xref: /netbsd-src/external/gpl3/gcc/dist/libstdc++-v3/include/bits/chrono.h (revision c42dbd0ed2e61fe6eda8590caa852ccf34719964)
1 // chrono::duration and chrono::time_point -*- C++ -*-
2 
3 // Copyright (C) 2008-2022 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library.  This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file include/bits/chrono.h
26  *  This is an internal header file, included by other library headers.
27  *  Do not attempt to use it directly. @headername{chrono}
28  */
29 
30 #ifndef _GLIBCXX_CHRONO_H
31 #define _GLIBCXX_CHRONO_H 1
32 
33 #pragma GCC system_header
34 
35 #if __cplusplus >= 201103L
36 
37 #include <ratio>
38 #include <type_traits>
39 #include <limits>
40 #include <ctime>
41 #include <bits/parse_numbers.h> // for literals support.
42 #if __cplusplus >= 202002L
43 # include <concepts>
44 # include <compare>
45 #endif
46 
47 namespace std _GLIBCXX_VISIBILITY(default)
48 {
49 _GLIBCXX_BEGIN_NAMESPACE_VERSION
50 
51 #if __cplusplus >= 201703L
52   namespace filesystem { struct __file_clock; };
53 #endif
54 
55   namespace chrono
56   {
57     /// @addtogroup chrono
58     /// @{
59 
60     /// `chrono::duration` represents a distance between two points in time
61     template<typename _Rep, typename _Period = ratio<1>>
62       class duration;
63 
64     /// `chrono::time_point` represents a point in time as measured by a clock
65     template<typename _Clock, typename _Dur = typename _Clock::duration>
66       class time_point;
67     /// @}
68   }
69 
70   /// @addtogroup chrono
71   /// @{
72 
73   // 20.11.4.3 specialization of common_type (for duration, sfinae-friendly)
74 
75   /// @cond undocumented
76 
77   template<typename _CT, typename _Period1, typename _Period2, typename = void>
78     struct __duration_common_type
79     { };
80 
81   template<typename _CT, typename _Period1, typename _Period2>
82     struct __duration_common_type<_CT, _Period1, _Period2,
83 				  __void_t<typename _CT::type>>
84     {
85     private:
86       using __gcd_num = __static_gcd<_Period1::num, _Period2::num>;
87       using __gcd_den = __static_gcd<_Period1::den, _Period2::den>;
88       using __cr = typename _CT::type;
89       using __r = ratio<__gcd_num::value,
90 			(_Period1::den / __gcd_den::value) * _Period2::den>;
91 
92     public:
93       using type = chrono::duration<__cr, typename __r::type>;
94     };
95 
96   /// @endcond
97 
98   /// @{
99   /// @relates chrono::duration
100 
101   /// Specialization of common_type for chrono::duration types.
102   template<typename _Rep1, typename _Period1, typename _Rep2, typename _Period2>
103     struct common_type<chrono::duration<_Rep1, _Period1>,
104 		       chrono::duration<_Rep2, _Period2>>
105     : __duration_common_type<common_type<_Rep1, _Rep2>,
106 			     typename _Period1::type,
107 			     typename _Period2::type>
108     { };
109 
110   /// Specialization of common_type for two identical chrono::duration types.
111   template<typename _Rep, typename _Period>
112     struct common_type<chrono::duration<_Rep, _Period>,
113 		       chrono::duration<_Rep, _Period>>
114     {
115       using type = chrono::duration<typename common_type<_Rep>::type,
116 				    typename _Period::type>;
117     };
118 
119   /// Specialization of common_type for one chrono::duration type.
120   template<typename _Rep, typename _Period>
121     struct common_type<chrono::duration<_Rep, _Period>>
122     {
123       using type = chrono::duration<typename common_type<_Rep>::type,
124 				    typename _Period::type>;
125     };
126   /// @}
127 
128   // 20.11.4.3 specialization of common_type (for time_point, sfinae-friendly)
129 
130   /// @cond undocumented
131 
132   template<typename _CT, typename _Clock, typename = void>
133     struct __timepoint_common_type
134     { };
135 
136   template<typename _CT, typename _Clock>
137     struct __timepoint_common_type<_CT, _Clock, __void_t<typename _CT::type>>
138     {
139       using type = chrono::time_point<_Clock, typename _CT::type>;
140     };
141 
142   /// @endcond
143 
144   /// @{
145   /// @relates chrono::time_point
146 
147   /// Specialization of common_type for chrono::time_point types.
148   template<typename _Clock, typename _Duration1, typename _Duration2>
149     struct common_type<chrono::time_point<_Clock, _Duration1>,
150 		       chrono::time_point<_Clock, _Duration2>>
151     : __timepoint_common_type<common_type<_Duration1, _Duration2>, _Clock>
152     { };
153 
154   /// Specialization of common_type for two identical chrono::time_point types.
155   template<typename _Clock, typename _Duration>
156     struct common_type<chrono::time_point<_Clock, _Duration>,
157 		       chrono::time_point<_Clock, _Duration>>
158     { using type = chrono::time_point<_Clock, _Duration>; };
159 
160   /// Specialization of common_type for one chrono::time_point type.
161   template<typename _Clock, typename _Duration>
162     struct common_type<chrono::time_point<_Clock, _Duration>>
163     { using type = chrono::time_point<_Clock, _Duration>; };
164   /// @}
165 
166   /// @} group chrono
167 
168   namespace chrono
169   {
170     /// @addtogroup chrono
171     /// @{
172 
173     /// @cond undocumented
174 
175     // Primary template for duration_cast impl.
176     template<typename _ToDur, typename _CF, typename _CR,
177 	     bool _NumIsOne = false, bool _DenIsOne = false>
178       struct __duration_cast_impl
179       {
180 	template<typename _Rep, typename _Period>
181 	  static constexpr _ToDur
182 	  __cast(const duration<_Rep, _Period>& __d)
183 	  {
184 	    typedef typename _ToDur::rep			__to_rep;
185 	    return _ToDur(static_cast<__to_rep>(static_cast<_CR>(__d.count())
186 	      * static_cast<_CR>(_CF::num)
187 	      / static_cast<_CR>(_CF::den)));
188 	  }
189       };
190 
191     template<typename _ToDur, typename _CF, typename _CR>
192       struct __duration_cast_impl<_ToDur, _CF, _CR, true, true>
193       {
194 	template<typename _Rep, typename _Period>
195 	  static constexpr _ToDur
196 	  __cast(const duration<_Rep, _Period>& __d)
197 	  {
198 	    typedef typename _ToDur::rep			__to_rep;
199 	    return _ToDur(static_cast<__to_rep>(__d.count()));
200 	  }
201       };
202 
203     template<typename _ToDur, typename _CF, typename _CR>
204       struct __duration_cast_impl<_ToDur, _CF, _CR, true, false>
205       {
206 	template<typename _Rep, typename _Period>
207 	  static constexpr _ToDur
208 	  __cast(const duration<_Rep, _Period>& __d)
209 	  {
210 	    typedef typename _ToDur::rep			__to_rep;
211 	    return _ToDur(static_cast<__to_rep>(
212 	      static_cast<_CR>(__d.count()) / static_cast<_CR>(_CF::den)));
213 	  }
214       };
215 
216     template<typename _ToDur, typename _CF, typename _CR>
217       struct __duration_cast_impl<_ToDur, _CF, _CR, false, true>
218       {
219 	template<typename _Rep, typename _Period>
220 	  static constexpr _ToDur
221 	  __cast(const duration<_Rep, _Period>& __d)
222 	  {
223 	    typedef typename _ToDur::rep			__to_rep;
224 	    return _ToDur(static_cast<__to_rep>(
225 	      static_cast<_CR>(__d.count()) * static_cast<_CR>(_CF::num)));
226 	  }
227       };
228 
229     template<typename _Tp>
230       struct __is_duration
231       : std::false_type
232       { };
233 
234     template<typename _Rep, typename _Period>
235       struct __is_duration<duration<_Rep, _Period>>
236       : std::true_type
237       { };
238 
239     template<typename _Tp>
240       using __enable_if_is_duration
241 	= typename enable_if<__is_duration<_Tp>::value, _Tp>::type;
242 
243     template<typename _Tp>
244       using __disable_if_is_duration
245 	= typename enable_if<!__is_duration<_Tp>::value, _Tp>::type;
246 
247     /// @endcond
248 
249     /** Convert a `duration` to type `ToDur`.
250      *
251      * If the duration cannot be represented accurately in the result type,
252      * returns the result of integer truncation (i.e., rounded towards zero).
253      *
254      * @tparam _ToDur The result type must be a `duration`.
255      * @param __d A duration.
256      * @return The value of `__d` converted to type `_ToDur`.
257      * @since C++11
258      */
259     template<typename _ToDur, typename _Rep, typename _Period>
260       _GLIBCXX_NODISCARD
261       constexpr __enable_if_is_duration<_ToDur>
262       duration_cast(const duration<_Rep, _Period>& __d)
263       {
264 	typedef typename _ToDur::period				__to_period;
265 	typedef typename _ToDur::rep				__to_rep;
266 	typedef ratio_divide<_Period, __to_period> 		__cf;
267 	typedef typename common_type<__to_rep, _Rep, intmax_t>::type __cr;
268 	typedef  __duration_cast_impl<_ToDur, __cf, __cr,
269 				      __cf::num == 1, __cf::den == 1> __dc;
270 	return __dc::__cast(__d);
271       }
272 
273     /** Trait indicating whether to treat a type as a floating-point type.
274      *
275      * The chrono library uses this trait to tell whether a `duration` can
276      * represent fractional values of the given precision, or only integral
277      * values.
278      *
279      * You should specialize this trait for your own numeric types that are
280      * used with `duration` and can represent non-integral values.
281      *
282      * @since C++11
283      */
284     template<typename _Rep>
285       struct treat_as_floating_point
286       : is_floating_point<_Rep>
287       { };
288 
289 #if __cplusplus > 201402L
290     template <typename _Rep>
291       inline constexpr bool treat_as_floating_point_v =
292 	treat_as_floating_point<_Rep>::value;
293 #endif // C++17
294 
295 #if __cplusplus > 201703L
296     template<typename _Tp>
297       struct is_clock;
298 
299     template<typename _Tp>
300       inline constexpr bool is_clock_v = is_clock<_Tp>::value;
301 
302 #if __cpp_lib_concepts
303     template<typename _Tp>
304       struct is_clock : false_type
305       { };
306 
307     template<typename _Tp>
308       requires requires {
309 	typename _Tp::rep;
310 	typename _Tp::period;
311 	typename _Tp::duration;
312 	typename _Tp::time_point::clock;
313 	typename _Tp::time_point::duration;
314 	{ &_Tp::is_steady } -> same_as<const bool*>;
315 	{ _Tp::now() } -> same_as<typename _Tp::time_point>;
316 	requires same_as<typename _Tp::duration,
317 			 duration<typename _Tp::rep, typename _Tp::period>>;
318 	requires same_as<typename _Tp::time_point::duration,
319 			 typename _Tp::duration>;
320       }
321       struct is_clock<_Tp> : true_type
322       { };
323 #else
324     template<typename _Tp, typename = void>
325       struct __is_clock_impl : false_type
326       { };
327 
328     template<typename _Tp>
329       struct __is_clock_impl<_Tp,
330 			     void_t<typename _Tp::rep, typename _Tp::period,
331 				    typename _Tp::duration,
332 				    typename _Tp::time_point::duration,
333 				    decltype(_Tp::is_steady),
334 				    decltype(_Tp::now())>>
335       : __and_<is_same<typename _Tp::duration,
336 		       duration<typename _Tp::rep, typename _Tp::period>>,
337 	       is_same<typename _Tp::time_point::duration,
338 		       typename _Tp::duration>,
339 	       is_same<decltype(&_Tp::is_steady), const bool*>,
340 	       is_same<decltype(_Tp::now()), typename _Tp::time_point>>::type
341       { };
342 
343     template<typename _Tp>
344       struct is_clock : __is_clock_impl<_Tp>::type
345       { };
346 #endif
347 #endif // C++20
348 
349 #if __cplusplus >= 201703L
350 # define __cpp_lib_chrono 201611L
351 
352     /** Convert a `duration` to type `ToDur` and round down.
353      *
354      * If the duration cannot be represented exactly in the result type,
355      * returns the closest value that is less than the argument.
356      *
357      * @tparam _ToDur The result type must be a `duration`.
358      * @param __d A duration.
359      * @return The value of `__d` converted to type `_ToDur`.
360      * @since C++17
361      */
362     template<typename _ToDur, typename _Rep, typename _Period>
363       [[nodiscard]] constexpr __enable_if_is_duration<_ToDur>
364       floor(const duration<_Rep, _Period>& __d)
365       {
366 	auto __to = chrono::duration_cast<_ToDur>(__d);
367 	if (__to > __d)
368 	  return __to - _ToDur{1};
369 	return __to;
370       }
371 
372     /** Convert a `duration` to type `ToDur` and round up.
373      *
374      * If the duration cannot be represented exactly in the result type,
375      * returns the closest value that is greater than the argument.
376      *
377      * @tparam _ToDur The result type must be a `duration`.
378      * @param __d A duration.
379      * @return The value of `__d` converted to type `_ToDur`.
380      * @since C++17
381      */
382     template<typename _ToDur, typename _Rep, typename _Period>
383       [[nodiscard]] constexpr __enable_if_is_duration<_ToDur>
384       ceil(const duration<_Rep, _Period>& __d)
385       {
386 	auto __to = chrono::duration_cast<_ToDur>(__d);
387 	if (__to < __d)
388 	  return __to + _ToDur{1};
389 	return __to;
390       }
391 
392     /** Convert a `duration` to type `ToDur` and round to the closest value.
393      *
394      * If the duration cannot be represented exactly in the result type,
395      * returns the closest value, rounding ties to even.
396      *
397      * @tparam _ToDur The result type must be a `duration` with a
398      *                non-floating-point `rep` type.
399      * @param __d A duration.
400      * @return The value of `__d` converted to type `_ToDur`.
401      * @since C++17
402      */
403     template <typename _ToDur, typename _Rep, typename _Period>
404       [[nodiscard]] constexpr
405       enable_if_t<
406 	__and_<__is_duration<_ToDur>,
407 	       __not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
408 	_ToDur>
409       round(const duration<_Rep, _Period>& __d)
410       {
411 	_ToDur __t0 = chrono::floor<_ToDur>(__d);
412 	_ToDur __t1 = __t0 + _ToDur{1};
413 	auto __diff0 = __d - __t0;
414 	auto __diff1 = __t1 - __d;
415 	if (__diff0 == __diff1)
416 	  {
417 	    if (__t0.count() & 1)
418 	      return __t1;
419 	    return __t0;
420 	  }
421 	else if (__diff0 < __diff1)
422 	  return __t0;
423 	return __t1;
424       }
425 
426     /** The absolute (non-negative) value of a duration.
427      *
428      * @param __d A duration with a signed `rep` type.
429      * @return A duration of the same type as the argument, with value |d|.
430      * @since C++17
431      */
432     template<typename _Rep, typename _Period>
433       [[nodiscard]] constexpr
434       enable_if_t<numeric_limits<_Rep>::is_signed, duration<_Rep, _Period>>
435       abs(duration<_Rep, _Period> __d)
436       {
437 	if (__d >= __d.zero())
438 	  return __d;
439 	return -__d;
440       }
441 
442     // Make chrono::ceil<D> also usable as chrono::__detail::ceil<D>.
443     namespace __detail { using chrono::ceil; }
444 
445 #else // ! C++17
446 
447     // We want to use ceil even when compiling for earlier standards versions.
448     // C++11 only allows a single statement in a constexpr function, so we
449     // need to move the comparison into a separate function, __ceil_impl.
450     namespace __detail
451     {
452       template<typename _Tp, typename _Up>
453 	constexpr _Tp
454 	__ceil_impl(const _Tp& __t, const _Up& __u)
455 	{
456 	  return (__t < __u) ? (__t + _Tp{1}) : __t;
457 	}
458 
459       // C++11-friendly version of std::chrono::ceil<D> for internal use.
460       template<typename _ToDur, typename _Rep, typename _Period>
461 	constexpr _ToDur
462 	ceil(const duration<_Rep, _Period>& __d)
463 	{
464 	  return __detail::__ceil_impl(chrono::duration_cast<_ToDur>(__d), __d);
465 	}
466     }
467 #endif // C++17
468 
469     /// duration_values
470     template<typename _Rep>
471       struct duration_values
472       {
473 	static constexpr _Rep
474 	zero() noexcept
475 	{ return _Rep(0); }
476 
477 	static constexpr _Rep
478 	max() noexcept
479 	{ return numeric_limits<_Rep>::max(); }
480 
481 	static constexpr _Rep
482 	min() noexcept
483 	{ return numeric_limits<_Rep>::lowest(); }
484       };
485 
486     /// @cond undocumented
487 
488     template<typename _Tp>
489       struct __is_ratio
490       : std::false_type
491       { };
492 
493     template<intmax_t _Num, intmax_t _Den>
494       struct __is_ratio<ratio<_Num, _Den>>
495       : std::true_type
496       { };
497 
498     /// @endcond
499 
500     template<typename _Rep, typename _Period>
501       class duration
502       {
503 	static_assert(!__is_duration<_Rep>::value, "rep cannot be a duration");
504 	static_assert(__is_ratio<_Period>::value,
505 		      "period must be a specialization of ratio");
506 	static_assert(_Period::num > 0, "period must be positive");
507 
508 	template<typename _Rep2>
509 	  using __is_float = treat_as_floating_point<_Rep2>;
510 
511 	static constexpr intmax_t
512 	_S_gcd(intmax_t __m, intmax_t __n) noexcept
513 	{
514 	  // Duration only allows positive periods so we don't need to
515 	  // handle negative values here (unlike __static_gcd and std::gcd).
516 #if __cplusplus >= 201402L
517 	  do
518 	    {
519 	      intmax_t __rem = __m % __n;
520 	      __m = __n;
521 	      __n = __rem;
522 	    }
523 	  while (__n != 0);
524 	  return __m;
525 #else
526 	  // C++11 doesn't allow loops in constexpr functions, but this
527 	  // recursive version can be more expensive to evaluate.
528 	  return (__n == 0) ? __m : _S_gcd(__n, __m % __n);
529 #endif
530 	}
531 
532 	// _GLIBCXX_RESOLVE_LIB_DEFECTS
533 	// 2094. overflow shouldn't participate in overload resolution
534 	// 3090. What is [2094] intended to mean?
535 	// This only produces a valid type if no overflow occurs.
536 	template<typename _R1, typename _R2,
537 		 intmax_t __gcd1 = _S_gcd(_R1::num, _R2::num),
538 		 intmax_t __gcd2 = _S_gcd(_R1::den, _R2::den)>
539 	  using __divide = ratio<(_R1::num / __gcd1) * (_R2::den / __gcd2),
540 				 (_R1::den / __gcd2) * (_R2::num / __gcd1)>;
541 
542 	// _Period2 is an exact multiple of _Period
543 	template<typename _Period2>
544 	  using __is_harmonic
545 	    = __bool_constant<__divide<_Period2, _Period>::den == 1>;
546 
547       public:
548 
549 	using rep = _Rep;
550 	using period = typename _Period::type;
551 
552 	// 20.11.5.1 construction / copy / destroy
553 	constexpr duration() = default;
554 
555 	duration(const duration&) = default;
556 
557 	// _GLIBCXX_RESOLVE_LIB_DEFECTS
558 	// 3050. Conversion specification problem in chrono::duration
559 	template<typename _Rep2, typename = _Require<
560 		 is_convertible<const _Rep2&, rep>,
561 		 __or_<__is_float<rep>, __not_<__is_float<_Rep2>>>>>
562 	  constexpr explicit duration(const _Rep2& __rep)
563 	  : __r(static_cast<rep>(__rep)) { }
564 
565 	template<typename _Rep2, typename _Period2, typename = _Require<
566 		 is_convertible<const _Rep2&, rep>,
567 		 __or_<__is_float<rep>,
568 		       __and_<__is_harmonic<_Period2>,
569 			      __not_<__is_float<_Rep2>>>>>>
570 	  constexpr duration(const duration<_Rep2, _Period2>& __d)
571 	  : __r(duration_cast<duration>(__d).count()) { }
572 
573 	~duration() = default;
574 	duration& operator=(const duration&) = default;
575 
576 	// 20.11.5.2 observer
577 	constexpr rep
578 	count() const
579 	{ return __r; }
580 
581 	// 20.11.5.3 arithmetic
582 
583 	constexpr duration<typename common_type<rep>::type, period>
584 	operator+() const
585 	{ return duration<typename common_type<rep>::type, period>(__r); }
586 
587 	constexpr duration<typename common_type<rep>::type, period>
588 	operator-() const
589 	{ return duration<typename common_type<rep>::type, period>(-__r); }
590 
591 	_GLIBCXX17_CONSTEXPR duration&
592 	operator++()
593 	{
594 	  ++__r;
595 	  return *this;
596 	}
597 
598 	_GLIBCXX17_CONSTEXPR duration
599 	operator++(int)
600 	{ return duration(__r++); }
601 
602 	_GLIBCXX17_CONSTEXPR duration&
603 	operator--()
604 	{
605 	  --__r;
606 	  return *this;
607 	}
608 
609 	_GLIBCXX17_CONSTEXPR duration
610 	operator--(int)
611 	{ return duration(__r--); }
612 
613 	_GLIBCXX17_CONSTEXPR duration&
614 	operator+=(const duration& __d)
615 	{
616 	  __r += __d.count();
617 	  return *this;
618 	}
619 
620 	_GLIBCXX17_CONSTEXPR duration&
621 	operator-=(const duration& __d)
622 	{
623 	  __r -= __d.count();
624 	  return *this;
625 	}
626 
627 	_GLIBCXX17_CONSTEXPR duration&
628 	operator*=(const rep& __rhs)
629 	{
630 	  __r *= __rhs;
631 	  return *this;
632 	}
633 
634 	_GLIBCXX17_CONSTEXPR duration&
635 	operator/=(const rep& __rhs)
636 	{
637 	  __r /= __rhs;
638 	  return *this;
639 	}
640 
641 	// DR 934.
642 	template<typename _Rep2 = rep>
643 	  _GLIBCXX17_CONSTEXPR
644 	  typename enable_if<!treat_as_floating_point<_Rep2>::value,
645 			     duration&>::type
646 	  operator%=(const rep& __rhs)
647 	  {
648 	    __r %= __rhs;
649 	    return *this;
650 	  }
651 
652 	template<typename _Rep2 = rep>
653 	  _GLIBCXX17_CONSTEXPR
654 	  typename enable_if<!treat_as_floating_point<_Rep2>::value,
655 			     duration&>::type
656 	  operator%=(const duration& __d)
657 	  {
658 	    __r %= __d.count();
659 	    return *this;
660 	  }
661 
662 	// 20.11.5.4 special values
663 	static constexpr duration
664 	zero() noexcept
665 	{ return duration(duration_values<rep>::zero()); }
666 
667 	static constexpr duration
668 	min() noexcept
669 	{ return duration(duration_values<rep>::min()); }
670 
671 	static constexpr duration
672 	max() noexcept
673 	{ return duration(duration_values<rep>::max()); }
674 
675       private:
676 	rep __r;
677       };
678 
679     /// @{
680     /// @relates std::chrono::duration
681 
682     /// The sum of two durations.
683     template<typename _Rep1, typename _Period1,
684 	     typename _Rep2, typename _Period2>
685       constexpr typename common_type<duration<_Rep1, _Period1>,
686 				     duration<_Rep2, _Period2>>::type
687       operator+(const duration<_Rep1, _Period1>& __lhs,
688 		const duration<_Rep2, _Period2>& __rhs)
689       {
690 	typedef duration<_Rep1, _Period1>			__dur1;
691 	typedef duration<_Rep2, _Period2>			__dur2;
692 	typedef typename common_type<__dur1,__dur2>::type	__cd;
693 	return __cd(__cd(__lhs).count() + __cd(__rhs).count());
694       }
695 
696     /// The difference between two durations.
697     template<typename _Rep1, typename _Period1,
698 	     typename _Rep2, typename _Period2>
699       constexpr typename common_type<duration<_Rep1, _Period1>,
700 				     duration<_Rep2, _Period2>>::type
701       operator-(const duration<_Rep1, _Period1>& __lhs,
702 		const duration<_Rep2, _Period2>& __rhs)
703       {
704 	typedef duration<_Rep1, _Period1>			__dur1;
705 	typedef duration<_Rep2, _Period2>			__dur2;
706 	typedef typename common_type<__dur1,__dur2>::type	__cd;
707 	return __cd(__cd(__lhs).count() - __cd(__rhs).count());
708       }
709 
710     /// @}
711 
712     /// @cond undocumented
713 
714     // SFINAE helper to obtain common_type<_Rep1, _Rep2> only if _Rep2
715     // is implicitly convertible to it.
716     // _GLIBCXX_RESOLVE_LIB_DEFECTS
717     // 3050. Conversion specification problem in chrono::duration constructor
718     template<typename _Rep1, typename _Rep2,
719 	     typename _CRep = typename common_type<_Rep1, _Rep2>::type>
720       using __common_rep_t = typename
721 	enable_if<is_convertible<const _Rep2&, _CRep>::value, _CRep>::type;
722 
723     /// @endcond
724 
725     /** @{
726      * Arithmetic operators for chrono::duration
727      * @relates std::chrono::duration
728      */
729 
730     template<typename _Rep1, typename _Period, typename _Rep2>
731       constexpr duration<__common_rep_t<_Rep1, _Rep2>, _Period>
732       operator*(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
733       {
734 	typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period>
735 	  __cd;
736 	return __cd(__cd(__d).count() * __s);
737       }
738 
739     template<typename _Rep1, typename _Rep2, typename _Period>
740       constexpr duration<__common_rep_t<_Rep2, _Rep1>, _Period>
741       operator*(const _Rep1& __s, const duration<_Rep2, _Period>& __d)
742       { return __d * __s; }
743 
744     template<typename _Rep1, typename _Period, typename _Rep2>
745       constexpr
746       duration<__common_rep_t<_Rep1, __disable_if_is_duration<_Rep2>>, _Period>
747       operator/(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
748       {
749 	typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period>
750 	  __cd;
751 	return __cd(__cd(__d).count() / __s);
752       }
753 
754     template<typename _Rep1, typename _Period1,
755 	     typename _Rep2, typename _Period2>
756       constexpr typename common_type<_Rep1, _Rep2>::type
757       operator/(const duration<_Rep1, _Period1>& __lhs,
758 		const duration<_Rep2, _Period2>& __rhs)
759       {
760 	typedef duration<_Rep1, _Period1>			__dur1;
761 	typedef duration<_Rep2, _Period2>			__dur2;
762 	typedef typename common_type<__dur1,__dur2>::type	__cd;
763 	return __cd(__lhs).count() / __cd(__rhs).count();
764       }
765 
766     // DR 934.
767     template<typename _Rep1, typename _Period, typename _Rep2>
768       constexpr
769       duration<__common_rep_t<_Rep1, __disable_if_is_duration<_Rep2>>, _Period>
770       operator%(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
771       {
772 	typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period>
773 	  __cd;
774 	return __cd(__cd(__d).count() % __s);
775       }
776 
777     template<typename _Rep1, typename _Period1,
778 	     typename _Rep2, typename _Period2>
779       constexpr typename common_type<duration<_Rep1, _Period1>,
780 				     duration<_Rep2, _Period2>>::type
781       operator%(const duration<_Rep1, _Period1>& __lhs,
782 		const duration<_Rep2, _Period2>& __rhs)
783       {
784 	typedef duration<_Rep1, _Period1>			__dur1;
785 	typedef duration<_Rep2, _Period2>			__dur2;
786 	typedef typename common_type<__dur1,__dur2>::type	__cd;
787 	return __cd(__cd(__lhs).count() % __cd(__rhs).count());
788       }
789     /// @}
790 
791     // comparisons
792 
793     /** @{
794      * Comparisons for chrono::duration
795      * @relates std::chrono::duration
796      */
797 
798     template<typename _Rep1, typename _Period1,
799 	     typename _Rep2, typename _Period2>
800       constexpr bool
801       operator==(const duration<_Rep1, _Period1>& __lhs,
802 		 const duration<_Rep2, _Period2>& __rhs)
803       {
804 	typedef duration<_Rep1, _Period1>			__dur1;
805 	typedef duration<_Rep2, _Period2>			__dur2;
806 	typedef typename common_type<__dur1,__dur2>::type	__ct;
807 	return __ct(__lhs).count() == __ct(__rhs).count();
808       }
809 
810     template<typename _Rep1, typename _Period1,
811 	     typename _Rep2, typename _Period2>
812       constexpr bool
813       operator<(const duration<_Rep1, _Period1>& __lhs,
814 		const duration<_Rep2, _Period2>& __rhs)
815       {
816 	typedef duration<_Rep1, _Period1>			__dur1;
817 	typedef duration<_Rep2, _Period2>			__dur2;
818 	typedef typename common_type<__dur1,__dur2>::type	__ct;
819 	return __ct(__lhs).count() < __ct(__rhs).count();
820       }
821 
822 #if __cpp_lib_three_way_comparison
823     template<typename _Rep1, typename _Period1,
824 	     typename _Rep2, typename _Period2>
825       requires three_way_comparable<common_type_t<_Rep1, _Rep2>>
826       constexpr auto
827       operator<=>(const duration<_Rep1, _Period1>& __lhs,
828 		  const duration<_Rep2, _Period2>& __rhs)
829       {
830 	using __ct = common_type_t<duration<_Rep1, _Period1>,
831 				   duration<_Rep2, _Period2>>;
832 	return __ct(__lhs).count() <=> __ct(__rhs).count();
833       }
834 #else
835     template<typename _Rep1, typename _Period1,
836 	     typename _Rep2, typename _Period2>
837       constexpr bool
838       operator!=(const duration<_Rep1, _Period1>& __lhs,
839 		 const duration<_Rep2, _Period2>& __rhs)
840       { return !(__lhs == __rhs); }
841 #endif
842 
843     template<typename _Rep1, typename _Period1,
844 	     typename _Rep2, typename _Period2>
845       constexpr bool
846       operator<=(const duration<_Rep1, _Period1>& __lhs,
847 		 const duration<_Rep2, _Period2>& __rhs)
848       { return !(__rhs < __lhs); }
849 
850     template<typename _Rep1, typename _Period1,
851 	     typename _Rep2, typename _Period2>
852       constexpr bool
853       operator>(const duration<_Rep1, _Period1>& __lhs,
854 		const duration<_Rep2, _Period2>& __rhs)
855       { return __rhs < __lhs; }
856 
857     template<typename _Rep1, typename _Period1,
858 	     typename _Rep2, typename _Period2>
859       constexpr bool
860       operator>=(const duration<_Rep1, _Period1>& __lhs,
861 		 const duration<_Rep2, _Period2>& __rhs)
862       { return !(__lhs < __rhs); }
863 
864     /// @}
865 
866     /// @cond undocumented
867 #ifdef _GLIBCXX_USE_C99_STDINT_TR1
868 # define _GLIBCXX_CHRONO_INT64_T int64_t
869 #elif defined __INT64_TYPE__
870 # define _GLIBCXX_CHRONO_INT64_T __INT64_TYPE__
871 #else
872     static_assert(std::numeric_limits<unsigned long long>::digits >= 64,
873 	"Representation type for nanoseconds must have at least 64 bits");
874 # define _GLIBCXX_CHRONO_INT64_T long long
875 #endif
876     /// @endcond
877 
878     /// nanoseconds
879     using nanoseconds	= duration<_GLIBCXX_CHRONO_INT64_T, nano>;
880 
881     /// microseconds
882     using microseconds	= duration<_GLIBCXX_CHRONO_INT64_T, micro>;
883 
884     /// milliseconds
885     using milliseconds	= duration<_GLIBCXX_CHRONO_INT64_T, milli>;
886 
887     /// seconds
888     using seconds	= duration<_GLIBCXX_CHRONO_INT64_T>;
889 
890     /// minutes
891     using minutes	= duration<_GLIBCXX_CHRONO_INT64_T, ratio< 60>>;
892 
893     /// hours
894     using hours		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<3600>>;
895 
896 #if __cplusplus > 201703L
897     /// days
898     using days		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<86400>>;
899 
900     /// weeks
901     using weeks		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<604800>>;
902 
903     /// years
904     using years		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<31556952>>;
905 
906     /// months
907     using months	= duration<_GLIBCXX_CHRONO_INT64_T, ratio<2629746>>;
908 #endif // C++20
909 
910 #undef _GLIBCXX_CHRONO_INT64_T
911 
912     template<typename _Clock, typename _Dur>
913       class time_point
914       {
915 	static_assert(__is_duration<_Dur>::value,
916 	    "duration must be a specialization of std::chrono::duration");
917 
918       public:
919 	typedef _Clock						clock;
920 	typedef _Dur						duration;
921 	typedef typename duration::rep				rep;
922 	typedef typename duration::period			period;
923 
924 	constexpr time_point() : __d(duration::zero())
925 	{ }
926 
927 	constexpr explicit time_point(const duration& __dur)
928 	: __d(__dur)
929 	{ }
930 
931 	// conversions
932 	template<typename _Dur2,
933 		 typename = _Require<is_convertible<_Dur2, _Dur>>>
934 	  constexpr time_point(const time_point<clock, _Dur2>& __t)
935 	  : __d(__t.time_since_epoch())
936 	  { }
937 
938 	// observer
939 	constexpr duration
940 	time_since_epoch() const
941 	{ return __d; }
942 
943 #if __cplusplus > 201703L
944 	constexpr time_point&
945 	operator++()
946 	{
947 	  ++__d;
948 	  return *this;
949 	}
950 
951 	constexpr time_point
952 	operator++(int)
953 	{ return time_point{__d++}; }
954 
955 	constexpr time_point&
956 	operator--()
957 	{
958 	  --__d;
959 	  return *this;
960 	}
961 
962 	constexpr time_point
963 	operator--(int)
964 	{ return time_point{__d--}; }
965 #endif
966 
967 	// arithmetic
968 	_GLIBCXX17_CONSTEXPR time_point&
969 	operator+=(const duration& __dur)
970 	{
971 	  __d += __dur;
972 	  return *this;
973 	}
974 
975 	_GLIBCXX17_CONSTEXPR time_point&
976 	operator-=(const duration& __dur)
977 	{
978 	  __d -= __dur;
979 	  return *this;
980 	}
981 
982 	// special values
983 	static constexpr time_point
984 	min() noexcept
985 	{ return time_point(duration::min()); }
986 
987 	static constexpr time_point
988 	max() noexcept
989 	{ return time_point(duration::max()); }
990 
991       private:
992 	duration __d;
993       };
994 
995     /** Convert a `time_point` to use `duration` type `ToDur`.
996      *
997      * The result is the same time point as measured by the same clock, but
998      * using the specified `duration` to represent the time.
999      * If the time point cannot be represented accurately in the result type,
1000      * returns the result of integer truncation (i.e., rounded towards zero).
1001      *
1002      * @tparam _ToDur The `duration` type to use for the result.
1003      * @param __t A time point.
1004      * @return The value of `__t` converted to use type `_ToDur`.
1005      * @since C++11
1006      */
1007     template<typename _ToDur, typename _Clock, typename _Dur>
1008       _GLIBCXX_NODISCARD constexpr
1009       __enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
1010       time_point_cast(const time_point<_Clock, _Dur>& __t)
1011       {
1012 	typedef time_point<_Clock, _ToDur>			__time_point;
1013 	return __time_point(duration_cast<_ToDur>(__t.time_since_epoch()));
1014       }
1015 
1016 #if __cplusplus > 201402L
1017     /** Convert a `time_point` to type `ToDur` and round down.
1018      *
1019      * The result is the same time point as measured by the same clock, but
1020      * using the specified `duration` to represent the time.
1021      * If the time point cannot be represented exactly in the result type,
1022      * returns the closest value that is less than the argument.
1023      *
1024      * @tparam _ToDur The `duration` type to use for the result.
1025      * @param __t A time point.
1026      * @return The value of `__d` converted to type `_ToDur`.
1027      * @since C++17
1028      */
1029     template<typename _ToDur, typename _Clock, typename _Dur>
1030       [[nodiscard]] constexpr
1031       enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
1032       floor(const time_point<_Clock, _Dur>& __tp)
1033       {
1034 	return time_point<_Clock, _ToDur>{
1035 	    chrono::floor<_ToDur>(__tp.time_since_epoch())};
1036       }
1037 
1038     /** Convert a `time_point` to type `ToDur` and round up.
1039      *
1040      * The result is the same time point as measured by the same clock, but
1041      * using the specified `duration` to represent the time.
1042      * If the time point cannot be represented exactly in the result type,
1043      * returns the closest value that is greater than the argument.
1044      *
1045      * @tparam _ToDur The `duration` type to use for the result.
1046      * @param __t A time point.
1047      * @return The value of `__d` converted to type `_ToDur`.
1048      * @since C++17
1049      */
1050     template<typename _ToDur, typename _Clock, typename _Dur>
1051       [[nodiscard]] constexpr
1052       enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
1053       ceil(const time_point<_Clock, _Dur>& __tp)
1054       {
1055 	return time_point<_Clock, _ToDur>{
1056 	    chrono::ceil<_ToDur>(__tp.time_since_epoch())};
1057       }
1058 
1059     /** Convert a `time_point` to type `ToDur` and round to the closest value.
1060      *
1061      * The result is the same time point as measured by the same clock, but
1062      * using the specified `duration` to represent the time.
1063      * If the time point cannot be represented exactly in the result type,
1064      * returns the closest value, rounding ties to even.
1065      *
1066      * @tparam _ToDur The `duration` type to use for the result,
1067      *                which must have a non-floating-point `rep` type.
1068      * @param __t A time point.
1069      * @return The value of `__d` converted to type `_ToDur`.
1070      * @since C++17
1071      */
1072     template<typename _ToDur, typename _Clock, typename _Dur>
1073       [[nodiscard]] constexpr
1074       enable_if_t<
1075 	__and_<__is_duration<_ToDur>,
1076 	       __not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
1077 	time_point<_Clock, _ToDur>>
1078       round(const time_point<_Clock, _Dur>& __tp)
1079       {
1080 	return time_point<_Clock, _ToDur>{
1081 	    chrono::round<_ToDur>(__tp.time_since_epoch())};
1082       }
1083 #endif // C++17
1084 
1085     /// @{
1086     /// @relates time_point
1087 
1088     /// Adjust a time point forwards by the given duration.
1089     template<typename _Clock, typename _Dur1,
1090 	     typename _Rep2, typename _Period2>
1091       constexpr time_point<_Clock,
1092 	typename common_type<_Dur1, duration<_Rep2, _Period2>>::type>
1093       operator+(const time_point<_Clock, _Dur1>& __lhs,
1094 		const duration<_Rep2, _Period2>& __rhs)
1095       {
1096 	typedef duration<_Rep2, _Period2>			__dur2;
1097 	typedef typename common_type<_Dur1,__dur2>::type	__ct;
1098 	typedef time_point<_Clock, __ct>			__time_point;
1099 	return __time_point(__lhs.time_since_epoch() + __rhs);
1100       }
1101 
1102     /// Adjust a time point forwards by the given duration.
1103     template<typename _Rep1, typename _Period1,
1104 	     typename _Clock, typename _Dur2>
1105       constexpr time_point<_Clock,
1106 	typename common_type<duration<_Rep1, _Period1>, _Dur2>::type>
1107       operator+(const duration<_Rep1, _Period1>& __lhs,
1108 		const time_point<_Clock, _Dur2>& __rhs)
1109       {
1110 	typedef duration<_Rep1, _Period1>			__dur1;
1111 	typedef typename common_type<__dur1,_Dur2>::type	__ct;
1112 	typedef time_point<_Clock, __ct>			__time_point;
1113 	return __time_point(__rhs.time_since_epoch() + __lhs);
1114       }
1115 
1116     /// Adjust a time point backwards by the given duration.
1117     template<typename _Clock, typename _Dur1,
1118 	     typename _Rep2, typename _Period2>
1119       constexpr time_point<_Clock,
1120 	typename common_type<_Dur1, duration<_Rep2, _Period2>>::type>
1121       operator-(const time_point<_Clock, _Dur1>& __lhs,
1122 		const duration<_Rep2, _Period2>& __rhs)
1123       {
1124 	typedef duration<_Rep2, _Period2>			__dur2;
1125 	typedef typename common_type<_Dur1,__dur2>::type	__ct;
1126 	typedef time_point<_Clock, __ct>			__time_point;
1127 	return __time_point(__lhs.time_since_epoch() -__rhs);
1128       }
1129 
1130     /// The difference between two time points (as a duration)
1131     template<typename _Clock, typename _Dur1, typename _Dur2>
1132       constexpr typename common_type<_Dur1, _Dur2>::type
1133       operator-(const time_point<_Clock, _Dur1>& __lhs,
1134 		const time_point<_Clock, _Dur2>& __rhs)
1135       { return __lhs.time_since_epoch() - __rhs.time_since_epoch(); }
1136     /// @}
1137 
1138     /** @{
1139      * Comparisons for time_point
1140      * @relates chrono::time_point
1141      */
1142 
1143     template<typename _Clock, typename _Dur1, typename _Dur2>
1144       constexpr bool
1145       operator==(const time_point<_Clock, _Dur1>& __lhs,
1146 		 const time_point<_Clock, _Dur2>& __rhs)
1147       { return __lhs.time_since_epoch() == __rhs.time_since_epoch(); }
1148 
1149 #if __cpp_lib_three_way_comparison
1150     template<typename _Clock, typename _Dur1,
1151 	     three_way_comparable_with<_Dur1> _Dur2>
1152       constexpr auto
1153       operator<=>(const time_point<_Clock, _Dur1>& __lhs,
1154 		  const time_point<_Clock, _Dur2>& __rhs)
1155       { return __lhs.time_since_epoch() <=> __rhs.time_since_epoch(); }
1156 #else
1157     template<typename _Clock, typename _Dur1, typename _Dur2>
1158       constexpr bool
1159       operator!=(const time_point<_Clock, _Dur1>& __lhs,
1160 		 const time_point<_Clock, _Dur2>& __rhs)
1161       { return !(__lhs == __rhs); }
1162 #endif
1163 
1164     template<typename _Clock, typename _Dur1, typename _Dur2>
1165       constexpr bool
1166       operator<(const time_point<_Clock, _Dur1>& __lhs,
1167 		const time_point<_Clock, _Dur2>& __rhs)
1168       { return  __lhs.time_since_epoch() < __rhs.time_since_epoch(); }
1169 
1170     template<typename _Clock, typename _Dur1, typename _Dur2>
1171       constexpr bool
1172       operator<=(const time_point<_Clock, _Dur1>& __lhs,
1173 		 const time_point<_Clock, _Dur2>& __rhs)
1174       { return !(__rhs < __lhs); }
1175 
1176     template<typename _Clock, typename _Dur1, typename _Dur2>
1177       constexpr bool
1178       operator>(const time_point<_Clock, _Dur1>& __lhs,
1179 		const time_point<_Clock, _Dur2>& __rhs)
1180       { return __rhs < __lhs; }
1181 
1182     template<typename _Clock, typename _Dur1, typename _Dur2>
1183       constexpr bool
1184       operator>=(const time_point<_Clock, _Dur1>& __lhs,
1185 		 const time_point<_Clock, _Dur2>& __rhs)
1186       { return !(__lhs < __rhs); }
1187 
1188     /// @}
1189     /// @} group chrono
1190 
1191     // Clocks.
1192 
1193     // Why nanosecond resolution as the default?
1194     // Why have std::system_clock always count in the highest
1195     // resolution (ie nanoseconds), even if on some OSes the low 3
1196     // or 9 decimal digits will be always zero? This allows later
1197     // implementations to change the system_clock::now()
1198     // implementation any time to provide better resolution without
1199     // changing function signature or units.
1200 
1201     // To support the (forward) evolution of the library's defined
1202     // clocks, wrap inside inline namespace so that the current
1203     // defintions of system_clock, steady_clock, and
1204     // high_resolution_clock types are uniquely mangled. This way, new
1205     // code can use the latests clocks, while the library can contain
1206     // compatibility definitions for previous versions.  At some
1207     // point, when these clocks settle down, the inlined namespaces
1208     // can be removed.  XXX GLIBCXX_ABI Deprecated
1209     inline namespace _V2 {
1210 
1211     /**
1212      *  @brief System clock.
1213      *
1214      *  Time returned represents wall time from the system-wide clock.
1215      *  @ingroup chrono
1216     */
1217     struct system_clock
1218     {
1219       typedef chrono::nanoseconds				duration;
1220       typedef duration::rep					rep;
1221       typedef duration::period					period;
1222       typedef chrono::time_point<system_clock, duration> 	time_point;
1223 
1224       static_assert(system_clock::duration::min()
1225 		    < system_clock::duration::zero(),
1226 		    "a clock's minimum duration cannot be less than its epoch");
1227 
1228       static constexpr bool is_steady = false;
1229 
1230       static time_point
1231       now() noexcept;
1232 
1233       // Map to C API
1234       static std::time_t
1235       to_time_t(const time_point& __t) noexcept
1236       {
1237 	return std::time_t(duration_cast<chrono::seconds>
1238 			   (__t.time_since_epoch()).count());
1239       }
1240 
1241       static time_point
1242       from_time_t(std::time_t __t) noexcept
1243       {
1244 	typedef chrono::time_point<system_clock, seconds>	__from;
1245 	return time_point_cast<system_clock::duration>
1246 	       (__from(chrono::seconds(__t)));
1247       }
1248     };
1249 
1250 
1251     /**
1252      *  @brief Monotonic clock
1253      *
1254      *  Time returned has the property of only increasing at a uniform rate.
1255      *  @ingroup chrono
1256     */
1257     struct steady_clock
1258     {
1259       typedef chrono::nanoseconds				duration;
1260       typedef duration::rep					rep;
1261       typedef duration::period					period;
1262       typedef chrono::time_point<steady_clock, duration>	time_point;
1263 
1264       static constexpr bool is_steady = true;
1265 
1266       static time_point
1267       now() noexcept;
1268     };
1269 
1270 
1271     /**
1272      *  @brief Highest-resolution clock
1273      *
1274      *  This is the clock "with the shortest tick period." Alias to
1275      *  std::system_clock until higher-than-nanosecond definitions
1276      *  become feasible.
1277      *  @ingroup chrono
1278     */
1279     using high_resolution_clock = system_clock;
1280 
1281     } // end inline namespace _V2
1282 
1283 #if __cplusplus >= 202002L
1284     /// @addtogroup chrono
1285     /// @{
1286     template<typename _Duration>
1287       using sys_time = time_point<system_clock, _Duration>;
1288     using sys_seconds = sys_time<seconds>;
1289     using sys_days = sys_time<days>;
1290 
1291     using file_clock = ::std::filesystem::__file_clock;
1292 
1293     template<typename _Duration>
1294       using file_time = time_point<file_clock, _Duration>;
1295 
1296     template<> struct is_clock<system_clock> : true_type { };
1297     template<> struct is_clock<steady_clock> : true_type { };
1298     template<> struct is_clock<file_clock> : true_type { };
1299 
1300     template<> inline constexpr bool is_clock_v<system_clock> = true;
1301     template<> inline constexpr bool is_clock_v<steady_clock> = true;
1302     template<> inline constexpr bool is_clock_v<file_clock> = true;
1303     /// @}
1304 #endif // C++20
1305   } // namespace chrono
1306 
1307 #if __cplusplus >= 201402L
1308 #define __cpp_lib_chrono_udls 201304L
1309 
1310   inline namespace literals
1311   {
1312   /** ISO C++ 2014  namespace for suffixes for duration literals.
1313    *
1314    * These suffixes can be used to create `chrono::duration` values with
1315    * tick periods of hours, minutes, seconds, milliseconds, microseconds
1316    * or nanoseconds. For example, `std::chrono::seconds(5)` can be written
1317    * as `5s` after making the suffix visible in the current scope.
1318    * The suffixes can be made visible by a using-directive or
1319    * using-declaration such as:
1320    *  - `using namespace std::chrono_literals;`
1321    *  - `using namespace std::literals;`
1322    *  - `using namespace std::chrono;`
1323    *  - `using namespace std;`
1324    *  - `using std::chrono_literals::operator""s;`
1325    *
1326    * The result of these suffixes on an integer literal is one of the
1327    * standard typedefs such as `std::chrono::hours`.
1328    * The result on a floating-point literal is a duration type with the
1329    * specified tick period and an unspecified floating-point representation,
1330    * for example `1.5e2ms` might be equivalent to
1331    * `chrono::duration<long double, chrono::milli>(1.5e2)`.
1332    *
1333    * @since C+14
1334    * @ingroup chrono
1335    */
1336   inline namespace chrono_literals
1337   {
1338     /// @addtogroup chrono
1339     /// @{
1340 
1341 #pragma GCC diagnostic push
1342 #pragma GCC diagnostic ignored "-Wliteral-suffix"
1343     /// @cond undocumented
1344     template<typename _Dur, char... _Digits>
1345       constexpr _Dur __check_overflow()
1346       {
1347 	using _Val = __parse_int::_Parse_int<_Digits...>;
1348 	constexpr typename _Dur::rep __repval = _Val::value;
1349 	static_assert(__repval >= 0 && __repval == _Val::value,
1350 		      "literal value cannot be represented by duration type");
1351 	return _Dur(__repval);
1352       }
1353     /// @endcond
1354 
1355     /// Literal suffix for durations representing non-integer hours
1356     constexpr chrono::duration<long double, ratio<3600,1>>
1357     operator""h(long double __hours)
1358     { return chrono::duration<long double, ratio<3600,1>>{__hours}; }
1359 
1360     /// Literal suffix for durations of type `std::chrono::hours`
1361     template <char... _Digits>
1362       constexpr chrono::hours
1363       operator""h()
1364       { return __check_overflow<chrono::hours, _Digits...>(); }
1365 
1366     /// Literal suffix for durations representing non-integer minutes
1367     constexpr chrono::duration<long double, ratio<60,1>>
1368     operator""min(long double __mins)
1369     { return chrono::duration<long double, ratio<60,1>>{__mins}; }
1370 
1371     /// Literal suffix for durations of type `std::chrono::minutes`
1372     template <char... _Digits>
1373       constexpr chrono::minutes
1374       operator""min()
1375       { return __check_overflow<chrono::minutes, _Digits...>(); }
1376 
1377     /// Literal suffix for durations representing non-integer seconds
1378     constexpr chrono::duration<long double>
1379     operator""s(long double __secs)
1380     { return chrono::duration<long double>{__secs}; }
1381 
1382     /// Literal suffix for durations of type `std::chrono::seconds`
1383     template <char... _Digits>
1384       constexpr chrono::seconds
1385       operator""s()
1386       { return __check_overflow<chrono::seconds, _Digits...>(); }
1387 
1388     /// Literal suffix for durations representing non-integer milliseconds
1389     constexpr chrono::duration<long double, milli>
1390     operator""ms(long double __msecs)
1391     { return chrono::duration<long double, milli>{__msecs}; }
1392 
1393     /// Literal suffix for durations of type `std::chrono::milliseconds`
1394     template <char... _Digits>
1395       constexpr chrono::milliseconds
1396       operator""ms()
1397       { return __check_overflow<chrono::milliseconds, _Digits...>(); }
1398 
1399     /// Literal suffix for durations representing non-integer microseconds
1400     constexpr chrono::duration<long double, micro>
1401     operator""us(long double __usecs)
1402     { return chrono::duration<long double, micro>{__usecs}; }
1403 
1404     /// Literal suffix for durations of type `std::chrono::microseconds`
1405     template <char... _Digits>
1406       constexpr chrono::microseconds
1407       operator""us()
1408       { return __check_overflow<chrono::microseconds, _Digits...>(); }
1409 
1410     /// Literal suffix for durations representing non-integer nanoseconds
1411     constexpr chrono::duration<long double, nano>
1412     operator""ns(long double __nsecs)
1413     { return chrono::duration<long double, nano>{__nsecs}; }
1414 
1415     /// Literal suffix for durations of type `std::chrono::nanoseconds`
1416     template <char... _Digits>
1417       constexpr chrono::nanoseconds
1418       operator""ns()
1419       { return __check_overflow<chrono::nanoseconds, _Digits...>(); }
1420 
1421 #pragma GCC diagnostic pop
1422     /// @}
1423   } // inline namespace chrono_literals
1424   } // inline namespace literals
1425 
1426   namespace chrono
1427   {
1428     using namespace literals::chrono_literals;
1429   } // namespace chrono
1430 #endif // C++14
1431 
1432 #if __cplusplus >= 201703L
1433   namespace filesystem
1434   {
1435     struct __file_clock
1436     {
1437       using duration                  = chrono::nanoseconds;
1438       using rep                       = duration::rep;
1439       using period                    = duration::period;
1440       using time_point                = chrono::time_point<__file_clock>;
1441       static constexpr bool is_steady = false;
1442 
1443       static time_point
1444       now() noexcept
1445       { return _S_from_sys(chrono::system_clock::now()); }
1446 
1447 #if __cplusplus > 201703L
1448       template<typename _Dur>
1449 	static
1450 	chrono::file_time<_Dur>
1451 	from_sys(const chrono::sys_time<_Dur>& __t) noexcept
1452 	{ return _S_from_sys(__t); }
1453 
1454       // For internal use only
1455       template<typename _Dur>
1456 	static
1457 	chrono::sys_time<_Dur>
1458 	to_sys(const chrono::file_time<_Dur>& __t) noexcept
1459 	{ return _S_to_sys(__t); }
1460 #endif // C++20
1461 
1462     private:
1463       using __sys_clock = chrono::system_clock;
1464 
1465       // This clock's (unspecified) epoch is 2174-01-01 00:00:00 UTC.
1466       // A signed 64-bit duration with nanosecond resolution gives roughly
1467       // +/- 292 years, which covers the 1901-2446 date range for ext4.
1468       static constexpr chrono::seconds _S_epoch_diff{6437664000};
1469 
1470     protected:
1471       // For internal use only
1472       template<typename _Dur>
1473 	static
1474 	chrono::time_point<__file_clock, _Dur>
1475 	_S_from_sys(const chrono::time_point<__sys_clock, _Dur>& __t) noexcept
1476 	{
1477 	  using __file_time = chrono::time_point<__file_clock, _Dur>;
1478 	  return __file_time{__t.time_since_epoch()} - _S_epoch_diff;
1479 	}
1480 
1481       // For internal use only
1482       template<typename _Dur>
1483 	static
1484 	chrono::time_point<__sys_clock, _Dur>
1485 	_S_to_sys(const chrono::time_point<__file_clock, _Dur>& __t) noexcept
1486 	{
1487 	  using __sys_time = chrono::time_point<__sys_clock, _Dur>;
1488 	  return __sys_time{__t.time_since_epoch()} + _S_epoch_diff;
1489 	}
1490     };
1491   } // namespace filesystem
1492 #endif // C++17
1493 
1494 _GLIBCXX_END_NAMESPACE_VERSION
1495 } // namespace std
1496 
1497 #endif // C++11
1498 
1499 #endif //_GLIBCXX_CHRONO_H
1500