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 #ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK 50 // steady_clock 51 52 const 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 65 static 66 steady_clock::rep 67 steady_simplified() 68 { 69 return static_cast<steady_clock::rep>(mach_absolute_time()); 70 } 71 72 static 73 double 74 compute_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 81 static 82 steady_clock::rep 83 steady_full() 84 { 85 static const double factor = compute_steady_factor(); 86 return static_cast<steady_clock::rep>(mach_absolute_time() * factor); 87 } 88 89 typedef steady_clock::rep (*FP)(); 90 91 static 92 FP 93 init_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 103 104 steady_clock::time_point 105 steady_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. 118 119 steady_clock::time_point 120 steady_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
