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       1             : // Numeric conversions (to_string, to_chars) -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2017-2021 Free Software Foundation, Inc.
       4             : //
       5             : // This file is part of the GNU ISO C++ Library.  This library is free
       6             : // software; you can redistribute it and/or modify it under the
       7             : // terms of the GNU General Public License as published by the
       8             : // Free Software Foundation; either version 3, or (at your option)
       9             : // any later version.
      10             : 
      11             : // This library is distributed in the hope that it will be useful,
      12             : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      13             : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14             : // GNU General Public License for more details.
      15             : 
      16             : // Under Section 7 of GPL version 3, you are granted additional
      17             : // permissions described in the GCC Runtime Library Exception, version
      18             : // 3.1, as published by the Free Software Foundation.
      19             : 
      20             : // You should have received a copy of the GNU General Public License and
      21             : // a copy of the GCC Runtime Library Exception along with this program;
      22             : // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23             : // <http://www.gnu.org/licenses/>.
      24             : 
      25             : /** @file bits/charconv.h
      26             :  *  This is an internal header file, included by other library headers.
      27             :  *  Do not attempt to use it directly. @headername{charconv}
      28             :  */
      29             : 
      30             : #ifndef _GLIBCXX_CHARCONV_H
      31             : #define _GLIBCXX_CHARCONV_H 1
      32             : 
      33             : #pragma GCC system_header
      34             : 
      35             : #if __cplusplus >= 201103L
      36             : 
      37             : #include <type_traits>
      38             : 
      39             : namespace std _GLIBCXX_VISIBILITY(default)
      40             : {
      41             : _GLIBCXX_BEGIN_NAMESPACE_VERSION
      42             : namespace __detail
      43             : {
      44             :   // Generic implementation for arbitrary bases.
      45             :   template<typename _Tp>
      46             :     _GLIBCXX14_CONSTEXPR unsigned
      47       44484 :     __to_chars_len(_Tp __value, int __base = 10) noexcept
      48             :     {
      49             :       static_assert(is_integral<_Tp>::value, "implementation bug");
      50             :       static_assert(is_unsigned<_Tp>::value, "implementation bug");
      51             : 
      52       44484 :       unsigned __n = 1;
      53       44484 :       const unsigned __b2 = __base  * __base;
      54       44484 :       const unsigned __b3 = __b2 * __base;
      55       44484 :       const unsigned long __b4 = __b3 * __base;
      56             :       for (;;)
      57             :         {
      58       96920 :           if (__value < (unsigned)__base) return __n;
      59       83548 :           if (__value < __b2) return __n + 1;
      60       61589 :           if (__value < __b3) return __n + 2;
      61       54554 :           if (__value < __b4) return __n + 3;
      62       52436 :           __value /= __b4;
      63       52436 :           __n += 4;
      64             :         }
      65             :     }
      66             : 
      67             :   // Write an unsigned integer value to the range [first,first+len).
      68             :   // The caller is required to provide a buffer of exactly the right size
      69             :   // (which can be determined by the __to_chars_len function).
      70             :   template<typename _Tp>
      71             :     void
      72       44484 :     __to_chars_10_impl(char* __first, unsigned __len, _Tp __val) noexcept
      73             :     {
      74             :       static_assert(is_integral<_Tp>::value, "implementation bug");
      75             :       static_assert(is_unsigned<_Tp>::value, "implementation bug");
      76             : 
      77             :       static constexpr char __digits[201] =
      78             :         "0001020304050607080910111213141516171819"
      79             :         "2021222324252627282930313233343536373839"
      80             :         "4041424344454647484950515253545556575859"
      81             :         "6061626364656667686970717273747576777879"
      82             :         "8081828384858687888990919293949596979899";
      83       44484 :       unsigned __pos = __len - 1;
      84      158509 :       while (__val >= 100)
      85             :         {
      86      114025 :           auto const __num = (__val % 100) * 2;
      87      114025 :           __val /= 100;
      88      114025 :           __first[__pos] = __digits[__num + 1];
      89      114025 :           __first[__pos - 1] = __digits[__num];
      90      114025 :           __pos -= 2;
      91             :         }
      92       44484 :       if (__val >= 10)
      93             :         {
      94       24077 :           auto const __num = __val * 2;
      95       24077 :           __first[1] = __digits[__num + 1];
      96       24077 :           __first[0] = __digits[__num];
      97             :         }
      98             :       else
      99       20407 :         __first[0] = '0' + __val;
     100       44484 :     }
     101             : 
     102             : } // namespace __detail
     103             : _GLIBCXX_END_NAMESPACE_VERSION
     104             : } // namespace std
     105             : #endif // C++11
     106             : #endif // _GLIBCXX_CHARCONV_H