libcxx/src/include/ryu/common.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // Copyright (c) Microsoft Corporation.
  10 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  11
  12 // Copyright 2018 Ulf Adams
  13 // Copyright (c) Microsoft Corporation. All rights reserved.
  14
  15 // Boost Software License - Version 1.0 - August 17th, 2003
  16
  17 // Permission is hereby granted, free of charge, to any person or organization
  18 // obtaining a copy of the software and accompanying documentation covered by
  19 // this license (the "Software") to use, reproduce, display, distribute,
  20 // execute, and transmit the Software, and to prepare derivative works of the
  21 // Software, and to permit third-parties to whom the Software is furnished to
  22 // do so, all subject to the following:
  23
  24 // The copyright notices in the Software and this entire statement, including
  25 // the above license grant, this restriction and the following disclaimer,
  26 // must be included in all copies of the Software, in whole or in part, and
  27 // all derivative works of the Software, unless such copies or derivative
  28 // works are solely in the form of machine-executable object code generated by
  29 // a source language processor.
  30
  31 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  32 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  33 // FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
  34 // SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
  35 // FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
  36 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  37 // DEALINGS IN THE SOFTWARE.
  38
  39 #ifndef _LIBCPP_SRC_INCLUDE_RYU_COMMON_H
  40 #define _LIBCPP_SRC_INCLUDE_RYU_COMMON_H
  41
  42 // Avoid formatting to keep the changes with the original code minimal.
  43 // clang-format off
  44
  45 #include <__assert>
  46 #include <__config>
  47 #include <cstring>
  48
  49 _LIBCPP_BEGIN_NAMESPACE_STD
  50
  51 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __decimalLength9(const uint32_t __v) {
  52   // Function precondition: __v is not a 10-digit number.
  53   // (f2s: 9 digits are sufficient for round-tripping.)
  54   // (d2fixed: We print 9-digit blocks.)
  55   _LIBCPP_ASSERT_INTERNAL(__v < 1000000000, "");
  56   if (__v >= 100000000) { return 9; }
  57   if (__v >= 10000000) { return 8; }
  58   if (__v >= 1000000) { return 7; }
  59   if (__v >= 100000) { return 6; }
  60   if (__v >= 10000) { return 5; }
  61   if (__v >= 1000) { return 4; }
  62   if (__v >= 100) { return 3; }
  63   if (__v >= 10) { return 2; }
  64   return 1;
  65 }
  66
  67 // Returns __e == 0 ? 1 : ceil(log_2(5^__e)).
  68 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI  inline int32_t __pow5bits(const int32_t __e) {
  69   // This approximation works up to the point that the multiplication overflows at __e = 3529.
  70   // If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater
  71   // than 2^9297.
  72   _LIBCPP_ASSERT_INTERNAL(__e >= 0, "");
  73   _LIBCPP_ASSERT_INTERNAL(__e <= 3528, "");
  74   return static_cast<int32_t>(((static_cast<uint32_t>(__e) * 1217359) >> 19) + 1);
  75 }
  76
  77 // Returns floor(log_10(2^__e)).
  78 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI  inline uint32_t __log10Pow2(const int32_t __e) {
  79   // The first value this approximation fails for is 2^1651 which is just greater than 10^297.
  80   _LIBCPP_ASSERT_INTERNAL(__e >= 0, "");
  81   _LIBCPP_ASSERT_INTERNAL(__e <= 1650, "");
  82   return (static_cast<uint32_t>(__e) * 78913) >> 18;
  83 }
  84
  85 // Returns floor(log_10(5^__e)).
  86 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __log10Pow5(const int32_t __e) {
  87   // The first value this approximation fails for is 5^2621 which is just greater than 10^1832.
  88   _LIBCPP_ASSERT_INTERNAL(__e >= 0, "");
  89   _LIBCPP_ASSERT_INTERNAL(__e <= 2620, "");
  90   return (static_cast<uint32_t>(__e) * 732923) >> 20;
  91 }
  92
  93 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __float_to_bits(const float __f) {
  94   uint32_t __bits = 0;
  95   std::memcpy(&__bits, &__f, sizeof(float));
  96   return __bits;
  97 }
  98
  99 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __double_to_bits(const double __d) {
 100   uint64_t __bits = 0;
 101   std::memcpy(&__bits, &__d, sizeof(double));
 102   return __bits;
 103 }
 104
 105 _LIBCPP_END_NAMESPACE_STD
 106
 107 // clang-format on
 108
 109 #endif // _LIBCPP_SRC_INCLUDE_RYU_COMMON_H