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 "cerrno" // errno 12 #include "system_error" // __throw_system_error 13 #include <time.h> // clock_gettime, CLOCK_MONOTONIC and CLOCK_REALTIME 14 15 #if !defined(CLOCK_REALTIME) 16 #include <sys/time.h> // for gettimeofday and timeval 17 #endif 18 19 #if !defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK) && !defined(CLOCK_MONOTONIC) 20 #if __APPLE__ 21 #include <mach/mach_time.h> // mach_absolute_time, mach_timebase_info_data_t 22 #else 23 #error "Monotonic clock not implemented" 24 #endif 25 #endif 26 27 _LIBCPP_BEGIN_NAMESPACE_STD 28 29 namespace chrono 30 { 31 32 // system_clock 33 34 const bool system_clock::is_steady; 35 36 system_clock::time_point 37 system_clock::now() _NOEXCEPT 38 { 39 #ifdef CLOCK_REALTIME 40 struct timespec tp; 41 if (0 != clock_gettime(CLOCK_REALTIME, &tp)) 42 __throw_system_error(errno, "clock_gettime(CLOCK_REALTIME) failed"); 43 return time_point(seconds(tp.tv_sec) + microseconds(tp.tv_nsec / 1000)); 44 #else // !CLOCK_REALTIME 45 timeval tv; 46 gettimeofday(&tv, 0); 47 return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec)); 48 #endif // CLOCK_REALTIME 49 } 50 51 time_t 52 system_clock::to_time_t(const time_point& t) _NOEXCEPT 53 { 54 return time_t(duration_cast<seconds>(t.time_since_epoch()).count()); 55 } 56 57 system_clock::time_point 58 system_clock::from_time_t(time_t t) _NOEXCEPT 59 { 60 return system_clock::time_point(seconds(t)); 61 } 62 63 #ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK 64 // steady_clock 65 // 66 // Warning: If this is not truly steady, then it is non-conforming. It is 67 // better for it to not exist and have the rest of libc++ use system_clock 68 // instead. 69 70 const bool steady_clock::is_steady; 71 72 #ifdef CLOCK_MONOTONIC 73 74 steady_clock::time_point 75 steady_clock::now() _NOEXCEPT 76 { 77 struct timespec tp; 78 if (0 != clock_gettime(CLOCK_MONOTONIC, &tp)) 79 __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed"); 80 return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec)); 81 } 82 83 #elif defined(__APPLE__) 84 85 // mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of 86 // nanoseconds since the computer booted up. MachInfo.numer and MachInfo.denom 87 // are run time constants supplied by the OS. This clock has no relationship 88 // to the Gregorian calendar. It's main use is as a high resolution timer. 89 90 // MachInfo.numer / MachInfo.denom is often 1 on the latest equipment. Specialize 91 // for that case as an optimization. 92 93 #pragma GCC visibility push(hidden) 94 95 static 96 steady_clock::rep 97 steady_simplified() 98 { 99 return static_cast<steady_clock::rep>(mach_absolute_time()); 100 } 101 102 static 103 double 104 compute_steady_factor() 105 { 106 mach_timebase_info_data_t MachInfo; 107 mach_timebase_info(&MachInfo); 108 return static_cast<double>(MachInfo.numer) / MachInfo.denom; 109 } 110 111 static 112 steady_clock::rep 113 steady_full() 114 { 115 static const double factor = compute_steady_factor(); 116 return static_cast<steady_clock::rep>(mach_absolute_time() * factor); 117 } 118 119 typedef steady_clock::rep (*FP)(); 120 121 static 122 FP 123 init_steady_clock() 124 { 125 mach_timebase_info_data_t MachInfo; 126 mach_timebase_info(&MachInfo); 127 if (MachInfo.numer == MachInfo.denom) 128 return &steady_simplified; 129 return &steady_full; 130 } 131 132 #pragma GCC visibility pop 133 134 steady_clock::time_point 135 steady_clock::now() _NOEXCEPT 136 { 137 static FP fp = init_steady_clock(); 138 return time_point(duration(fp())); 139 } 140 141 #else 142 #error "Monotonic clock not implemented" 143 #endif 144 145 #endif // !_LIBCPP_HAS_NO_MONOTONIC_CLOCK 146 147 } 148 149 _LIBCPP_END_NAMESPACE_STD 150
