include/ylt/util/dragonbox_to_chars.h (464 lines of code) (raw):
/*
* Copyright (c) 2023, Alibaba Group Holding Limited;
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Copyright 2020-2022 Junekey Jeon
//
// The contents of this file may be used under the terms of
// the Apache License v2.0 with LLVM Exceptions.
//
// (See accompanying file LICENSE-Apache or copy at
// https://llvm.org/foundation/relicensing/LICENSE.txt)
//
// Alternatively, the contents of this file may be used under the terms of
// the Boost Software License, Version 1.0.
// (See accompanying file LICENSE-Boost or copy at
// https://www.boost.org/LICENSE_1_0.txt)
//
// Unless required by applicable law or agreed to in writing, this software
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.
#ifndef JKJ_HEADER_DRAGONBOX_TO_CHARS
#define JKJ_HEADER_DRAGONBOX_TO_CHARS
#include "dragonbox.h"
#if defined(__GNUC__) || defined(__clang__)
#define JKJ_FORCEINLINE inline __attribute__((always_inline))
#elif defined(_MSC_VER)
#define JKJ_FORCEINLINE __forceinline
#else
#define JKJ_FORCEINLINE inline
#endif
namespace jkj::dragonbox {
namespace to_chars_detail {
template <class Float, class FloatTraits>
extern char *to_chars(typename FloatTraits::carrier_uint significand,
int exponent, char *buffer) noexcept;
// These "//"'s are to prevent clang-format to ruin this nice alignment.
// Thanks to reddit user u/mcmcc:
// https://www.reddit.com/r/cpp/comments/so3wx9/dragonbox_110_is_released_a_fast_floattostring/hw8z26r/?context=3
static constexpr char radix_100_table[] = {
'0', '0', '0', '1', '0', '2', '0', '3', '0', '4', //
'0', '5', '0', '6', '0', '7', '0', '8', '0', '9', //
'1', '0', '1', '1', '1', '2', '1', '3', '1', '4', //
'1', '5', '1', '6', '1', '7', '1', '8', '1', '9', //
'2', '0', '2', '1', '2', '2', '2', '3', '2', '4', //
'2', '5', '2', '6', '2', '7', '2', '8', '2', '9', //
'3', '0', '3', '1', '3', '2', '3', '3', '3', '4', //
'3', '5', '3', '6', '3', '7', '3', '8', '3', '9', //
'4', '0', '4', '1', '4', '2', '4', '3', '4', '4', //
'4', '5', '4', '6', '4', '7', '4', '8', '4', '9', //
'5', '0', '5', '1', '5', '2', '5', '3', '5', '4', //
'5', '5', '5', '6', '5', '7', '5', '8', '5', '9', //
'6', '0', '6', '1', '6', '2', '6', '3', '6', '4', //
'6', '5', '6', '6', '6', '7', '6', '8', '6', '9', //
'7', '0', '7', '1', '7', '2', '7', '3', '7', '4', //
'7', '5', '7', '6', '7', '7', '7', '8', '7', '9', //
'8', '0', '8', '1', '8', '2', '8', '3', '8', '4', //
'8', '5', '8', '6', '8', '7', '8', '8', '8', '9', //
'9', '0', '9', '1', '9', '2', '9', '3', '9', '4', //
'9', '5', '9', '6', '9', '7', '9', '8', '9', '9' //
};
static constexpr char radix_100_head_table[] = {
'0', '.', '1', '.', '2', '.', '3', '.', '4', '.', //
'5', '.', '6', '.', '7', '.', '8', '.', '9', '.', //
'1', '.', '1', '.', '1', '.', '1', '.', '1', '.', //
'1', '.', '1', '.', '1', '.', '1', '.', '1', '.', //
'2', '.', '2', '.', '2', '.', '2', '.', '2', '.', //
'2', '.', '2', '.', '2', '.', '2', '.', '2', '.', //
'3', '.', '3', '.', '3', '.', '3', '.', '3', '.', //
'3', '.', '3', '.', '3', '.', '3', '.', '3', '.', //
'4', '.', '4', '.', '4', '.', '4', '.', '4', '.', //
'4', '.', '4', '.', '4', '.', '4', '.', '4', '.', //
'5', '.', '5', '.', '5', '.', '5', '.', '5', '.', //
'5', '.', '5', '.', '5', '.', '5', '.', '5', '.', //
'6', '.', '6', '.', '6', '.', '6', '.', '6', '.', //
'6', '.', '6', '.', '6', '.', '6', '.', '6', '.', //
'7', '.', '7', '.', '7', '.', '7', '.', '7', '.', //
'7', '.', '7', '.', '7', '.', '7', '.', '7', '.', //
'8', '.', '8', '.', '8', '.', '8', '.', '8', '.', //
'8', '.', '8', '.', '8', '.', '8', '.', '8', '.', //
'9', '.', '9', '.', '9', '.', '9', '.', '9', '.', //
'9', '.', '9', '.', '9', '.', '9', '.', '9', '.' //
};
// These digit generation routines are inspired by James Anhalt's itoa
// algorithm: https://github.com/jeaiii/itoa The main idea is for given n, find
// y such that floor(10^k * y / 2^32) = n holds, where k is an appropriate
// integer depending on the length of n. For example, if n = 1234567, we set k
// = 6. In this case, we have floor(y / 2^32) = 1, floor(10^2 * ((10^0 * y) mod
// 2^32) / 2^32) = 23, floor(10^2 * ((10^2 * y) mod 2^32) / 2^32) = 45, and
// floor(10^2 * ((10^4 * y) mod 2^32) / 2^32) = 67.
// See https://jk-jeon.github.io/posts/2022/02/jeaiii-algorithm/ for more
// explanation.
JKJ_FORCEINLINE static void print_9_digits(std::uint32_t s32, int &exponent,
char *&buffer) noexcept {
// -- IEEE-754 binary32
// Since we do not cut trailing zeros in advance, s32 must be of 6~9 digits
// unless the original input was subnormal.
// In particular, when it is of 9 digits it shouldn't have any trailing zeros.
// -- IEEE-754 binary64
// In this case, s32 must be of 7~9 digits unless the input is subnormal,
// and it shouldn't have any trailing zeros if it is of 9 digits.
if (s32 >= 1'0000'0000) {
// 9 digits.
// 1441151882 = ceil(2^57 / 1'0000'0000) + 1
auto prod = s32 * std::uint64_t(1441151882);
prod >>= 25;
std::memcpy(buffer, radix_100_head_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 2, radix_100_table + std::uint32_t(prod >> 32) * 2, 2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 4, radix_100_table + std::uint32_t(prod >> 32) * 2, 2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 6, radix_100_table + std::uint32_t(prod >> 32) * 2, 2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 8, radix_100_table + std::uint32_t(prod >> 32) * 2, 2);
exponent += 8;
buffer += 10;
}
else if (s32 >= 100'0000) {
// 7 or 8 digits.
// 281474978 = ceil(2^48 / 100'0000) + 1
auto prod = s32 * std::uint64_t(281474978);
prod >>= 16;
auto two_digits = std::uint32_t(prod >> 32);
// If s32 is of 8 digits, increase the exponent by 7.
// Otherwise, increase it by 6.
exponent += (6 + unsigned(two_digits >= 10));
// Write the first digit and the decimal point.
std::memcpy(buffer, radix_100_head_table + two_digits * 2, 2);
// This third character may be overwritten later but we don't care.
buffer[2] = radix_100_table[two_digits * 2 + 1];
// Remaining 6 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 100'0000)) {
// The number of characters actually written is:
// 1, if only the first digit is nonzero, which means that either s32 is
// of 7 digits or it is of 8 digits but the second digit is zero, or 3,
// otherwise.
// Note that buffer[2] is never zero if s32 is of 7 digits, because the
// input is never zero.
buffer +=
(1 + (unsigned(two_digits >= 10) & unsigned(buffer[2] > '0')) * 2);
}
else {
// At least one of the remaining 6 digits are nonzero.
// After this adjustment, now the first destination becomes buffer + 2.
buffer += unsigned(two_digits >= 10);
// Obtain the next two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 2, radix_100_table + two_digits * 2, 2);
// Remaining 4 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 1'0000)) {
buffer += (3 + unsigned(buffer[3] > '0'));
}
else {
// At least one of the remaining 4 digits are nonzero.
// Obtain the next two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 4, radix_100_table + two_digits * 2, 2);
// Remaining 2 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 100)) {
buffer += (5 + unsigned(buffer[5] > '0'));
}
else {
// Obtain the last two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 6, radix_100_table + two_digits * 2, 2);
buffer += (7 + unsigned(buffer[7] > '0'));
}
}
}
}
else if (s32 >= 1'0000) {
// 5 or 6 digits.
// 429497 = ceil(2^32 / 1'0000)
auto prod = s32 * std::uint64_t(429497);
auto two_digits = std::uint32_t(prod >> 32);
// If s32 is of 6 digits, increase the exponent by 5.
// Otherwise, increase it by 4.
exponent += (4 + unsigned(two_digits >= 10));
// Write the first digit and the decimal point.
std::memcpy(buffer, radix_100_head_table + two_digits * 2, 2);
// This third character may be overwritten later but we don't care.
buffer[2] = radix_100_table[two_digits * 2 + 1];
// Remaining 4 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 1'0000)) {
// The number of characters actually written is 1 or 3, similarly to the
// case of 7 or 8 digits.
buffer +=
(1 + (unsigned(two_digits >= 10) & unsigned(buffer[2] > '0')) * 2);
}
else {
// At least one of the remaining 4 digits are nonzero.
// After this adjustment, now the first destination becomes buffer + 2.
buffer += unsigned(two_digits >= 10);
// Obtain the next two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 2, radix_100_table + two_digits * 2, 2);
// Remaining 2 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 100)) {
buffer += (3 + unsigned(buffer[3] > '0'));
}
else {
// Obtain the last two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 4, radix_100_table + two_digits * 2, 2);
buffer += (5 + unsigned(buffer[5] > '0'));
}
}
}
else if (s32 >= 100) {
// 3 or 4 digits.
// 42949673 = ceil(2^32 / 100)
auto prod = s32 * std::uint64_t(42949673);
auto two_digits = std::uint32_t(prod >> 32);
// If s32 is of 4 digits, increase the exponent by 3.
// Otherwise, increase it by 2.
exponent += (2 + int(two_digits >= 10));
// Write the first digit and the decimal point.
std::memcpy(buffer, radix_100_head_table + two_digits * 2, 2);
// This third character may be overwritten later but we don't care.
buffer[2] = radix_100_table[two_digits * 2 + 1];
// Remaining 2 digits are all zero?
if (std::uint32_t(prod) <= std::uint32_t((std::uint64_t(1) << 32) / 100)) {
// The number of characters actually written is 1 or 3, similarly to the
// case of 7 or 8 digits.
buffer +=
(1 + (unsigned(two_digits >= 10) & unsigned(buffer[2] > '0')) * 2);
}
else {
// At least one of the remaining 2 digits are nonzero.
// After this adjustment, now the first destination becomes buffer + 2.
buffer += unsigned(two_digits >= 10);
// Obtain the last two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 2, radix_100_table + two_digits * 2, 2);
buffer += (3 + unsigned(buffer[3] > '0'));
}
}
else {
// 1 or 2 digits.
// If s32 is of 2 digits, increase the exponent by 1.
exponent += int(s32 >= 10);
// Write the first digit and the decimal point.
std::memcpy(buffer, radix_100_head_table + s32 * 2, 2);
// This third character may be overwritten later but we don't care.
buffer[2] = radix_100_table[s32 * 2 + 1];
// The number of characters actually written is 1 or 3, similarly to the
// case of 7 or 8 digits.
buffer += (1 + (unsigned(s32 >= 10) & unsigned(buffer[2] > '0')) * 2);
}
}
template <>
inline char *to_chars<float, default_float_traits<float>>(
std::uint32_t s32, int exponent, char *buffer) noexcept {
// Print significand.
print_9_digits(s32, exponent, buffer);
// Print exponent and return
if (exponent < 0) {
std::memcpy(buffer, "E-", 2);
buffer += 2;
exponent = -exponent;
}
else {
buffer[0] = 'E';
buffer += 1;
}
if (exponent >= 10) {
std::memcpy(buffer, &radix_100_table[exponent * 2], 2);
buffer += 2;
}
else {
buffer[0] = char('0' + exponent);
buffer += 1;
}
return buffer;
}
template <>
inline char *to_chars<double, default_float_traits<double>>(
std::uint64_t const significand, int exponent, char *buffer) noexcept {
// Print significand by decomposing it into a 9-digit block and a 8-digit
// block.
std::uint32_t first_block, second_block;
bool no_second_block;
if (significand >= 1'0000'0000) {
first_block = std::uint32_t(significand / 1'0000'0000);
second_block = std::uint32_t(significand) - first_block * 1'0000'0000;
exponent += 8;
no_second_block = (second_block == 0);
}
else {
first_block = std::uint32_t(significand);
no_second_block = true;
}
if (no_second_block) {
print_9_digits(first_block, exponent, buffer);
}
else {
// We proceed similarly to print_9_digits(), but since we do not need to
// remove trailing zeros, the procedure is a bit simpler.
if (first_block >= 1'0000'0000) {
// The input is of 17 digits, thus there should be no trailing zero at
// all. The first block is of 9 digits. 1441151882 = ceil(2^57 /
// 1'0000'0000) + 1
auto prod = first_block * std::uint64_t(1441151882);
prod >>= 25;
std::memcpy(buffer, radix_100_head_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 2, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 4, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 6, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 8, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
// The second block is of 8 digits.
// 281474978 = ceil(2^48 / 100'0000) + 1
prod = second_block * std::uint64_t(281474978);
prod >>= 16;
prod += 1;
std::memcpy(buffer + 10, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 12, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 14, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 16, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
exponent += 8;
buffer += 18;
}
else {
if (first_block >= 100'0000) {
// 7 or 8 digits.
// 281474978 = ceil(2^48 / 100'0000) + 1
auto prod = first_block * std::uint64_t(281474978);
prod >>= 16;
auto two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer, radix_100_head_table + two_digits * 2, 2);
buffer[2] = radix_100_table[two_digits * 2 + 1];
exponent += (6 + unsigned(two_digits >= 10));
buffer += unsigned(two_digits >= 10);
// Print remaining 6 digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 2, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 4, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 6, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
buffer += 8;
}
else if (first_block >= 1'0000) {
// 5 or 6 digits.
// 429497 = ceil(2^32 / 1'0000)
auto prod = first_block * std::uint64_t(429497);
auto two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer, radix_100_head_table + two_digits * 2, 2);
buffer[2] = radix_100_table[two_digits * 2 + 1];
exponent += (4 + unsigned(two_digits >= 10));
buffer += unsigned(two_digits >= 10);
// Print remaining 4 digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 2, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 4, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
buffer += 6;
}
else if (first_block >= 100) {
// 3 or 4 digits.
// 42949673 = ceil(2^32 / 100)
auto prod = first_block * std::uint64_t(42949673);
auto two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer, radix_100_head_table + two_digits * 2, 2);
buffer[2] = radix_100_table[two_digits * 2 + 1];
exponent += (2 + unsigned(two_digits >= 10));
buffer += unsigned(two_digits >= 10);
// Print remaining 2 digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
std::memcpy(buffer + 2, radix_100_table + std::uint32_t(prod >> 32) * 2,
2);
buffer += 4;
}
else {
// 1 or 2 digits.
std::memcpy(buffer, radix_100_head_table + first_block * 2, 2);
buffer[2] = radix_100_table[first_block * 2 + 1];
exponent += unsigned(first_block >= 10);
buffer += (2 + unsigned(first_block >= 10));
}
// Next, print the second block.
// The second block is of 8 digits, but we may have trailing zeros.
// 281474978 = ceil(2^48 / 100'0000) + 1
auto prod = second_block * std::uint64_t(281474978);
prod >>= 16;
prod += 1;
auto two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer, radix_100_table + two_digits * 2, 2);
// Remaining 6 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 100'0000)) {
buffer += (1 + unsigned(buffer[1] > '0'));
}
else {
// Obtain the next two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 2, radix_100_table + two_digits * 2, 2);
// Remaining 4 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 1'0000)) {
buffer += (3 + unsigned(buffer[3] > '0'));
}
else {
// Obtain the next two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 4, radix_100_table + two_digits * 2, 2);
// Remaining 2 digits are all zero?
if (std::uint32_t(prod) <=
std::uint32_t((std::uint64_t(1) << 32) / 100)) {
buffer += (5 + unsigned(buffer[5] > '0'));
}
else {
// Obtain the last two digits.
prod = std::uint32_t(prod) * std::uint64_t(100);
two_digits = std::uint32_t(prod >> 32);
std::memcpy(buffer + 6, radix_100_table + two_digits * 2, 2);
buffer += (7 + unsigned(buffer[7] > '0'));
}
}
}
}
}
// Print exponent and return
if (exponent < 0) {
std::memcpy(buffer, "E-", 2);
buffer += 2;
exponent = -exponent;
}
else {
buffer[0] = 'E';
buffer += 1;
}
if (exponent >= 100) {
// d1 = exponent / 10; d2 = exponent % 10;
// 6554 = ceil(2^16 / 10)
auto prod = std::uint32_t(exponent) * std::uint32_t(6554);
auto d1 = prod >> 16;
prod = std::uint16_t(prod) * std::uint32_t(5); // * 10
auto d2 = prod >> 15; // >> 16
std::memcpy(buffer, &radix_100_table[d1 * 2], 2);
buffer[2] = char('0' + d2);
buffer += 3;
}
else if (exponent >= 10) {
std::memcpy(buffer, &radix_100_table[exponent * 2], 2);
buffer += 2;
}
else {
buffer[0] = char('0' + exponent);
buffer += 1;
}
return buffer;
}
// Avoid needless ABI overhead incurred by tag dispatch.
template <class PolicyHolder, class Float, class FloatTraits>
inline char *to_chars_n_impl(float_bits<Float, FloatTraits> br,
char *buffer) noexcept {
auto const exponent_bits = br.extract_exponent_bits();
auto const s = br.remove_exponent_bits(exponent_bits);
if (br.is_finite(exponent_bits)) {
if (s.is_negative()) {
*buffer = '-';
++buffer;
}
if (br.is_nonzero()) {
auto result = to_decimal<Float, FloatTraits>(
s, exponent_bits, policy::sign::ignore, policy::trailing_zero::ignore,
typename PolicyHolder::decimal_to_binary_rounding_policy{},
typename PolicyHolder::binary_to_decimal_rounding_policy{},
typename PolicyHolder::cache_policy{});
return to_chars_detail::to_chars<Float, FloatTraits>(
result.significand, result.exponent, buffer);
}
else {
std::memcpy(buffer, "0E0", 3);
return buffer + 3;
}
}
else {
if (s.has_all_zero_significand_bits()) {
if (s.is_negative()) {
*buffer = '-';
++buffer;
}
std::memcpy(buffer, "Infinity", 8);
return buffer + 8;
}
else {
std::memcpy(buffer, "NaN", 3);
return buffer + 3;
}
}
}
} // namespace to_chars_detail
// Returns the next-to-end position
template <class Float, class FloatTraits = default_float_traits<Float>,
class... Policies>
inline char *to_chars_n(Float x, char *buffer, Policies... policies) noexcept {
using namespace jkj::dragonbox::detail::policy_impl;
using policy_holder = decltype(make_policy_holder(
base_default_pair_list<
base_default_pair<decimal_to_binary_rounding::base,
decimal_to_binary_rounding::nearest_to_even>,
base_default_pair<binary_to_decimal_rounding::base,
binary_to_decimal_rounding::to_even>,
base_default_pair<cache::base, cache::full>>{},
policies...));
return to_chars_detail::to_chars_n_impl<policy_holder>(
float_bits<Float, FloatTraits>(x), buffer);
}
// Null-terminate and bypass the return value of fp_to_chars_n
template <class Float, class FloatTraits = default_float_traits<Float>,
class... Policies>
inline char *to_chars(Float x, char *buffer, Policies... policies) noexcept {
auto ptr = to_chars_n<Float, FloatTraits>(x, buffer, policies...);
*ptr = '\0';
return ptr;
}
// Maximum required buffer size (excluding null-terminator)
template <class FloatFormat>
inline constexpr std::size_t max_output_string_length =
std::is_same_v<FloatFormat, ieee754_binary32>
?
// sign(1) + significand(9) + decimal_point(1) + exp_marker(1) +
// exp_sign(1) + exp(2)
(1 + 9 + 1 + 1 + 1 + 2)
:
// format == ieee754_format::binary64
// sign(1) + significand(17) + decimal_point(1) + exp_marker(1) +
// exp_sign(1) + exp(3)
(1 + 17 + 1 + 1 + 1 + 3);
} // namespace jkj::dragonbox
#endif