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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-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H11#define _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H12 13#include <__algorithm/copy_n.h>14#include <__assert>15#include <__charconv/tables.h>16#include <__config>17#include <cstdint>18#include <limits>19 20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)21# pragma GCC system_header22#endif23 24_LIBCPP_PUSH_MACROS25#include <__undef_macros>26 27_LIBCPP_BEGIN_NAMESPACE_STD28 29namespace __itoa {30 31_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append1(char* __first, uint32_t __value) _NOEXCEPT {32 *__first = '0' + static_cast<char>(__value);33 return __first + 1;34}35 36_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append2(char* __first, uint32_t __value) _NOEXCEPT {37 return std::copy_n(&__digits_base_10[__value * 2], 2, __first);38}39 40_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append3(char* __first, uint32_t __value) _NOEXCEPT {41 return __itoa::__append2(__itoa::__append1(__first, __value / 100), __value % 100);42}43 44_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append4(char* __first, uint32_t __value) _NOEXCEPT {45 return __itoa::__append2(__itoa::__append2(__first, __value / 100), __value % 100);46}47 48_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append5(char* __first, uint32_t __value) _NOEXCEPT {49 return __itoa::__append4(__itoa::__append1(__first, __value / 10000), __value % 10000);50}51 52_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append6(char* __first, uint32_t __value) _NOEXCEPT {53 return __itoa::__append4(__itoa::__append2(__first, __value / 10000), __value % 10000);54}55 56_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append7(char* __first, uint32_t __value) _NOEXCEPT {57 return __itoa::__append6(__itoa::__append1(__first, __value / 1000000), __value % 1000000);58}59 60_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append8(char* __first, uint32_t __value) _NOEXCEPT {61 return __itoa::__append6(__itoa::__append2(__first, __value / 1000000), __value % 1000000);62}63 64_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append9(char* __first, uint32_t __value) _NOEXCEPT {65 return __itoa::__append8(__itoa::__append1(__first, __value / 100000000), __value % 100000000);66}67 68template <class _Tp>69_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __append10(char* __first, _Tp __value) _NOEXCEPT {70 return __itoa::__append8(__itoa::__append2(__first, static_cast<uint32_t>(__value / 100000000)),71 static_cast<uint32_t>(__value % 100000000));72}73 74_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*75__base_10_u32(char* __first, uint32_t __value) _NOEXCEPT {76 if (__value < 1000000) {77 if (__value < 10000) {78 if (__value < 100) {79 // 0 <= __value < 10080 if (__value < 10)81 return __itoa::__append1(__first, __value);82 return __itoa::__append2(__first, __value);83 }84 // 100 <= __value < 10'00085 if (__value < 1000)86 return __itoa::__append3(__first, __value);87 return __itoa::__append4(__first, __value);88 }89 90 // 10'000 <= __value < 1'000'00091 if (__value < 100000)92 return __itoa::__append5(__first, __value);93 return __itoa::__append6(__first, __value);94 }95 96 // __value => 1'000'00097 if (__value < 100000000) {98 // 1'000'000 <= __value < 100'000'00099 if (__value < 10000000)100 return __itoa::__append7(__first, __value);101 return __itoa::__append8(__first, __value);102 }103 104 // 100'000'000 <= __value < max105 if (__value < 1000000000)106 return __itoa::__append9(__first, __value);107 return __itoa::__append10(__first, __value);108}109 110_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*111__base_10_u64(char* __buffer, uint64_t __value) _NOEXCEPT {112 if (__value <= UINT32_MAX)113 return __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value));114 115 // Numbers in the range UINT32_MAX <= val < 10'000'000'000 always contain 10116 // digits and are outputted after this if statement.117 if (__value >= 10000000000) {118 // This function properly deterimines the first non-zero leading digit.119 __buffer = __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value / 10000000000));120 __value %= 10000000000;121 }122 return __itoa::__append10(__buffer, __value);123}124 125# if _LIBCPP_HAS_INT128126/// \returns 10^\a exp127///128/// \pre \a exp [19, 39]129///130/// \note The lookup table contains a partial set of exponents limiting the131/// range that can be used. However the range is sufficient for132/// \ref __base_10_u128.133_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline __uint128_t __pow_10(int __exp) _NOEXCEPT {134 _LIBCPP_ASSERT_INTERNAL(__exp >= __pow10_128_offset, "Index out of bounds");135 return __pow10_128[__exp - __pow10_128_offset];136}137 138_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*139__base_10_u128(char* __buffer, __uint128_t __value) _NOEXCEPT {140 _LIBCPP_ASSERT_INTERNAL(141 __value > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fails when this isn't true.");142 143 // Unlike the 64 to 32 bit case the 128 bit case the "upper half" can't be144 // stored in the "lower half". Instead we first need to handle the top most145 // digits separately.146 //147 // Maximum unsigned values148 // 64 bit 18'446'744'073'709'551'615 (20 digits)149 // 128 bit 340'282'366'920'938'463'463'374'607'431'768'211'455 (39 digits)150 // step 1 ^ ([0-1] digits)151 // step 2 ^^^^^^^^^^^^^^^^^^^^^^^^^ ([0-19] digits)152 // step 3 ^^^^^^^^^^^^^^^^^^^^^^^^^ (19 digits)153 if (__value >= __itoa::__pow_10(38)) {154 // step 1155 __buffer = __itoa::__append1(__buffer, static_cast<uint32_t>(__value / __itoa::__pow_10(38)));156 __value %= __itoa::__pow_10(38);157 158 // step 2 always 19 digits.159 // They are handled here since leading zeros need to be appended to the buffer,160 __buffer = __itoa::__append9(__buffer, static_cast<uint32_t>(__value / __itoa::__pow_10(29)));161 __value %= __itoa::__pow_10(29);162 __buffer = __itoa::__append10(__buffer, static_cast<uint64_t>(__value / __itoa::__pow_10(19)));163 __value %= __itoa::__pow_10(19);164 } else {165 // step 2166 // This version needs to determine the position of the leading non-zero digit.167 __buffer = __base_10_u64(__buffer, static_cast<uint64_t>(__value / __itoa::__pow_10(19)));168 __value %= __itoa::__pow_10(19);169 }170 171 // Step 3172 __buffer = __itoa::__append9(__buffer, static_cast<uint32_t>(__value / 10000000000));173 __buffer = __itoa::__append10(__buffer, static_cast<uint64_t>(__value % 10000000000));174 175 return __buffer;176}177# endif178} // namespace __itoa179 180_LIBCPP_END_NAMESPACE_STD181 182_LIBCPP_POP_MACROS183 184#endif // _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H185