contrib/libc++/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(_LIBCPP_WIN32API)
  16 #define WIN32_LEAN_AND_MEAN
  17 #define VC_EXTRA_LEAN
  18 #include <Windows.h>
  19 #if _WIN32_WINNT >= _WIN32_WINNT_WIN8
  20 #include <winapifamily.h>
  21 #endif
  22 #else
  23 #if !defined(CLOCK_REALTIME)
  24 #include <sys/time.h>        // for gettimeofday and timeval
  25 #endif // !defined(CLOCK_REALTIME)
  26 #endif // defined(_LIBCPP_WIN32API)
  27
  28 #if !defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK)
  29 #if __APPLE__
  30 #include <mach/mach_time.h>  // mach_absolute_time, mach_timebase_info_data_t
  31 #elif !defined(_LIBCPP_WIN32API) && !defined(CLOCK_MONOTONIC)
  32 #error "Monotonic clock not implemented"
  33 #endif
  34 #endif
  35
  36 _LIBCPP_BEGIN_NAMESPACE_STD
  37
  38 namespace chrono
  39 {
  40
  41 // system_clock
  42
  43 const bool system_clock::is_steady;
  44
  45 system_clock::time_point
  46 system_clock::now() _NOEXCEPT
  47 {
  48 #if defined(_LIBCPP_WIN32API)
  49   // FILETIME is in 100ns units
  50   using filetime_duration =
  51       _VSTD::chrono::duration<__int64,
  52                               _VSTD::ratio_multiply<_VSTD::ratio<100, 1>,
  53                                                     nanoseconds::period>>;
  54
  55   // The Windows epoch is Jan 1 1601, the Unix epoch Jan 1 1970.
  56   static _LIBCPP_CONSTEXPR const seconds nt_to_unix_epoch{11644473600};
  57
  58   FILETIME ft;
  59 #if _WIN32_WINNT >= _WIN32_WINNT_WIN8
  60 #if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
  61   GetSystemTimePreciseAsFileTime(&ft);
  62 #else
  63   GetSystemTimeAsFileTime(&ft);
  64 #endif
  65 #else
  66   GetSystemTimeAsFileTime(&ft);
  67 #endif
  68
  69   filetime_duration d{(static_cast<__int64>(ft.dwHighDateTime) << 32) |
  70                        static_cast<__int64>(ft.dwLowDateTime)};
  71   return time_point(duration_cast<duration>(d - nt_to_unix_epoch));
  72 #else
  73 #ifdef CLOCK_REALTIME
  74     struct timespec tp;
  75     if (0 != clock_gettime(CLOCK_REALTIME, &tp))
  76         __throw_system_error(errno, "clock_gettime(CLOCK_REALTIME) failed");
  77     return time_point(seconds(tp.tv_sec) + microseconds(tp.tv_nsec / 1000));
  78 #else  // !CLOCK_REALTIME
  79     timeval tv;
  80     gettimeofday(&tv, 0);
  81     return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
  82 #endif  // CLOCK_REALTIME
  83 #endif
  84 }
  85
  86 time_t
  87 system_clock::to_time_t(const time_point& t) _NOEXCEPT
  88 {
  89     return time_t(duration_cast<seconds>(t.time_since_epoch()).count());
  90 }
  91
  92 system_clock::time_point
  93 system_clock::from_time_t(time_t t) _NOEXCEPT
  94 {
  95     return system_clock::time_point(seconds(t));
  96 }
  97
  98 #ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK
  99 // steady_clock
 100 //
 101 // Warning:  If this is not truly steady, then it is non-conforming.  It is
 102 //  better for it to not exist and have the rest of libc++ use system_clock
 103 //  instead.
 104
 105 const bool steady_clock::is_steady;
 106
 107 #if defined(__APPLE__)
 108
 109 //   mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
 110 //   nanoseconds since the computer booted up.  MachInfo.numer and MachInfo.denom
 111 //   are run time constants supplied by the OS.  This clock has no relationship
 112 //   to the Gregorian calendar.  It's main use is as a high resolution timer.
 113
 114 // MachInfo.numer / MachInfo.denom is often 1 on the latest equipment.  Specialize
 115 //   for that case as an optimization.
 116
 117 static
 118 steady_clock::rep
 119 steady_simplified()
 120 {
 121     return static_cast<steady_clock::rep>(mach_absolute_time());
 122 }
 123
 124 static
 125 double
 126 compute_steady_factor()
 127 {
 128     mach_timebase_info_data_t MachInfo;
 129     mach_timebase_info(&MachInfo);
 130     return static_cast<double>(MachInfo.numer) / MachInfo.denom;
 131 }
 132
 133 static
 134 steady_clock::rep
 135 steady_full()
 136 {
 137     static const double factor = compute_steady_factor();
 138     return static_cast<steady_clock::rep>(mach_absolute_time() * factor);
 139 }
 140
 141 typedef steady_clock::rep (*FP)();
 142
 143 static
 144 FP
 145 init_steady_clock()
 146 {
 147     mach_timebase_info_data_t MachInfo;
 148     mach_timebase_info(&MachInfo);
 149     if (MachInfo.numer == MachInfo.denom)
 150         return &steady_simplified;
 151     return &steady_full;
 152 }
 153
 154 steady_clock::time_point
 155 steady_clock::now() _NOEXCEPT
 156 {
 157     static FP fp = init_steady_clock();
 158     return time_point(duration(fp()));
 159 }
 160
 161 #elif defined(_LIBCPP_WIN32API)
 162
 163 steady_clock::time_point
 164 steady_clock::now() _NOEXCEPT
 165 {
 166   static LARGE_INTEGER freq;
 167   static BOOL initialized = FALSE;
 168   if (!initialized)
 169     initialized = QueryPerformanceFrequency(&freq); // always succceeds
 170
 171   LARGE_INTEGER counter;
 172   QueryPerformanceCounter(&counter);
 173   return time_point(duration(counter.QuadPart * nano::den / freq.QuadPart));
 174 }
 175
 176 #elif defined(CLOCK_MONOTONIC)
 177
 178 steady_clock::time_point
 179 steady_clock::now() _NOEXCEPT
 180 {
 181     struct timespec tp;
 182     if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
 183         __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
 184     return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
 185 }
 186
 187 #else
 188 #error "Monotonic clock not implemented"
 189 #endif
 190
 191 #endif // !_LIBCPP_HAS_NO_MONOTONIC_CLOCK
 192
 193 }
 194
 195 _LIBCPP_END_NAMESPACE_STD