xref: /freebsd/contrib/llvm-project/libcxx/include/charconv (revision 81ad626541db97eb356e2c1d4a20eb2a26a766ab)
1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP_CHARCONV
11#define _LIBCPP_CHARCONV
12
13/*
14    charconv synopsis
15
16namespace std {
17
18  // floating-point format for primitive numerical conversion
19  enum class chars_format {
20    scientific = unspecified,
21    fixed = unspecified,
22    hex = unspecified,
23    general = fixed | scientific
24  };
25
26  // 23.20.2, primitive numerical output conversion
27  struct to_chars_result {
28    char* ptr;
29    errc ec;
30    friend bool operator==(const to_chars_result&, const to_chars_result&) = default; // since C++20
31  };
32
33  to_chars_result to_chars(char* first, char* last, see below value,
34                           int base = 10);
35  to_chars_result to_chars(char* first, char* last, bool value,
36                           int base = 10) = delete;
37
38  to_chars_result to_chars(char* first, char* last, float value);
39  to_chars_result to_chars(char* first, char* last, double value);
40  to_chars_result to_chars(char* first, char* last, long double value);
41
42  to_chars_result to_chars(char* first, char* last, float value,
43                           chars_format fmt);
44  to_chars_result to_chars(char* first, char* last, double value,
45                           chars_format fmt);
46  to_chars_result to_chars(char* first, char* last, long double value,
47                           chars_format fmt);
48
49  to_chars_result to_chars(char* first, char* last, float value,
50                           chars_format fmt, int precision);
51  to_chars_result to_chars(char* first, char* last, double value,
52                           chars_format fmt, int precision);
53  to_chars_result to_chars(char* first, char* last, long double value,
54                           chars_format fmt, int precision);
55
56  // 23.20.3, primitive numerical input conversion
57  struct from_chars_result {
58    const char* ptr;
59    errc ec;
60    friend bool operator==(const from_chars_result&, const from_chars_result&) = default; // since C++20
61  };
62
63  from_chars_result from_chars(const char* first, const char* last,
64                               see below& value, int base = 10);
65
66  from_chars_result from_chars(const char* first, const char* last,
67                               float& value,
68                               chars_format fmt = chars_format::general);
69  from_chars_result from_chars(const char* first, const char* last,
70                               double& value,
71                               chars_format fmt = chars_format::general);
72  from_chars_result from_chars(const char* first, const char* last,
73                               long double& value,
74                               chars_format fmt = chars_format::general);
75
76} // namespace std
77
78*/
79
80#include <__assert> // all public C++ headers provide the assertion handler
81#include <__availability>
82#include <__bits>
83#include <__charconv/chars_format.h>
84#include <__charconv/from_chars_result.h>
85#include <__charconv/tables.h>
86#include <__charconv/to_chars_base_10.h>
87#include <__charconv/to_chars_result.h>
88#include <__config>
89#include <__debug>
90#include <__errc>
91#include <__utility/unreachable.h>
92#include <cmath> // for log2f
93#include <cstdint>
94#include <cstdlib>
95#include <cstring>
96#include <limits>
97#include <type_traits>
98
99#ifndef _LIBCPP_REMOVE_TRANSITIVE_INCLUDES
100#  include <iosfwd>
101#endif
102
103#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
104#  pragma GCC system_header
105#endif
106
107_LIBCPP_PUSH_MACROS
108#include <__undef_macros>
109
110_LIBCPP_BEGIN_NAMESPACE_STD
111
112#ifndef _LIBCPP_CXX03_LANG
113
114to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
115from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;
116
117namespace __itoa
118{
119
120
121template <typename _Tp, typename = void>
122struct _LIBCPP_HIDDEN __traits_base
123{
124    using type = uint64_t;
125
126    static _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
127    {
128        auto __t = (64 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
129        return __t - (__v < __table<>::__pow10_64[__t]) + 1;
130    }
131
132    static _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v)
133    {
134        return __itoa::__base_10_u64(__p, __v);
135    }
136
137    static _LIBCPP_HIDE_FROM_ABI decltype(__table<>::__pow10_64)& __pow() { return __table<>::__pow10_64; }
138};
139
140template <typename _Tp>
141struct _LIBCPP_HIDDEN
142    __traits_base<_Tp, decltype(void(uint32_t{declval<_Tp>()}))>
143{
144    using type = uint32_t;
145
146    static _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
147    {
148        auto __t = (32 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
149        return __t - (__v < __table<>::__pow10_32[__t]) + 1;
150    }
151
152    static _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v)
153    {
154        return __itoa::__base_10_u32(__p, __v);
155    }
156
157    static _LIBCPP_HIDE_FROM_ABI decltype(__table<>::__pow10_32)& __pow() { return __table<>::__pow10_32; }
158};
159
160template <typename _Tp>
161inline _LIBCPP_HIDE_FROM_ABI bool
162__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r)
163{
164    auto __c = __a * __b;
165    __r = __c;
166    return __c > numeric_limits<unsigned char>::max();
167}
168
169template <typename _Tp>
170inline _LIBCPP_HIDE_FROM_ABI bool
171__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r)
172{
173    auto __c = __a * __b;
174    __r = __c;
175    return __c > numeric_limits<unsigned short>::max();
176}
177
178template <typename _Tp>
179inline _LIBCPP_HIDE_FROM_ABI bool
180__mul_overflowed(_Tp __a, _Tp __b, _Tp& __r)
181{
182    static_assert(is_unsigned<_Tp>::value, "");
183#if !defined(_LIBCPP_COMPILER_MSVC)
184    return __builtin_mul_overflow(__a, __b, &__r);
185#else
186    bool __did = __b && (numeric_limits<_Tp>::max() / __b) < __a;
187    __r = __a * __b;
188    return __did;
189#endif
190}
191
192template <typename _Tp, typename _Up>
193inline _LIBCPP_HIDE_FROM_ABI bool
194__mul_overflowed(_Tp __a, _Up __b, _Tp& __r)
195{
196    return __mul_overflowed(__a, static_cast<_Tp>(__b), __r);
197}
198
199template <typename _Tp>
200struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp>
201{
202    static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
203    using __traits_base<_Tp>::__pow;
204    using typename __traits_base<_Tp>::type;
205
206    // precondition: at least one non-zero character available
207    static _LIBCPP_HIDE_FROM_ABI char const*
208    __read(char const* __p, char const* __ep, type& __a, type& __b)
209    {
210        type __cprod[digits];
211        int __j = digits - 1;
212        int __i = digits;
213        do
214        {
215            if (!('0' <= *__p && *__p <= '9'))
216                break;
217            __cprod[--__i] = *__p++ - '0';
218        } while (__p != __ep && __i != 0);
219
220        __a = __inner_product(__cprod + __i + 1, __cprod + __j, __pow() + 1,
221                              __cprod[__i]);
222        if (__mul_overflowed(__cprod[__j], __pow()[__j - __i], __b))
223            --__p;
224        return __p;
225    }
226
227    template <typename _It1, typename _It2, class _Up>
228    static _LIBCPP_HIDE_FROM_ABI _Up
229    __inner_product(_It1 __first1, _It1 __last1, _It2 __first2, _Up __init)
230    {
231        for (; __first1 < __last1; ++__first1, ++__first2)
232            __init = __init + *__first1 * *__first2;
233        return __init;
234    }
235};
236
237}  // namespace __itoa
238
239template <typename _Tp>
240inline _LIBCPP_HIDE_FROM_ABI _Tp
241__complement(_Tp __x)
242{
243    static_assert(is_unsigned<_Tp>::value, "cast to unsigned first");
244    return _Tp(~__x + 1);
245}
246
247template <typename _Tp>
248inline _LIBCPP_HIDE_FROM_ABI to_chars_result
249__to_chars_itoa(char* __first, char* __last, _Tp __value, true_type)
250{
251    auto __x = __to_unsigned_like(__value);
252    if (__value < 0 && __first != __last)
253    {
254        *__first++ = '-';
255        __x = __complement(__x);
256    }
257
258    return __to_chars_itoa(__first, __last, __x, false_type());
259}
260
261template <typename _Tp>
262inline _LIBCPP_HIDE_FROM_ABI to_chars_result
263__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type)
264{
265    using __tx = __itoa::__traits<_Tp>;
266    auto __diff = __last - __first;
267
268    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
269        return {__tx::__convert(__first, __value), errc(0)};
270    else
271        return {__last, errc::value_too_large};
272}
273
274template <typename _Tp>
275inline _LIBCPP_HIDE_FROM_ABI to_chars_result
276__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
277                    true_type)
278{
279    auto __x = __to_unsigned_like(__value);
280    if (__value < 0 && __first != __last)
281    {
282        *__first++ = '-';
283        __x = __complement(__x);
284    }
285
286    return __to_chars_integral(__first, __last, __x, __base, false_type());
287}
288
289namespace __itoa {
290
291template <unsigned _Base>
292struct _LIBCPP_HIDDEN __integral;
293
294template <>
295struct _LIBCPP_HIDDEN __integral<2> {
296  template <typename _Tp>
297  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
298    // If value == 0 still need one digit. If the value != this has no
299    // effect since the code scans for the most significant bit set. (Note
300    // that __libcpp_clz doesn't work for 0.)
301    return numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1);
302  }
303
304  template <typename _Tp>
305  _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
306    ptrdiff_t __cap = __last - __first;
307    int __n = __width(__value);
308    if (__n > __cap)
309      return {__last, errc::value_too_large};
310
311    __last = __first + __n;
312    char* __p = __last;
313    const unsigned __divisor = 16;
314    while (__value > __divisor) {
315      unsigned __c = __value % __divisor;
316      __value /= __divisor;
317      __p -= 4;
318      std::memcpy(__p, &__table<>::__base_2_lut[4 * __c], 4);
319    }
320    do {
321      unsigned __c = __value % 2;
322      __value /= 2;
323      *--__p = "01"[__c];
324    } while (__value != 0);
325    return {__last, errc(0)};
326  }
327};
328
329template <>
330struct _LIBCPP_HIDDEN __integral<8> {
331  template <typename _Tp>
332  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
333    // If value == 0 still need one digit. If the value != this has no
334    // effect since the code scans for the most significat bit set. (Note
335    // that __libcpp_clz doesn't work for 0.)
336    return ((numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1)) + 2) / 3;
337  }
338
339  template <typename _Tp>
340  _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
341    ptrdiff_t __cap = __last - __first;
342    int __n = __width(__value);
343    if (__n > __cap)
344      return {__last, errc::value_too_large};
345
346    __last = __first + __n;
347    char* __p = __last;
348    unsigned __divisor = 64;
349    while (__value > __divisor) {
350      unsigned __c = __value % __divisor;
351      __value /= __divisor;
352      __p -= 2;
353      std::memcpy(__p, &__table<>::__base_8_lut[2 * __c], 2);
354    }
355    do {
356      unsigned __c = __value % 8;
357      __value /= 8;
358      *--__p = "01234567"[__c];
359    } while (__value != 0);
360    return {__last, errc(0)};
361  }
362
363};
364
365template <>
366struct _LIBCPP_HIDDEN __integral<16> {
367  template <typename _Tp>
368  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
369    // If value == 0 still need one digit. If the value != this has no
370    // effect since the code scans for the most significat bit set. (Note
371    // that __libcpp_clz doesn't work for 0.)
372    return (numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1) + 3) / 4;
373  }
374
375  template <typename _Tp>
376  _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
377    ptrdiff_t __cap = __last - __first;
378    int __n = __width(__value);
379    if (__n > __cap)
380      return {__last, errc::value_too_large};
381
382    __last = __first + __n;
383    char* __p = __last;
384    unsigned __divisor = 256;
385    while (__value > __divisor) {
386      unsigned __c = __value % __divisor;
387      __value /= __divisor;
388      __p -= 2;
389      std::memcpy(__p, &__table<>::__base_16_lut[2 * __c], 2);
390    }
391    if (__first != __last)
392      do {
393        unsigned __c = __value % 16;
394        __value /= 16;
395        *--__p = "0123456789abcdef"[__c];
396      } while (__value != 0);
397    return {__last, errc(0)};
398  }
399};
400
401} // namespace __itoa
402
403template <unsigned _Base, typename _Tp,
404          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
405_LIBCPP_HIDE_FROM_ABI int
406__to_chars_integral_width(_Tp __value) {
407  return __itoa::__integral<_Base>::__width(__value);
408}
409
410template <unsigned _Base, typename _Tp,
411          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
412_LIBCPP_HIDE_FROM_ABI int
413__to_chars_integral_width(_Tp __value) {
414  return std::__to_chars_integral_width<_Base>(static_cast<unsigned>(__value));
415}
416
417template <unsigned _Base, typename _Tp,
418          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
419_LIBCPP_HIDE_FROM_ABI to_chars_result
420__to_chars_integral(char* __first, char* __last, _Tp __value) {
421  return __itoa::__integral<_Base>::__to_chars(__first, __last, __value);
422}
423
424template <unsigned _Base, typename _Tp,
425          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
426_LIBCPP_HIDE_FROM_ABI to_chars_result
427__to_chars_integral(char* __first, char* __last, _Tp __value) {
428  return std::__to_chars_integral<_Base>(__first, __last, static_cast<unsigned>(__value));
429}
430
431template <typename _Tp>
432_LIBCPP_HIDE_FROM_ABI int
433__to_chars_integral_width(_Tp __value, unsigned __base) {
434  _LIBCPP_ASSERT(__value >= 0, "The function requires a non-negative value.");
435
436  unsigned __base_2 = __base * __base;
437  unsigned __base_3 = __base_2 * __base;
438  unsigned __base_4 = __base_2 * __base_2;
439
440  int __r = 0;
441  while (true) {
442    if (__value < __base)
443      return __r + 1;
444    if (__value < __base_2)
445      return __r + 2;
446    if (__value < __base_3)
447      return __r + 3;
448    if (__value < __base_4)
449      return __r + 4;
450
451    __value /= __base_4;
452    __r += 4;
453  }
454
455  __libcpp_unreachable();
456}
457
458template <typename _Tp>
459inline _LIBCPP_HIDE_FROM_ABI to_chars_result
460__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
461                    false_type)
462{
463  if (__base == 10) [[likely]]
464    return __to_chars_itoa(__first, __last, __value, false_type());
465
466  switch (__base) {
467  case 2:
468    return __to_chars_integral<2>(__first, __last, __value);
469  case 8:
470    return __to_chars_integral<8>(__first, __last, __value);
471  case 16:
472    return __to_chars_integral<16>(__first, __last, __value);
473  }
474
475  ptrdiff_t __cap = __last - __first;
476  int __n = __to_chars_integral_width(__value, __base);
477  if (__n > __cap)
478    return {__last, errc::value_too_large};
479
480  __last = __first + __n;
481  char* __p = __last;
482  do {
483    unsigned __c = __value % __base;
484    __value /= __base;
485    *--__p = "0123456789abcdefghijklmnopqrstuvwxyz"[__c];
486  } while (__value != 0);
487  return {__last, errc(0)};
488}
489
490template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
491inline _LIBCPP_HIDE_FROM_ABI to_chars_result
492to_chars(char* __first, char* __last, _Tp __value)
493{
494  using _Type = __make_32_64_or_128_bit_t<_Tp>;
495  static_assert(!is_same<_Type, void>::value, "unsupported integral type used in to_chars");
496  static_assert(sizeof(_Tp) <= sizeof(int64_t), "128-bit integral support isn't available yet in to_chars");
497  return std::__to_chars_itoa(__first, __last, static_cast<_Type>(__value), is_signed<_Tp>());
498}
499
500template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
501inline _LIBCPP_HIDE_FROM_ABI to_chars_result
502to_chars(char* __first, char* __last, _Tp __value, int __base)
503{
504  _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
505
506  using _Type = __make_32_64_or_128_bit_t<_Tp>;
507  static_assert(sizeof(_Tp) <= sizeof(int64_t), "128-bit integral support isn't available yet in to_chars");
508  return std::__to_chars_integral(__first, __last, static_cast<_Type>(__value), __base, is_signed<_Tp>());
509}
510
511template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
512inline _LIBCPP_HIDE_FROM_ABI from_chars_result
513__sign_combinator(_It __first, _It __last, _Tp& __value, _Fn __f, _Ts... __args)
514{
515    using __tl = numeric_limits<_Tp>;
516    decltype(__to_unsigned_like(__value)) __x;
517
518    bool __neg = (__first != __last && *__first == '-');
519    auto __r = __f(__neg ? __first + 1 : __first, __last, __x, __args...);
520    switch (__r.ec)
521    {
522    case errc::invalid_argument:
523        return {__first, __r.ec};
524    case errc::result_out_of_range:
525        return __r;
526    default:
527        break;
528    }
529
530    if (__neg)
531    {
532        if (__x <= __complement(__to_unsigned_like(__tl::min())))
533        {
534            __x = __complement(__x);
535            std::memcpy(&__value, &__x, sizeof(__x));
536            return __r;
537        }
538    }
539    else
540    {
541        if (__x <= __to_unsigned_like(__tl::max()))
542        {
543            __value = __x;
544            return __r;
545        }
546    }
547
548    return {__r.ptr, errc::result_out_of_range};
549}
550
551template <typename _Tp>
552inline _LIBCPP_HIDE_FROM_ABI bool
553__in_pattern(_Tp __c)
554{
555    return '0' <= __c && __c <= '9';
556}
557
558struct _LIBCPP_HIDDEN __in_pattern_result
559{
560    bool __ok;
561    int __val;
562
563    explicit _LIBCPP_HIDE_FROM_ABI operator bool() const { return __ok; }
564};
565
566template <typename _Tp>
567inline _LIBCPP_HIDE_FROM_ABI __in_pattern_result
568__in_pattern(_Tp __c, int __base)
569{
570    if (__base <= 10)
571        return {'0' <= __c && __c < '0' + __base, __c - '0'};
572    else if (__in_pattern(__c))
573        return {true, __c - '0'};
574    else if ('a' <= __c && __c < 'a' + __base - 10)
575        return {true, __c - 'a' + 10};
576    else
577        return {'A' <= __c && __c < 'A' + __base - 10, __c - 'A' + 10};
578}
579
580template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
581inline _LIBCPP_HIDE_FROM_ABI from_chars_result
582__subject_seq_combinator(_It __first, _It __last, _Tp& __value, _Fn __f,
583                         _Ts... __args)
584{
585    auto __find_non_zero = [](_It __firstit, _It __lastit) {
586        for (; __firstit != __lastit; ++__firstit)
587            if (*__firstit != '0')
588                break;
589        return __firstit;
590    };
591
592    auto __p = __find_non_zero(__first, __last);
593    if (__p == __last || !__in_pattern(*__p, __args...))
594    {
595        if (__p == __first)
596            return {__first, errc::invalid_argument};
597        else
598        {
599            __value = 0;
600            return {__p, {}};
601        }
602    }
603
604    auto __r = __f(__p, __last, __value, __args...);
605    if (__r.ec == errc::result_out_of_range)
606    {
607        for (; __r.ptr != __last; ++__r.ptr)
608        {
609            if (!__in_pattern(*__r.ptr, __args...))
610                break;
611        }
612    }
613
614    return __r;
615}
616
617template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
618inline _LIBCPP_HIDE_FROM_ABI from_chars_result
619__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
620{
621    using __tx = __itoa::__traits<_Tp>;
622    using __output_type = typename __tx::type;
623
624    return __subject_seq_combinator(
625        __first, __last, __value,
626        [](const char* _First, const char* _Last,
627           _Tp& __val) -> from_chars_result {
628            __output_type __a, __b;
629            auto __p = __tx::__read(_First, _Last, __a, __b);
630            if (__p == _Last || !__in_pattern(*__p))
631            {
632                __output_type __m = numeric_limits<_Tp>::max();
633                if (__m >= __a && __m - __a >= __b)
634                {
635                    __val = __a + __b;
636                    return {__p, {}};
637                }
638            }
639            return {__p, errc::result_out_of_range};
640        });
641}
642
643template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
644inline _LIBCPP_HIDE_FROM_ABI from_chars_result
645__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
646{
647    using __t = decltype(__to_unsigned_like(__value));
648    return __sign_combinator(__first, __last, __value, __from_chars_atoi<__t>);
649}
650
651template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
652inline _LIBCPP_HIDE_FROM_ABI from_chars_result
653__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
654                      int __base)
655{
656    if (__base == 10)
657        return __from_chars_atoi(__first, __last, __value);
658
659    return __subject_seq_combinator(
660        __first, __last, __value,
661        [](const char* __p, const char* __lastp, _Tp& __val,
662           int _Base) -> from_chars_result {
663            using __tl = numeric_limits<_Tp>;
664            auto __digits = __tl::digits / log2f(float(_Base));
665            _Tp __a = __in_pattern(*__p++, _Base).__val, __b = 0;
666
667            for (int __i = 1; __p != __lastp; ++__i, ++__p)
668            {
669                if (auto __c = __in_pattern(*__p, _Base))
670                {
671                    if (__i < __digits - 1)
672                        __a = __a * _Base + __c.__val;
673                    else
674                    {
675                        if (!__itoa::__mul_overflowed(__a, _Base, __a))
676                            ++__p;
677                        __b = __c.__val;
678                        break;
679                    }
680                }
681                else
682                    break;
683            }
684
685            if (__p == __lastp || !__in_pattern(*__p, _Base))
686            {
687                if (__tl::max() - __a >= __b)
688                {
689                    __val = __a + __b;
690                    return {__p, {}};
691                }
692            }
693            return {__p, errc::result_out_of_range};
694        },
695        __base);
696}
697
698template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
699inline _LIBCPP_HIDE_FROM_ABI from_chars_result
700__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
701                      int __base)
702{
703    using __t = decltype(__to_unsigned_like(__value));
704    return __sign_combinator(__first, __last, __value,
705                             __from_chars_integral<__t>, __base);
706}
707
708template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
709inline _LIBCPP_HIDE_FROM_ABI from_chars_result
710from_chars(const char* __first, const char* __last, _Tp& __value)
711{
712    return __from_chars_atoi(__first, __last, __value);
713}
714
715template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
716inline _LIBCPP_HIDE_FROM_ABI from_chars_result
717from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
718{
719    _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
720    return __from_chars_integral(__first, __last, __value, __base);
721}
722
723// Floating-point implementation starts here.
724// Unlike the other parts of charconv this is only available in C++17 and newer.
725#if _LIBCPP_STD_VER > 14
726
727_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
728to_chars_result to_chars(char* __first, char* __last, float __value);
729
730_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
731to_chars_result to_chars(char* __first, char* __last, double __value);
732
733_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
734to_chars_result to_chars(char* __first, char* __last, long double __value);
735
736_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
737to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt);
738
739_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
740to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt);
741
742_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
743to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt);
744
745_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
746to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision);
747
748_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
749to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision);
750
751_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
752to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision);
753
754#  endif // _LIBCPP_STD_VER > 14
755#endif // _LIBCPP_CXX03_LANG
756
757_LIBCPP_END_NAMESPACE_STD
758
759_LIBCPP_POP_MACROS
760
761#endif // _LIBCPP_CHARCONV
762