<h2>File Contents: //usr/include/c++/8/charconv</h2><form method='POST' action=''><input type='hidden' name='edit_file' value='//usr/include/c++/8/charconv'><textarea name='file_content' rows='10' cols='50'>// Primitive numeric conversions (to_chars and from_chars) -*- C++ -*-

// Copyright (C) 2017-2018 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
// &lt;http://www.gnu.org/licenses/&gt;.

/** @file include/charconv
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_CHARCONV
#define _GLIBCXX_CHARCONV 1

#pragma GCC system_header

#if __cplusplus &gt;= 201402L

#include &lt;type_traits&gt;
#include &lt;limits&gt;
#include &lt;cctype&gt;
#include &lt;bits/error_constants.h&gt; // for std::errc

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /// Result type of std::to_chars
  struct to_chars_result
  {
    char* ptr;
    errc ec;
  };

  /// Result type of std::from_chars
  struct from_chars_result
  {
    const char* ptr;
    errc ec;
  };

namespace __detail
{
  template&lt;typename _Tp, typename... _Types&gt;
    using __is_one_of = __or_&lt;is_same&lt;_Tp, _Types&gt;...&gt;;

  template&lt;typename _Tp&gt;
    using __is_int_to_chars_type = __and_&lt;is_integral&lt;_Tp&gt;,
	  __not_&lt;__is_one_of&lt;_Tp, bool, char16_t, char32_t
#if _GLIBCXX_USE_WCHAR_T
	  , wchar_t
#endif
	    &gt;&gt;&gt;;

  template&lt;typename _Tp&gt;
    using __integer_to_chars_result_type
      = enable_if_t&lt;__is_int_to_chars_type&lt;_Tp&gt;::value, to_chars_result&gt;;

  template&lt;typename _Tp&gt;
    using __unsigned_least_t
      = conditional_t&lt;(sizeof(_Tp) &lt;= sizeof(int)), unsigned int,
	conditional_t&lt;(sizeof(_Tp) &lt;= sizeof(long)), unsigned long,
	conditional_t&lt;(sizeof(_Tp) &lt;= sizeof(long long)), unsigned long long,
#if _GLIBCXX_USE_INT128
	conditional_t&lt;(sizeof(_Tp) &lt;= sizeof(__int128)), unsigned __int128,
#endif
	void
#if _GLIBCXX_USE_INT128
	&gt;
#endif
	&gt;&gt;&gt;;

  // Generic implementation for arbitrary bases.
  template&lt;typename _Tp&gt;
    constexpr unsigned
    __to_chars_len(_Tp __value, int __base = 10) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      unsigned __n = 1;
      const int __b2 = __base  * __base;
      const int __b3 = __b2 * __base;
      const int __b4 = __b3 * __base;
      for (;;)
	{
	  if (__value &lt; __base) return __n;
	  if (__value &lt; __b2) return __n + 1;
	  if (__value &lt; __b3) return __n + 2;
	  if (__value &lt; __b4) return __n + 3;
	  __value /= (unsigned)__b4;
	  __n += 4;
	}
    }

  template&lt;typename _Tp&gt;
    constexpr unsigned
    __to_chars_len_2(_Tp __value) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);

      // N.B. __builtin_clzll is undefined if __value == 0, but std::to_chars
      // handles zero values directly.

      // For sizeof(_Tp) &gt; 1 this is an order of magnitude faster than
      // the generic __to_chars_len.
      return __nbits
	- (__builtin_clzll(__value)
	    - ((__CHAR_BIT__ * sizeof(long long)) - __nbits));
    }

  template&lt;typename _Tp&gt;
    constexpr unsigned
    __to_chars_len_8(_Tp __value) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);

      if _GLIBCXX17_CONSTEXPR (__nbits &lt;= 16)
	{
	  return __value &gt; 077777u ? 6u
	    : __value &gt; 07777u ? 5u
	    : __value &gt; 0777u ? 4u
	    : __value &gt; 077u ? 3u
	    : __value &gt; 07u ? 2u
	    : 1u;
	}
      else
	return __to_chars_len(__value, 8);
    }

  // Generic implementation for arbitrary bases.
  template&lt;typename _Tp&gt;
    to_chars_result
    __to_chars(char* __first, char* __last, _Tp __val, int __base) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      to_chars_result __res;

      const unsigned __len = __to_chars_len(__val, __base);

      if (__builtin_expect((__last - __first) &lt; __len, 0))
	{
	  __res.ptr = __last;
	  __res.ec = errc::value_too_large;
	  return __res;
	}

      unsigned __pos = __len - 1;

      static constexpr char __digits[]
	= &quot;0123456789abcdefghijklmnopqrstuvwxyz&quot;;

      while (__val &gt;= __base)
	{
	  auto const __quo = __val / __base;
	  auto const __rem = __val % __base;
	  __first[__pos--] = __digits[__rem];
	  __val = __quo;
	}
      *__first = __digits[__val];

      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }

  template&lt;typename _Tp&gt;
    __integer_to_chars_result_type&lt;_Tp&gt;
    __to_chars_16(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      to_chars_result __res;

      const unsigned __len = __to_chars_len(__val, 0x10);

      if (__builtin_expect((__last - __first) &lt; __len, 0))
	{
	  __res.ptr = __last;
	  __res.ec = errc::value_too_large;
	  return __res;
	}

      static constexpr char __digits[513] =
	&quot;000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f&quot;
	&quot;202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f&quot;
	&quot;404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f&quot;
	&quot;606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f&quot;
	&quot;808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f&quot;
	&quot;a0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebf&quot;
	&quot;c0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedf&quot;
	&quot;e0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff&quot;;
      unsigned __pos = __len - 1;
      while (__val &gt;= 0x100)
	{
	  auto const __num = (__val % 0x100) * 2;
	  __val /= 0x100;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	  __pos -= 2;
	}
      if (__val &gt;= 0x10)
	{
	  auto const __num = __val * 2;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	}
      else
	__first[__pos] = &quot;0123456789abcdef&quot;[__val];
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }

  template&lt;typename _Tp&gt;
    __integer_to_chars_result_type&lt;_Tp&gt;
    __to_chars_10(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      to_chars_result __res;

      const unsigned __len = __to_chars_len(__val, 10);

      if (__builtin_expect((__last - __first) &lt; __len, 0))
	{
	  __res.ptr = __last;
	  __res.ec = errc::value_too_large;
	  return __res;
	}

      static constexpr char __digits[201] =
	&quot;0001020304050607080910111213141516171819&quot;
	&quot;2021222324252627282930313233343536373839&quot;
	&quot;4041424344454647484950515253545556575859&quot;
	&quot;6061626364656667686970717273747576777879&quot;
	&quot;8081828384858687888990919293949596979899&quot;;
      unsigned __pos = __len - 1;
      while (__val &gt;= 100)
	{
	  auto const __num = (__val % 100) * 2;
	  __val /= 100;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	  __pos -= 2;
	}
      if (__val &gt;= 10)
	{
	  auto const __num = __val * 2;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	}
      else
	__first[__pos] = '0' + __val;
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }

  template&lt;typename _Tp&gt;
    __integer_to_chars_result_type&lt;_Tp&gt;
    __to_chars_8(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      to_chars_result __res;

      const unsigned __len = __to_chars_len_8(__val);

      if (__builtin_expect((__last - __first) &lt; __len, 0))
	{
	  __res.ptr = __last;
	  __res.ec = errc::value_too_large;
	  return __res;
	}

      static constexpr char __digits[129] =
	&quot;00010203040506071011121314151617&quot;
	&quot;20212223242526273031323334353637&quot;
	&quot;40414243444546475051525354555657&quot;
	&quot;60616263646566677071727374757677&quot;;
      unsigned __pos = __len - 1;
      while (__val &gt;= 0100)
	{
	  auto const __num = (__val % 0100) * 2;
	  __val /= 0100;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	  __pos -= 2;
	}
      if (__val &gt;= 010)
	{
	  auto const __num = __val * 2;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	}
      else
	__first[__pos] = '0' + __val;
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }

  template&lt;typename _Tp&gt;
    __integer_to_chars_result_type&lt;_Tp&gt;
    __to_chars_2(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      to_chars_result __res;

      const unsigned __len = __to_chars_len_2(__val);

      if (__builtin_expect((__last - __first) &lt; __len, 0))
	{
	  __res.ptr = __last;
	  __res.ec = errc::value_too_large;
	  return __res;
	}

      unsigned __pos = __len - 1;

      while (__pos)
	{
	  __first[__pos--] = '0' + (__val &amp; 1);
	  __val &gt;&gt;= 1;
	}
      *__first = '0' + (__val &amp; 1);

      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }

} // namespace __detail

  template&lt;typename _Tp&gt;
    __detail::__integer_to_chars_result_type&lt;_Tp&gt;
    to_chars(char* __first, char* __last, _Tp __value, int __base = 10)
    {
      __glibcxx_assert(2 &lt;= __base &amp;&amp; __base &lt;= 36);

      using _Up = __detail::__unsigned_least_t&lt;_Tp&gt;;
      _Up __unsigned_val = __value;

      if (__value == 0 &amp;&amp; __first != __last)
	{
	  *__first = '0';
	  return { __first + 1, errc{} };
	}

      if _GLIBCXX17_CONSTEXPR (std::is_signed&lt;_Tp&gt;::value)
	if (__value &lt; 0)
	  {
	    if (__builtin_expect(__first != __last, 1))
	      *__first++ = '-';
	    __unsigned_val = _Up(~__value) + _Up(1);
	  }

      switch (__base)
      {
      case 16:
	return __detail::__to_chars_16(__first, __last, __unsigned_val);
      case 10:
	return __detail::__to_chars_10(__first, __last, __unsigned_val);
      case 8:
	return __detail::__to_chars_8(__first, __last, __unsigned_val);
      case 2:
	return __detail::__to_chars_2(__first, __last, __unsigned_val);
      default:
	return __detail::__to_chars(__first, __last, __unsigned_val, __base);
      }
    }

namespace __detail
{
  template&lt;typename _Tp&gt;
    bool
    __raise_and_add(_Tp&amp; __val, int __base, unsigned char __c)
    {
      if (__builtin_mul_overflow(__val, __base, &amp;__val)
	  || __builtin_add_overflow(__val, __c, &amp;__val))
	return false;
      return true;
    }

  /// std::from_chars implementation for integers in base 2.
  template&lt;typename _Tp&gt;
    bool
    __from_chars_binary(const char*&amp; __first, const char* __last, _Tp&amp; __val)
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      const ptrdiff_t __len = __last - __first;
      int __i = 0;
      while (__i &lt; __len)
	{
	  const unsigned char __c = (unsigned)__first[__i] - '0';
	  if (__c &lt; 2)
	    __val = (__val &lt;&lt; 1) | __c;
	  else
	    break;
	  __i++;
	}
      __first += __i;
      return __i &lt;= (sizeof(_Tp) * __CHAR_BIT__);
    }

  /// std::from_chars implementation for integers in bases 3 to 10.
  template&lt;typename _Tp&gt;
    bool
    __from_chars_digit(const char*&amp; __first, const char* __last, _Tp&amp; __val,
		       int __base)
    {
      static_assert(is_integral&lt;_Tp&gt;::value, &quot;implementation bug&quot;);
      static_assert(is_unsigned&lt;_Tp&gt;::value, &quot;implementation bug&quot;);

      auto __matches = [__base](char __c) {
	  return '0' &lt;= __c &amp;&amp; __c &lt;= ('0' + (__base - 1));
      };

      while (__first != __last)
	{
	  const char __c = *__first;
	  if (__matches(__c))
	  {
	    if (!__raise_and_add(__val, __base, __c - '0'))
	      {
		while (++__first != __last &amp;&amp; __matches(*__first))
		  ;
		return false;
	      }
	    __first++;
	  }
	  else
	    return true;
	}
      return true;
    }

  constexpr unsigned char
  __from_chars_alpha_to_num(char __c)
  {
    switch (__c)
    {
    case 'a':
    case 'A':
      return 10;
    case 'b':
    case 'B':
      return 11;
    case 'c':
    case 'C':
      return 12;
    case 'd':
    case 'D':
      return 13;
    case 'e':
    case 'E':
      return 14;
    case 'f':
    case 'F':
      return 15;
    case 'g':
    case 'G':
      return 16;
    case 'h':
    case 'H':
      return 17;
    case 'i':
    case 'I':
      return 18;
    case 'j':
    case 'J':
      return 19;
    case 'k':
    case 'K':
      return 20;
    case 'l':
    case 'L':
      return 21;
    case 'm':
    case 'M':
      return 22;
    case 'n':
    case 'N':
      return 23;
    case 'o':
    case 'O':
      return 24;
    case 'p':
    case 'P':
      return 25;
    case 'q':
    case 'Q':
      return 26;
    case 'r':
    case 'R':
      return 27;
    case 's':
    case 'S':
      return 28;
    case 't':
    case 'T':
      return 29;
    case 'u':
    case 'U':
      return 30;
    case 'v':
    case 'V':
      return 31;
    case 'w':
    case 'W':
      return 32;
    case 'x':
    case 'X':
      return 33;
    case 'y':
    case 'Y':
      return 34;
    case 'z':
    case 'Z':
      return 35;
    }
    return std::numeric_limits&lt;unsigned char&gt;::max();
  }

  /// std::from_chars implementation for integers in bases 11 to 26.
  template&lt;typename _Tp&gt;
    bool
    __from_chars_alnum(const char*&amp; __first, const char* __last, _Tp&amp; __val,
		       int __base)
    {
      bool __valid = true;
      while (__first != __last)
	{
	  unsigned char __c = *__first;
	  if (std::isdigit(__c))
	    __c -= '0';
	  else
	    {
	      __c = __from_chars_alpha_to_num(__c);
	      if (__c &gt;= __base)
		break;
	    }

	  if (__builtin_expect(__valid, 1))
	    __valid = __raise_and_add(__val, __base, __c);
	  __first++;
	}
      return __valid;
    }

  template&lt;typename _Tp&gt;
    using __integer_from_chars_result_type
      = enable_if_t&lt;__is_int_to_chars_type&lt;_Tp&gt;::value, from_chars_result&gt;;

} // namespace __detail

  /// std::from_chars for integral types.
  template&lt;typename _Tp&gt;
    __detail::__integer_from_chars_result_type&lt;_Tp&gt;
    from_chars(const char* __first, const char* __last, _Tp&amp; __value,
	       int __base = 10)
    {
      __glibcxx_assert(2 &lt;= __base &amp;&amp; __base &lt;= 36);

      from_chars_result __res{__first, {}};

      int __sign = 1;
      if _GLIBCXX17_CONSTEXPR (std::is_signed&lt;_Tp&gt;::value)
	if (__first != __last &amp;&amp; *__first == '-')
	  {
	    __sign = -1;
	    ++__first;
	  }

      using _Up = __detail::__unsigned_least_t&lt;_Tp&gt;;
      _Up __val = 0;

      const auto __start = __first;
      bool __valid;
      if (__base == 2)
	__valid = __detail::__from_chars_binary(__first, __last, __val);
      else if (__base &lt;= 10)
	__valid = __detail::__from_chars_digit(__first, __last, __val, __base);
      else
	__valid = __detail::__from_chars_alnum(__first, __last, __val, __base);

      if (__builtin_expect(__first == __start, 0))
	__res.ec = errc::invalid_argument;
      else
	{
	  __res.ptr = __first;
	  if (!__valid)
	    __res.ec = errc::result_out_of_range;
	  else
	    {
	      if _GLIBCXX17_CONSTEXPR (std::is_signed&lt;_Tp&gt;::value)
		{
		  _Tp __tmp;
		  if (__builtin_mul_overflow(__val, __sign, &amp;__tmp))
		    __res.ec = errc::result_out_of_range;
		  else
		    __value = __tmp;
		}
	      else
		{
		  if _GLIBCXX17_CONSTEXPR
		    (numeric_limits&lt;_Up&gt;::max() &gt; numeric_limits&lt;_Tp&gt;::max())
		    {
		      if (__val &gt; numeric_limits&lt;_Tp&gt;::max())
			__res.ec = errc::result_out_of_range;
		      else
			__value = __val;
		    }
		  else
		    __value = __val;
		}
	    }
	}
      return __res;
    }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++14
#endif // _GLIBCXX_CHARCONV
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