charconv

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// Primitive numeric conversions (to_chars and from_chars) -*- C++ -*-
 
// Copyright (C) 2017-2023 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
 
#include <bits/requires_hosted.h> // for error codes
 
// As an extension we support <charconv> in C++14, but this header should not
// be included by any other library headers in C++14 mode. This ensures that
// the names defined in this header are not added to namespace std unless a
// user explicitly includes <charconv> in C++14 code.
#if __cplusplus >= 201402L
 
#include <type_traits>
#include <bit>                  // for __bit_width
#include <bits/charconv.h>      // for __to_chars_len, __to_chars_10_impl
#include <bits/error_constants.h> // for std::errc
#include <ext/numeric_traits.h>
 
#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 \
    && __SIZE_WIDTH__ >= 32 && _GLIBCXX_HOSTED
# define __cpp_lib_to_chars 201611L
#endif
 
#if __cplusplus > 202002L
# define __cpp_lib_constexpr_charconv 202207L
#endif
 
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
  /// Result type of std::to_chars
  struct to_chars_result
  {
    char* ptr;
    errc ec;
 
#if __cplusplus > 201703L && __cpp_impl_three_way_comparison >= 201907L
    friend bool
    operator==(const to_chars_result&, const to_chars_result&) = default;
#endif
  };
 
  /// Result type of std::from_chars
  struct from_chars_result
  {
    const char* ptr;
    errc ec;
 
#if __cplusplus > 201703L && __cpp_impl_three_way_comparison >= 201907L
    friend bool
    operator==(const from_chars_result&, const from_chars_result&) = default;
#endif
  };
 
namespace __detail
{
  template<typename _Tp>
    using __integer_to_chars_result_type
      = enable_if_t<__or_<__is_signed_integer<_Tp>,
                          __is_unsigned_integer<_Tp>,
#if defined __SIZEOF_INT128__ && defined __STRICT_ANSI__
                          is_same<_Tp, signed __int128>,
                          is_same<_Tp, unsigned __int128>,
#endif
                          is_same<char, remove_cv_t<_Tp>>>::value,
                    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 __SIZEOF_INT128__ > __SIZEOF_LONG_LONG__
        , 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
    { return std::__bit_width(__value); }
 
  // Generic implementation for arbitrary bases.
  template<typename _Tp>
    constexpr to_chars_result
    __to_chars(char* __first, char* __last, _Tp __val, int __base) noexcept
    {
      static_assert(__integer_to_chars_is_unsigned<_Tp>, "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;
 
      constexpr char __digits[] = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
        'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
        'u', 'v', 'w', 'x', 'y', 'z'
      };
 
      while (__val >= (unsigned)__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>
    constexpr __integer_to_chars_result_type<_Tp>
    __to_chars_16(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(__integer_to_chars_is_unsigned<_Tp>, "implementation bug");
 
      to_chars_result __res;
 
      const unsigned __len = (__to_chars_len_2(__val) + 3) / 4;
 
      if (__builtin_expect((__last - __first) < __len, 0))
        {
          __res.ptr = __last;
          __res.ec = errc::value_too_large;
          return __res;
        }
 
      constexpr char __digits[] = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        'a', 'b', 'c', 'd', 'e', 'f'
      };
      unsigned __pos = __len - 1;
      while (__val >= 0x100)
        {
          auto __num = __val & 0xF;
          __val >>= 4;
          __first[__pos] = __digits[__num];
          __num = __val & 0xF;
          __val >>= 4;
          __first[__pos - 1] = __digits[__num];
          __pos -= 2;
        }
      if (__val >= 0x10)
        {
          const auto __num = __val & 0xF;
          __val >>= 4;
          __first[1] = __digits[__num];
          __first[0] = __digits[__val];
        }
      else
        __first[0] = __digits[__val];
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }
 
  template<typename _Tp>
    constexpr __integer_to_chars_result_type<_Tp>
    __to_chars_10(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(__integer_to_chars_is_unsigned<_Tp>, "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>
    constexpr __integer_to_chars_result_type<_Tp>
    __to_chars_8(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(__integer_to_chars_is_unsigned<_Tp>, "implementation bug");
 
      to_chars_result __res;
      unsigned __len;
 
      if _GLIBCXX17_CONSTEXPR (__gnu_cxx::__int_traits<_Tp>::__digits <= 16)
        {
          __len = __val > 077777u ? 6u
            : __val > 07777u ? 5u
            : __val > 0777u ? 4u
            : __val > 077u ? 3u
            : __val > 07u ? 2u
            : 1u;
        }
      else
        __len = (__to_chars_len_2(__val) + 2) / 3;
 
      if (__builtin_expect((__last - __first) < __len, 0))
        {
          __res.ptr = __last;
          __res.ec = errc::value_too_large;
          return __res;
        }
 
      unsigned __pos = __len - 1;
      while (__val >= 0100)
        {
          auto __num = __val & 7;
          __val >>= 3;
          __first[__pos] = '0' + __num;
          __num = __val & 7;
          __val >>= 3;
          __first[__pos - 1] = '0' + __num;
          __pos -= 2;
        }
      if (__val >= 010)
        {
          auto const __num = __val & 7;
          __val >>= 3;
          __first[1] = '0' + __num;
          __first[0] = '0' + __val;
        }
      else
        __first[0] = '0' + __val;
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }
 
  template<typename _Tp>
    constexpr __integer_to_chars_result_type<_Tp>
    __to_chars_2(char* __first, char* __last, _Tp __val) noexcept
    {
      static_assert(__integer_to_chars_is_unsigned<_Tp>, "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 digit is always '1' because __to_chars_len_2 skips
      // leading zero bits and std::to_chars handles zero values
      // directly.
      __first[0] = '1';
 
      __res.ptr = __first + __len;
      __res.ec = {};
      return __res;
    }
 
} // namespace __detail
 
  template<typename _Tp>
    constexpr __detail::__integer_to_chars_result_type<_Tp>
    __to_chars_i(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 (__first == __last) [[__unlikely__]]
        return { __last, errc::value_too_large };
 
      if (__value == 0)
        {
          *__first = '0';
          return { __first + 1, errc{} };
        }
      else if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
        if (__value < 0)
          {
            *__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);
      }
    }
 
#define _GLIBCXX_TO_CHARS(T) \
  _GLIBCXX23_CONSTEXPR inline to_chars_result \
  to_chars(char* __first, char* __last, T __value, int __base = 10) \
  { return std::__to_chars_i<T>(__first, __last, __value, __base); }
_GLIBCXX_TO_CHARS(char)
_GLIBCXX_TO_CHARS(signed char)
_GLIBCXX_TO_CHARS(unsigned char)
_GLIBCXX_TO_CHARS(signed short)
_GLIBCXX_TO_CHARS(unsigned short)
_GLIBCXX_TO_CHARS(signed int)
_GLIBCXX_TO_CHARS(unsigned int)
_GLIBCXX_TO_CHARS(signed long)
_GLIBCXX_TO_CHARS(unsigned long)
_GLIBCXX_TO_CHARS(signed long long)
_GLIBCXX_TO_CHARS(unsigned long long)
#if defined(__GLIBCXX_TYPE_INT_N_0)
_GLIBCXX_TO_CHARS(signed __GLIBCXX_TYPE_INT_N_0)
_GLIBCXX_TO_CHARS(unsigned __GLIBCXX_TYPE_INT_N_0)
#endif
#if defined(__GLIBCXX_TYPE_INT_N_1)
_GLIBCXX_TO_CHARS(signed __GLIBCXX_TYPE_INT_N_1)
_GLIBCXX_TO_CHARS(unsigned __GLIBCXX_TYPE_INT_N_1)
#endif
#if defined(__GLIBCXX_TYPE_INT_N_2)
_GLIBCXX_TO_CHARS(signed __GLIBCXX_TYPE_INT_N_2)
_GLIBCXX_TO_CHARS(unsigned __GLIBCXX_TYPE_INT_N_2)
#endif
#if defined(__GLIBCXX_TYPE_INT_N_3)
_GLIBCXX_TO_CHARS(signed __GLIBCXX_TYPE_INT_N_3)
_GLIBCXX_TO_CHARS(unsigned __GLIBCXX_TYPE_INT_N_3)
#endif
#undef _GLIBCXX_TO_CHARS
 
  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 3266. to_chars(bool) should be deleted
  to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
 
namespace __detail
{
  template<typename _Tp>
    constexpr 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;
    }
 
  template<bool _DecOnly>
    struct __from_chars_alnum_to_val_table
    {
      struct type { unsigned char __data[1u << __CHAR_BIT__] = {}; };
 
      // Construct and return a lookup table that maps 0-9, A-Z and a-z to their
      // corresponding base-36 value and maps all other characters to 127.
      static constexpr type
      _S_make_table()
      {
        constexpr unsigned char __lower_letters[27] = "abcdefghijklmnopqrstuvwxyz";
        constexpr unsigned char __upper_letters[27] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        type __table;
        for (auto& __entry : __table.__data)
          __entry = 127;
        for (int __i = 0; __i < 10; ++__i)
          __table.__data['0' + __i] = __i;
        for (int __i = 0; __i < 26; ++__i)
          {
            __table.__data[__lower_letters[__i]] = 10 + __i;
            __table.__data[__upper_letters[__i]] = 10 + __i;
          }
        return __table;
      }
 
      // This initializer is made superficially dependent in order
      // to prevent the compiler from wastefully constructing the
      // table ahead of time when it's not needed.
      static constexpr type value = (_DecOnly, _S_make_table());
    };
 
#if ! __cpp_inline_variables
  template<bool _DecOnly>
    const typename __from_chars_alnum_to_val_table<_DecOnly>::type
      __from_chars_alnum_to_val_table<_DecOnly>::value;
#endif
 
  // If _DecOnly is true: if the character is a decimal digit, then
  // return its corresponding base-10 value, otherwise return a value >= 127.
  // If _DecOnly is false: if the character is an alphanumeric digit, then
  // return its corresponding base-36 value, otherwise return a value >= 127.
  template<bool _DecOnly = false>
    _GLIBCXX20_CONSTEXPR unsigned char
    __from_chars_alnum_to_val(unsigned char __c)
    {
      if _GLIBCXX17_CONSTEXPR (_DecOnly)
        return static_cast<unsigned char>(__c - '0');
      else
        return __from_chars_alnum_to_val_table<_DecOnly>::value.__data[__c];
    }
 
  /// std::from_chars implementation for integers in a power-of-two base.
  /// If _DecOnly is true, then we may assume __base is at most 8.
  template<bool _DecOnly, typename _Tp>
    _GLIBCXX23_CONSTEXPR bool
    __from_chars_pow2_base(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");
 
      // __glibcxx_assert((__base & (__base - 1)) == 0);
      // __glibcxx_assert(_DecOnly ? __base <= 8 : __base <= 32);
      const int __log2_base = __countr_zero(__base);
 
      const ptrdiff_t __len = __last - __first;
      ptrdiff_t __i = 0;
      while (__i < __len && __first[__i] == '0')
        ++__i;
      const ptrdiff_t __leading_zeroes = __i;
      if (__i >= __len) [[__unlikely__]]
        {
          __first += __i;
          return true;
        }
 
      // Remember the leading significant digit value if necessary.
      unsigned char __leading_c = 0;
      if (__base != 2)
        {
          __leading_c = __from_chars_alnum_to_val<_DecOnly>(__first[__i]);
          // __glibcxx_assert(__leading_c != 0);
          if (__leading_c >= __base) [[__unlikely__]]
            {
              __first += __i;
              return true;
            }
          __val = __leading_c;
          ++__i;
        }
 
      for (; __i < __len; ++__i)
        {
          const unsigned char __c = __from_chars_alnum_to_val<_DecOnly>(__first[__i]);
          if (__c >= __base)
            break;
          __val = (__val << __log2_base) | __c;
        }
      __first += __i;
      auto __significant_bits = (__i - __leading_zeroes) * __log2_base;
      if (__base != 2)
        // Compensate for a leading significant digit that didn't use all
        // of its available bits.
        __significant_bits -= __log2_base - __bit_width(__leading_c);
      // __glibcxx_assert(__significant_bits >= 0);
      return __significant_bits <= __gnu_cxx::__int_traits<_Tp>::__digits;
    }
 
  /// std::from_chars implementation for integers in any base.
  /// If _DecOnly is true, then we may assume __base is at most 10.
  template<bool _DecOnly, typename _Tp>
    constexpr bool
    __from_chars_alnum(const char*& __first, const char* __last, _Tp& __val,
                       int __base)
    {
      // __glibcxx_assert(!_DecOnly || __base <= 10);
 
      const int __bits_per_digit = __bit_width(__base);
      int __unused_bits_lower_bound = __gnu_cxx::__int_traits<_Tp>::__digits;
      for (; __first != __last; ++__first)
        {
          const unsigned char __c = __from_chars_alnum_to_val<_DecOnly>(*__first);
          if (__c >= __base)
            return true;
 
          __unused_bits_lower_bound -= __bits_per_digit;
          if (__unused_bits_lower_bound >= 0) [[__likely__]]
            // We're definitely not going to overflow.
            __val = __val * __base + __c;
          else if (!__raise_and_add(__val, __base, __c)) [[__unlikely__]]
            {
              while (++__first != __last
                     && __from_chars_alnum_to_val<_DecOnly>(*__first) < __base)
                ;
              return false;
            }
        }
      return true;
    }
 
  template<typename _Tp>
    using __integer_from_chars_result_type
      = enable_if_t<__or_<__is_signed_integer<_Tp>,
                          __is_unsigned_integer<_Tp>,
                          is_same<char, remove_cv_t<_Tp>>>::value,
                    from_chars_result>;
 
} // namespace __detail
 
  /// std::from_chars for integral types.
  template<typename _Tp>
    _GLIBCXX23_CONSTEXPR __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 & (__base - 1)) == 0)
        {
          if (__base <= 8)
            __valid = __detail::__from_chars_pow2_base<true>(__first, __last, __val, __base);
          else
            __valid = __detail::__from_chars_pow2_base<false>(__first, __last, __val, __base);
        }
      else if (__base <= 10)
        __valid = __detail::__from_chars_alnum<true>(__first, __last, __val, __base);
      else
        __valid = __detail::__from_chars_alnum<false>(__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 (__gnu_cxx::__int_traits<_Up>::__max
                      > __gnu_cxx::__int_traits<_Tp>::__max)
                    {
                      if (__val > __gnu_cxx::__int_traits<_Tp>::__max)
                        __res.ec = errc::result_out_of_range;
                      else
                        __value = __val;
                    }
                  else
                    __value = __val;
                }
            }
        }
      return __res;
    }
 
  /// floating-point format for primitive numerical conversion
  enum class chars_format
  {
    scientific = 1, fixed = 2, hex = 4, general = fixed | scientific
  };
 
  constexpr chars_format
  operator|(chars_format __lhs, chars_format __rhs) noexcept
  { return (chars_format)((unsigned)__lhs | (unsigned)__rhs); }
 
  constexpr chars_format
  operator&(chars_format __lhs, chars_format __rhs) noexcept
  { return (chars_format)((unsigned)__lhs & (unsigned)__rhs); }
 
  constexpr chars_format
  operator^(chars_format __lhs, chars_format __rhs) noexcept
  { return (chars_format)((unsigned)__lhs ^ (unsigned)__rhs); }
 
  constexpr chars_format
  operator~(chars_format __fmt) noexcept
  { return (chars_format)~(unsigned)__fmt; }
 
  constexpr chars_format&
  operator|=(chars_format& __lhs, chars_format __rhs) noexcept
  { return __lhs = __lhs | __rhs; }
 
  constexpr chars_format&
  operator&=(chars_format& __lhs, chars_format __rhs) noexcept
  { return __lhs = __lhs & __rhs; }
 
  constexpr chars_format&
  operator^=(chars_format& __lhs, chars_format __rhs) noexcept
  { return __lhs = __lhs ^ __rhs; }
 
#if defined __cpp_lib_to_chars || _GLIBCXX_HAVE_USELOCALE
  from_chars_result
  from_chars(const char* __first, const char* __last, float& __value,
             chars_format __fmt = chars_format::general) noexcept;
 
  from_chars_result
  from_chars(const char* __first, const char* __last, double& __value,
             chars_format __fmt = chars_format::general) noexcept;
 
  from_chars_result
  from_chars(const char* __first, const char* __last, long double& __value,
             chars_format __fmt = chars_format::general) noexcept;
 
  // Library routines for 16-bit extended floating point formats
  // using float as interchange format.
  from_chars_result
  __from_chars_float16_t(const char* __first, const char* __last,
                         float& __value,
                         chars_format __fmt = chars_format::general) noexcept;
  from_chars_result
  __from_chars_bfloat16_t(const char* __first, const char* __last,
                          float& __value,
                          chars_format __fmt = chars_format::general) noexcept;
 
#if defined(__STDCPP_FLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32) \
    && defined(__cpp_lib_to_chars)
  inline from_chars_result
  from_chars(const char* __first, const char* __last, _Float16& __value,
             chars_format __fmt = chars_format::general) noexcept
  {
    float __val;
    from_chars_result __res
      = __from_chars_float16_t(__first, __last, __val, __fmt);
    if (__res.ec == errc{})
      __value = __val;
    return __res;
  }
#endif
 
#if defined(__STDCPP_FLOAT32_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
  inline from_chars_result
  from_chars(const char* __first, const char* __last, _Float32& __value,
             chars_format __fmt = chars_format::general) noexcept
  {
    float __val;
    from_chars_result __res = from_chars(__first, __last, __val, __fmt);
    if (__res.ec == errc{})
      __value = __val;
    return __res;
  }
#endif
 
#if defined(__STDCPP_FLOAT64_T__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64)
  inline from_chars_result
  from_chars(const char* __first, const char* __last, _Float64& __value,
             chars_format __fmt = chars_format::general) noexcept
  {
    double __val;
    from_chars_result __res = from_chars(__first, __last, __val, __fmt);
    if (__res.ec == errc{})
      __value = __val;
    return __res;
  }
#endif
 
#if defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_LDOUBLE_IS_IEEE_BINARY128)
  inline from_chars_result
  from_chars(const char* __first, const char* __last, _Float128& __value,
             chars_format __fmt = chars_format::general) noexcept
  {
    long double __val;
    from_chars_result __res = from_chars(__first, __last, __val, __fmt);
    if (__res.ec == errc{})
      __value = __val;
    return __res;
  }
#elif defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_HAVE_FLOAT128_MATH)
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
  __extension__ from_chars_result
  from_chars(const char* __first, const char* __last, __ieee128& __value,
             chars_format __fmt = chars_format::general) noexcept;
 
  inline from_chars_result
  from_chars(const char* __first, const char* __last, _Float128& __value,
             chars_format __fmt = chars_format::general) noexcept
  {
    __extension__ __ieee128 __val;
    from_chars_result __res = from_chars(__first, __last, __val, __fmt);
    if (__res.ec == errc{})
      __value = __val;
    return __res;
  }
#else
  from_chars_result
  from_chars(const char* __first, const char* __last, _Float128& __value,
             chars_format __fmt = chars_format::general) noexcept;
#endif
#endif
 
#if defined(__STDCPP_BFLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32) \
    && defined(__cpp_lib_to_chars)
  inline from_chars_result
  from_chars(const char* __first, const char* __last,
             __gnu_cxx::__bfloat16_t & __value,
             chars_format __fmt = chars_format::general) noexcept
  {
    float __val;
    from_chars_result __res
      = __from_chars_bfloat16_t(__first, __last, __val, __fmt);
    if (__res.ec == errc{})
      __value = __val;
    return __res;
  }
#endif
#endif
 
#if defined __cpp_lib_to_chars
  // Floating-point std::to_chars
 
  // Overloads for float.
  to_chars_result to_chars(char* __first, char* __last, float __value) noexcept;
  to_chars_result to_chars(char* __first, char* __last, float __value,
                           chars_format __fmt) noexcept;
  to_chars_result to_chars(char* __first, char* __last, float __value,
                           chars_format __fmt, int __precision) noexcept;
 
  // Overloads for double.
  to_chars_result to_chars(char* __first, char* __last, double __value) noexcept;
  to_chars_result to_chars(char* __first, char* __last, double __value,
                           chars_format __fmt) noexcept;
  to_chars_result to_chars(char* __first, char* __last, double __value,
                           chars_format __fmt, int __precision) noexcept;
 
  // Overloads for long double.
  to_chars_result to_chars(char* __first, char* __last, long double __value)
    noexcept;
  to_chars_result to_chars(char* __first, char* __last, long double __value,
                           chars_format __fmt) noexcept;
  to_chars_result to_chars(char* __first, char* __last, long double __value,
                           chars_format __fmt, int __precision) noexcept;
 
  // Library routines for 16-bit extended floating point formats
  // using float as interchange format.
  to_chars_result __to_chars_float16_t(char* __first, char* __last,
                                       float __value,
                                       chars_format __fmt) noexcept;
  to_chars_result __to_chars_bfloat16_t(char* __first, char* __last,
                                        float __value,
                                        chars_format __fmt) noexcept;
 
#if defined(__STDCPP_FLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float16 __value) noexcept
  {
    return __to_chars_float16_t(__first, __last, float(__value),
                                chars_format{});
  }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float16 __value,
           chars_format __fmt) noexcept
  { return __to_chars_float16_t(__first, __last, float(__value), __fmt); }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float16 __value,
           chars_format __fmt, int __precision) noexcept
  { return to_chars(__first, __last, float(__value), __fmt, __precision); }
#endif
 
#if defined(__STDCPP_FLOAT32_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float32 __value) noexcept
  { return to_chars(__first, __last, float(__value)); }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float32 __value,
           chars_format __fmt) noexcept
  { return to_chars(__first, __last, float(__value), __fmt); }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float32 __value,
           chars_format __fmt, int __precision) noexcept
  { return to_chars(__first, __last, float(__value), __fmt, __precision); }
#endif
 
#if defined(__STDCPP_FLOAT64_T__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64)
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float64 __value) noexcept
  { return to_chars(__first, __last, double(__value)); }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float64 __value,
           chars_format __fmt) noexcept
  { return to_chars(__first, __last, double(__value), __fmt); }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float64 __value,
           chars_format __fmt, int __precision) noexcept
  { return to_chars(__first, __last, double(__value), __fmt, __precision); }
#endif
 
#if defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_LDOUBLE_IS_IEEE_BINARY128)
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float128 __value) noexcept
  { return to_chars(__first, __last, static_cast<long double>(__value)); }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float128 __value,
           chars_format __fmt) noexcept
  {
    return to_chars(__first, __last, static_cast<long double>(__value), __fmt);
  }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float128 __value,
           chars_format __fmt, int __precision) noexcept
  {
    return to_chars(__first, __last, static_cast<long double>(__value), __fmt,
                    __precision);
  }
#elif defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_HAVE_FLOAT128_MATH)
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
  __extension__ to_chars_result
  to_chars(char* __first, char* __last, __float128 __value) noexcept;
  __extension__ to_chars_result
  to_chars(char* __first, char* __last, __float128 __value,
           chars_format __fmt) noexcept;
  __extension__ to_chars_result
  to_chars(char* __first, char* __last, __float128 __value,
           chars_format __fmt, int __precision) noexcept;
 
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float128 __value) noexcept
  {
    return __extension__ to_chars(__first, __last,
                                  static_cast<__float128>(__value));
  }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float128 __value,
           chars_format __fmt) noexcept
  {
 
    return __extension__ to_chars(__first, __last,
                                  static_cast<__float128>(__value), __fmt);
  }
  inline to_chars_result
  to_chars(char* __first, char* __last, _Float128 __value,
           chars_format __fmt, int __precision) noexcept
  {
 
    return __extension__ to_chars(__first, __last,
                                  static_cast<__float128>(__value), __fmt,
                                  __precision);
  }
#else
  to_chars_result to_chars(char* __first, char* __last, _Float128 __value)
    noexcept;
  to_chars_result to_chars(char* __first, char* __last, _Float128 __value,
                           chars_format __fmt) noexcept;
  to_chars_result to_chars(char* __first, char* __last, _Float128 __value,
                           chars_format __fmt, int __precision) noexcept;
#endif
#endif
 
#if defined(__STDCPP_BFLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
  inline to_chars_result
  to_chars(char* __first, char* __last,
           __gnu_cxx::__bfloat16_t __value) noexcept
  {
    return __to_chars_bfloat16_t(__first, __last, float(__value),
                                 chars_format{});
  }
  inline to_chars_result
  to_chars(char* __first, char* __last, __gnu_cxx::__bfloat16_t __value,
           chars_format __fmt) noexcept
  { return __to_chars_bfloat16_t(__first, __last, float(__value), __fmt); }
  inline to_chars_result
  to_chars(char* __first, char* __last, __gnu_cxx::__bfloat16_t __value,
           chars_format __fmt, int __precision) noexcept
  { return to_chars(__first, __last, float(__value), __fmt, __precision); }
#endif
#endif
 
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++14
#endif // _GLIBCXX_CHARCONV