[thirdparty/gcc.git] / libstdc++-v3 / include / std / charconv

// Primitive numeric conversions (to_chars and from_chars) -*- C++ -*-

// Copyright (C) 2017-2019 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 include/charconv
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_CHARCONV
#define _GLIBCXX_CHARCONV 1

#pragma GCC system_header

#if __cplusplus >= 201402L

#include <type_traits>
#include <limits>
#include <cctype>
#include <bits/charconv.h> // for __to_chars_len, __to_chars_10_impl
#include <bits/error_constants.h> // for std::errc

// Define when floating point is supported: #define __cpp_lib_to_chars 201611L

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<typename _Tp>
    using __integer_to_chars_result_type
      = enable_if_t<__or_v<__is_signed_integer<_Tp>,
			   __is_unsigned_integer<_Tp>,
			   is_same<char, remove_cv_t<_Tp>>>,
		    to_chars_result>;

  // Pick an unsigned type of suitable size. This is used to reduce the
  // number of specializations of __to_chars_len, __to_chars etc. that
  // get instantiated. For example, to_chars<char> and to_chars<short>
  // and to_chars<unsigned> will all use the same code, and so will
  // to_chars<long> when sizeof(int) == sizeof(long).
  template<typename _Tp>
    struct __to_chars_unsigned_type : __make_unsigned_selector_base
    {
      using _UInts = _List<unsigned int, unsigned long, unsigned long long
#if _GLIBCXX_USE_INT128
	, unsigned __int128
#endif
	>;
      using type = typename __select<sizeof(_Tp), _UInts>::__type;
    };

  template<typename _Tp>
    using __unsigned_least_t = typename __to_chars_unsigned_type<_Tp>::type;

  // Generic implementation for arbitrary bases.
  // Defined in <bits/charconv.h>.
  template<typename _Tp>
    constexpr unsigned
    __to_chars_len(_Tp __value, int __base /* = 10 */) noexcept;

  template<typename _Tp>
    constexpr unsigned
    __to_chars_len_2(_Tp __value) noexcept
    {
      static_assert(is_integral<_Tp>::value, "implementation bug");
      static_assert(is_unsigned<_Tp>::value, "implementation bug");

      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) > 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<typename _Tp>
    constexpr unsigned
    __to_chars_len_8(_Tp __value) noexcept
    {
      static_assert(is_integral<_Tp>::value, "implementation bug");
      static_assert(is_unsigned<_Tp>::value, "implementation bug");

      constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);

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

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

      to_chars_result __res;

      const unsigned __len = __to_chars_len(__val, __base);

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

      unsigned __pos = __len - 1;

      static constexpr char __digits[]
	= "0123456789abcdefghijklmnopqrstuvwxyz";

      while (__val >= __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<typename _Tp>
    __integer_to_chars_result_type<_Tp>
    __to_chars_16(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral<_Tp>::value, "implementation bug");
      static_assert(is_unsigned<_Tp>::value, "implementation bug");

      to_chars_result __res;

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

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

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

  template<typename _Tp>
    inline __integer_to_chars_result_type<_Tp>
    __to_chars_10(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral<_Tp>::value, "implementation bug");
      static_assert(is_unsigned<_Tp>::value, "implementation bug");

      to_chars_result __res;

      const unsigned __len = __to_chars_len(__val, 10);

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

      __detail::__to_chars_10_impl(__first, __len, __val);
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }

  template<typename _Tp>
    __integer_to_chars_result_type<_Tp>
    __to_chars_8(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral<_Tp>::value, "implementation bug");
      static_assert(is_unsigned<_Tp>::value, "implementation bug");

      to_chars_result __res;

      const unsigned __len = __to_chars_len_8(__val);

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

      static constexpr char __digits[129] =
	"00010203040506071011121314151617"
	"20212223242526273031323334353637"
	"40414243444546475051525354555657"
	"60616263646566677071727374757677";
      unsigned __pos = __len - 1;
      while (__val >= 0100)
	{
	  auto const __num = (__val % 0100) * 2;
	  __val /= 0100;
	  __first[__pos] = __digits[__num + 1];
	  __first[__pos - 1] = __digits[__num];
	  __pos -= 2;
	}
      if (__val >= 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<typename _Tp>
    __integer_to_chars_result_type<_Tp>
    __to_chars_2(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(is_integral<_Tp>::value, "implementation bug");
      static_assert(is_unsigned<_Tp>::value, "implementation bug");

      to_chars_result __res;

      const unsigned __len = __to_chars_len_2(__val);

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

      unsigned __pos = __len - 1;

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

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

} // namespace __detail

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

      using _Up = __detail::__unsigned_least_t<_Tp>;
      _Up __unsigned_val = __value;

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

      if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
	if (__value < 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<typename _Tp>
    bool
    __raise_and_add(_Tp& __val, int __base, unsigned char __c)
    {
      if (__builtin_mul_overflow(__val, __base, &__val)
	  || __builtin_add_overflow(__val, __c, &__val))
	return false;
      return true;
    }

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

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

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

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

      while (__first != __last)
	{
	  const char __c = *__first;
	  if (__matches(__c))
	  {
	    if (!__raise_and_add(__val, __base, __c - '0'))
	      {
		while (++__first != __last && __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<unsigned char>::max();
  }

  /// std::from_chars implementation for integers in bases 11 to 26.
  template<typename _Tp>
    bool
    __from_chars_alnum(const char*& __first, const char* __last, _Tp& __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 >= __base)
		break;
	    }

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

  template<typename _Tp>
    using __integer_from_chars_result_type
      = enable_if_t<__or_v<__is_signed_integer<_Tp>,
			   __is_unsigned_integer<_Tp>,
			   is_same<char, remove_cv_t<_Tp>>>,
		    from_chars_result>;

} // namespace __detail

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

      from_chars_result __res{__first, {}};

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

      using _Up = __detail::__unsigned_least_t<_Tp>;
      _Up __val = 0;

      const auto __start = __first;
      bool __valid;
      if (__base == 2)
	__valid = __detail::__from_chars_binary(__first, __last, __val);
      else if (__base <= 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<_Tp>::value)
		{
		  _Tp __tmp;
		  if (__builtin_mul_overflow(__val, __sign, &__tmp))
		    __res.ec = errc::result_out_of_range;
		  else
		    __value = __tmp;
		}
	      else
		{
		  if _GLIBCXX17_CONSTEXPR
		    (numeric_limits<_Up>::max() > numeric_limits<_Tp>::max())
		    {
		      if (__val > numeric_limits<_Tp>::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
Commit	Line	Data
6b513475	1	// Primitive numeric conversions (to_chars and from_chars) -- C++ --
6b513475	2
fbd26352	3	// Copyright (C) 2017-2019 Free Software Foundation, Inc.
6b513475	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 include/charconv
	26	* This is a Standard C++ Library header.
	27	*/
	28
	29	#ifndef _GLIBCXX_CHARCONV
	30	#define _GLIBCXX_CHARCONV 1
	31
	32	#pragma GCC system_header
	33
	34	#if __cplusplus >= 201402L
	35
	36	#include <type_traits>
	37	#include <limits>
	38	#include <cctype>
00f08bc3	39	#include <bits/charconv.h> // for __to_chars_len, __to_chars_10_impl
6b513475	40	#include <bits/error_constants.h> // for std::errc
6b513475	41
00f08bc3	42	// Define when floating point is supported: #define __cpp_lib_to_chars 201611L
00f08bc3	43
6b513475	44	namespace std _GLIBCXX_VISIBILITY(default)
	45	{
	46	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	47
	48	/// Result type of std::to_chars
	49	struct to_chars_result
	50	{
	51	char* ptr;
	52	errc ec;
	53	};
	54
	55	/// Result type of std::from_chars
	56	struct from_chars_result
	57	{
	58	const char* ptr;
	59	errc ec;
	60	};
	61
	62	namespace __detail
	63	{
6b513475	64	template<typename _Tp>
6b513475	65	using __integer_to_chars_result_type
95d16249	66	= enable_if_t<__or_v<__is_signed_integer<_Tp>,
	67	__is_unsigned_integer<_Tp>,
	68	is_same<char, remove_cv_t<_Tp>>>,
	69	to_chars_result>;
6b513475	70
00f08bc3	71	// Pick an unsigned type of suitable size. This is used to reduce the
	72	// number of specializations of __to_chars_len, __to_chars etc. that
	73	// get instantiated. For example, to_chars<char> and to_chars<short>
	74	// and to_chars<unsigned> will all use the same code, and so will
	75	// to_chars<long> when sizeof(int) == sizeof(long).
6b513475	76	template<typename _Tp>
00f08bc3	77	struct __to_chars_unsigned_type : __make_unsigned_selector_base
	78	{
	79	using _UInts = _List<unsigned int, unsigned long, unsigned long long
50521ed1	80	#if _GLIBCXX_USE_INT128
00f08bc3	81	, unsigned __int128
50521ed1	82	#endif
00f08bc3	83	>;
	84	using type = typename __select<sizeof(_Tp), _UInts>::__type;
	85	};
	86
	87	template<typename _Tp>
	88	using __unsigned_least_t = typename __to_chars_unsigned_type<_Tp>::type;
6b513475	89
6b513475	90	// Generic implementation for arbitrary bases.
00f08bc3	91	// Defined in <bits/charconv.h>.
6b513475	92	template<typename _Tp>
6b513475	93	constexpr unsigned
00f08bc3	94	__to_chars_len(_Tp __value, int __base /* = 10 */) noexcept;
6b513475	95
	96	template<typename _Tp>
	97	constexpr unsigned
	98	__to_chars_len_2(_Tp __value) noexcept
	99	{
	100	static_assert(is_integral<_Tp>::value, "implementation bug");
	101	static_assert(is_unsigned<_Tp>::value, "implementation bug");
	102
	103	constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);
	104
	105	// N.B. __builtin_clzll is undefined if __value == 0, but std::to_chars
	106	// handles zero values directly.
	107
	108	// For sizeof(_Tp) > 1 this is an order of magnitude faster than
	109	// the generic __to_chars_len.
	110	return __nbits
	111	- (__builtin_clzll(__value)
	112	- ((__CHAR_BIT__ * sizeof(long long)) - __nbits));
	113	}
	114
	115	template<typename _Tp>
	116	constexpr unsigned
	117	__to_chars_len_8(_Tp __value) noexcept
	118	{
	119	static_assert(is_integral<_Tp>::value, "implementation bug");
	120	static_assert(is_unsigned<_Tp>::value, "implementation bug");
	121
	122	constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);
	123
	124	if _GLIBCXX17_CONSTEXPR (__nbits <= 16)
	125	{
	126	return __value > 077777u ? 6u
	127	: __value > 07777u ? 5u
	128	: __value > 0777u ? 4u
	129	: __value > 077u ? 3u
	130	: __value > 07u ? 2u
	131	: 1u;
	132	}
	133	else
	134	return __to_chars_len(__value, 8);
	135	}
	136
	137	// Generic implementation for arbitrary bases.
	138	template<typename _Tp>
	139	to_chars_result
	140	__to_chars(char* __first, char* __last, _Tp __val, int __base) noexcept
	141	{
	142	static_assert(is_integral<_Tp>::value, "implementation bug");
	143	static_assert(is_unsigned<_Tp>::value, "implementation bug");
	144
	145	to_chars_result __res;
	146
	147	const unsigned __len = __to_chars_len(__val, __base);
	148
	149	if (__builtin_expect((__last - __first) < __len, 0))
	150	{
	151	__res.ptr = __last;
	152	__res.ec = errc::value_too_large;
	153	return __res;
	154	}
	155
	156	unsigned __pos = __len - 1;
	157
	158	static constexpr char __digits[]
159	= "0123456789abcdefghijklmnopqrstuvwxyz";
160
161	while (__val >= __base)
162	{
163	auto const __quo = __val / __base;
164	auto const __rem = __val % __base;
165	__first[__pos--] = __digits[__rem];
166	__val = __quo;
167	}
168	*__first = __digits[__val];
169
170	__res.ptr = __first + __len;
171	__res.ec = {};
172	return __res;
173	}
174
175	template<typename _Tp>
176	__integer_to_chars_result_type<_Tp>
177	__to_chars_16(char* __first, char* __last, _Tp __val) noexcept
178	{
179	static_assert(is_integral<_Tp>::value, "implementation bug");
180	static_assert(is_unsigned<_Tp>::value, "implementation bug");
181
182	to_chars_result __res;
183
184	const unsigned __len = __to_chars_len(__val, 0x10);
185
186	if (__builtin_expect((__last - __first) < __len, 0))
187	{
188	__res.ptr = __last;
189	__res.ec = errc::value_too_large;
190	return __res;
191	}
192
193	static constexpr char __digits[513] =
194	"000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f"
195	"202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f"
196	"404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f"
197	"606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f"
198	"808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f"
199	"a0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebf"
200	"c0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedf"
201	"e0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";
202	unsigned __pos = __len - 1;
203	while (__val >= 0x100)
204	{
205	auto const __num = (__val % 0x100) * 2;
206	__val /= 0x100;
207	__first[__pos] = __digits[__num + 1];
208	__first[__pos - 1] = __digits[__num];
209	__pos -= 2;
210	}
211	if (__val >= 0x10)
212	{
213	auto const __num = __val * 2;
214	__first[__pos] = __digits[__num + 1];
215	__first[__pos - 1] = __digits[__num];
216	}
217	else
218	__first[__pos] = "0123456789abcdef"[__val];
219	__res.ptr = __first + __len;
220	__res.ec = {};
221	return __res;
222	}
223
224	template<typename _Tp>
00f08bc3	225	inline __integer_to_chars_result_type<_Tp>
6b513475	226	__to_chars_10(char* __first, char* __last, _Tp __val) noexcept
	227	{
	228	static_assert(is_integral<_Tp>::value, "implementation bug");
	229	static_assert(is_unsigned<_Tp>::value, "implementation bug");
	230
	231	to_chars_result __res;
	232
	233	const unsigned __len = __to_chars_len(__val, 10);
	234
	235	if (__builtin_expect((__last - __first) < __len, 0))
	236	{
	237	__res.ptr = __last;
	238	__res.ec = errc::value_too_large;
	239	return __res;
	240	}
	241
00f08bc3	242	__detail::__to_chars_10_impl(__first, __len, __val);
6b513475	243	__res.ptr = __first + __len;
	244	__res.ec = {};
	245	return __res;
	246	}
	247
	248	template<typename _Tp>
	249	__integer_to_chars_result_type<_Tp>
	250	__to_chars_8(char* __first, char* __last, _Tp __val) noexcept
	251	{
	252	static_assert(is_integral<_Tp>::value, "implementation bug");
	253	static_assert(is_unsigned<_Tp>::value, "implementation bug");
	254
	255	to_chars_result __res;
	256
	257	const unsigned __len = __to_chars_len_8(__val);
	258
	259	if (__builtin_expect((__last - __first) < __len, 0))
	260	{
	261	__res.ptr = __last;
	262	__res.ec = errc::value_too_large;
	263	return __res;
	264	}
	265
	266	static constexpr char __digits[129] =
	267	"00010203040506071011121314151617"
	268	"20212223242526273031323334353637"
	269	"40414243444546475051525354555657"
	270	"60616263646566677071727374757677";
	271	unsigned __pos = __len - 1;
	272	while (__val >= 0100)
	273	{
	274	auto const __num = (__val % 0100) * 2;
	275	__val /= 0100;
	276	__first[__pos] = __digits[__num + 1];
	277	__first[__pos - 1] = __digits[__num];
	278	__pos -= 2;
	279	}
	280	if (__val >= 010)
	281	{
	282	auto const __num = __val * 2;
	283	__first[__pos] = __digits[__num + 1];
	284	__first[__pos - 1] = __digits[__num];
	285	}
	286	else
	287	__first[__pos] = '0' + __val;
	288	__res.ptr = __first + __len;
	289	__res.ec = {};
	290	return __res;
	291	}
	292
	293	template<typename _Tp>
	294	__integer_to_chars_result_type<_Tp>
	295	__to_chars_2(char* __first, char* __last, _Tp __val) noexcept
	296	{
	297	static_assert(is_integral<_Tp>::value, "implementation bug");
	298	static_assert(is_unsigned<_Tp>::value, "implementation bug");
	299
	300	to_chars_result __res;
	301
	302	const unsigned __len = __to_chars_len_2(__val);
	303
	304	if (__builtin_expect((__last - __first) < __len, 0))
	305	{
	306	__res.ptr = __last;
307	__res.ec = errc::value_too_large;
308	return __res;
309	}
310
311	unsigned __pos = __len - 1;
312
313	while (__pos)
314	{
315	__first[__pos--] = '0' + (__val & 1);
316	__val >>= 1;
317	}
318	*__first = '0' + (__val & 1);
319
320	__res.ptr = __first + __len;
321	__res.ec = {};
322	return __res;
323	}
324
325	} // namespace __detail
326
327	template<typename _Tp>
328	__detail::__integer_to_chars_result_type<_Tp>
329	to_chars(char* __first, char* __last, _Tp __value, int __base = 10)
330	{
331	__glibcxx_assert(2 <= __base && __base <= 36);
332
333	using _Up = __detail::__unsigned_least_t<_Tp>;
334	_Up __unsigned_val = __value;
335
336	if (__value == 0 && __first != __last)
337	{
338	*__first = '0';
339	return { __first + 1, errc{} };
340	}
341
342	if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
343	if (__value < 0)
344	{
345	if (__builtin_expect(__first != __last, 1))
346	*__first++ = '-';
347	__unsigned_val = _Up(~__value) + _Up(1);
348	}
349
350	switch (__base)
351	{
352	case 16:
353	return __detail::__to_chars_16(__first, __last, __unsigned_val);
354	case 10:
355	return __detail::__to_chars_10(__first, __last, __unsigned_val);
356	case 8:
357	return __detail::__to_chars_8(__first, __last, __unsigned_val);
358	case 2:
359	return __detail::__to_chars_2(__first, __last, __unsigned_val);
360	default:
361	return __detail::__to_chars(__first, __last, __unsigned_val, __base);
362	}
363	}
364
365	namespace __detail
366	{
367	template<typename _Tp>
368	bool
369	__raise_and_add(_Tp& __val, int __base, unsigned char __c)
370	{
371	if (__builtin_mul_overflow(__val, __base, &__val)
372	\|\| __builtin_add_overflow(__val, __c, &__val))
373	return false;
374	return true;
375	}
376
377	/// std::from_chars implementation for integers in base 2.
378	template<typename _Tp>
379	bool
380	__from_chars_binary(const char& __first, const char __last, _Tp& __val)
381	{
382	static_assert(is_integral<_Tp>::value, "implementation bug");
383	static_assert(is_unsigned<_Tp>::value, "implementation bug");
384
385	const ptrdiff_t __len = __last - __first;
386	int __i = 0;
387	while (__i < __len)
388	{
389	const unsigned char __c = (unsigned)__first[__i] - '0';
390	if (__c < 2)
391	__val = (__val << 1) \| __c;
392	else
393	break;
394	__i++;
395	}
396	__first += __i;
397	return __i <= (sizeof(_Tp) * __CHAR_BIT__);
398	}
399
400	/// std::from_chars implementation for integers in bases 3 to 10.
401	template<typename _Tp>
402	bool
403	__from_chars_digit(const char& __first, const char __last, _Tp& __val,
404	int __base)
405	{
406	static_assert(is_integral<_Tp>::value, "implementation bug");
407	static_assert(is_unsigned<_Tp>::value, "implementation bug");
408
409	auto __matches = [__base](char __c) {
410	return '0' <= __c && __c <= ('0' + (__base - 1));
411	};
412
413	while (__first != __last)
414	{
415	const char __c = *__first;
416	if (__matches(__c))
417	{
418	if (!__raise_and_add(__val, __base, __c - '0'))
419	{
420	while (++__first != __last && __matches(*__first))
421	;
422	return false;
423	}
424	__first++;
425	}
426	else
427	return true;
428	}
429	return true;
430	}
431
432	constexpr unsigned char
433	__from_chars_alpha_to_num(char __c)
434	{
435	switch (__c)
436	{
437	case 'a':
438	case 'A':
439	return 10;
440	case 'b':
441	case 'B':
442	return 11;
443	case 'c':
444	case 'C':
445	return 12;
446	case 'd':
447	case 'D':
448	return 13;
449	case 'e':
450	case 'E':
451	return 14;
452	case 'f':
453	case 'F':
454	return 15;
455	case 'g':
456	case 'G':
457	return 16;
458	case 'h':
459	case 'H':
460	return 17;
461	case 'i':
462	case 'I':
463	return 18;
464	case 'j':
465	case 'J':
466	return 19;
467	case 'k':
468	case 'K':
469	return 20;
470	case 'l':
471	case 'L':
472	return 21;
473	case 'm':
474	case 'M':
475	return 22;
476	case 'n':
477	case 'N':
478	return 23;
479	case 'o':
480	case 'O':
481	return 24;
482	case 'p':
483	case 'P':
484	return 25;
485	case 'q':
486	case 'Q':
487	return 26;
488	case 'r':
489	case 'R':
490	return 27;
491	case 's':
492	case 'S':
493	return 28;
494	case 't':
495	case 'T':
496	return 29;
497	case 'u':
498	case 'U':
499	return 30;
500	case 'v':
501	case 'V':
502	return 31;
503	case 'w':
504	case 'W':
505	return 32;
506	case 'x':
507	case 'X':
508	return 33;
509	case 'y':
510	case 'Y':
511	return 34;
512	case 'z':
513	case 'Z':
514	return 35;
515	}
516	return std::numeric_limits<unsigned char>::max();
517	}
518
519	/// std::from_chars implementation for integers in bases 11 to 26.
520	template<typename _Tp>
521	bool
522	__from_chars_alnum(const char& __first, const char __last, _Tp& __val,
523	int __base)
524	{
525	bool __valid = true;
526	while (__first != __last)
527	{
528	unsigned char __c = *__first;
529	if (std::isdigit(__c))
530	__c -= '0';
531	else
532	{
533	__c = __from_chars_alpha_to_num(__c);
534	if (__c >= __base)
535	break;
536	}
537
538	if (__builtin_expect(__valid, 1))
539	__valid = __raise_and_add(__val, __base, __c);
540	__first++;
541	}
542	return __valid;
543	}
544
545	template<typename _Tp>
546	using __integer_from_chars_result_type
95d16249	547	= enable_if_t<__or_v<__is_signed_integer<_Tp>,
	548	__is_unsigned_integer<_Tp>,
	549	is_same<char, remove_cv_t<_Tp>>>,
	550	from_chars_result>;
6b513475	551
	552	} // namespace __detail
	553
	554	/// std::from_chars for integral types.
	555	template<typename _Tp>
	556	__detail::__integer_from_chars_result_type<_Tp>
	557	from_chars(const char* __first, const char* __last, _Tp& __value,
	558	int __base = 10)
	559	{
	560	__glibcxx_assert(2 <= __base && __base <= 36);
	561
	562	from_chars_result __res{__first, {}};
	563
	564	int __sign = 1;
	565	if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
	566	if (__first != __last && *__first == '-')
	567	{
	568	__sign = -1;
	569	++__first;
	570	}
	571
	572	using _Up = __detail::__unsigned_least_t<_Tp>;
	573	_Up __val = 0;
	574
	575	const auto __start = __first;
	576	bool __valid;
	577	if (__base == 2)
	578	__valid = __detail::__from_chars_binary(__first, __last, __val);
	579	else if (__base <= 10)
	580	__valid = __detail::__from_chars_digit(__first, __last, __val, __base);
	581	else
	582	__valid = __detail::__from_chars_alnum(__first, __last, __val, __base);
	583
	584	if (__builtin_expect(__first == __start, 0))
	585	__res.ec = errc::invalid_argument;
	586	else
	587	{
	588	__res.ptr = __first;
	589	if (!__valid)
	590	__res.ec = errc::result_out_of_range;
	591	else
	592	{
	593	if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
	594	{
	595	_Tp __tmp;
	596	if (__builtin_mul_overflow(__val, __sign, &__tmp))
	597	__res.ec = errc::result_out_of_range;
	598	else
	599	__value = __tmp;
	600	}
	601	else
	602	{
	603	if _GLIBCXX17_CONSTEXPR
	604	(numeric_limits<_Up>::max() > numeric_limits<_Tp>::max())
	605	{
	606	if (__val > numeric_limits<_Tp>::max())
	607	__res.ec = errc::result_out_of_range;
	608	else
	609	__value = __val;
	610	}
	611	else
	612	__value = __val;
	613	}
	614	}
615	}
616	return __res;
617	}
618
619	_GLIBCXX_END_NAMESPACE_VERSION
620	} // namespace std
621	#endif // C++14
622	#endif // _GLIBCXX_CHARCONV