diff options
Diffstat (limited to 'lib/libcxx/src/ryu/d2fixed.cpp')
| -rw-r--r-- | lib/libcxx/src/ryu/d2fixed.cpp | 669 |
1 files changed, 669 insertions, 0 deletions
diff --git a/lib/libcxx/src/ryu/d2fixed.cpp b/lib/libcxx/src/ryu/d2fixed.cpp new file mode 100644 index 0000000000..699f9158f4 --- /dev/null +++ b/lib/libcxx/src/ryu/d2fixed.cpp @@ -0,0 +1,669 @@ +//===----------------------------------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +// Copyright (c) Microsoft Corporation. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception + +// Copyright 2018 Ulf Adams +// Copyright (c) Microsoft Corporation. All rights reserved. + +// Boost Software License - Version 1.0 - August 17th, 2003 + +// Permission is hereby granted, free of charge, to any person or organization +// obtaining a copy of the software and accompanying documentation covered by +// this license (the "Software") to use, reproduce, display, distribute, +// execute, and transmit the Software, and to prepare derivative works of the +// Software, and to permit third-parties to whom the Software is furnished to +// do so, all subject to the following: + +// The copyright notices in the Software and this entire statement, including +// the above license grant, this restriction and the following disclaimer, +// must be included in all copies of the Software, in whole or in part, and +// all derivative works of the Software, unless such copies or derivative +// works are solely in the form of machine-executable object code generated by +// a source language processor. + +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT +// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE +// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, +// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +// DEALINGS IN THE SOFTWARE. + +// Avoid formatting to keep the changes with the original code minimal. +// clang-format off + +#include "__config" +#include "charconv" +#include "cstring" +#include "system_error" + +#include "include/ryu/common.h" +#include "include/ryu/d2fixed.h" +#include "include/ryu/d2fixed_full_table.h" +#include "include/ryu/d2s.h" +#include "include/ryu/d2s_intrinsics.h" +#include "include/ryu/digit_table.h" + +_LIBCPP_BEGIN_NAMESPACE_STD + +inline constexpr int __POW10_ADDITIONAL_BITS = 120; + +#ifdef _LIBCPP_INTRINSIC128 +// Returns the low 64 bits of the high 128 bits of the 256-bit product of a and b. +[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __umul256_hi128_lo64( + const uint64_t __aHi, const uint64_t __aLo, const uint64_t __bHi, const uint64_t __bLo) { + uint64_t __b00Hi; + const uint64_t __b00Lo = __ryu_umul128(__aLo, __bLo, &__b00Hi); + uint64_t __b01Hi; + const uint64_t __b01Lo = __ryu_umul128(__aLo, __bHi, &__b01Hi); + uint64_t __b10Hi; + const uint64_t __b10Lo = __ryu_umul128(__aHi, __bLo, &__b10Hi); + uint64_t __b11Hi; + const uint64_t __b11Lo = __ryu_umul128(__aHi, __bHi, &__b11Hi); + (void) __b00Lo; // unused + (void) __b11Hi; // unused + const uint64_t __temp1Lo = __b10Lo + __b00Hi; + const uint64_t __temp1Hi = __b10Hi + (__temp1Lo < __b10Lo); + const uint64_t __temp2Lo = __b01Lo + __temp1Lo; + const uint64_t __temp2Hi = __b01Hi + (__temp2Lo < __b01Lo); + return __b11Lo + __temp1Hi + __temp2Hi; +} + +[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __uint128_mod1e9(const uint64_t __vHi, const uint64_t __vLo) { + // After multiplying, we're going to shift right by 29, then truncate to uint32_t. + // This means that we need only 29 + 32 = 61 bits, so we can truncate to uint64_t before shifting. + const uint64_t __multiplied = __umul256_hi128_lo64(__vHi, __vLo, 0x89705F4136B4A597u, 0x31680A88F8953031u); + + // For uint32_t truncation, see the __mod1e9() comment in d2s_intrinsics.h. + const uint32_t __shifted = static_cast<uint32_t>(__multiplied >> 29); + + return static_cast<uint32_t>(__vLo) - 1000000000 * __shifted; +} +#endif // ^^^ intrinsics available ^^^ + +[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mulShift_mod1e9(const uint64_t __m, const uint64_t* const __mul, const int32_t __j) { + uint64_t __high0; // 64 + const uint64_t __low0 = __ryu_umul128(__m, __mul[0], &__high0); // 0 + uint64_t __high1; // 128 + const uint64_t __low1 = __ryu_umul128(__m, __mul[1], &__high1); // 64 + uint64_t __high2; // 192 + const uint64_t __low2 = __ryu_umul128(__m, __mul[2], &__high2); // 128 + const uint64_t __s0low = __low0; // 0 + (void) __s0low; // unused + const uint64_t __s0high = __low1 + __high0; // 64 + const uint32_t __c1 = __s0high < __low1; + const uint64_t __s1low = __low2 + __high1 + __c1; // 128 + const uint32_t __c2 = __s1low < __low2; // __high1 + __c1 can't overflow, so compare against __low2 + const uint64_t __s1high = __high2 + __c2; // 192 + _LIBCPP_ASSERT(__j >= 128, ""); + _LIBCPP_ASSERT(__j <= 180, ""); +#ifdef _LIBCPP_INTRINSIC128 + const uint32_t __dist = static_cast<uint32_t>(__j - 128); // __dist: [0, 52] + const uint64_t __shiftedhigh = __s1high >> __dist; + const uint64_t __shiftedlow = __ryu_shiftright128(__s1low, __s1high, __dist); + return __uint128_mod1e9(__shiftedhigh, __shiftedlow); +#else // ^^^ intrinsics available ^^^ / vvv intrinsics unavailable vvv + if (__j < 160) { // __j: [128, 160) + const uint64_t __r0 = __mod1e9(__s1high); + const uint64_t __r1 = __mod1e9((__r0 << 32) | (__s1low >> 32)); + const uint64_t __r2 = ((__r1 << 32) | (__s1low & 0xffffffff)); + return __mod1e9(__r2 >> (__j - 128)); + } else { // __j: [160, 192) + const uint64_t __r0 = __mod1e9(__s1high); + const uint64_t __r1 = ((__r0 << 32) | (__s1low >> 32)); + return __mod1e9(__r1 >> (__j - 160)); + } +#endif // ^^^ intrinsics unavailable ^^^ +} + +void __append_n_digits(const uint32_t __olength, uint32_t __digits, char* const __result) { + uint32_t __i = 0; + while (__digits >= 10000) { +#ifdef __clang__ // TRANSITION, LLVM-38217 + const uint32_t __c = __digits - 10000 * (__digits / 10000); +#else + const uint32_t __c = __digits % 10000; +#endif + __digits /= 10000; + const uint32_t __c0 = (__c % 100) << 1; + const uint32_t __c1 = (__c / 100) << 1; + _VSTD::memcpy(__result + __olength - __i - 2, __DIGIT_TABLE + __c0, 2); + _VSTD::memcpy(__result + __olength - __i - 4, __DIGIT_TABLE + __c1, 2); + __i += 4; + } + if (__digits >= 100) { + const uint32_t __c = (__digits % 100) << 1; + __digits /= 100; + _VSTD::memcpy(__result + __olength - __i - 2, __DIGIT_TABLE + __c, 2); + __i += 2; + } + if (__digits >= 10) { + const uint32_t __c = __digits << 1; + _VSTD::memcpy(__result + __olength - __i - 2, __DIGIT_TABLE + __c, 2); + } else { + __result[0] = static_cast<char>('0' + __digits); + } +} + +_LIBCPP_HIDE_FROM_ABI inline void __append_d_digits(const uint32_t __olength, uint32_t __digits, char* const __result) { + uint32_t __i = 0; + while (__digits >= 10000) { +#ifdef __clang__ // TRANSITION, LLVM-38217 + const uint32_t __c = __digits - 10000 * (__digits / 10000); +#else + const uint32_t __c = __digits % 10000; +#endif + __digits /= 10000; + const uint32_t __c0 = (__c % 100) << 1; + const uint32_t __c1 = (__c / 100) << 1; + _VSTD::memcpy(__result + __olength + 1 - __i - 2, __DIGIT_TABLE + __c0, 2); + _VSTD::memcpy(__result + __olength + 1 - __i - 4, __DIGIT_TABLE + __c1, 2); + __i += 4; + } + if (__digits >= 100) { + const uint32_t __c = (__digits % 100) << 1; + __digits /= 100; + _VSTD::memcpy(__result + __olength + 1 - __i - 2, __DIGIT_TABLE + __c, 2); + __i += 2; + } + if (__digits >= 10) { + const uint32_t __c = __digits << 1; + __result[2] = __DIGIT_TABLE[__c + 1]; + __result[1] = '.'; + __result[0] = __DIGIT_TABLE[__c]; + } else { + __result[1] = '.'; + __result[0] = static_cast<char>('0' + __digits); + } +} + +_LIBCPP_HIDE_FROM_ABI inline void __append_c_digits(const uint32_t __count, uint32_t __digits, char* const __result) { + uint32_t __i = 0; + for (; __i < __count - 1; __i += 2) { + const uint32_t __c = (__digits % 100) << 1; + __digits /= 100; + _VSTD::memcpy(__result + __count - __i - 2, __DIGIT_TABLE + __c, 2); + } + if (__i < __count) { + const char __c = static_cast<char>('0' + (__digits % 10)); + __result[__count - __i - 1] = __c; + } +} + +void __append_nine_digits(uint32_t __digits, char* const __result) { + if (__digits == 0) { + _VSTD::memset(__result, '0', 9); + return; + } + + for (uint32_t __i = 0; __i < 5; __i += 4) { +#ifdef __clang__ // TRANSITION, LLVM-38217 + const uint32_t __c = __digits - 10000 * (__digits / 10000); +#else + const uint32_t __c = __digits % 10000; +#endif + __digits /= 10000; + const uint32_t __c0 = (__c % 100) << 1; + const uint32_t __c1 = (__c / 100) << 1; + _VSTD::memcpy(__result + 7 - __i, __DIGIT_TABLE + __c0, 2); + _VSTD::memcpy(__result + 5 - __i, __DIGIT_TABLE + __c1, 2); + } + __result[0] = static_cast<char>('0' + __digits); +} + +[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __indexForExponent(const uint32_t __e) { + return (__e + 15) / 16; +} + +[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __pow10BitsForIndex(const uint32_t __idx) { + return 16 * __idx + __POW10_ADDITIONAL_BITS; +} + +[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __lengthForIndex(const uint32_t __idx) { + // +1 for ceil, +16 for mantissa, +8 to round up when dividing by 9 + return (__log10Pow2(16 * static_cast<int32_t>(__idx)) + 1 + 16 + 8) / 9; +} + +[[nodiscard]] to_chars_result __d2fixed_buffered_n(char* _First, char* const _Last, const double __d, + const uint32_t __precision) { + char* const _Original_first = _First; + + const uint64_t __bits = __double_to_bits(__d); + + // Case distinction; exit early for the easy cases. + if (__bits == 0) { + const int32_t _Total_zero_length = 1 // leading zero + + static_cast<int32_t>(__precision != 0) // possible decimal point + + static_cast<int32_t>(__precision); // zeroes after decimal point + + if (_Last - _First < _Total_zero_length) { + return { _Last, errc::value_too_large }; + } + + *_First++ = '0'; + if (__precision > 0) { + *_First++ = '.'; + _VSTD::memset(_First, '0', __precision); + _First += __precision; + } + return { _First, errc{} }; + } + + // Decode __bits into mantissa and exponent. + const uint64_t __ieeeMantissa = __bits & ((1ull << __DOUBLE_MANTISSA_BITS) - 1); + const uint32_t __ieeeExponent = static_cast<uint32_t>(__bits >> __DOUBLE_MANTISSA_BITS); + + int32_t __e2; + uint64_t __m2; + if (__ieeeExponent == 0) { + __e2 = 1 - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS; + __m2 = __ieeeMantissa; + } else { + __e2 = static_cast<int32_t>(__ieeeExponent) - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS; + __m2 = (1ull << __DOUBLE_MANTISSA_BITS) | __ieeeMantissa; + } + + bool __nonzero = false; + if (__e2 >= -52) { + const uint32_t __idx = __e2 < 0 ? 0 : __indexForExponent(static_cast<uint32_t>(__e2)); + const uint32_t __p10bits = __pow10BitsForIndex(__idx); + const int32_t __len = static_cast<int32_t>(__lengthForIndex(__idx)); + for (int32_t __i = __len - 1; __i >= 0; --__i) { + const uint32_t __j = __p10bits - __e2; + // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is + // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers. + const uint32_t __digits = __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT[__POW10_OFFSET[__idx] + __i], + static_cast<int32_t>(__j + 8)); + if (__nonzero) { + if (_Last - _First < 9) { + return { _Last, errc::value_too_large }; + } + __append_nine_digits(__digits, _First); + _First += 9; + } else if (__digits != 0) { + const uint32_t __olength = __decimalLength9(__digits); + if (_Last - _First < static_cast<ptrdiff_t>(__olength)) { + return { _Last, errc::value_too_large }; + } + __append_n_digits(__olength, __digits, _First); + _First += __olength; + __nonzero = true; + } + } + } + if (!__nonzero) { + if (_First == _Last) { + return { _Last, errc::value_too_large }; + } + *_First++ = '0'; + } + if (__precision > 0) { + if (_First == _Last) { + return { _Last, errc::value_too_large }; + } + *_First++ = '.'; + } + if (__e2 < 0) { + const int32_t __idx = -__e2 / 16; + const uint32_t __blocks = __precision / 9 + 1; + // 0 = don't round up; 1 = round up unconditionally; 2 = round up if odd. + int __roundUp = 0; + uint32_t __i = 0; + if (__blocks <= __MIN_BLOCK_2[__idx]) { + __i = __blocks; + if (_Last - _First < static_cast<ptrdiff_t>(__precision)) { + return { _Last, errc::value_too_large }; + } + _VSTD::memset(_First, '0', __precision); + _First += __precision; + } else if (__i < __MIN_BLOCK_2[__idx]) { + __i = __MIN_BLOCK_2[__idx]; + if (_Last - _First < static_cast<ptrdiff_t>(9 * __i)) { + return { _Last, errc::value_too_large }; + } + _VSTD::memset(_First, '0', 9 * __i); + _First += 9 * __i; + } + for (; __i < __blocks; ++__i) { + const int32_t __j = __ADDITIONAL_BITS_2 + (-__e2 - 16 * __idx); + const uint32_t __p = __POW10_OFFSET_2[__idx] + __i - __MIN_BLOCK_2[__idx]; + if (__p >= __POW10_OFFSET_2[__idx + 1]) { + // If the remaining digits are all 0, then we might as well use memset. + // No rounding required in this case. + const uint32_t __fill = __precision - 9 * __i; + if (_Last - _First < static_cast<ptrdiff_t>(__fill)) { + return { _Last, errc::value_too_large }; + } + _VSTD::memset(_First, '0', __fill); + _First += __fill; + break; + } + // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is + // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers. + uint32_t __digits = __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT_2[__p], __j + 8); + if (__i < __blocks - 1) { + if (_Last - _First < 9) { + return { _Last, errc::value_too_large }; + } + __append_nine_digits(__digits, _First); + _First += 9; + } else { + const uint32_t __maximum = __precision - 9 * __i; + uint32_t __lastDigit = 0; + for (uint32_t __k = 0; __k < 9 - __maximum; ++__k) { + __lastDigit = __digits % 10; + __digits /= 10; + } + if (__lastDigit != 5) { + __roundUp = __lastDigit > 5; + } else { + // Is m * 10^(additionalDigits + 1) / 2^(-__e2) integer? + const int32_t __requiredTwos = -__e2 - static_cast<int32_t>(__precision) - 1; + const bool __trailingZeros = __requiredTwos <= 0 + || (__requiredTwos < 60 && __multipleOfPowerOf2(__m2, static_cast<uint32_t>(__requiredTwos))); + __roundUp = __trailingZeros ? 2 : 1; + } + if (__maximum > 0) { + if (_Last - _First < static_cast<ptrdiff_t>(__maximum)) { + return { _Last, errc::value_too_large }; + } + __append_c_digits(__maximum, __digits, _First); + _First += __maximum; + } + break; + } + } + if (__roundUp != 0) { + char* _Round = _First; + char* _Dot = _Last; + while (true) { + if (_Round == _Original_first) { + _Round[0] = '1'; + if (_Dot != _Last) { + _Dot[0] = '0'; + _Dot[1] = '.'; + } + if (_First == _Last) { + return { _Last, errc::value_too_large }; + } + *_First++ = '0'; + break; + } + --_Round; + const char __c = _Round[0]; + if (__c == '.') { + _Dot = _Round; + } else if (__c == '9') { + _Round[0] = '0'; + __roundUp = 1; + } else { + if (__roundUp == 1 || __c % 2 != 0) { + _Round[0] = __c + 1; + } + break; + } + } + } + } else { + if (_Last - _First < static_cast<ptrdiff_t>(__precision)) { + return { _Last, errc::value_too_large }; + } + _VSTD::memset(_First, '0', __precision); + _First += __precision; + } + return { _First, errc{} }; +} + +[[nodiscard]] to_chars_result __d2exp_buffered_n(char* _First, char* const _Last, const double __d, + uint32_t __precision) { + char* const _Original_first = _First; + + const uint64_t __bits = __double_to_bits(__d); + + // Case distinction; exit early for the easy cases. + if (__bits == 0) { + const int32_t _Total_zero_length = 1 // leading zero + + static_cast<int32_t>(__precision != 0) // possible decimal point + + static_cast<int32_t>(__precision) // zeroes after decimal point + + 4; // "e+00" + if (_Last - _First < _Total_zero_length) { + return { _Last, errc::value_too_large }; + } + *_First++ = '0'; + if (__precision > 0) { + *_First++ = '.'; + _VSTD::memset(_First, '0', __precision); + _First += __precision; + } + _VSTD::memcpy(_First, "e+00", 4); + _First += 4; + return { _First, errc{} }; + } + + // Decode __bits into mantissa and exponent. + const uint64_t __ieeeMantissa = __bits & ((1ull << __DOUBLE_MANTISSA_BITS) - 1); + const uint32_t __ieeeExponent = static_cast<uint32_t>(__bits >> __DOUBLE_MANTISSA_BITS); + + int32_t __e2; + uint64_t __m2; + if (__ieeeExponent == 0) { + __e2 = 1 - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS; + __m2 = __ieeeMantissa; + } else { + __e2 = static_cast<int32_t>(__ieeeExponent) - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS; + __m2 = (1ull << __DOUBLE_MANTISSA_BITS) | __ieeeMantissa; + } + + const bool __printDecimalPoint = __precision > 0; + ++__precision; + uint32_t __digits = 0; + uint32_t __printedDigits = 0; + uint32_t __availableDigits = 0; + int32_t __exp = 0; + if (__e2 >= -52) { + const uint32_t __idx = __e2 < 0 ? 0 : __indexForExponent(static_cast<uint32_t>(__e2)); + const uint32_t __p10bits = __pow10BitsForIndex(__idx); + const int32_t __len = static_cast<int32_t>(__lengthForIndex(__idx)); + for (int32_t __i = __len - 1; __i >= 0; --__i) { + const uint32_t __j = __p10bits - __e2; + // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is + // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers. + __digits = __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT[__POW10_OFFSET[__idx] + __i], + static_cast<int32_t>(__j + 8)); + if (__printedDigits != 0) { + if (__printedDigits + 9 > __precision) { + __availableDigits = 9; + break; + } + if (_Last - _First < 9) { + return { _Last, errc::value_too_large }; + } + __append_nine_digits(__digits, _First); + _First += 9; + __printedDigits += 9; + } else if (__digits != 0) { + __availableDigits = __decimalLength9(__digits); + __exp = __i * 9 + static_cast<int32_t>(__availableDigits) - 1; + if (__availableDigits > __precision) { + break; + } + if (__printDecimalPoint) { + if (_Last - _First < static_cast<ptrdiff_t>(__availableDigits + 1)) { + return { _Last, errc::value_too_large }; + } + __append_d_digits(__availableDigits, __digits, _First); + _First += __availableDigits + 1; // +1 for decimal point + } else { + if (_First == _Last) { + return { _Last, errc::value_too_large }; + } + *_First++ = static_cast<char>('0' + __digits); + } + __printedDigits = __availableDigits; + __availableDigits = 0; + } + } + } + + if (__e2 < 0 && __availableDigits == 0) { + const int32_t __idx = -__e2 / 16; + for (int32_t __i = __MIN_BLOCK_2[__idx]; __i < 200; ++__i) { + const int32_t __j = __ADDITIONAL_BITS_2 + (-__e2 - 16 * __idx); + const uint32_t __p = __POW10_OFFSET_2[__idx] + static_cast<uint32_t>(__i) - __MIN_BLOCK_2[__idx]; + // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is + // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers. + __digits = (__p >= __POW10_OFFSET_2[__idx + 1]) ? 0 : __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT_2[__p], __j + 8); + if (__printedDigits != 0) { + if (__printedDigits + 9 > __precision) { + __availableDigits = 9; + break; + } + if (_Last - _First < 9) { + return { _Last, errc::value_too_large }; + } + __append_nine_digits(__digits, _First); + _First += 9; + __printedDigits += 9; + } else if (__digits != 0) { + __availableDigits = __decimalLength9(__digits); + __exp = -(__i + 1) * 9 + static_cast<int32_t>(__availableDigits) - 1; + if (__availableDigits > __precision) { + break; + } + if (__printDecimalPoint) { + if (_Last - _First < static_cast<ptrdiff_t>(__availableDigits + 1)) { + return { _Last, errc::value_too_large }; + } + __append_d_digits(__availableDigits, __digits, _First); + _First += __availableDigits + 1; // +1 for decimal point + } else { + if (_First == _Last) { + return { _Last, errc::value_too_large }; + } + *_First++ = static_cast<char>('0' + __digits); + } + __printedDigits = __availableDigits; + __availableDigits = 0; + } + } + } + + const uint32_t __maximum = __precision - __printedDigits; + if (__availableDigits == 0) { + __digits = 0; + } + uint32_t __lastDigit = 0; + if (__availableDigits > __maximum) { + for (uint32_t __k = 0; __k < __availableDigits - __maximum; ++__k) { + __lastDigit = __digits % 10; + __digits /= 10; + } + } + // 0 = don't round up; 1 = round up unconditionally; 2 = round up if odd. + int __roundUp = 0; + if (__lastDigit != 5) { + __roundUp = __lastDigit > 5; + } else { + // Is m * 2^__e2 * 10^(__precision + 1 - __exp) integer? + // __precision was already increased by 1, so we don't need to write + 1 here. + const int32_t __rexp = static_cast<int32_t>(__precision) - __exp; + const int32_t __requiredTwos = -__e2 - __rexp; + bool __trailingZeros = __requiredTwos <= 0 + || (__requiredTwos < 60 && __multipleOfPowerOf2(__m2, static_cast<uint32_t>(__requiredTwos))); + if (__rexp < 0) { + const int32_t __requiredFives = -__rexp; + __trailingZeros = __trailingZeros && __multipleOfPowerOf5(__m2, static_cast<uint32_t>(__requiredFives)); + } + __roundUp = __trailingZeros ? 2 : 1; + } + if (__printedDigits != 0) { + if (_Last - _First < static_cast<ptrdiff_t>(__maximum)) { + return { _Last, errc::value_too_large }; + } + if (__digits == 0) { + _VSTD::memset(_First, '0', __maximum); + } else { + __append_c_digits(__maximum, __digits, _First); + } + _First += __maximum; + } else { + if (__printDecimalPoint) { + if (_Last - _First < static_cast<ptrdiff_t>(__maximum + 1)) { + return { _Last, errc::value_too_large }; + } + __append_d_digits(__maximum, __digits, _First); + _First += __maximum + 1; // +1 for decimal point + } else { + if (_First == _Last) { + return { _Last, errc::value_too_large }; + } + *_First++ = static_cast<char>('0' + __digits); + } + } + if (__roundUp != 0) { + char* _Round = _First; + while (true) { + if (_Round == _Original_first) { + _Round[0] = '1'; + ++__exp; + break; + } + --_Round; + const char __c = _Round[0]; + if (__c == '.') { + // Keep going. + } else if (__c == '9') { + _Round[0] = '0'; + __roundUp = 1; + } else { + if (__roundUp == 1 || __c % 2 != 0) { + _Round[0] = __c + 1; + } + break; + } + } + } + + char _Sign_character; + + if (__exp < 0) { + _Sign_character = '-'; + __exp = -__exp; + } else { + _Sign_character = '+'; + } + + const int _Exponent_part_length = __exp >= 100 + ? 5 // "e+NNN" + : 4; // "e+NN" + + if (_Last - _First < _Exponent_part_length) { + return { _Last, errc::value_too_large }; + } + + *_First++ = 'e'; + *_First++ = _Sign_character; + + if (__exp >= 100) { + const int32_t __c = __exp % 10; + _VSTD::memcpy(_First, __DIGIT_TABLE + 2 * (__exp / 10), 2); + _First[2] = static_cast<char>('0' + __c); + _First += 3; + } else { + _VSTD::memcpy(_First, __DIGIT_TABLE + 2 * __exp, 2); + _First += 2; + } + + return { _First, errc{} }; +} + +_LIBCPP_END_NAMESPACE_STD + +// clang-format on |