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
  14 // Copyright 2018 Ulf Adams
  15 // Copyright (c) Microsoft Corporation. All rights reserved.
  16
  17 // Boost Software License - Version 1.0 - August 17th, 2003
  18
  19 // Permission is hereby granted, free of charge, to any person or organization
  20 // obtaining a copy of the software and accompanying documentation covered by
  21 // this license (the "Software") to use, reproduce, display, distribute,
  22 // execute, and transmit the Software, and to prepare derivative works of the
  23 // Software, and to permit third-parties to whom the Software is furnished to
  24 // do so, all subject to the following:
  25
  26 // The copyright notices in the Software and this entire statement, including
  27 // the above license grant, this restriction and the following disclaimer,
  28 // must be included in all copies of the Software, in whole or in part, and
  29 // all derivative works of the Software, unless such copies or derivative
  30 // works are solely in the form of machine-executable object code generated by
  31 // a source language processor.
  32
  33 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  34 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  35 // FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
  36 // SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
  37 // FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
  38 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  39 // DEALINGS IN THE SOFTWARE.
  40
  41 #ifndef _LIBCPP_SRC_INCLUDE_RYU_RYU_H
  42 #define _LIBCPP_SRC_INCLUDE_RYU_RYU_H
  43
  44 // Avoid formatting to keep the changes with the original code minimal.
  45 // clang-format off
  46
  47 #include <__charconv/chars_format.h>
  48 #include <__charconv/to_chars_result.h>
  49 #include <__config>
  50 #include <__debug>
  51 #include <__errc>
  52 #include <cstdint>
  53 #include <cstring>
  54 #include <type_traits>
  55
  56 #include "include/ryu/f2s.h"
  57 #include "include/ryu/d2s.h"
  58 #include "include/ryu/d2fixed.h"
  59
  60 #if defined(_MSC_VER)
  61 #include <intrin.h> // for _umul128(), __shiftright128(), _BitScanForward{,64}
  62 #endif // defined(_MSC_VER)
  63
  64 #if defined(_WIN64) || defined(_M_AMD64) || defined(__x86_64__) ||  defined(__aarch64__)
  65 #define _LIBCPP_64_BIT
  66 #endif
  67
  68 _LIBCPP_BEGIN_NAMESPACE_STD
  69
  70 // https://github.com/ulfjack/ryu/tree/59661c3/ryu
  71
  72 #if !defined(_MSC_VER)
  73 _LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward64(unsigned long* __index, unsigned long long __mask) {
  74   if (__mask == 0) {
  75     return false;
  76   }
  77   *__index = __builtin_ctzll(__mask);
  78   return true;
  79 }
  80
  81 _LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward(unsigned long* __index, unsigned int __mask) {
  82   if (__mask == 0) {
  83     return false;
  84   }
  85   *__index = __builtin_ctz(__mask);
  86   return true;
  87 }
  88 #endif  // !_MSC_VER
  89
  90 template <class _Floating>
  91 [[nodiscard]] to_chars_result _Floating_to_chars_ryu(
  92     char* const _First, char* const _Last, const _Floating _Value, const chars_format _Fmt) noexcept {
  93     if constexpr (_IsSame<_Floating, float>::value) {
  94         return __f2s_buffered_n(_First, _Last, _Value, _Fmt);
  95     } else {
  96         return __d2s_buffered_n(_First, _Last, _Value, _Fmt);
  97     }
  98 }
  99
 100 template <class _Floating>
 101 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_scientific_precision(
 102     char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
 103
 104     // C11 7.21.6.1 "The fprintf function"/5:
 105     // "A negative precision argument is taken as if the precision were omitted."
 106     // /8: "e,E [...] if the precision is missing, it is taken as 6"
 107
 108     if (_Precision < 0) {
 109         _Precision = 6;
 110     } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
 111         // _Precision is ok.
 112     } else {
 113         // Avoid integer overflow.
 114         // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
 115         return {_Last, errc::value_too_large};
 116     }
 117
 118     return __d2exp_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
 119 }
 120
 121 template <class _Floating>
 122 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_fixed_precision(
 123     char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
 124
 125     // C11 7.21.6.1 "The fprintf function"/5:
 126     // "A negative precision argument is taken as if the precision were omitted."
 127     // /8: "f,F [...] If the precision is missing, it is taken as 6"
 128
 129     if (_Precision < 0) {
 130         _Precision = 6;
 131     } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
 132         // _Precision is ok.
 133     } else {
 134         // Avoid integer overflow.
 135         // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
 136         return {_Last, errc::value_too_large};
 137     }
 138
 139     return __d2fixed_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
 140 }
 141
 142 #undef _LIBCPP_64_BIT
 143 #undef _LIBCPP_INTRINSIC128
 144
 145 _LIBCPP_END_NAMESPACE_STD
 146
 147 // clang-format on
 148
 149 #endif // _LIBCPP_SRC_INCLUDE_RYU_RYU_H