xref: /freebsd/contrib/llvm-project/libcxx/include/__chrono/formatter.h (revision fe75646a0234a261c0013bf1840fdac4acaf0cec)
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___CHRONO_FORMATTER_H
11 #define _LIBCPP___CHRONO_FORMATTER_H
12 
13 #include <__chrono/calendar.h>
14 #include <__chrono/concepts.h>
15 #include <__chrono/convert_to_tm.h>
16 #include <__chrono/day.h>
17 #include <__chrono/duration.h>
18 #include <__chrono/file_clock.h>
19 #include <__chrono/hh_mm_ss.h>
20 #include <__chrono/month.h>
21 #include <__chrono/month_weekday.h>
22 #include <__chrono/monthday.h>
23 #include <__chrono/ostream.h>
24 #include <__chrono/parser_std_format_spec.h>
25 #include <__chrono/statically_widen.h>
26 #include <__chrono/system_clock.h>
27 #include <__chrono/time_point.h>
28 #include <__chrono/weekday.h>
29 #include <__chrono/year.h>
30 #include <__chrono/year_month.h>
31 #include <__chrono/year_month_day.h>
32 #include <__chrono/year_month_weekday.h>
33 #include <__concepts/arithmetic.h>
34 #include <__concepts/same_as.h>
35 #include <__config>
36 #include <__format/concepts.h>
37 #include <__format/format_error.h>
38 #include <__format/format_functions.h>
39 #include <__format/format_parse_context.h>
40 #include <__format/formatter.h>
41 #include <__format/parser_std_format_spec.h>
42 #include <__format/write_escaped.h>
43 #include <__memory/addressof.h>
44 #include <cmath>
45 #include <ctime>
46 #include <sstream>
47 #include <string_view>
48 
49 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
50 #  pragma GCC system_header
51 #endif
52 
53 _LIBCPP_BEGIN_NAMESPACE_STD
54 
55 #if _LIBCPP_STD_VER >= 20
56 
57 namespace __formatter {
58 
59 /// Formats a time based on a tm struct.
60 ///
61 /// This formatter passes the formatting to time_put which uses strftime. When
62 /// the value is outside the valid range it's unspecified what strftime will
63 /// output. For example weekday 8 can print 1 when the day is processed modulo
64 /// 7 since that handles the Sunday for 0-based weekday. It can also print 8 if
65 /// 7 is handled as a special case.
66 ///
67 /// The Standard doesn't specify what to do in this case so the result depends
68 /// on the result of the underlying code.
69 ///
70 /// \pre When the (abbreviated) weekday or month name are used, the caller
71 ///      validates whether the value is valid. So the caller handles that
72 ///      requirement of Table 97: Meaning of conversion specifiers
73 ///      [tab:time.format.spec].
74 ///
75 /// When no chrono-specs are provided it uses the stream formatter.
76 
77 // For tiny ratios it's not possible to convert a duration to a hh_mm_ss. This
78 // fails compile-time due to the limited precision of the ratio (64-bit is too
79 // small). Therefore a duration uses its own conversion.
80 template <class _CharT, class _Rep, class _Period>
81 _LIBCPP_HIDE_FROM_ABI void
82 __format_sub_seconds(const chrono::duration<_Rep, _Period>& __value, basic_stringstream<_CharT>& __sstr) {
83   __sstr << std::use_facet<numpunct<_CharT>>(__sstr.getloc()).decimal_point();
84 
85   using __duration = chrono::duration<_Rep, _Period>;
86 
87   auto __fraction = __value - chrono::duration_cast<chrono::seconds>(__value);
88   if constexpr (chrono::treat_as_floating_point_v<_Rep>)
89     // When the floating-point value has digits itself they are ignored based
90     // on the wording in [tab:time.format.spec]
91     //   If the precision of the input cannot be exactly represented with
92     //   seconds, then the format is a decimal floating-point number with a
93     //   fixed format and a precision matching that of the precision of the
94     //   input (or to a microseconds precision if the conversion to
95     //   floating-point decimal seconds cannot be made within 18 fractional
96     //   digits).
97     //
98     // This matches the behaviour of MSVC STL, fmtlib interprets this
99     // differently and uses 3 decimals.
100     // https://godbolt.org/z/6dsbnW8ba
101     std::format_to(std::ostreambuf_iterator<_CharT>{__sstr},
102                    _LIBCPP_STATICALLY_WIDEN(_CharT, "{:0{}.0f}"),
103                    chrono::duration_cast<typename chrono::hh_mm_ss<__duration>::precision>(__fraction).count(),
104                    chrono::hh_mm_ss<__duration>::fractional_width);
105   else
106     std::format_to(std::ostreambuf_iterator<_CharT>{__sstr},
107                    _LIBCPP_STATICALLY_WIDEN(_CharT, "{:0{}}"),
108                    chrono::duration_cast<typename chrono::hh_mm_ss<__duration>::precision>(__fraction).count(),
109                    chrono::hh_mm_ss<__duration>::fractional_width);
110 }
111 
112 template <class _CharT, __is_time_point _Tp>
113 _LIBCPP_HIDE_FROM_ABI void __format_sub_seconds(const _Tp& __value, basic_stringstream<_CharT>& __sstr) {
114   __formatter::__format_sub_seconds(__value.time_since_epoch(), __sstr);
115 }
116 
117 template <class _CharT, class _Duration>
118 _LIBCPP_HIDE_FROM_ABI void
119 __format_sub_seconds(const chrono::hh_mm_ss<_Duration>& __value, basic_stringstream<_CharT>& __sstr) {
120   __sstr << std::use_facet<numpunct<_CharT>>(__sstr.getloc()).decimal_point();
121   if constexpr (chrono::treat_as_floating_point_v<typename _Duration::rep>)
122     std::format_to(std::ostreambuf_iterator<_CharT>{__sstr},
123                    _LIBCPP_STATICALLY_WIDEN(_CharT, "{:0{}.0f}"),
124                    __value.subseconds().count(),
125                    __value.fractional_width);
126   else
127     std::format_to(std::ostreambuf_iterator<_CharT>{__sstr},
128                    _LIBCPP_STATICALLY_WIDEN(_CharT, "{:0{}}"),
129                    __value.subseconds().count(),
130                    __value.fractional_width);
131 }
132 
133 template <class _Tp>
134 consteval bool __use_fraction() {
135   if constexpr (__is_time_point<_Tp>)
136     return chrono::hh_mm_ss<typename _Tp::duration>::fractional_width;
137   else if constexpr (chrono::__is_duration<_Tp>::value)
138     return chrono::hh_mm_ss<_Tp>::fractional_width;
139   else if constexpr (__is_hh_mm_ss<_Tp>)
140     return _Tp::fractional_width;
141   else
142     return false;
143 }
144 
145 template <class _CharT>
146 _LIBCPP_HIDE_FROM_ABI void __format_year(int __year, basic_stringstream<_CharT>& __sstr) {
147   if (__year < 0) {
148     __sstr << _CharT('-');
149     __year = -__year;
150   }
151 
152   // TODO FMT Write an issue
153   //   If the result has less than four digits it is zero-padded with 0 to two digits.
154   // is less -> has less
155   // left-padded -> zero-padded, otherwise the proper value would be 000-0.
156 
157   // Note according to the wording it should be left padded, which is odd.
158   __sstr << std::format(_LIBCPP_STATICALLY_WIDEN(_CharT, "{:04}"), __year);
159 }
160 
161 template <class _CharT>
162 _LIBCPP_HIDE_FROM_ABI void __format_century(int __year, basic_stringstream<_CharT>& __sstr) {
163   // TODO FMT Write an issue
164   // [tab:time.format.spec]
165   //   %C The year divided by 100 using floored division. If the result is a
166   //   single decimal digit, it is prefixed with 0.
167 
168   bool __negative = __year < 0;
169   int __century   = (__year - (99 * __negative)) / 100; // floored division
170   __sstr << std::format(_LIBCPP_STATICALLY_WIDEN(_CharT, "{:02}"), __century);
171 }
172 
173 template <class _CharT, class _Tp>
174 _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
175     const _Tp& __value, basic_stringstream<_CharT>& __sstr, basic_string_view<_CharT> __chrono_specs) {
176   tm __t              = std::__convert_to_tm<tm>(__value);
177   const auto& __facet = std::use_facet<time_put<_CharT>>(__sstr.getloc());
178   for (auto __it = __chrono_specs.begin(); __it != __chrono_specs.end(); ++__it) {
179     if (*__it == _CharT('%')) {
180       auto __s = __it;
181       ++__it;
182       // We only handle the types that can't be directly handled by time_put.
183       // (as an optimization n, t, and % are also handled directly.)
184       switch (*__it) {
185       case _CharT('n'):
186         __sstr << _CharT('\n');
187         break;
188       case _CharT('t'):
189         __sstr << _CharT('\t');
190         break;
191       case _CharT('%'):
192         __sstr << *__it;
193         break;
194 
195       case _CharT('C'): {
196         // strftime's output is only defined in the range [00, 99].
197         int __year = __t.tm_year + 1900;
198         if (__year < 1000 || __year > 9999)
199           __formatter::__format_century(__year, __sstr);
200         else
201           __facet.put({__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
202       } break;
203 
204       case _CharT('j'):
205         if constexpr (chrono::__is_duration<_Tp>::value)
206           // Converting a duration where the period has a small ratio to days
207           // may fail to compile. This due to loss of precision in the
208           // conversion. In order to avoid that issue convert to seconds as
209           // an intemediate step.
210           __sstr << chrono::duration_cast<chrono::days>(chrono::duration_cast<chrono::seconds>(__value)).count();
211         else
212           __facet.put({__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
213         break;
214 
215       case _CharT('q'):
216         if constexpr (chrono::__is_duration<_Tp>::value) {
217           __sstr << chrono::__units_suffix<_CharT, typename _Tp::period>();
218           break;
219         }
220         __builtin_unreachable();
221 
222       case _CharT('Q'):
223         // TODO FMT Determine the proper ideas
224         // - Should it honour the precision?
225         // - Shoult it honour the locale setting for the separators?
226         // The wording for Q doesn't use the word locale and the effect of
227         // precision is unspecified.
228         //
229         // MSVC STL ignores precision but uses separator
230         // FMT honours precision and has a bug for separator
231         // https://godbolt.org/z/78b7sMxns
232         if constexpr (chrono::__is_duration<_Tp>::value) {
233           __sstr << std::format(_LIBCPP_STATICALLY_WIDEN(_CharT, "{}"), __value.count());
234           break;
235         }
236         __builtin_unreachable();
237 
238       case _CharT('S'):
239       case _CharT('T'):
240         __facet.put({__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
241         if constexpr (__use_fraction<_Tp>())
242           __formatter::__format_sub_seconds(__value, __sstr);
243         break;
244 
245         // Unlike time_put and strftime the formatting library requires %Y
246         //
247         // [tab:time.format.spec]
248         //   The year as a decimal number. If the result is less than four digits
249         //   it is left-padded with 0 to four digits.
250         //
251         // This means years in the range (-1000, 1000) need manual formatting.
252         // It's unclear whether %EY needs the same treatment. For example the
253         // Japanese EY contains the era name and year. This is zero-padded to 2
254         // digits in time_put (note that older glibc versions didn't do
255         // padding.) However most eras won't reach 100 years, let alone 1000.
256         // So padding to 4 digits seems unwanted for Japanese.
257         //
258         // The same applies to %Ex since that too depends on the era.
259         //
260         // %x the locale's date representation is currently doesn't handle the
261         // zero-padding too.
262         //
263         // The 4 digits can be implemented better at a later time. On POSIX
264         // systems the required information can be extracted by nl_langinfo
265         // https://man7.org/linux/man-pages/man3/nl_langinfo.3.html
266         //
267         // Note since year < -1000 is expected to be rare it uses the more
268         // expensive year routine.
269         //
270         // TODO FMT evaluate the comment above.
271 
272 #  if defined(__GLIBC__) || defined(_AIX) || defined(_WIN32)
273       case _CharT('y'):
274         // Glibc fails for negative values, AIX for positive values too.
275         __sstr << std::format(_LIBCPP_STATICALLY_WIDEN(_CharT, "{:02}"), (std::abs(__t.tm_year + 1900)) % 100);
276         break;
277 #  endif // defined(__GLIBC__) || defined(_AIX) || defined(_WIN32)
278 
279       case _CharT('Y'):
280         // Depending on the platform's libc the range of supported years is
281         // limited. Intead of of testing all conditions use the internal
282         // implementation unconditionally.
283         __formatter::__format_year(__t.tm_year + 1900, __sstr);
284         break;
285 
286       case _CharT('F'): {
287         int __year = __t.tm_year + 1900;
288         if (__year < 1000) {
289           __formatter::__format_year(__year, __sstr);
290           __sstr << std::format(_LIBCPP_STATICALLY_WIDEN(_CharT, "-{:02}-{:02}"), __t.tm_mon + 1, __t.tm_mday);
291         } else
292           __facet.put({__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
293       } break;
294 
295       case _CharT('Z'):
296         // TODO FMT Add proper timezone support.
297         __sstr << _LIBCPP_STATICALLY_WIDEN(_CharT, "UTC");
298         break;
299 
300       case _CharT('O'):
301         if constexpr (__use_fraction<_Tp>()) {
302           // Handle OS using the normal representation for the non-fractional
303           // part. There seems to be no locale information regarding how the
304           // fractional part should be formatted.
305           if (*(__it + 1) == 'S') {
306             ++__it;
307             __facet.put({__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
308             __formatter::__format_sub_seconds(__value, __sstr);
309             break;
310           }
311         }
312         [[fallthrough]];
313       case _CharT('E'):
314         ++__it;
315         [[fallthrough]];
316       default:
317         __facet.put({__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
318         break;
319       }
320     } else {
321       __sstr << *__it;
322     }
323   }
324 }
325 
326 template <class _Tp>
327 _LIBCPP_HIDE_FROM_ABI constexpr bool __weekday_ok(const _Tp& __value) {
328   if constexpr (__is_time_point<_Tp>)
329     return true;
330   else if constexpr (same_as<_Tp, chrono::day>)
331     return true;
332   else if constexpr (same_as<_Tp, chrono::month>)
333     return __value.ok();
334   else if constexpr (same_as<_Tp, chrono::year>)
335     return true;
336   else if constexpr (same_as<_Tp, chrono::weekday>)
337     return true;
338   else if constexpr (same_as<_Tp, chrono::weekday_indexed>)
339     return true;
340   else if constexpr (same_as<_Tp, chrono::weekday_last>)
341     return true;
342   else if constexpr (same_as<_Tp, chrono::month_day>)
343     return true;
344   else if constexpr (same_as<_Tp, chrono::month_day_last>)
345     return true;
346   else if constexpr (same_as<_Tp, chrono::month_weekday>)
347     return true;
348   else if constexpr (same_as<_Tp, chrono::month_weekday_last>)
349     return true;
350   else if constexpr (same_as<_Tp, chrono::year_month>)
351     return true;
352   else if constexpr (same_as<_Tp, chrono::year_month_day>)
353     return __value.ok();
354   else if constexpr (same_as<_Tp, chrono::year_month_day_last>)
355     return __value.ok();
356   else if constexpr (same_as<_Tp, chrono::year_month_weekday>)
357     return __value.weekday().ok();
358   else if constexpr (same_as<_Tp, chrono::year_month_weekday_last>)
359     return __value.weekday().ok();
360   else if constexpr (__is_hh_mm_ss<_Tp>)
361     return true;
362   else
363     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
364 }
365 
366 template <class _Tp>
367 _LIBCPP_HIDE_FROM_ABI constexpr bool __weekday_name_ok(const _Tp& __value) {
368   if constexpr (__is_time_point<_Tp>)
369     return true;
370   else if constexpr (same_as<_Tp, chrono::day>)
371     return true;
372   else if constexpr (same_as<_Tp, chrono::month>)
373     return __value.ok();
374   else if constexpr (same_as<_Tp, chrono::year>)
375     return true;
376   else if constexpr (same_as<_Tp, chrono::weekday>)
377     return __value.ok();
378   else if constexpr (same_as<_Tp, chrono::weekday_indexed>)
379     return __value.weekday().ok();
380   else if constexpr (same_as<_Tp, chrono::weekday_last>)
381     return __value.weekday().ok();
382   else if constexpr (same_as<_Tp, chrono::month_day>)
383     return true;
384   else if constexpr (same_as<_Tp, chrono::month_day_last>)
385     return true;
386   else if constexpr (same_as<_Tp, chrono::month_weekday>)
387     return __value.weekday_indexed().ok();
388   else if constexpr (same_as<_Tp, chrono::month_weekday_last>)
389     return __value.weekday_indexed().ok();
390   else if constexpr (same_as<_Tp, chrono::year_month>)
391     return true;
392   else if constexpr (same_as<_Tp, chrono::year_month_day>)
393     return __value.ok();
394   else if constexpr (same_as<_Tp, chrono::year_month_day_last>)
395     return __value.ok();
396   else if constexpr (same_as<_Tp, chrono::year_month_weekday>)
397     return __value.weekday().ok();
398   else if constexpr (same_as<_Tp, chrono::year_month_weekday_last>)
399     return __value.weekday().ok();
400   else if constexpr (__is_hh_mm_ss<_Tp>)
401     return true;
402   else
403     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
404 }
405 
406 template <class _Tp>
407 _LIBCPP_HIDE_FROM_ABI constexpr bool __date_ok(const _Tp& __value) {
408   if constexpr (__is_time_point<_Tp>)
409     return true;
410   else if constexpr (same_as<_Tp, chrono::day>)
411     return true;
412   else if constexpr (same_as<_Tp, chrono::month>)
413     return __value.ok();
414   else if constexpr (same_as<_Tp, chrono::year>)
415     return true;
416   else if constexpr (same_as<_Tp, chrono::weekday>)
417     return true;
418   else if constexpr (same_as<_Tp, chrono::weekday_indexed>)
419     return true;
420   else if constexpr (same_as<_Tp, chrono::weekday_last>)
421     return true;
422   else if constexpr (same_as<_Tp, chrono::month_day>)
423     return true;
424   else if constexpr (same_as<_Tp, chrono::month_day_last>)
425     return true;
426   else if constexpr (same_as<_Tp, chrono::month_weekday>)
427     return true;
428   else if constexpr (same_as<_Tp, chrono::month_weekday_last>)
429     return true;
430   else if constexpr (same_as<_Tp, chrono::year_month>)
431     return true;
432   else if constexpr (same_as<_Tp, chrono::year_month_day>)
433     return __value.ok();
434   else if constexpr (same_as<_Tp, chrono::year_month_day_last>)
435     return __value.ok();
436   else if constexpr (same_as<_Tp, chrono::year_month_weekday>)
437     return __value.ok();
438   else if constexpr (same_as<_Tp, chrono::year_month_weekday_last>)
439     return __value.ok();
440   else if constexpr (__is_hh_mm_ss<_Tp>)
441     return true;
442   else
443     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
444 }
445 
446 template <class _Tp>
447 _LIBCPP_HIDE_FROM_ABI constexpr bool __month_name_ok(const _Tp& __value) {
448   if constexpr (__is_time_point<_Tp>)
449     return true;
450   else if constexpr (same_as<_Tp, chrono::day>)
451     return true;
452   else if constexpr (same_as<_Tp, chrono::month>)
453     return __value.ok();
454   else if constexpr (same_as<_Tp, chrono::year>)
455     return true;
456   else if constexpr (same_as<_Tp, chrono::weekday>)
457     return true;
458   else if constexpr (same_as<_Tp, chrono::weekday_indexed>)
459     return true;
460   else if constexpr (same_as<_Tp, chrono::weekday_last>)
461     return true;
462   else if constexpr (same_as<_Tp, chrono::month_day>)
463     return __value.month().ok();
464   else if constexpr (same_as<_Tp, chrono::month_day_last>)
465     return __value.month().ok();
466   else if constexpr (same_as<_Tp, chrono::month_weekday>)
467     return __value.month().ok();
468   else if constexpr (same_as<_Tp, chrono::month_weekday_last>)
469     return __value.month().ok();
470   else if constexpr (same_as<_Tp, chrono::year_month>)
471     return __value.month().ok();
472   else if constexpr (same_as<_Tp, chrono::year_month_day>)
473     return __value.month().ok();
474   else if constexpr (same_as<_Tp, chrono::year_month_day_last>)
475     return __value.month().ok();
476   else if constexpr (same_as<_Tp, chrono::year_month_weekday>)
477     return __value.month().ok();
478   else if constexpr (same_as<_Tp, chrono::year_month_weekday_last>)
479     return __value.month().ok();
480   else if constexpr (__is_hh_mm_ss<_Tp>)
481     return true;
482   else
483     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
484 }
485 
486 template <class _CharT, class _Tp, class _FormatContext>
487 _LIBCPP_HIDE_FROM_ABI auto
488 __format_chrono(const _Tp& __value,
489                 _FormatContext& __ctx,
490                 __format_spec::__parsed_specifications<_CharT> __specs,
491                 basic_string_view<_CharT> __chrono_specs) {
492   basic_stringstream<_CharT> __sstr;
493   // [time.format]/2
494   // 2.1 - the "C" locale if the L option is not present in chrono-format-spec, otherwise
495   // 2.2 - the locale passed to the formatting function if any, otherwise
496   // 2.3 - the global locale.
497   // Note that the __ctx's locale() call does 2.2 and 2.3.
498   if (__specs.__chrono_.__locale_specific_form_)
499     __sstr.imbue(__ctx.locale());
500   else
501     __sstr.imbue(locale::classic());
502 
503   if (__chrono_specs.empty())
504     __sstr << __value;
505   else {
506     if constexpr (chrono::__is_duration<_Tp>::value) {
507       if (__value < __value.zero())
508         __sstr << _CharT('-');
509       __formatter::__format_chrono_using_chrono_specs(chrono::abs(__value), __sstr, __chrono_specs);
510       // TODO FMT When keeping the precision it will truncate the string.
511       // Note that the behaviour what the precision does isn't specified.
512       __specs.__precision_ = -1;
513     } else {
514       // Test __weekday_name_ before __weekday_ to give a better error.
515       if (__specs.__chrono_.__weekday_name_ && !__formatter::__weekday_name_ok(__value))
516         std::__throw_format_error("Formatting a weekday name needs a valid weekday");
517 
518       if (__specs.__chrono_.__weekday_ && !__formatter::__weekday_ok(__value))
519         std::__throw_format_error("Formatting a weekday needs a valid weekday");
520 
521       if (__specs.__chrono_.__day_of_year_ && !__formatter::__date_ok(__value))
522         std::__throw_format_error("Formatting a day of year needs a valid date");
523 
524       if (__specs.__chrono_.__week_of_year_ && !__formatter::__date_ok(__value))
525         std::__throw_format_error("Formatting a week of year needs a valid date");
526 
527       if (__specs.__chrono_.__month_name_ && !__formatter::__month_name_ok(__value))
528         std::__throw_format_error("Formatting a month name from an invalid month number");
529 
530       if constexpr (__is_hh_mm_ss<_Tp>) {
531         // Note this is a pedantic intepretation of the Standard. A hh_mm_ss
532         // is no longer a time_of_day and can store an arbitrary number of
533         // hours. A number of hours in a 12 or 24 hour clock can't represent
534         // 24 hours or more. The functions std::chrono::make12 and
535         // std::chrono::make24 reaffirm this view point.
536         //
537         // Interestingly this will be the only output stream function that
538         // throws.
539         //
540         // TODO FMT The wording probably needs to be adapted to
541         // - The displayed hours is hh_mm_ss.hours() % 24
542         // - It should probably allow %j in the same fashion as duration.
543         // - The stream formatter should change its output when hours >= 24
544         //   - Write it as not valid,
545         //   - or write the number of days.
546         if (__specs.__chrono_.__hour_ && __value.hours().count() > 23)
547           std::__throw_format_error("Formatting a hour needs a valid value");
548 
549         if (__value.is_negative())
550           __sstr << _CharT('-');
551       }
552 
553       __formatter::__format_chrono_using_chrono_specs(__value, __sstr, __chrono_specs);
554     }
555   }
556 
557   return __formatter::__write_string(__sstr.view(), __ctx.out(), __specs);
558 }
559 
560 } // namespace __formatter
561 
562 template <__fmt_char_type _CharT>
563 struct _LIBCPP_TEMPLATE_VIS __formatter_chrono {
564 public:
565   template <class _ParseContext>
566   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator
567   __parse(_ParseContext& __ctx, __format_spec::__fields __fields, __format_spec::__flags __flags) {
568     return __parser_.__parse(__ctx, __fields, __flags);
569   }
570 
571   template <class _Tp, class _FormatContext>
572   _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(const _Tp& __value, _FormatContext& __ctx) const {
573     return __formatter::__format_chrono(
574         __value, __ctx, __parser_.__parser_.__get_parsed_chrono_specifications(__ctx), __parser_.__chrono_specs_);
575   }
576 
577   __format_spec::__parser_chrono<_CharT> __parser_;
578 };
579 
580 template <class _Duration, __fmt_char_type _CharT>
581 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::sys_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
582 public:
583   using _Base = __formatter_chrono<_CharT>;
584 
585   template <class _ParseContext>
586   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
587     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
588   }
589 };
590 
591 template <class _Duration, __fmt_char_type _CharT>
592 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::file_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
593 public:
594   using _Base = __formatter_chrono<_CharT>;
595 
596   template <class _ParseContext>
597   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
598     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
599   }
600 };
601 
602 template <class _Duration, __fmt_char_type _CharT>
603 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::local_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
604 public:
605   using _Base = __formatter_chrono<_CharT>;
606 
607   template <class _ParseContext>
608   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
609     // The flags are not __clock since there is no associated time-zone.
610     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date_time);
611   }
612 };
613 
614 template <class _Rep, class _Period, __fmt_char_type _CharT>
615 struct formatter<chrono::duration<_Rep, _Period>, _CharT> : public __formatter_chrono<_CharT> {
616 public:
617   using _Base = __formatter_chrono<_CharT>;
618 
619   template <class _ParseContext>
620   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
621     // [time.format]/1
622     // Giving a precision specification in the chrono-format-spec is valid only
623     // for std::chrono::duration types where the representation type Rep is a
624     // floating-point type. For all other Rep types, an exception of type
625     // format_error is thrown if the chrono-format-spec contains a precision
626     // specification.
627     //
628     // Note this doesn't refer to chrono::treat_as_floating_point_v<_Rep>.
629     if constexpr (std::floating_point<_Rep>)
630       return _Base::__parse(__ctx, __format_spec::__fields_chrono_fractional, __format_spec::__flags::__duration);
631     else
632       return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__duration);
633   }
634 };
635 
636 template <__fmt_char_type _CharT>
637 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::day, _CharT>
638     : public __formatter_chrono<_CharT> {
639 public:
640   using _Base = __formatter_chrono<_CharT>;
641 
642   template <class _ParseContext>
643   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
644     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__day);
645   }
646 };
647 
648 template <__fmt_char_type _CharT>
649 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month, _CharT>
650     : public __formatter_chrono<_CharT> {
651 public:
652   using _Base = __formatter_chrono<_CharT>;
653 
654   template <class _ParseContext>
655   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
656     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month);
657   }
658 };
659 
660 template <__fmt_char_type _CharT>
661 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year, _CharT>
662     : public __formatter_chrono<_CharT> {
663 public:
664   using _Base = __formatter_chrono<_CharT>;
665 
666   template <class _ParseContext>
667   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
668     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__year);
669   }
670 };
671 
672 template <__fmt_char_type _CharT>
673 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::weekday, _CharT>
674     : public __formatter_chrono<_CharT> {
675 public:
676   using _Base = __formatter_chrono<_CharT>;
677 
678   template <class _ParseContext>
679   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
680     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
681   }
682 };
683 
684 template <__fmt_char_type _CharT>
685 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::weekday_indexed, _CharT>
686     : public __formatter_chrono<_CharT> {
687 public:
688   using _Base = __formatter_chrono<_CharT>;
689 
690   template <class _ParseContext>
691   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
692     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
693   }
694 };
695 
696 template <__fmt_char_type _CharT>
697 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::weekday_last, _CharT>
698     : public __formatter_chrono<_CharT> {
699 public:
700   using _Base = __formatter_chrono<_CharT>;
701 
702   template <class _ParseContext>
703   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
704     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__weekday);
705   }
706 };
707 
708 template <__fmt_char_type _CharT>
709 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_day, _CharT>
710     : public __formatter_chrono<_CharT> {
711 public:
712   using _Base = __formatter_chrono<_CharT>;
713 
714   template <class _ParseContext>
715   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
716     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_day);
717   }
718 };
719 
720 template <__fmt_char_type _CharT>
721 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_day_last, _CharT>
722     : public __formatter_chrono<_CharT> {
723 public:
724   using _Base = __formatter_chrono<_CharT>;
725 
726   template <class _ParseContext>
727   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
728     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month);
729   }
730 };
731 
732 template <__fmt_char_type _CharT>
733 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_weekday, _CharT>
734     : public __formatter_chrono<_CharT> {
735 public:
736   using _Base = __formatter_chrono<_CharT>;
737 
738   template <class _ParseContext>
739   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
740     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_weekday);
741   }
742 };
743 
744 template <__fmt_char_type _CharT>
745 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::month_weekday_last, _CharT>
746     : public __formatter_chrono<_CharT> {
747 public:
748   using _Base = __formatter_chrono<_CharT>;
749 
750   template <class _ParseContext>
751   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
752     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__month_weekday);
753   }
754 };
755 
756 template <__fmt_char_type _CharT>
757 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month, _CharT>
758     : public __formatter_chrono<_CharT> {
759 public:
760   using _Base = __formatter_chrono<_CharT>;
761 
762   template <class _ParseContext>
763   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
764     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__year_month);
765   }
766 };
767 
768 template <__fmt_char_type _CharT>
769 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_day, _CharT>
770     : public __formatter_chrono<_CharT> {
771 public:
772   using _Base = __formatter_chrono<_CharT>;
773 
774   template <class _ParseContext>
775   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
776     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
777   }
778 };
779 
780 template <__fmt_char_type _CharT>
781 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_day_last, _CharT>
782     : public __formatter_chrono<_CharT> {
783 public:
784   using _Base = __formatter_chrono<_CharT>;
785 
786   template <class _ParseContext>
787   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
788     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
789   }
790 };
791 
792 template <__fmt_char_type _CharT>
793 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_weekday, _CharT>
794     : public __formatter_chrono<_CharT> {
795 public:
796   using _Base = __formatter_chrono<_CharT>;
797 
798   template <class _ParseContext>
799   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
800     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
801   }
802 };
803 
804 template <__fmt_char_type _CharT>
805 struct _LIBCPP_TEMPLATE_VIS formatter<chrono::year_month_weekday_last, _CharT>
806     : public __formatter_chrono<_CharT> {
807 public:
808   using _Base = __formatter_chrono<_CharT>;
809 
810   template <class _ParseContext>
811   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
812     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__date);
813   }
814 };
815 
816 template <class _Duration, __fmt_char_type _CharT>
817 struct formatter<chrono::hh_mm_ss<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
818 public:
819   using _Base = __formatter_chrono<_CharT>;
820 
821   template <class _ParseContext>
822   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
823     return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__time);
824   }
825 };
826 #endif // if _LIBCPP_STD_VER >= 20
827 
828 _LIBCPP_END_NAMESPACE_STD
829 
830 #endif //  _LIBCPP___CHRONO_FORMATTER_H
831