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// steady_clock 50 51const bool steady_clock::is_steady; 52 53#ifdef __APPLE__ 54// mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of 55// nanoseconds since the computer booted up. MachInfo.numer and MachInfo.denom 56// are run time constants supplied by the OS. This clock has no relationship 57// to the Gregorian calendar. It's main use is as a high resolution timer. 58 59// MachInfo.numer / MachInfo.denom is often 1 on the latest equipment. Specialize 60// for that case as an optimization. 61 62#pragma GCC visibility push(hidden) 63 64static 65steady_clock::rep 66steady_simplified() 67{ 68 return static_cast<steady_clock::rep>(mach_absolute_time()); 69} 70 71static 72double 73compute_steady_factor() 74{ 75 mach_timebase_info_data_t MachInfo; 76 mach_timebase_info(&MachInfo); 77 return static_cast<double>(MachInfo.numer) / MachInfo.denom; 78} 79 80static 81steady_clock::rep 82steady_full() 83{ 84 static const double factor = compute_steady_factor(); 85 return static_cast<steady_clock::rep>(mach_absolute_time() * factor); 86} 87 88typedef steady_clock::rep (*FP)(); 89 90static 91FP 92init_steady_clock() 93{ 94 mach_timebase_info_data_t MachInfo; 95 mach_timebase_info(&MachInfo); 96 if (MachInfo.numer == MachInfo.denom) 97 return &steady_simplified; 98 return &steady_full; 99} 100 101#pragma GCC visibility pop 102 103steady_clock::time_point 104steady_clock::now() _NOEXCEPT 105{ 106 static FP fp = init_steady_clock(); 107 return time_point(duration(fp())); 108} 109 110#else // __APPLE__ 111// FIXME: We assume that clock_gettime(CLOCK_MONOTONIC) works on 112// non-apple systems. Instead, we should check _POSIX_TIMERS and 113// _POSIX_MONOTONIC_CLOCK and fall back to something else if those 114// don't exist. 115 116// Warning: If this is not truly steady, then it is non-conforming. It is 117// better for it to not exist and have the rest of libc++ use system_clock 118// instead. 119 120steady_clock::time_point 121steady_clock::now() _NOEXCEPT 122{ 123 struct timespec tp; 124 if (0 != clock_gettime(CLOCK_MONOTONIC, &tp)) 125 __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed"); 126 return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec)); 127} 128#endif // __APPLE__ 129 130} 131 132_LIBCPP_END_NAMESPACE_STD 133