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 #ifndef _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H 11 #define _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H 12 13 #include <__algorithm/copy_n.h> 14 #include <__charconv/tables.h> 15 #include <__config> 16 #include <cstdint> 17 #include <limits> 18 19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20 # pragma GCC system_header 21 #endif 22 23 _LIBCPP_PUSH_MACROS 24 #include <__undef_macros> 25 26 _LIBCPP_BEGIN_NAMESPACE_STD 27 28 #if _LIBCPP_STD_VER > 14 29 30 namespace __itoa { 31 32 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append1(char* __first, uint32_t __value) noexcept { 33 *__first = '0' + static_cast<char>(__value); 34 return __first + 1; 35 } 36 37 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append2(char* __first, uint32_t __value) noexcept { 38 return std::copy_n(&__digits_base_10[__value * 2], 2, __first); 39 } 40 41 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append3(char* __first, uint32_t __value) noexcept { 42 return __itoa::__append2(__itoa::__append1(__first, __value / 100), __value % 100); 43 } 44 45 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append4(char* __first, uint32_t __value) noexcept { 46 return __itoa::__append2(__itoa::__append2(__first, __value / 100), __value % 100); 47 } 48 49 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append5(char* __first, uint32_t __value) noexcept { 50 return __itoa::__append4(__itoa::__append1(__first, __value / 10000), __value % 10000); 51 } 52 53 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append6(char* __first, uint32_t __value) noexcept { 54 return __itoa::__append4(__itoa::__append2(__first, __value / 10000), __value % 10000); 55 } 56 57 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append7(char* __first, uint32_t __value) noexcept { 58 return __itoa::__append6(__itoa::__append1(__first, __value / 1000000), __value % 1000000); 59 } 60 61 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append8(char* __first, uint32_t __value) noexcept { 62 return __itoa::__append6(__itoa::__append2(__first, __value / 1000000), __value % 1000000); 63 } 64 65 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append9(char* __first, uint32_t __value) noexcept { 66 return __itoa::__append8(__itoa::__append1(__first, __value / 100000000), __value % 100000000); 67 } 68 69 template <class _Tp> 70 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __append10(char* __first, _Tp __value) noexcept { 71 return __itoa::__append8(__itoa::__append2(__first, static_cast<uint32_t>(__value / 100000000)), 72 static_cast<uint32_t>(__value % 100000000)); 73 } 74 75 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __base_10_u32(char* __first, uint32_t __value) noexcept { 76 if (__value < 1000000) { 77 if (__value < 10000) { 78 if (__value < 100) { 79 // 0 <= __value < 100 80 if (__value < 10) 81 return __itoa::__append1(__first, __value); 82 return __itoa::__append2(__first, __value); 83 } 84 // 100 <= __value < 10'000 85 if (__value < 1000) 86 return __itoa::__append3(__first, __value); 87 return __itoa::__append4(__first, __value); 88 } 89 90 // 10'000 <= __value < 1'000'000 91 if (__value < 100000) 92 return __itoa::__append5(__first, __value); 93 return __itoa::__append6(__first, __value); 94 } 95 96 // __value => 1'000'000 97 if (__value < 100000000) { 98 // 1'000'000 <= __value < 100'000'000 99 if (__value < 10000000) 100 return __itoa::__append7(__first, __value); 101 return __itoa::__append8(__first, __value); 102 } 103 104 // 100'000'000 <= __value < max 105 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* __base_10_u64(char* __buffer, uint64_t __value) noexcept { 111 if (__value <= UINT32_MAX) 112 return __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value)); 113 114 // Numbers in the range UINT32_MAX <= val < 10'000'000'000 always contain 10 115 // digits and are outputted after this if statement. 116 if (__value >= 10000000000) { 117 // This function properly deterimines the first non-zero leading digit. 118 __buffer = __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value / 10000000000)); 119 __value %= 10000000000; 120 } 121 return __itoa::__append10(__buffer, __value); 122 } 123 124 # ifndef _LIBCPP_HAS_NO_INT128 125 /// \returns 10^\a exp 126 /// 127 /// \pre \a exp [19, 39] 128 /// 129 /// \note The lookup table contains a partial set of exponents limiting the 130 /// range that can be used. However the range is sufficient for 131 /// \ref __base_10_u128. 132 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline __uint128_t __pow_10(int __exp) noexcept { 133 _LIBCPP_ASSERT(__exp >= __pow10_128_offset, "Index out of bounds"); 134 return __pow10_128[__exp - __pow10_128_offset]; 135 } 136 137 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __base_10_u128(char* __buffer, __uint128_t __value) noexcept { 138 _LIBCPP_ASSERT( 139 __value > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fail when this isn't true."); 140 141 // Unlike the 64 to 32 bit case the 128 bit case the "upper half" can't be 142 // stored in the "lower half". Instead we first need to handle the top most 143 // digits separately. 144 // 145 // Maximum unsigned values 146 // 64 bit 18'446'744'073'709'551'615 (20 digits) 147 // 128 bit 340'282'366'920'938'463'463'374'607'431'768'211'455 (39 digits) 148 // step 1 ^ ([0-1] digits) 149 // step 2 ^^^^^^^^^^^^^^^^^^^^^^^^^ ([0-19] digits) 150 // step 3 ^^^^^^^^^^^^^^^^^^^^^^^^^ (19 digits) 151 if (__value >= __itoa::__pow_10(38)) { 152 // step 1 153 __buffer = __itoa::__append1(__buffer, static_cast<uint32_t>(__value / __itoa::__pow_10(38))); 154 __value %= __itoa::__pow_10(38); 155 156 // step 2 always 19 digits. 157 // They are handled here since leading zeros need to be appended to the buffer, 158 __buffer = __itoa::__append9(__buffer, static_cast<uint32_t>(__value / __itoa::__pow_10(29))); 159 __value %= __itoa::__pow_10(29); 160 __buffer = __itoa::__append10(__buffer, static_cast<uint64_t>(__value / __itoa::__pow_10(19))); 161 __value %= __itoa::__pow_10(19); 162 } 163 else { 164 // step 2 165 // This version needs to determine the position of the leading non-zero digit. 166 __buffer = __base_10_u64(__buffer, static_cast<uint64_t>(__value / __itoa::__pow_10(19))); 167 __value %= __itoa::__pow_10(19); 168 } 169 170 // Step 3 171 __buffer = __itoa::__append9(__buffer, static_cast<uint32_t>(__value / 10000000000)); 172 __buffer = __itoa::__append10(__buffer, static_cast<uint64_t>(__value % 10000000000)); 173 174 return __buffer; 175 } 176 # endif 177 } // namespace __itoa 178 179 #endif // _LIBCPP_STD_VER > 14 180 181 _LIBCPP_END_NAMESPACE_STD 182 183 _LIBCPP_POP_MACROS 184 185 #endif // _LIBCPP___CHARCONV_TO_CHARS_BASE_10_H 186