1//===------------------------- chrono.cpp ---------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is dual licensed under the MIT and the University of Illinois Open 6// Source Licenses. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9 10#include "chrono" 11#include <sys/time.h> //for gettimeofday and timeval 12#ifdef __APPLE__ 13#include <mach/mach_time.h> // mach_absolute_time, mach_timebase_info_data_t 14#else /* !__APPLE__ */ 15#include <cerrno> // errno 16#include <system_error> // __throw_system_error 17#include <time.h> // clock_gettime, CLOCK_MONOTONIC 18#endif // __APPLE__ 19 20_LIBCPP_BEGIN_NAMESPACE_STD 21 22namespace chrono 23{ 24 25// system_clock 26 27const bool system_clock::is_steady; 28 29system_clock::time_point 30system_clock::now() _NOEXCEPT 31{ 32 timeval tv; 33 gettimeofday(&tv, 0); 34 return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec)); 35} 36 37time_t 38system_clock::to_time_t(const time_point& t) _NOEXCEPT 39{ 40 return time_t(duration_cast<seconds>(t.time_since_epoch()).count()); 41} 42 43system_clock::time_point 44system_clock::from_time_t(time_t t) _NOEXCEPT 45{ 46 return system_clock::time_point(seconds(t)); 47} 48 49#ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK 50// steady_clock 51 52const bool steady_clock::is_steady; 53 54#ifdef __APPLE__ 55// mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of 56// nanoseconds since the computer booted up. MachInfo.numer and MachInfo.denom 57// are run time constants supplied by the OS. This clock has no relationship 58// to the Gregorian calendar. It's main use is as a high resolution timer. 59 60// MachInfo.numer / MachInfo.denom is often 1 on the latest equipment. Specialize 61// for that case as an optimization. 62 63#pragma GCC visibility push(hidden) 64 65static 66steady_clock::rep 67steady_simplified() 68{ 69 return static_cast<steady_clock::rep>(mach_absolute_time()); 70} 71 72static 73double 74compute_steady_factor() 75{ 76 mach_timebase_info_data_t MachInfo; 77 mach_timebase_info(&MachInfo); 78 return static_cast<double>(MachInfo.numer) / MachInfo.denom; 79} 80 81static 82steady_clock::rep 83steady_full() 84{ 85 static const double factor = compute_steady_factor(); 86 return static_cast<steady_clock::rep>(mach_absolute_time() * factor); 87} 88 89typedef steady_clock::rep (*FP)(); 90 91static 92FP 93init_steady_clock() 94{ 95 mach_timebase_info_data_t MachInfo; 96 mach_timebase_info(&MachInfo); 97 if (MachInfo.numer == MachInfo.denom) 98 return &steady_simplified; 99 return &steady_full; 100} 101 102#pragma GCC visibility pop 103 104steady_clock::time_point 105steady_clock::now() _NOEXCEPT 106{ 107 static FP fp = init_steady_clock(); 108 return time_point(duration(fp())); 109} 110 111#else // __APPLE__ 112// FIXME: if _LIBCPP_HAS_NO_MONOTONIC_CLOCK, then clock_gettime isn't going to 113// work. It may be possible to fall back on something else, depending on the system. 114 115// Warning: If this is not truly steady, then it is non-conforming. It is 116// better for it to not exist and have the rest of libc++ use system_clock 117// instead. 118 119steady_clock::time_point 120steady_clock::now() _NOEXCEPT 121{ 122 struct timespec tp; 123 if (0 != clock_gettime(CLOCK_MONOTONIC, &tp)) 124 __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed"); 125 return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec)); 126} 127#endif // __APPLE__ 128 129#endif // !_LIBCPP_HAS_NO_MONOTONIC_CLOCK 130 131} 132 133_LIBCPP_END_NAMESPACE_STD 134