ydb/contrib/libs/cxxsupp/libcxx/include/charconv

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_CHARCONV
#define _LIBCPP_CHARCONV

/*
    charconv synopsis

namespace std {

  // floating-point format for primitive numerical conversion
  enum class chars_format {
    scientific = unspecified,
    fixed = unspecified,
    hex = unspecified,
    general = fixed | scientific
  };

  // 23.20.2, primitive numerical output conversion
  struct to_chars_result {
    char* ptr;
    errc ec;
    friend bool operator==(const to_chars_result&, const to_chars_result&) = default; // since C++20
  };

  to_chars_result to_chars(char* first, char* last, see below value,
                           int base = 10);
  to_chars_result to_chars(char* first, char* last, bool value,
                           int base = 10) = delete;

  to_chars_result to_chars(char* first, char* last, float value);
  to_chars_result to_chars(char* first, char* last, double value);
  to_chars_result to_chars(char* first, char* last, long double value);

  to_chars_result to_chars(char* first, char* last, float value,
                           chars_format fmt);
  to_chars_result to_chars(char* first, char* last, double value,
                           chars_format fmt);
  to_chars_result to_chars(char* first, char* last, long double value,
                           chars_format fmt);

  to_chars_result to_chars(char* first, char* last, float value,
                           chars_format fmt, int precision);
  to_chars_result to_chars(char* first, char* last, double value,
                           chars_format fmt, int precision);
  to_chars_result to_chars(char* first, char* last, long double value,
                           chars_format fmt, int precision);

  // 23.20.3, primitive numerical input conversion
  struct from_chars_result {
    const char* ptr;
    errc ec;
    friend bool operator==(const from_chars_result&, const from_chars_result&) = default; // since C++20
  };

  from_chars_result from_chars(const char* first, const char* last,
                               see below& value, int base = 10);

  from_chars_result from_chars(const char* first, const char* last,
                               float& value,
                               chars_format fmt = chars_format::general);
  from_chars_result from_chars(const char* first, const char* last,
                               double& value,
                               chars_format fmt = chars_format::general);
  from_chars_result from_chars(const char* first, const char* last,
                               long double& value,
                               chars_format fmt = chars_format::general);

} // namespace std

*/

#include <__assert> // all public C++ headers provide the assertion handler
#include <__availability>
#include <__bits>
#include <__charconv/chars_format.h>
#include <__charconv/from_chars_result.h>
#include <__charconv/to_chars_result.h>
#include <__config>
#include <__debug>
#include <__errc>
#include <__utility/unreachable.h>
#include <cmath> // for log2f
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <type_traits>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

#ifndef _LIBCPP_CXX03_LANG

namespace __itoa {
_LIBCPP_AVAILABILITY_TO_CHARS _LIBCPP_FUNC_VIS char* __u64toa(uint64_t __value, char* __buffer) noexcept;
_LIBCPP_AVAILABILITY_TO_CHARS _LIBCPP_FUNC_VIS char* __u32toa(uint32_t __value, char* __buffer) noexcept;
} // namespace __itoa

to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;

namespace __itoa
{

static constexpr uint64_t __pow10_64[] = {
    UINT64_C(0),
    UINT64_C(10),
    UINT64_C(100),
    UINT64_C(1000),
    UINT64_C(10000),
    UINT64_C(100000),
    UINT64_C(1000000),
    UINT64_C(10000000),
    UINT64_C(100000000),
    UINT64_C(1000000000),
    UINT64_C(10000000000),
    UINT64_C(100000000000),
    UINT64_C(1000000000000),
    UINT64_C(10000000000000),
    UINT64_C(100000000000000),
    UINT64_C(1000000000000000),
    UINT64_C(10000000000000000),
    UINT64_C(100000000000000000),
    UINT64_C(1000000000000000000),
    UINT64_C(10000000000000000000),
};

static constexpr uint32_t __pow10_32[] = {
    UINT32_C(0),          UINT32_C(10),       UINT32_C(100),
    UINT32_C(1000),       UINT32_C(10000),    UINT32_C(100000),
    UINT32_C(1000000),    UINT32_C(10000000), UINT32_C(100000000),
    UINT32_C(1000000000),
};

template <typename _Tp, typename = void>
struct _LIBCPP_HIDDEN __traits_base
{
    using type = uint64_t;

    static _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
    {
        auto __t = (64 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
        return __t - (__v < __pow10_64[__t]) + 1;
    }

    _LIBCPP_AVAILABILITY_TO_CHARS
    static _LIBCPP_HIDE_FROM_ABI char* __convert(_Tp __v, char* __p)
    {
        return __u64toa(__v, __p);
    }

    static _LIBCPP_HIDE_FROM_ABI decltype(__pow10_64)& __pow() { return __pow10_64; }
};

template <typename _Tp>
struct _LIBCPP_HIDDEN
    __traits_base<_Tp, decltype(void(uint32_t{declval<_Tp>()}))>
{
    using type = uint32_t;

    static _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
    {
        auto __t = (32 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
        return __t - (__v < __pow10_32[__t]) + 1;
    }

    _LIBCPP_AVAILABILITY_TO_CHARS
    static _LIBCPP_HIDE_FROM_ABI char* __convert(_Tp __v, char* __p)
    {
        return __u32toa(__v, __p);
    }

    static _LIBCPP_HIDE_FROM_ABI decltype(__pow10_32)& __pow() { return __pow10_32; }
};

template <typename _Tp>
inline _LIBCPP_HIDE_FROM_ABI bool
__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r)
{
    auto __c = __a * __b;
    __r = __c;
    return __c > numeric_limits<unsigned char>::max();
}

template <typename _Tp>
inline _LIBCPP_HIDE_FROM_ABI bool
__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r)
{
    auto __c = __a * __b;
    __r = __c;
    return __c > numeric_limits<unsigned short>::max();
}

template <typename _Tp>
inline _LIBCPP_HIDE_FROM_ABI bool
__mul_overflowed(_Tp __a, _Tp __b, _Tp& __r)
{
    static_assert(is_unsigned<_Tp>::value, "");
#if !defined(_LIBCPP_COMPILER_MSVC)
    return __builtin_mul_overflow(__a, __b, &__r);
#else
    bool __did = __b && (numeric_limits<_Tp>::max() / __b) < __a;
    __r = __a * __b;
    return __did;
#endif
}

template <typename _Tp, typename _Up>
inline _LIBCPP_HIDE_FROM_ABI bool
__mul_overflowed(_Tp __a, _Up __b, _Tp& __r)
{
    return __mul_overflowed(__a, static_cast<_Tp>(__b), __r);
}

template <typename _Tp>
struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp>
{
    static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
    using __traits_base<_Tp>::__pow;
    using typename __traits_base<_Tp>::type;

    // precondition: at least one non-zero character available
    static _LIBCPP_HIDE_FROM_ABI char const*
    __read(char const* __p, char const* __ep, type& __a, type& __b)
    {
        type __cprod[digits];
        int __j = digits - 1;
        int __i = digits;
        do
        {
            if (!('0' <= *__p && *__p <= '9'))
                break;
            __cprod[--__i] = *__p++ - '0';
        } while (__p != __ep && __i != 0);

        __a = __inner_product(__cprod + __i + 1, __cprod + __j, __pow() + 1,
                              __cprod[__i]);
        if (__mul_overflowed(__cprod[__j], __pow()[__j - __i], __b))
            --__p;
        return __p;
    }

    template <typename _It1, typename _It2, class _Up>
    static _LIBCPP_HIDE_FROM_ABI _Up
    __inner_product(_It1 __first1, _It1 __last1, _It2 __first2, _Up __init)
    {
        for (; __first1 < __last1; ++__first1, ++__first2)
            __init = __init + *__first1 * *__first2;
        return __init;
    }
};

}  // namespace __itoa

template <typename _Tp>
inline _LIBCPP_HIDE_FROM_ABI _Tp
__complement(_Tp __x)
{
    static_assert(is_unsigned<_Tp>::value, "cast to unsigned first");
    return _Tp(~__x + 1);
}

template <typename _Tp>
_LIBCPP_AVAILABILITY_TO_CHARS
inline _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_itoa(char* __first, char* __last, _Tp __value, true_type)
{
    auto __x = __to_unsigned_like(__value);
    if (__value < 0 && __first != __last)
    {
        *__first++ = '-';
        __x = __complement(__x);
    }

    return __to_chars_itoa(__first, __last, __x, false_type());
}

template <typename _Tp>
_LIBCPP_AVAILABILITY_TO_CHARS
inline _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type)
{
    using __tx = __itoa::__traits<_Tp>;
    auto __diff = __last - __first;

    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
        return {__tx::__convert(__value, __first), errc(0)};
    else
        return {__last, errc::value_too_large};
}

template <typename _Tp>
_LIBCPP_AVAILABILITY_TO_CHARS
inline _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
                    true_type)
{
    auto __x = __to_unsigned_like(__value);
    if (__value < 0 && __first != __last)
    {
        *__first++ = '-';
        __x = __complement(__x);
    }

    return __to_chars_integral(__first, __last, __x, __base, false_type());
}

namespace __itoa {

static constexpr char __base_2_lut[64] = {
  '0', '0', '0', '0',
  '0', '0', '0', '1',
  '0', '0', '1', '0',
  '0', '0', '1', '1',
  '0', '1', '0', '0',
  '0', '1', '0', '1',
  '0', '1', '1', '0',
  '0', '1', '1', '1',
  '1', '0', '0', '0',
  '1', '0', '0', '1',
  '1', '0', '1', '0',
  '1', '0', '1', '1',
  '1', '1', '0', '0',
  '1', '1', '0', '1',
  '1', '1', '1', '0',
  '1', '1', '1', '1'
};

static constexpr char __base_8_lut[128] = {
  '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7',
  '1', '0', '1', '1', '1', '2', '1', '3', '1', '4', '1', '5', '1', '6', '1', '7',
  '2', '0', '2', '1', '2', '2', '2', '3', '2', '4', '2', '5', '2', '6', '2', '7',
  '3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3', '7',
  '4', '0', '4', '1', '4', '2', '4', '3', '4', '4', '4', '5', '4', '6', '4', '7',
  '5', '0', '5', '1', '5', '2', '5', '3', '5', '4', '5', '5', '5', '6', '5', '7',
  '6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6', '6', '7',
  '7', '0', '7', '1', '7', '2', '7', '3', '7', '4', '7', '5', '7', '6', '7', '7'
};

static constexpr char __base_16_lut[512] = {
  '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7', '0', '8', '0', '9', '0', 'a', '0', 'b', '0', 'c', '0', 'd', '0', 'e', '0', 'f',
  '1', '0', '1', '1', '1', '2', '1', '3', '1', '4', '1', '5', '1', '6', '1', '7', '1', '8', '1', '9', '1', 'a', '1', 'b', '1', 'c', '1', 'd', '1', 'e', '1', 'f',
  '2', '0', '2', '1', '2', '2', '2', '3', '2', '4', '2', '5', '2', '6', '2', '7', '2', '8', '2', '9', '2', 'a', '2', 'b', '2', 'c', '2', 'd', '2', 'e', '2', 'f',
  '3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3', '7', '3', '8', '3', '9', '3', 'a', '3', 'b', '3', 'c', '3', 'd', '3', 'e', '3', 'f',
  '4', '0', '4', '1', '4', '2', '4', '3', '4', '4', '4', '5', '4', '6', '4', '7', '4', '8', '4', '9', '4', 'a', '4', 'b', '4', 'c', '4', 'd', '4', 'e', '4', 'f',
  '5', '0', '5', '1', '5', '2', '5', '3', '5', '4', '5', '5', '5', '6', '5', '7', '5', '8', '5', '9', '5', 'a', '5', 'b', '5', 'c', '5', 'd', '5', 'e', '5', 'f',
  '6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6', '6', '7', '6', '8', '6', '9', '6', 'a', '6', 'b', '6', 'c', '6', 'd', '6', 'e', '6', 'f',
  '7', '0', '7', '1', '7', '2', '7', '3', '7', '4', '7', '5', '7', '6', '7', '7', '7', '8', '7', '9', '7', 'a', '7', 'b', '7', 'c', '7', 'd', '7', 'e', '7', 'f',
  '8', '0', '8', '1', '8', '2', '8', '3', '8', '4', '8', '5', '8', '6', '8', '7', '8', '8', '8', '9', '8', 'a', '8', 'b', '8', 'c', '8', 'd', '8', 'e', '8', 'f',
  '9', '0', '9', '1', '9', '2', '9', '3', '9', '4', '9', '5', '9', '6', '9', '7', '9', '8', '9', '9', '9', 'a', '9', 'b', '9', 'c', '9', 'd', '9', 'e', '9', 'f',
  'a', '0', 'a', '1', 'a', '2', 'a', '3', 'a', '4', 'a', '5', 'a', '6', 'a', '7', 'a', '8', 'a', '9', 'a', 'a', 'a', 'b', 'a', 'c', 'a', 'd', 'a', 'e', 'a', 'f',
  'b', '0', 'b', '1', 'b', '2', 'b', '3', 'b', '4', 'b', '5', 'b', '6', 'b', '7', 'b', '8', 'b', '9', 'b', 'a', 'b', 'b', 'b', 'c', 'b', 'd', 'b', 'e', 'b', 'f',
  'c', '0', 'c', '1', 'c', '2', 'c', '3', 'c', '4', 'c', '5', 'c', '6', 'c', '7', 'c', '8', 'c', '9', 'c', 'a', 'c', 'b', 'c', 'c', 'c', 'd', 'c', 'e', 'c', 'f',
  'd', '0', 'd', '1', 'd', '2', 'd', '3', 'd', '4', 'd', '5', 'd', '6', 'd', '7', 'd', '8', 'd', '9', 'd', 'a', 'd', 'b', 'd', 'c', 'd', 'd', 'd', 'e', 'd', 'f',
  'e', '0', 'e', '1', 'e', '2', 'e', '3', 'e', '4', 'e', '5', 'e', '6', 'e', '7', 'e', '8', 'e', '9', 'e', 'a', 'e', 'b', 'e', 'c', 'e', 'd', 'e', 'e', 'e', 'f',
  'f', '0', 'f', '1', 'f', '2', 'f', '3', 'f', '4', 'f', '5', 'f', '6', 'f', '7', 'f', '8', 'f', '9', 'f', 'a', 'f', 'b', 'f', 'c', 'f', 'd', 'f', 'e', 'f', 'f'
};

template <unsigned _Base>
struct _LIBCPP_HIDDEN __integral;

template <>
struct _LIBCPP_HIDDEN __integral<2> {
  template <typename _Tp>
  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
    // If value == 0 still need one digit. If the value != this has no
    // effect since the code scans for the most significant bit set. (Note
    // that __libcpp_clz doesn't work for 0.)
    return numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1);
  }

  template <typename _Tp>
  _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
    ptrdiff_t __cap = __last - __first;
    int __n = __width(__value);
    if (__n > __cap)
      return {__last, errc::value_too_large};

    __last = __first + __n;
    char* __p = __last;
    const unsigned __divisor = 16;
    while (__value > __divisor) {
      unsigned __c = __value % __divisor;
      __value /= __divisor;
      __p -= 4;
      std::memcpy(__p, &__base_2_lut[4 * __c], 4);
    }
    do {
      unsigned __c = __value % 2;
      __value /= 2;
      *--__p = "01"[__c];
    } while (__value != 0);
    return {__last, errc(0)};
  }
};

template <>
struct _LIBCPP_HIDDEN __integral<8> {
  template <typename _Tp>
  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
    // If value == 0 still need one digit. If the value != this has no
    // effect since the code scans for the most significat bit set. (Note
    // that __libcpp_clz doesn't work for 0.)
    return ((numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1)) + 2) / 3;
  }

  template <typename _Tp>
  _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
    ptrdiff_t __cap = __last - __first;
    int __n = __width(__value);
    if (__n > __cap)
      return {__last, errc::value_too_large};

    __last = __first + __n;
    char* __p = __last;
    unsigned __divisor = 64;
    while (__value > __divisor) {
      unsigned __c = __value % __divisor;
      __value /= __divisor;
      __p -= 2;
      std::memcpy(__p, &__base_8_lut[2 * __c], 2);
    }
    do {
      unsigned __c = __value % 8;
      __value /= 8;
      *--__p = "01234567"[__c];
    } while (__value != 0);
    return {__last, errc(0)};
  }

};

template <>
struct _LIBCPP_HIDDEN __integral<16> {
  template <typename _Tp>
  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
    // If value == 0 still need one digit. If the value != this has no
    // effect since the code scans for the most significat bit set. (Note
    // that __libcpp_clz doesn't work for 0.)
    return (numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1) + 3) / 4;
  }

  template <typename _Tp>
  _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
    ptrdiff_t __cap = __last - __first;
    int __n = __width(__value);
    if (__n > __cap)
      return {__last, errc::value_too_large};

    __last = __first + __n;
    char* __p = __last;
    unsigned __divisor = 256;
    while (__value > __divisor) {
      unsigned __c = __value % __divisor;
      __value /= __divisor;
      __p -= 2;
      std::memcpy(__p, &__base_16_lut[2 * __c], 2);
    }
    if (__first != __last)
      do {
        unsigned __c = __value % 16;
        __value /= 16;
        *--__p = "0123456789abcdef"[__c];
      } while (__value != 0);
    return {__last, errc(0)};
  }
};

} // namespace __itoa

template <unsigned _Base, typename _Tp,
          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
_LIBCPP_HIDE_FROM_ABI int
__to_chars_integral_width(_Tp __value) {
  return __itoa::__integral<_Base>::__width(__value);
}

template <unsigned _Base, typename _Tp,
          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
_LIBCPP_HIDE_FROM_ABI int
__to_chars_integral_width(_Tp __value) {
  return std::__to_chars_integral_width<_Base>(static_cast<unsigned>(__value));
}

template <unsigned _Base, typename _Tp,
          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
_LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value) {
  return __itoa::__integral<_Base>::__to_chars(__first, __last, __value);
}

template <unsigned _Base, typename _Tp,
          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
_LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value) {
  return std::__to_chars_integral<_Base>(__first, __last, static_cast<unsigned>(__value));
}

template <typename _Tp>
_LIBCPP_AVAILABILITY_TO_CHARS _LIBCPP_HIDE_FROM_ABI int
__to_chars_integral_width(_Tp __value, unsigned __base) {
  _LIBCPP_ASSERT(__value >= 0, "The function requires a non-negative value.");

  unsigned __base_2 = __base * __base;
  unsigned __base_3 = __base_2 * __base;
  unsigned __base_4 = __base_2 * __base_2;

  int __r = 0;
  while (true) {
    if (__value < __base)
      return __r + 1;
    if (__value < __base_2)
      return __r + 2;
    if (__value < __base_3)
      return __r + 3;
    if (__value < __base_4)
      return __r + 4;

    __value /= __base_4;
    __r += 4;
  }

  __libcpp_unreachable();
}

template <typename _Tp>
_LIBCPP_AVAILABILITY_TO_CHARS
inline _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
                    false_type)
{
  if (__base == 10) [[likely]]
    return __to_chars_itoa(__first, __last, __value, false_type());

  switch (__base) {
  case 2:
    return __to_chars_integral<2>(__first, __last, __value);
  case 8:
    return __to_chars_integral<8>(__first, __last, __value);
  case 16:
    return __to_chars_integral<16>(__first, __last, __value);
  }

  ptrdiff_t __cap = __last - __first;
  int __n = __to_chars_integral_width(__value, __base);
  if (__n > __cap)
    return {__last, errc::value_too_large};

  __last = __first + __n;
  char* __p = __last;
  do {
    unsigned __c = __value % __base;
    __value /= __base;
    *--__p = "0123456789abcdefghijklmnopqrstuvwxyz"[__c];
  } while (__value != 0);
  return {__last, errc(0)};
}

template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
_LIBCPP_AVAILABILITY_TO_CHARS
inline _LIBCPP_HIDE_FROM_ABI to_chars_result
to_chars(char* __first, char* __last, _Tp __value)
{
    return __to_chars_itoa(__first, __last, __value, is_signed<_Tp>());
}

template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
_LIBCPP_AVAILABILITY_TO_CHARS
inline _LIBCPP_HIDE_FROM_ABI to_chars_result
to_chars(char* __first, char* __last, _Tp __value, int __base)
{
    _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
    return __to_chars_integral(__first, __last, __value, __base,
                               is_signed<_Tp>());
}

template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
__sign_combinator(_It __first, _It __last, _Tp& __value, _Fn __f, _Ts... __args)
{
    using __tl = numeric_limits<_Tp>;
    decltype(__to_unsigned_like(__value)) __x;

    bool __neg = (__first != __last && *__first == '-');
    auto __r = __f(__neg ? __first + 1 : __first, __last, __x, __args...);
    switch (__r.ec)
    {
    case errc::invalid_argument:
        return {__first, __r.ec};
    case errc::result_out_of_range:
        return __r;
    default:
        break;
    }

    if (__neg)
    {
        if (__x <= __complement(__to_unsigned_like(__tl::min())))
        {
            __x = __complement(__x);
            std::memcpy(&__value, &__x, sizeof(__x));
            return __r;
        }
    }
    else
    {
        if (__x <= __to_unsigned_like(__tl::max()))
        {
            __value = __x;
            return __r;
        }
    }

    return {__r.ptr, errc::result_out_of_range};
}

template <typename _Tp>
inline _LIBCPP_HIDE_FROM_ABI bool
__in_pattern(_Tp __c)
{
    return '0' <= __c && __c <= '9';
}

struct _LIBCPP_HIDDEN __in_pattern_result
{
    bool __ok;
    int __val;

    explicit _LIBCPP_HIDE_FROM_ABI operator bool() const { return __ok; }
};

template <typename _Tp>
inline _LIBCPP_HIDE_FROM_ABI __in_pattern_result
__in_pattern(_Tp __c, int __base)
{
    if (__base <= 10)
        return {'0' <= __c && __c < '0' + __base, __c - '0'};
    else if (__in_pattern(__c))
        return {true, __c - '0'};
    else if ('a' <= __c && __c < 'a' + __base - 10)
        return {true, __c - 'a' + 10};
    else
        return {'A' <= __c && __c < 'A' + __base - 10, __c - 'A' + 10};
}

template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
__subject_seq_combinator(_It __first, _It __last, _Tp& __value, _Fn __f,
                         _Ts... __args)
{
    auto __find_non_zero = [](_It __firstit, _It __lastit) {
        for (; __firstit != __lastit; ++__firstit)
            if (*__firstit != '0')
                break;
        return __firstit;
    };

    auto __p = __find_non_zero(__first, __last);
    if (__p == __last || !__in_pattern(*__p, __args...))
    {
        if (__p == __first)
            return {__first, errc::invalid_argument};
        else
        {
            __value = 0;
            return {__p, {}};
        }
    }

    auto __r = __f(__p, __last, __value, __args...);
    if (__r.ec == errc::result_out_of_range)
    {
        for (; __r.ptr != __last; ++__r.ptr)
        {
            if (!__in_pattern(*__r.ptr, __args...))
                break;
        }
    }

    return __r;
}

template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
{
    using __tx = __itoa::__traits<_Tp>;
    using __output_type = typename __tx::type;

    return __subject_seq_combinator(
        __first, __last, __value,
        [](const char* _First, const char* _Last,
           _Tp& __val) -> from_chars_result {
            __output_type __a, __b;
            auto __p = __tx::__read(_First, _Last, __a, __b);
            if (__p == _Last || !__in_pattern(*__p))
            {
                __output_type __m = numeric_limits<_Tp>::max();
                if (__m >= __a && __m - __a >= __b)
                {
                    __val = __a + __b;
                    return {__p, {}};
                }
            }
            return {__p, errc::result_out_of_range};
        });
}

template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
{
    using __t = decltype(__to_unsigned_like(__value));
    return __sign_combinator(__first, __last, __value, __from_chars_atoi<__t>);
}

template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
                      int __base)
{
    if (__base == 10)
        return __from_chars_atoi(__first, __last, __value);

    return __subject_seq_combinator(
        __first, __last, __value,
        [](const char* __p, const char* __lastp, _Tp& __val,
           int _Base) -> from_chars_result {
            using __tl = numeric_limits<_Tp>;
            auto __digits = __tl::digits / log2f(float(_Base));
            _Tp __a = __in_pattern(*__p++, _Base).__val, __b = 0;

            for (int __i = 1; __p != __lastp; ++__i, ++__p)
            {
                if (auto __c = __in_pattern(*__p, _Base))
                {
                    if (__i < __digits - 1)
                        __a = __a * _Base + __c.__val;
                    else
                    {
                        if (!__itoa::__mul_overflowed(__a, _Base, __a))
                            ++__p;
                        __b = __c.__val;
                        break;
                    }
                }
                else
                    break;
            }

            if (__p == __lastp || !__in_pattern(*__p, _Base))
            {
                if (__tl::max() - __a >= __b)
                {
                    __val = __a + __b;
                    return {__p, {}};
                }
            }
            return {__p, errc::result_out_of_range};
        },
        __base);
}

template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
                      int __base)
{
    using __t = decltype(__to_unsigned_like(__value));
    return __sign_combinator(__first, __last, __value,
                             __from_chars_integral<__t>, __base);
}

template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
from_chars(const char* __first, const char* __last, _Tp& __value)
{
    return __from_chars_atoi(__first, __last, __value);
}

template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
inline _LIBCPP_HIDE_FROM_ABI from_chars_result
from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
{
    _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
    return __from_chars_integral(__first, __last, __value, __base);
}

// Floating-point implementation starts here.
// Unlike the other parts of charconv this is only available in C++17 and newer.
#if _LIBCPP_STD_VER > 14

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, float __value);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, double __value);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, long double __value);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision);

_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision);

#  endif // _LIBCPP_STD_VER > 14
#endif // _LIBCPP_CXX03_LANG

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP_CHARCONV