charconv.h
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// Numeric conversions (to_string, to_chars) -*- C++ -*-
// Copyright (C) 2017-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file bits/charconv.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{charconv}
*/
#ifndef _GLIBCXX_CHARCONV_H
#define _GLIBCXX_CHARCONV_H 1
#pragma GCC system_header
#if __cplusplus >= 201103L
#include <type_traits>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __detail
{
// Generic implementation for arbitrary bases.
template<typename _Tp>
_GLIBCXX14_CONSTEXPR unsigned
__to_chars_len(_Tp __value, int __base = 10) noexcept
{
static_assert(is_integral<_Tp>::value, "implementation bug");
static_assert(is_unsigned<_Tp>::value, "implementation bug");
unsigned __n = 1;
const unsigned __b2 = __base * __base;
const unsigned __b3 = __b2 * __base;
const unsigned long __b4 = __b3 * __base;
for (;;)
{
if (__value < (unsigned)__base) return __n;
if (__value < __b2) return __n + 1;
if (__value < __b3) return __n + 2;
if (__value < __b4) return __n + 3;
__value /= __b4;
__n += 4;
}
}
// Write an unsigned integer value to the range [first,first+len).
// The caller is required to provide a buffer of exactly the right size
// (which can be determined by the __to_chars_len function).
template<typename _Tp>
void
__to_chars_10_impl(char* __first, unsigned __len, _Tp __val) noexcept
{
static_assert(is_integral<_Tp>::value, "implementation bug");
static_assert(is_unsigned<_Tp>::value, "implementation bug");
static constexpr char __digits[201] =
"0001020304050607080910111213141516171819"
"2021222324252627282930313233343536373839"
"4041424344454647484950515253545556575859"
"6061626364656667686970717273747576777879"
"8081828384858687888990919293949596979899";
unsigned __pos = __len - 1;
while (__val >= 100)
{
auto const __num = (__val % 100) * 2;
__val /= 100;
__first[__pos] = __digits[__num + 1];
__first[__pos - 1] = __digits[__num];
__pos -= 2;
}
if (__val >= 10)
{
auto const __num = __val * 2;
__first[1] = __digits[__num + 1];
__first[0] = __digits[__num];
}
else
__first[0] = '0' + __val;
}
} // namespace __detail
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++11
#endif // _GLIBCXX_CHARCONV_H
std
ISO C++ entities toplevel namespace is std.
__gnu_debug::__base
constexpr _Iterator __base(_Iterator __it)
Definition: helper_functions.h:315
type_traits