| // Numeric conversions (to_string, to_chars) -*- C++ -*- |
| |
| // Copyright (C) 2017-2020 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 |