1 // <chrono> -*- C++ -*- 2 3 // Copyright (C) 2008-2013 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/chrono 26 * This is a Standard C++ Library header. 27 */ 28 29 #ifndef _GLIBCXX_CHRONO 30 #define _GLIBCXX_CHRONO 1 31 32 #pragma GCC system_header 33 34 #if __cplusplus < 201103L 35 # include <bits/c++0x_warning.h> 36 #else 37 38 #include <ratio> 39 #include <type_traits> 40 #include <limits> 41 #include <ctime> 42 43 #ifdef _GLIBCXX_USE_C99_STDINT_TR1 44 45 namespace std _GLIBCXX_VISIBILITY(default) 46 { 47 /** 48 * @defgroup chrono Time 49 * @ingroup utilities 50 * 51 * Classes and functions for time. 52 * @{ 53 */ 54 55 /** @namespace std::chrono 56 * @brief ISO C++ 2011 entities sub-namespace for time and date. 57 */ 58 namespace chrono 59 { 60 _GLIBCXX_BEGIN_NAMESPACE_VERSION 61 62 template<typename _Rep, typename _Period = ratio<1>> 63 struct duration; 64 65 template<typename _Clock, typename _Dur = typename _Clock::duration> 66 struct time_point; 67 68 _GLIBCXX_END_NAMESPACE_VERSION 69 } 70 71 _GLIBCXX_BEGIN_NAMESPACE_VERSION 72 73 // 20.11.4.3 specialization of common_type (for duration, sfinae-friendly) 74 75 template<typename _CT, typename _Period1, typename _Period2> 76 struct __duration_common_type_wrapper 77 { 78 private: 79 typedef __static_gcd<_Period1::num, _Period2::num> __gcd_num; 80 typedef __static_gcd<_Period1::den, _Period2::den> __gcd_den; 81 typedef typename _CT::type __cr; 82 typedef ratio<__gcd_num::value, 83 (_Period1::den / __gcd_den::value) * _Period2::den> __r; 84 public: 85 typedef __success_type<chrono::duration<__cr, __r>> type; 86 }; 87 88 template<typename _Period1, typename _Period2> 89 struct __duration_common_type_wrapper<__failure_type, _Period1, _Period2> 90 { typedef __failure_type type; }; 91 92 template<typename _Rep1, typename _Period1, typename _Rep2, typename _Period2> 93 struct common_type<chrono::duration<_Rep1, _Period1>, 94 chrono::duration<_Rep2, _Period2>> 95 : public __duration_common_type_wrapper<typename __member_type_wrapper< 96 common_type<_Rep1, _Rep2>>::type, _Period1, _Period2>::type 97 { }; 98 99 // 20.11.4.3 specialization of common_type (for time_point, sfinae-friendly) 100 101 template<typename _CT, typename _Clock> 102 struct __timepoint_common_type_wrapper 103 { 104 typedef __success_type<chrono::time_point<_Clock, typename _CT::type>> 105 type; 106 }; 107 108 template<typename _Clock> 109 struct __timepoint_common_type_wrapper<__failure_type, _Clock> 110 { typedef __failure_type type; }; 111 112 template<typename _Clock, typename _Duration1, typename _Duration2> 113 struct common_type<chrono::time_point<_Clock, _Duration1>, 114 chrono::time_point<_Clock, _Duration2>> 115 : public __timepoint_common_type_wrapper<typename __member_type_wrapper< 116 common_type<_Duration1, _Duration2>>::type, _Clock>::type 117 { }; 118 119 _GLIBCXX_END_NAMESPACE_VERSION 120 121 namespace chrono 122 { 123 _GLIBCXX_BEGIN_NAMESPACE_VERSION 124 125 // Primary template for duration_cast impl. 126 template<typename _ToDur, typename _CF, typename _CR, 127 bool _NumIsOne = false, bool _DenIsOne = false> 128 struct __duration_cast_impl 129 { 130 template<typename _Rep, typename _Period> 131 static constexpr _ToDur 132 __cast(const duration<_Rep, _Period>& __d) 133 { 134 typedef typename _ToDur::rep __to_rep; 135 return _ToDur(static_cast<__to_rep>(static_cast<_CR>(__d.count()) 136 * static_cast<_CR>(_CF::num) 137 / static_cast<_CR>(_CF::den))); 138 } 139 }; 140 141 template<typename _ToDur, typename _CF, typename _CR> 142 struct __duration_cast_impl<_ToDur, _CF, _CR, true, true> 143 { 144 template<typename _Rep, typename _Period> 145 static constexpr _ToDur 146 __cast(const duration<_Rep, _Period>& __d) 147 { 148 typedef typename _ToDur::rep __to_rep; 149 return _ToDur(static_cast<__to_rep>(__d.count())); 150 } 151 }; 152 153 template<typename _ToDur, typename _CF, typename _CR> 154 struct __duration_cast_impl<_ToDur, _CF, _CR, true, false> 155 { 156 template<typename _Rep, typename _Period> 157 static constexpr _ToDur 158 __cast(const duration<_Rep, _Period>& __d) 159 { 160 typedef typename _ToDur::rep __to_rep; 161 return _ToDur(static_cast<__to_rep>( 162 static_cast<_CR>(__d.count()) / static_cast<_CR>(_CF::den))); 163 } 164 }; 165 166 template<typename _ToDur, typename _CF, typename _CR> 167 struct __duration_cast_impl<_ToDur, _CF, _CR, false, true> 168 { 169 template<typename _Rep, typename _Period> 170 static constexpr _ToDur 171 __cast(const duration<_Rep, _Period>& __d) 172 { 173 typedef typename _ToDur::rep __to_rep; 174 return _ToDur(static_cast<__to_rep>( 175 static_cast<_CR>(__d.count()) * static_cast<_CR>(_CF::num))); 176 } 177 }; 178 179 template<typename _Tp> 180 struct __is_duration 181 : std::false_type 182 { }; 183 184 template<typename _Rep, typename _Period> 185 struct __is_duration<duration<_Rep, _Period>> 186 : std::true_type 187 { }; 188 189 /// duration_cast 190 template<typename _ToDur, typename _Rep, typename _Period> 191 constexpr typename enable_if<__is_duration<_ToDur>::value, 192 _ToDur>::type 193 duration_cast(const duration<_Rep, _Period>& __d) 194 { 195 typedef typename _ToDur::period __to_period; 196 typedef typename _ToDur::rep __to_rep; 197 typedef ratio_divide<_Period, __to_period> __cf; 198 typedef typename common_type<__to_rep, _Rep, intmax_t>::type 199 __cr; 200 typedef __duration_cast_impl<_ToDur, __cf, __cr, 201 __cf::num == 1, __cf::den == 1> __dc; 202 return __dc::__cast(__d); 203 } 204 205 /// treat_as_floating_point 206 template<typename _Rep> 207 struct treat_as_floating_point 208 : is_floating_point<_Rep> 209 { }; 210 211 /// duration_values 212 template<typename _Rep> 213 struct duration_values 214 { 215 static constexpr _Rep 216 zero() 217 { return _Rep(0); } 218 219 static constexpr _Rep 220 max() 221 { return numeric_limits<_Rep>::max(); } 222 223 static constexpr _Rep 224 min() 225 { return numeric_limits<_Rep>::lowest(); } 226 }; 227 228 template<typename _Tp> 229 struct __is_ratio 230 : std::false_type 231 { }; 232 233 template<intmax_t _Num, intmax_t _Den> 234 struct __is_ratio<ratio<_Num, _Den>> 235 : std::true_type 236 { }; 237 238 /// duration 239 template<typename _Rep, typename _Period> 240 struct duration 241 { 242 typedef _Rep rep; 243 typedef _Period period; 244 245 static_assert(!__is_duration<_Rep>::value, "rep cannot be a duration"); 246 static_assert(__is_ratio<_Period>::value, 247 "period must be a specialization of ratio"); 248 static_assert(_Period::num > 0, "period must be positive"); 249 250 // 20.11.5.1 construction / copy / destroy 251 constexpr duration() = default; 252 253 // NB: Make constexpr implicit. This cannot be explicitly 254 // constexpr, as any UDT that is not a literal type with a 255 // constexpr copy constructor will be ill-formed. 256 duration(const duration&) = default; 257 258 template<typename _Rep2, typename = typename 259 enable_if<is_convertible<_Rep2, rep>::value 260 && (treat_as_floating_point<rep>::value 261 || !treat_as_floating_point<_Rep2>::value)>::type> 262 constexpr explicit duration(const _Rep2& __rep) 263 : __r(static_cast<rep>(__rep)) { } 264 265 template<typename _Rep2, typename _Period2, typename = typename 266 enable_if<treat_as_floating_point<rep>::value 267 || (ratio_divide<_Period2, period>::den == 1 268 && !treat_as_floating_point<_Rep2>::value)>::type> 269 constexpr duration(const duration<_Rep2, _Period2>& __d) 270 : __r(duration_cast<duration>(__d).count()) { } 271 272 ~duration() = default; 273 duration& operator=(const duration&) = default; 274 275 // 20.11.5.2 observer 276 constexpr rep 277 count() const 278 { return __r; } 279 280 // 20.11.5.3 arithmetic 281 constexpr duration 282 operator+() const 283 { return *this; } 284 285 constexpr duration 286 operator-() const 287 { return duration(-__r); } 288 289 duration& 290 operator++() 291 { 292 ++__r; 293 return *this; 294 } 295 296 duration 297 operator++(int) 298 { return duration(__r++); } 299 300 duration& 301 operator--() 302 { 303 --__r; 304 return *this; 305 } 306 307 duration 308 operator--(int) 309 { return duration(__r--); } 310 311 duration& 312 operator+=(const duration& __d) 313 { 314 __r += __d.count(); 315 return *this; 316 } 317 318 duration& 319 operator-=(const duration& __d) 320 { 321 __r -= __d.count(); 322 return *this; 323 } 324 325 duration& 326 operator*=(const rep& __rhs) 327 { 328 __r *= __rhs; 329 return *this; 330 } 331 332 duration& 333 operator/=(const rep& __rhs) 334 { 335 __r /= __rhs; 336 return *this; 337 } 338 339 // DR 934. 340 template<typename _Rep2 = rep> 341 typename enable_if<!treat_as_floating_point<_Rep2>::value, 342 duration&>::type 343 operator%=(const rep& __rhs) 344 { 345 __r %= __rhs; 346 return *this; 347 } 348 349 template<typename _Rep2 = rep> 350 typename enable_if<!treat_as_floating_point<_Rep2>::value, 351 duration&>::type 352 operator%=(const duration& __d) 353 { 354 __r %= __d.count(); 355 return *this; 356 } 357 358 // 20.11.5.4 special values 359 static constexpr duration 360 zero() 361 { return duration(duration_values<rep>::zero()); } 362 363 static constexpr duration 364 min() 365 { return duration(duration_values<rep>::min()); } 366 367 static constexpr duration 368 max() 369 { return duration(duration_values<rep>::max()); } 370 371 private: 372 rep __r; 373 }; 374 375 template<typename _Rep1, typename _Period1, 376 typename _Rep2, typename _Period2> 377 constexpr typename common_type<duration<_Rep1, _Period1>, 378 duration<_Rep2, _Period2>>::type 379 operator+(const duration<_Rep1, _Period1>& __lhs, 380 const duration<_Rep2, _Period2>& __rhs) 381 { 382 typedef duration<_Rep1, _Period1> __dur1; 383 typedef duration<_Rep2, _Period2> __dur2; 384 typedef typename common_type<__dur1,__dur2>::type __cd; 385 return __cd(__cd(__lhs).count() + __cd(__rhs).count()); 386 } 387 388 template<typename _Rep1, typename _Period1, 389 typename _Rep2, typename _Period2> 390 constexpr typename common_type<duration<_Rep1, _Period1>, 391 duration<_Rep2, _Period2>>::type 392 operator-(const duration<_Rep1, _Period1>& __lhs, 393 const duration<_Rep2, _Period2>& __rhs) 394 { 395 typedef duration<_Rep1, _Period1> __dur1; 396 typedef duration<_Rep2, _Period2> __dur2; 397 typedef typename common_type<__dur1,__dur2>::type __cd; 398 return __cd(__cd(__lhs).count() - __cd(__rhs).count()); 399 } 400 401 template<typename _Rep1, typename _Rep2, bool = 402 is_convertible<_Rep2, 403 typename common_type<_Rep1, _Rep2>::type>::value> 404 struct __common_rep_type { }; 405 406 template<typename _Rep1, typename _Rep2> 407 struct __common_rep_type<_Rep1, _Rep2, true> 408 { typedef typename common_type<_Rep1, _Rep2>::type type; }; 409 410 template<typename _Rep1, typename _Period, typename _Rep2> 411 constexpr 412 duration<typename __common_rep_type<_Rep1, _Rep2>::type, _Period> 413 operator*(const duration<_Rep1, _Period>& __d, const _Rep2& __s) 414 { 415 typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period> 416 __cd; 417 return __cd(__cd(__d).count() * __s); 418 } 419 420 template<typename _Rep1, typename _Rep2, typename _Period> 421 constexpr 422 duration<typename __common_rep_type<_Rep2, _Rep1>::type, _Period> 423 operator*(const _Rep1& __s, const duration<_Rep2, _Period>& __d) 424 { return __d * __s; } 425 426 template<typename _Rep1, typename _Period, typename _Rep2> 427 constexpr duration<typename __common_rep_type<_Rep1, typename 428 enable_if<!__is_duration<_Rep2>::value, _Rep2>::type>::type, _Period> 429 operator/(const duration<_Rep1, _Period>& __d, const _Rep2& __s) 430 { 431 typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period> 432 __cd; 433 return __cd(__cd(__d).count() / __s); 434 } 435 436 template<typename _Rep1, typename _Period1, 437 typename _Rep2, typename _Period2> 438 constexpr typename common_type<_Rep1, _Rep2>::type 439 operator/(const duration<_Rep1, _Period1>& __lhs, 440 const duration<_Rep2, _Period2>& __rhs) 441 { 442 typedef duration<_Rep1, _Period1> __dur1; 443 typedef duration<_Rep2, _Period2> __dur2; 444 typedef typename common_type<__dur1,__dur2>::type __cd; 445 return __cd(__lhs).count() / __cd(__rhs).count(); 446 } 447 448 // DR 934. 449 template<typename _Rep1, typename _Period, typename _Rep2> 450 constexpr duration<typename __common_rep_type<_Rep1, typename 451 enable_if<!__is_duration<_Rep2>::value, _Rep2>::type>::type, _Period> 452 operator%(const duration<_Rep1, _Period>& __d, const _Rep2& __s) 453 { 454 typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period> 455 __cd; 456 return __cd(__cd(__d).count() % __s); 457 } 458 459 template<typename _Rep1, typename _Period1, 460 typename _Rep2, typename _Period2> 461 constexpr typename common_type<duration<_Rep1, _Period1>, 462 duration<_Rep2, _Period2>>::type 463 operator%(const duration<_Rep1, _Period1>& __lhs, 464 const duration<_Rep2, _Period2>& __rhs) 465 { 466 typedef duration<_Rep1, _Period1> __dur1; 467 typedef duration<_Rep2, _Period2> __dur2; 468 typedef typename common_type<__dur1,__dur2>::type __cd; 469 return __cd(__cd(__lhs).count() % __cd(__rhs).count()); 470 } 471 472 // comparisons 473 template<typename _Rep1, typename _Period1, 474 typename _Rep2, typename _Period2> 475 constexpr bool 476 operator==(const duration<_Rep1, _Period1>& __lhs, 477 const duration<_Rep2, _Period2>& __rhs) 478 { 479 typedef duration<_Rep1, _Period1> __dur1; 480 typedef duration<_Rep2, _Period2> __dur2; 481 typedef typename common_type<__dur1,__dur2>::type __ct; 482 return __ct(__lhs).count() == __ct(__rhs).count(); 483 } 484 485 template<typename _Rep1, typename _Period1, 486 typename _Rep2, typename _Period2> 487 constexpr bool 488 operator<(const duration<_Rep1, _Period1>& __lhs, 489 const duration<_Rep2, _Period2>& __rhs) 490 { 491 typedef duration<_Rep1, _Period1> __dur1; 492 typedef duration<_Rep2, _Period2> __dur2; 493 typedef typename common_type<__dur1,__dur2>::type __ct; 494 return __ct(__lhs).count() < __ct(__rhs).count(); 495 } 496 497 template<typename _Rep1, typename _Period1, 498 typename _Rep2, typename _Period2> 499 constexpr bool 500 operator!=(const duration<_Rep1, _Period1>& __lhs, 501 const duration<_Rep2, _Period2>& __rhs) 502 { return !(__lhs == __rhs); } 503 504 template<typename _Rep1, typename _Period1, 505 typename _Rep2, typename _Period2> 506 constexpr bool 507 operator<=(const duration<_Rep1, _Period1>& __lhs, 508 const duration<_Rep2, _Period2>& __rhs) 509 { return !(__rhs < __lhs); } 510 511 template<typename _Rep1, typename _Period1, 512 typename _Rep2, typename _Period2> 513 constexpr bool 514 operator>(const duration<_Rep1, _Period1>& __lhs, 515 const duration<_Rep2, _Period2>& __rhs) 516 { return __rhs < __lhs; } 517 518 template<typename _Rep1, typename _Period1, 519 typename _Rep2, typename _Period2> 520 constexpr bool 521 operator>=(const duration<_Rep1, _Period1>& __lhs, 522 const duration<_Rep2, _Period2>& __rhs) 523 { return !(__lhs < __rhs); } 524 525 /// nanoseconds 526 typedef duration<int64_t, nano> nanoseconds; 527 528 /// microseconds 529 typedef duration<int64_t, micro> microseconds; 530 531 /// milliseconds 532 typedef duration<int64_t, milli> milliseconds; 533 534 /// seconds 535 typedef duration<int64_t> seconds; 536 537 /// minutes 538 typedef duration<int, ratio< 60>> minutes; 539 540 /// hours 541 typedef duration<int, ratio<3600>> hours; 542 543 /// time_point 544 template<typename _Clock, typename _Dur> 545 struct time_point 546 { 547 typedef _Clock clock; 548 typedef _Dur duration; 549 typedef typename duration::rep rep; 550 typedef typename duration::period period; 551 552 constexpr time_point() : __d(duration::zero()) 553 { } 554 555 constexpr explicit time_point(const duration& __dur) 556 : __d(__dur) 557 { } 558 559 // conversions 560 template<typename _Dur2> 561 constexpr time_point(const time_point<clock, _Dur2>& __t) 562 : __d(__t.time_since_epoch()) 563 { } 564 565 // observer 566 constexpr duration 567 time_since_epoch() const 568 { return __d; } 569 570 // arithmetic 571 time_point& 572 operator+=(const duration& __dur) 573 { 574 __d += __dur; 575 return *this; 576 } 577 578 time_point& 579 operator-=(const duration& __dur) 580 { 581 __d -= __dur; 582 return *this; 583 } 584 585 // special values 586 static constexpr time_point 587 min() 588 { return time_point(duration::min()); } 589 590 static constexpr time_point 591 max() 592 { return time_point(duration::max()); } 593 594 private: 595 duration __d; 596 }; 597 598 /// time_point_cast 599 template<typename _ToDur, typename _Clock, typename _Dur> 600 constexpr typename enable_if<__is_duration<_ToDur>::value, 601 time_point<_Clock, _ToDur>>::type 602 time_point_cast(const time_point<_Clock, _Dur>& __t) 603 { 604 typedef time_point<_Clock, _ToDur> __time_point; 605 return __time_point(duration_cast<_ToDur>(__t.time_since_epoch())); 606 } 607 608 template<typename _Clock, typename _Dur1, 609 typename _Rep2, typename _Period2> 610 constexpr time_point<_Clock, 611 typename common_type<_Dur1, duration<_Rep2, _Period2>>::type> 612 operator+(const time_point<_Clock, _Dur1>& __lhs, 613 const duration<_Rep2, _Period2>& __rhs) 614 { 615 typedef duration<_Rep2, _Period2> __dur2; 616 typedef typename common_type<_Dur1,__dur2>::type __ct; 617 typedef time_point<_Clock, __ct> __time_point; 618 return __time_point(__lhs.time_since_epoch() + __rhs); 619 } 620 621 template<typename _Rep1, typename _Period1, 622 typename _Clock, typename _Dur2> 623 constexpr time_point<_Clock, 624 typename common_type<duration<_Rep1, _Period1>, _Dur2>::type> 625 operator+(const duration<_Rep1, _Period1>& __lhs, 626 const time_point<_Clock, _Dur2>& __rhs) 627 { 628 typedef duration<_Rep1, _Period1> __dur1; 629 typedef typename common_type<__dur1,_Dur2>::type __ct; 630 typedef time_point<_Clock, __ct> __time_point; 631 return __time_point(__rhs.time_since_epoch() + __lhs); 632 } 633 634 template<typename _Clock, typename _Dur1, 635 typename _Rep2, typename _Period2> 636 constexpr time_point<_Clock, 637 typename common_type<_Dur1, duration<_Rep2, _Period2>>::type> 638 operator-(const time_point<_Clock, _Dur1>& __lhs, 639 const duration<_Rep2, _Period2>& __rhs) 640 { 641 typedef duration<_Rep2, _Period2> __dur2; 642 typedef typename common_type<_Dur1,__dur2>::type __ct; 643 typedef time_point<_Clock, __ct> __time_point; 644 return __time_point(__lhs.time_since_epoch() -__rhs); 645 } 646 647 template<typename _Clock, typename _Dur1, typename _Dur2> 648 constexpr typename common_type<_Dur1, _Dur2>::type 649 operator-(const time_point<_Clock, _Dur1>& __lhs, 650 const time_point<_Clock, _Dur2>& __rhs) 651 { return __lhs.time_since_epoch() - __rhs.time_since_epoch(); } 652 653 template<typename _Clock, typename _Dur1, typename _Dur2> 654 constexpr bool 655 operator==(const time_point<_Clock, _Dur1>& __lhs, 656 const time_point<_Clock, _Dur2>& __rhs) 657 { return __lhs.time_since_epoch() == __rhs.time_since_epoch(); } 658 659 template<typename _Clock, typename _Dur1, typename _Dur2> 660 constexpr bool 661 operator!=(const time_point<_Clock, _Dur1>& __lhs, 662 const time_point<_Clock, _Dur2>& __rhs) 663 { return !(__lhs == __rhs); } 664 665 template<typename _Clock, typename _Dur1, typename _Dur2> 666 constexpr bool 667 operator<(const time_point<_Clock, _Dur1>& __lhs, 668 const time_point<_Clock, _Dur2>& __rhs) 669 { return __lhs.time_since_epoch() < __rhs.time_since_epoch(); } 670 671 template<typename _Clock, typename _Dur1, typename _Dur2> 672 constexpr bool 673 operator<=(const time_point<_Clock, _Dur1>& __lhs, 674 const time_point<_Clock, _Dur2>& __rhs) 675 { return !(__rhs < __lhs); } 676 677 template<typename _Clock, typename _Dur1, typename _Dur2> 678 constexpr bool 679 operator>(const time_point<_Clock, _Dur1>& __lhs, 680 const time_point<_Clock, _Dur2>& __rhs) 681 { return __rhs < __lhs; } 682 683 template<typename _Clock, typename _Dur1, typename _Dur2> 684 constexpr bool 685 operator>=(const time_point<_Clock, _Dur1>& __lhs, 686 const time_point<_Clock, _Dur2>& __rhs) 687 { return !(__lhs < __rhs); } 688 689 690 // Clocks. 691 692 // Why nanosecond resolution as the default? 693 // Why have std::system_clock always count in the higest 694 // resolution (ie nanoseconds), even if on some OSes the low 3 695 // or 9 decimal digits will be always zero? This allows later 696 // implementations to change the system_clock::now() 697 // implementation any time to provide better resolution without 698 // changing function signature or units. 699 700 // To support the (forward) evolution of the library's defined 701 // clocks, wrap inside inline namespace so that the current 702 // defintions of system_clock, steady_clock, and 703 // high_resolution_clock types are uniquely mangled. This way, new 704 // code can use the latests clocks, while the library can contain 705 // compatibility definitions for previous versions. At some 706 // point, when these clocks settle down, the inlined namespaces 707 // can be removed. XXX GLIBCXX_ABI Deprecated 708 inline namespace _V2 { 709 710 /** 711 * @brief System clock. 712 * 713 * Time returned represents wall time from the system-wide clock. 714 */ 715 struct system_clock 716 { 717 typedef chrono::nanoseconds duration; 718 typedef duration::rep rep; 719 typedef duration::period period; 720 typedef chrono::time_point<system_clock, duration> time_point; 721 722 static_assert(system_clock::duration::min() 723 < system_clock::duration::zero(), 724 "a clock's minimum duration cannot be less than its epoch"); 725 726 static constexpr bool is_steady = false; 727 728 static time_point 729 now() noexcept; 730 731 // Map to C API 732 static std::time_t 733 to_time_t(const time_point& __t) noexcept 734 { 735 return std::time_t(duration_cast<chrono::seconds> 736 (__t.time_since_epoch()).count()); 737 } 738 739 static time_point 740 from_time_t(std::time_t __t) noexcept 741 { 742 typedef chrono::time_point<system_clock, seconds> __from; 743 return time_point_cast<system_clock::duration> 744 (__from(chrono::seconds(__t))); 745 } 746 }; 747 748 749 /** 750 * @brief Monotonic clock 751 * 752 * Time returned has the property of only increasing at a uniform rate. 753 */ 754 struct steady_clock 755 { 756 typedef chrono::nanoseconds duration; 757 typedef duration::rep rep; 758 typedef duration::period period; 759 typedef chrono::time_point<steady_clock, duration> time_point; 760 761 static constexpr bool is_steady = true; 762 763 static time_point 764 now() noexcept; 765 }; 766 767 768 /** 769 * @brief Highest-resolution clock 770 * 771 * This is the clock "with the shortest tick period." Alias to 772 * std::system_clock until higher-than-nanosecond definitions 773 * become feasible. 774 */ 775 using high_resolution_clock = system_clock; 776 777 } // end inline namespace _V2 778 779 _GLIBCXX_END_NAMESPACE_VERSION 780 } // namespace chrono 781 782 // @} group chrono 783 } // namespace 784 785 #endif //_GLIBCXX_USE_C99_STDINT_TR1 786 787 #endif // C++11 788 789 #endif //_GLIBCXX_CHRONO 790
