external/bsd/libc++/dist/libcxx/src/chrono.cpp

   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