftright128(), _BitScanForward{,64}
  60 #endif // defined(_MSC_VER)
  61
  62 #if defined(_WIN64) || defined(_M_AMD64) || defined(__x86_64__) ||  defined(__aarch64__)
  63 #define _LIBCPP_64_BIT
  64 #endif
  65
  66 _LIBCPP_BEGIN_NAMESPACE_STD
  67
  68 // https://github.com/ulfjack/ryu/tree/59661c3/ryu
  69
  70 #if !defined(_MSC_VER)
  71 _LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward64(unsigned long* __index, unsigned long long __mask) {
  72   if (__mask == 0) {
  73     return false;
  74   }
  75   *__index = __builtin_ctzll(__mask);
  76   return true;
  77 }
  78
  79 _LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward(unsigned long* __index, unsigned int __mask) {
  80   if (__mask == 0) {
  81     return false;
  82   }
  83   *__index = __builtin_ctz(__mask);
  84   return true;
  85 }
  86 #endif  // !_MSC_VER
  87
  88 template <class _Floating>
  89 [[nodiscard]] to_chars_result _Floating_to_chars_ryu(
  90     char* const _First, char* const _Last, const _Floating _Value, const chars_format _Fmt) noexcept {
  91     if constexpr (_IsSame<_Floating, float>::value) {
  92         return __f2s_buffered_n(_First, _Last, _Value, _Fmt);
  93     } else {
  94         return __d2s_buffered_n(_First, _Last, _Value, _Fmt);
  95     }
  96 }
  97
  98 template <class _Floating>
  99 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_scientific_precision(
 100     char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
 101
 102     // C11 7.21.6.1 "The fprintf function"/5:
 103     // "A negative precision argument is taken as if the precision were omitted."
 104     // /8: "e,E [...] if the precision is missing, it is taken as 6"
 105
 106     if (_Precision < 0) {
 107         _Precision = 6;
 108     } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
 109         // _Precision is ok.
 110     } else {
 111         // Avoid integer overflow.
 112         // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
 113         return {_Last, errc::value_too_large};
 114     }
 115
 116     return __d2exp_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
 117 }
 118
 119 template <class _Floating>
 120 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_fixed_precision(
 121     char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
 122
 123     // C11 7.21.6.1 "The fprintf function"/5:
 124     // "A negative precision argument is taken as if the precision were omitted."
 125     // /8: "f,F [...] If the precision is missing, it is taken as 6"
 126
 127     if (_Precision < 0) {
 128         _Precision = 6;
 129     } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
 130         // _Precision is ok.
 131     } else {
 132         // Avoid integer overflow.
 133         // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
 134         return {_Last, errc::value_too_large};
 135     }
 136
 137     return __d2fixed_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
 138 }
 139
 140 #undef _LIBCPP_64_BIT
 141 #undef _LIBCPP_INTRINSIC128
 142
 143 _LIBCPP_END_NAMESPACE_STD
 144
 145 // clang-format on
 146
 147 #endif // _LIBCPP_SRC_INCLUDE_RYU_RYU_H