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 22 namespace chrono 23 { 24 25 // system_clock 26 27 const bool system_clock::is_steady; 28 29 system_clock::time_point 30 system_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 37 time_t 38 system_clock::to_time_t(const time_point& t) _NOEXCEPT 39 { 40 return time_t(duration_cast<seconds>(t.time_since_epoch()).count()); 41 } 42 43 system_clock::time_point 44 system_clock::from_time_t(time_t t) _NOEXCEPT 45 { 46 return system_clock::time_point(seconds(t)); 47 } 48 49 // steady_clock 50 51 const 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 64 static 65 steady_clock::rep 66 steady_simplified() 67 { 68 return static_cast<steady_clock::rep>(mach_absolute_time()); 69 } 70 71 static 72 double 73 compute_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 80 static 81 steady_clock::rep 82 steady_full() 83 { 84 static const double factor = compute_steady_factor(); 85 return static_cast<steady_clock::rep>(mach_absolute_time() * factor); 86 } 87 88 typedef steady_clock::rep (*FP)(); 89 90 static 91 FP 92 init_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 102 103 steady_clock::time_point 104 steady_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. 119 120 steady_clock::time_point 121 steady_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
