xref: /freebsd/contrib/llvm-project/libcxx/include/charconv (revision 9f23cbd6cae82fd77edfad7173432fa8dccd0a95) 
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  constexpr to_chars_result to_chars(char* first, char* last, see below value,
34                                     int base = 10);                                  // constexpr since C++23
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  constexpr from_chars_result from_chars(const char* first, const char* last,
64                               see below& value, int base = 10);                         // constexpr since C++23
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 <__algorithm/copy_n.h>
81#include <__assert> // all public C++ headers provide the assertion handler
82#include <__availability>
83#include <__bit/countl.h>
84#include <__charconv/chars_format.h>
85#include <__charconv/from_chars_result.h>
86#include <__charconv/tables.h>
87#include <__charconv/to_chars_base_10.h>
88#include <__charconv/to_chars_result.h>
89#include <__config>
90#include <__debug>
91#include <__errc>
92#include <__memory/addressof.h>
93#include <__type_traits/make_32_64_or_128_bit.h>
94#include <__utility/unreachable.h>
95#include <cmath> // for log2f
96#include <cstdint>
97#include <cstdlib>
98#include <cstring>
99#include <limits>
100#include <type_traits>
101
102#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
103#  pragma GCC system_header
104#endif
105
106_LIBCPP_PUSH_MACROS
107#include <__undef_macros>
108
109_LIBCPP_BEGIN_NAMESPACE_STD
110
111#if _LIBCPP_STD_VER > 14
112
113to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
114from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;
115
116namespace __itoa
117{
118
119template <typename _Tp, typename = void>
120struct _LIBCPP_HIDDEN __traits_base;
121
122template <typename _Tp>
123struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) <= sizeof(uint32_t)>>
124{
125    using type = uint32_t;
126
127    /// The width estimation using a log10 algorithm.
128    ///
129    /// The algorithm is based on
130    /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
131    /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
132    /// function requires its input to have at least one bit set the value of
133    /// zero is set to one. This means the first element of the lookup table is
134    /// zero.
135    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
136    {
137        auto __t = (32 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
138        return __t - (__v < __itoa::__pow10_32[__t]) + 1;
139    }
140
141    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v)
142    {
143        return __itoa::__base_10_u32(__p, __v);
144    }
145
146    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_32)& __pow() { return __itoa::__pow10_32; }
147};
148
149template <typename _Tp>
150struct _LIBCPP_HIDDEN
151    __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uint64_t)>> {
152  using type = uint64_t;
153
154  /// The width estimation using a log10 algorithm.
155  ///
156  /// The algorithm is based on
157  /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
158  /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
159  /// function requires its input to have at least one bit set the value of
160  /// zero is set to one. This means the first element of the lookup table is
161  /// zero.
162  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
163    auto __t = (64 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
164    return __t - (__v < __itoa::__pow10_64[__t]) + 1;
165  }
166
167  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) { return __itoa::__base_10_u64(__p, __v); }
168
169  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_64)& __pow() { return __itoa::__pow10_64; }
170};
171
172
173#  ifndef _LIBCPP_HAS_NO_INT128
174template <typename _Tp>
175struct _LIBCPP_HIDDEN
176    __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(__uint128_t)> > {
177  using type = __uint128_t;
178
179  /// The width estimation using a log10 algorithm.
180  ///
181  /// The algorithm is based on
182  /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
183  /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
184  /// function requires its input to have at least one bit set the value of
185  /// zero is set to one. This means the first element of the lookup table is
186  /// zero.
187  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
188    _LIBCPP_ASSERT(__v > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fail when this isn't true.");
189    // There's always a bit set in the upper 64-bits.
190    auto __t = (128 - std::__libcpp_clz(static_cast<uint64_t>(__v >> 64))) * 1233 >> 12;
191    _LIBCPP_ASSERT(__t >= __itoa::__pow10_128_offset, "Index out of bounds");
192    // __t is adjusted since the lookup table misses the lower entries.
193    return __t - (__v < __itoa::__pow10_128[__t - __itoa::__pow10_128_offset]) + 1;
194  }
195
196  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) { return __itoa::__base_10_u128(__p, __v); }
197
198  // TODO FMT This pow function should get an index.
199  // By moving this to its own header it can be reused by the pow function in to_chars_base_10.
200  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_128)& __pow() { return __itoa::__pow10_128; }
201};
202#endif
203
204template <typename _Tp>
205inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
206__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r)
207{
208    auto __c = __a * __b;
209    __r = __c;
210    return __c > numeric_limits<unsigned char>::max();
211}
212
213template <typename _Tp>
214inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
215__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r)
216{
217    auto __c = __a * __b;
218    __r = __c;
219    return __c > numeric_limits<unsigned short>::max();
220}
221
222template <typename _Tp>
223inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
224__mul_overflowed(_Tp __a, _Tp __b, _Tp& __r)
225{
226    static_assert(is_unsigned<_Tp>::value, "");
227    return __builtin_mul_overflow(__a, __b, &__r);
228}
229
230template <typename _Tp, typename _Up>
231inline _LIBCPP_HIDE_FROM_ABI bool
232_LIBCPP_CONSTEXPR_SINCE_CXX23 __mul_overflowed(_Tp __a, _Up __b, _Tp& __r)
233{
234    return __itoa::__mul_overflowed(__a, static_cast<_Tp>(__b), __r);
235}
236
237template <typename _Tp>
238struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp>
239{
240    static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
241    using __traits_base<_Tp>::__pow;
242    using typename __traits_base<_Tp>::type;
243
244    // precondition: at least one non-zero character available
245    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char const*
246    __read(char const* __p, char const* __ep, type& __a, type& __b)
247    {
248        type __cprod[digits];
249        int __j = digits - 1;
250        int __i = digits;
251        do
252        {
253            if (*__p < '0' || *__p > '9')
254                break;
255            __cprod[--__i] = *__p++ - '0';
256        } while (__p != __ep && __i != 0);
257
258        __a = __inner_product(__cprod + __i + 1, __cprod + __j, __pow() + 1,
259                              __cprod[__i]);
260        if (__itoa::__mul_overflowed(__cprod[__j], __pow()[__j - __i], __b))
261            --__p;
262        return __p;
263    }
264
265    template <typename _It1, typename _It2, class _Up>
266    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Up
267    __inner_product(_It1 __first1, _It1 __last1, _It2 __first2, _Up __init)
268    {
269        for (; __first1 < __last1; ++__first1, ++__first2)
270            __init = __init + *__first1 * *__first2;
271        return __init;
272    }
273};
274
275}  // namespace __itoa
276
277template <typename _Tp>
278inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Tp
279__complement(_Tp __x)
280{
281    static_assert(is_unsigned<_Tp>::value, "cast to unsigned first");
282    return _Tp(~__x + 1);
283}
284
285template <typename _Tp>
286inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
287__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type);
288
289template <typename _Tp>
290inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
291__to_chars_itoa(char* __first, char* __last, _Tp __value, true_type)
292{
293    auto __x = std::__to_unsigned_like(__value);
294    if (__value < 0 && __first != __last)
295    {
296        *__first++ = '-';
297        __x = std::__complement(__x);
298    }
299
300    return std::__to_chars_itoa(__first, __last, __x, false_type());
301}
302
303template <typename _Tp>
304inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
305__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type)
306{
307    using __tx = __itoa::__traits<_Tp>;
308    auto __diff = __last - __first;
309
310    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
311        return {__tx::__convert(__first, __value), errc(0)};
312    else
313        return {__last, errc::value_too_large};
314}
315
316#  ifndef _LIBCPP_HAS_NO_INT128
317template <>
318inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
319__to_chars_itoa(char* __first, char* __last, __uint128_t __value, false_type)
320{
321    // When the value fits in 64-bits use the 64-bit code path. This reduces
322    // the number of expensive calculations on 128-bit values.
323    //
324    // NOTE the 128-bit code path requires this optimization.
325    if(__value <= numeric_limits<uint64_t>::max())
326        return __to_chars_itoa(__first, __last, static_cast<uint64_t>(__value), false_type());
327
328    using __tx = __itoa::__traits<__uint128_t>;
329    auto __diff = __last - __first;
330
331    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
332        return {__tx::__convert(__first, __value), errc(0)};
333    else
334        return {__last, errc::value_too_large};
335}
336#endif
337
338template <class _Tp>
339inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
340__to_chars_integral(char* __first, char* __last, _Tp __value, int __base, false_type);
341
342template <typename _Tp>
343inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
344__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
345                    true_type)
346{
347    auto __x = std::__to_unsigned_like(__value);
348    if (__value < 0 && __first != __last)
349    {
350        *__first++ = '-';
351        __x = std::__complement(__x);
352    }
353
354    return std::__to_chars_integral(__first, __last, __x, __base, false_type());
355}
356
357namespace __itoa {
358
359template <unsigned _Base>
360struct _LIBCPP_HIDDEN __integral;
361
362template <>
363struct _LIBCPP_HIDDEN __integral<2> {
364  template <typename _Tp>
365  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
366    // If value == 0 still need one digit. If the value != this has no
367    // effect since the code scans for the most significant bit set. (Note
368    // that __libcpp_clz doesn't work for 0.)
369    return numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1);
370  }
371
372  template <typename _Tp>
373  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
374    ptrdiff_t __cap = __last - __first;
375    int __n = __width(__value);
376    if (__n > __cap)
377      return {__last, errc::value_too_large};
378
379    __last = __first + __n;
380    char* __p = __last;
381    const unsigned __divisor = 16;
382    while (__value > __divisor) {
383      unsigned __c = __value % __divisor;
384      __value /= __divisor;
385      __p -= 4;
386      std::copy_n(&__base_2_lut[4 * __c], 4, __p);
387    }
388    do {
389      unsigned __c = __value % 2;
390      __value /= 2;
391      *--__p = "01"[__c];
392    } while (__value != 0);
393    return {__last, errc(0)};
394  }
395};
396
397template <>
398struct _LIBCPP_HIDDEN __integral<8> {
399  template <typename _Tp>
400  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
401    // If value == 0 still need one digit. If the value != this has no
402    // effect since the code scans for the most significat bit set. (Note
403    // that __libcpp_clz doesn't work for 0.)
404    return ((numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1)) + 2) / 3;
405  }
406
407  template <typename _Tp>
408  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
409    ptrdiff_t __cap = __last - __first;
410    int __n = __width(__value);
411    if (__n > __cap)
412      return {__last, errc::value_too_large};
413
414    __last = __first + __n;
415    char* __p = __last;
416    unsigned __divisor = 64;
417    while (__value > __divisor) {
418      unsigned __c = __value % __divisor;
419      __value /= __divisor;
420      __p -= 2;
421      std::copy_n(&__base_8_lut[2 * __c], 2, __p);
422    }
423    do {
424      unsigned __c = __value % 8;
425      __value /= 8;
426      *--__p = "01234567"[__c];
427    } while (__value != 0);
428    return {__last, errc(0)};
429  }
430
431};
432
433template <>
434struct _LIBCPP_HIDDEN __integral<16> {
435  template <typename _Tp>
436  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
437    // If value == 0 still need one digit. If the value != this has no
438    // effect since the code scans for the most significat bit set. (Note
439    // that __libcpp_clz doesn't work for 0.)
440    return (numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1) + 3) / 4;
441  }
442
443  template <typename _Tp>
444  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
445    ptrdiff_t __cap = __last - __first;
446    int __n = __width(__value);
447    if (__n > __cap)
448      return {__last, errc::value_too_large};
449
450    __last = __first + __n;
451    char* __p = __last;
452    unsigned __divisor = 256;
453    while (__value > __divisor) {
454      unsigned __c = __value % __divisor;
455      __value /= __divisor;
456      __p -= 2;
457      std::copy_n(&__base_16_lut[2 * __c], 2, __p);
458    }
459    if (__first != __last)
460      do {
461        unsigned __c = __value % 16;
462        __value /= 16;
463        *--__p = "0123456789abcdef"[__c];
464      } while (__value != 0);
465    return {__last, errc(0)};
466  }
467};
468
469} // namespace __itoa
470
471template <unsigned _Base, typename _Tp,
472          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
473_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
474__to_chars_integral_width(_Tp __value) {
475  return __itoa::__integral<_Base>::__width(__value);
476}
477
478template <unsigned _Base, typename _Tp,
479          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
480_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
481__to_chars_integral_width(_Tp __value) {
482  return std::__to_chars_integral_width<_Base>(static_cast<unsigned>(__value));
483}
484
485template <unsigned _Base, typename _Tp,
486          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
487_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
488__to_chars_integral(char* __first, char* __last, _Tp __value) {
489  return __itoa::__integral<_Base>::__to_chars(__first, __last, __value);
490}
491
492template <unsigned _Base, typename _Tp,
493          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
494_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
495__to_chars_integral(char* __first, char* __last, _Tp __value) {
496  return std::__to_chars_integral<_Base>(__first, __last, static_cast<unsigned>(__value));
497}
498
499template <typename _Tp>
500_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
501__to_chars_integral_width(_Tp __value, unsigned __base) {
502  _LIBCPP_ASSERT(__value >= 0, "The function requires a non-negative value.");
503
504  unsigned __base_2 = __base * __base;
505  unsigned __base_3 = __base_2 * __base;
506  unsigned __base_4 = __base_2 * __base_2;
507
508  int __r = 0;
509  while (true) {
510    if (__value < __base)
511      return __r + 1;
512    if (__value < __base_2)
513      return __r + 2;
514    if (__value < __base_3)
515      return __r + 3;
516    if (__value < __base_4)
517      return __r + 4;
518
519    __value /= __base_4;
520    __r += 4;
521  }
522
523  __libcpp_unreachable();
524}
525
526template <typename _Tp>
527inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
528__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
529                    false_type)
530{
531  if (__base == 10) [[likely]]
532    return std::__to_chars_itoa(__first, __last, __value, false_type());
533
534  switch (__base) {
535  case 2:
536    return std::__to_chars_integral<2>(__first, __last, __value);
537  case 8:
538    return std::__to_chars_integral<8>(__first, __last, __value);
539  case 16:
540    return std::__to_chars_integral<16>(__first, __last, __value);
541  }
542
543  ptrdiff_t __cap = __last - __first;
544  int __n = std::__to_chars_integral_width(__value, __base);
545  if (__n > __cap)
546    return {__last, errc::value_too_large};
547
548  __last = __first + __n;
549  char* __p = __last;
550  do {
551    unsigned __c = __value % __base;
552    __value /= __base;
553    *--__p = "0123456789abcdefghijklmnopqrstuvwxyz"[__c];
554  } while (__value != 0);
555  return {__last, errc(0)};
556}
557
558template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
559inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
560to_chars(char* __first, char* __last, _Tp __value)
561{
562  using _Type = __make_32_64_or_128_bit_t<_Tp>;
563  static_assert(!is_same<_Type, void>::value, "unsupported integral type used in to_chars");
564  return std::__to_chars_itoa(__first, __last, static_cast<_Type>(__value), is_signed<_Tp>());
565}
566
567template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
568inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
569to_chars(char* __first, char* __last, _Tp __value, int __base)
570{
571  _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
572
573  using _Type = __make_32_64_or_128_bit_t<_Tp>;
574  return std::__to_chars_integral(__first, __last, static_cast<_Type>(__value), __base, is_signed<_Tp>());
575}
576
577template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
578inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
579__sign_combinator(_It __first, _It __last, _Tp& __value, _Fn __f, _Ts... __args)
580{
581    using __tl = numeric_limits<_Tp>;
582    decltype(std::__to_unsigned_like(__value)) __x;
583
584    bool __neg = (__first != __last && *__first == '-');
585    auto __r = __f(__neg ? __first + 1 : __first, __last, __x, __args...);
586    switch (__r.ec)
587    {
588    case errc::invalid_argument:
589        return {__first, __r.ec};
590    case errc::result_out_of_range:
591        return __r;
592    default:
593        break;
594    }
595
596    if (__neg)
597    {
598        if (__x <= std::__complement(std::__to_unsigned_like(__tl::min())))
599        {
600            __x = std::__complement(__x);
601            std::copy_n(std::addressof(__x), 1, std::addressof(__value));
602            return __r;
603        }
604    }
605    else
606    {
607        if (__x <= std::__to_unsigned_like(__tl::max()))
608        {
609            __value = __x;
610            return __r;
611        }
612    }
613
614    return {__r.ptr, errc::result_out_of_range};
615}
616
617template <typename _Tp>
618inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
619__in_pattern(_Tp __c)
620{
621    return '0' <= __c && __c <= '9';
622}
623
624struct _LIBCPP_HIDDEN __in_pattern_result
625{
626    bool __ok;
627    int __val;
628
629    explicit _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI operator bool() const { return __ok; }
630};
631
632template <typename _Tp>
633inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI __in_pattern_result
634__in_pattern(_Tp __c, int __base)
635{
636    if (__base <= 10)
637        return {'0' <= __c && __c < '0' + __base, __c - '0'};
638    else if (std::__in_pattern(__c))
639        return {true, __c - '0'};
640    else if ('a' <= __c && __c < 'a' + __base - 10)
641        return {true, __c - 'a' + 10};
642    else
643        return {'A' <= __c && __c < 'A' + __base - 10, __c - 'A' + 10};
644}
645
646template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
647inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
648__subject_seq_combinator(_It __first, _It __last, _Tp& __value, _Fn __f,
649                         _Ts... __args)
650{
651    auto __find_non_zero = [](_It __firstit, _It __lastit) {
652        for (; __firstit != __lastit; ++__firstit)
653            if (*__firstit != '0')
654                break;
655        return __firstit;
656    };
657
658    auto __p = __find_non_zero(__first, __last);
659    if (__p == __last || !std::__in_pattern(*__p, __args...))
660    {
661        if (__p == __first)
662            return {__first, errc::invalid_argument};
663        else
664        {
665            __value = 0;
666            return {__p, {}};
667        }
668    }
669
670    auto __r = __f(__p, __last, __value, __args...);
671    if (__r.ec == errc::result_out_of_range)
672    {
673        for (; __r.ptr != __last; ++__r.ptr)
674        {
675            if (!std::__in_pattern(*__r.ptr, __args...))
676                break;
677        }
678    }
679
680    return __r;
681}
682
683template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
684inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
685__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
686{
687    using __tx = __itoa::__traits<_Tp>;
688    using __output_type = typename __tx::type;
689
690    return std::__subject_seq_combinator(
691        __first, __last, __value,
692        [](const char* __f, const char* __l,
693           _Tp& __val) -> from_chars_result {
694            __output_type __a, __b;
695            auto __p = __tx::__read(__f, __l, __a, __b);
696            if (__p == __l || !std::__in_pattern(*__p))
697            {
698                __output_type __m = numeric_limits<_Tp>::max();
699                if (__m >= __a && __m - __a >= __b)
700                {
701                    __val = __a + __b;
702                    return {__p, {}};
703                }
704            }
705            return {__p, errc::result_out_of_range};
706        });
707}
708
709template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
710inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
711__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
712{
713    using __t = decltype(std::__to_unsigned_like(__value));
714    return std::__sign_combinator(__first, __last, __value, __from_chars_atoi<__t>);
715}
716
717
718/*
719// Code used to generate __from_chars_log2f_lut.
720#include <cmath>
721#include <iostream>
722#include <format>
723
724int main() {
725  for (int i = 2; i <= 36; ++i)
726    std::cout << std::format("{},\n", log2f(i));
727}
728*/
729/// log2f table for bases [2, 36].
730inline constexpr float __from_chars_log2f_lut[35] = {
731    1,         1.5849625, 2,         2.321928, 2.5849626, 2.807355, 3,        3.169925,  3.321928,
732    3.4594316, 3.5849626, 3.7004397, 3.807355, 3.9068906, 4,        4.087463, 4.169925,  4.2479277,
733    4.321928,  4.3923173, 4.4594316, 4.523562, 4.5849624, 4.643856, 4.70044,  4.7548876, 4.807355,
734    4.857981,  4.9068904, 4.9541965, 5,        5.044394,  5.087463, 5.129283, 5.169925};
735
736template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
737inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
738__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
739                      int __base)
740{
741    if (__base == 10)
742        return std::__from_chars_atoi(__first, __last, __value);
743
744    return std::__subject_seq_combinator(
745        __first, __last, __value,
746        [](const char* __p, const char* __lastp, _Tp& __val,
747           int __b) -> from_chars_result {
748            using __tl = numeric_limits<_Tp>;
749            // __base is always between 2 and 36 inclusive.
750            auto __digits = __tl::digits / __from_chars_log2f_lut[__b - 2];
751            _Tp __x = __in_pattern(*__p++, __b).__val, __y = 0;
752
753            for (int __i = 1; __p != __lastp; ++__i, ++__p)
754            {
755                if (auto __c = __in_pattern(*__p, __b))
756                {
757                    if (__i < __digits - 1)
758                        __x = __x * __b + __c.__val;
759                    else
760                    {
761                        if (!__itoa::__mul_overflowed(__x, __b, __x))
762                            ++__p;
763                        __y = __c.__val;
764                        break;
765                    }
766                }
767                else
768                    break;
769            }
770
771            if (__p == __lastp || !__in_pattern(*__p, __b))
772            {
773                if (__tl::max() - __x >= __y)
774                {
775                    __val = __x + __y;
776                    return {__p, {}};
777                }
778            }
779            return {__p, errc::result_out_of_range};
780        },
781        __base);
782}
783
784template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
785inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
786__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
787                      int __base)
788{
789    using __t = decltype(std::__to_unsigned_like(__value));
790    return std::__sign_combinator(__first, __last, __value,
791                                  __from_chars_integral<__t>, __base);
792}
793
794template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
795inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
796from_chars(const char* __first, const char* __last, _Tp& __value)
797{
798    return std::__from_chars_atoi(__first, __last, __value);
799}
800
801template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
802inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
803from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
804{
805    _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
806    return std::__from_chars_integral(__first, __last, __value, __base);
807}
808
809_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
810to_chars_result to_chars(char* __first, char* __last, float __value);
811
812_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
813to_chars_result to_chars(char* __first, char* __last, double __value);
814
815_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
816to_chars_result to_chars(char* __first, char* __last, long double __value);
817
818_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
819to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt);
820
821_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
822to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt);
823
824_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
825to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt);
826
827_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
828to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision);
829
830_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
831to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision);
832
833_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
834to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision);
835
836#endif // _LIBCPP_STD_VER > 14
837
838_LIBCPP_END_NAMESPACE_STD
839
840_LIBCPP_POP_MACROS
841
842#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
843#  include <concepts>
844#  include <iosfwd>
845#endif
846
847#endif // _LIBCPP_CHARCONV
848