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 <__system_error/errc.h>
  51 #include <cstdint>
  52 #include <cstring>
  53 #include <type_traits>
  54
  55 #include "include/ryu/f2s.h"
  56 #include "include/ryu/d2s.h"
  57 #include "include/ryu/d2fixed.h"
  58
  59 #if defined(_MSC_VER)
  60 #include <intrin.h> // for _umul128(), __shiftright128(), _BitScanForward{,64}
  61 #endif // defined(_MSC_VER)
  62
  63 #if defined(_WIN64) || defined(_M_AMD64) || defined(__x86_64__) ||  defined(__aarch64__)
  64 #define _LIBCPP_64_BIT
  65 #endif
  66
  67 _LIBCPP_BEGIN_NAMESPACE_STD
  68
  69 // https://github.com/ulfjack/ryu/tree/59661c3/ryu
  70
  71 #if !defined(_MSC_VER)
  72 _LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward64(unsigned long* __index, unsigned long long __mask) {
  73   if (__mask == 0) {
  74     return false;
  75   }
  76   *__index = __builtin_ctzll(__mask);
  77   return true;
  78 }
  79
  80 _LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward(unsigned long* __index, unsigned int __mask) {
  81   if (__mask == 0) {
  82     return false;
  83   }
  84   *__index = __builtin_ctz(__mask);
  85   return true;
  86 }
  87 #endif  // !_MSC_VER
  88
  89 template <class _Floating>
  90 [[nodiscard]] to_chars_result _Floating_to_chars_ryu(
  91     char* const _First, char* const _Last, const _Floating _Value, const chars_format _Fmt) noexcept {
  92     if constexpr (_IsSame<_Floating, float>::value) {
  93         return __f2s_buffered_n(_First, _Last, _Value, _Fmt);
  94     } else {
  95         return __d2s_buffered_n(_First, _Last, _Value, _Fmt);
  96     }
  97 }
  98
  99 template <class _Floating>
 100 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_scientific_precision(
 101     char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
 102
 103     // C11 7.21.6.1 "The fprintf function"/5:
 104     // "A negative precision argument is taken as if the precision were omitted."
 105     // /8: "e,E [...] if the precision is missing, it is taken as 6"
 106
 107     if (_Precision < 0) {
 108         _Precision = 6;
 109     } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
 110         // _Precision is ok.
 111     } else {
 112         // Avoid integer overflow.
 113         // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
 114         return {_Last, errc::value_too_large};
 115     }
 116
 117     return __d2exp_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
 118 }
 119
 120 template <class _Floating>
 121 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_fixed_precision(
 122     char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
 123
 124     // C11 7.21.6.1 "The fprintf function"/5:
 125     // "A negative precision argument is taken as if the precision were omitted."
 126     // /8: "f,F [...] If the precision is missing, it is taken as 6"
 127
 128     if (_Precision < 0) {
 129         _Precision = 6;
 130     } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
 131         // _Precision is ok.
 132     } else {
 133         // Avoid integer overflow.
 134         // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
 135         return {_Last, errc::value_too_large};
 136     }
 137
 138     return __d2fixed_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
 139 }
 140
 141 #undef _LIBCPP_64_BIT
 142 #undef _LIBCPP_INTRINSIC128
 143
 144 _LIBCPP_END_NAMESPACE_STD
 145
 146 // clang-format on
 147
 148 #endif // _LIBCPP_SRC_INCLUDE_RYU_RYU_H