base/time_mac.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/time.h"
   6
   7 #include <CoreFoundation/CFDate.h>
   8 #include <CoreFoundation/CFTimeZone.h>
   9 #include <mach/mach_time.h>
  10 #include <sys/sysctl.h>
  11 #include <sys/time.h>
  12 #include <sys/types.h>
  13 #include <time.h>
  14
  15 #include "base/basictypes.h"
  16 #include "base/logging.h"
  17 #include "base/mac/scoped_cftyperef.h"
  18
  19 namespace {
  20
  21 uint64_t ComputeCurrentTicks() {
  22 #if defined(OS_IOS)
  23   // On iOS mach_absolute_time stops while the device is sleeping. Instead use
  24   // now - KERN_BOOTTIME to get a time difference that is not impacted by clock
  25   // changes. KERN_BOOTTIME will be updated by the system whenever the system
  26   // clock change.
  27   struct timeval boottime;
  28   int mib[2] = {CTL_KERN, KERN_BOOTTIME};
  29   size_t size = sizeof(boottime);
  30   int kr = sysctl(mib, arraysize(mib), &boottime, &size, NULL, 0);
  31   DCHECK_EQ(KERN_SUCCESS, kr);
  32   base::TimeDelta time_difference = base::Time::Now() -
  33       (base::Time::FromTimeT(boottime.tv_sec) +
  34        base::TimeDelta::FromMicroseconds(boottime.tv_usec));
  35   return time_difference.InMicroseconds();
  36 #else
  37   uint64_t absolute_micro;
  38
  39   static mach_timebase_info_data_t timebase_info;
  40   if (timebase_info.denom == 0) {
  41     // Zero-initialization of statics guarantees that denom will be 0 before
  42     // calling mach_timebase_info.  mach_timebase_info will never set denom to
  43     // 0 as that would be invalid, so the zero-check can be used to determine
  44     // whether mach_timebase_info has already been called.  This is
  45     // recommended by Apple's QA1398.
  46     kern_return_t kr = mach_timebase_info(&timebase_info);
  47     DCHECK_EQ(KERN_SUCCESS, kr);
  48   }
  49
  50   // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
  51   // with less precision (such as TickCount) just call through to
  52   // mach_absolute_time.
  53
  54   // timebase_info converts absolute time tick units into nanoseconds.  Convert
  55   // to microseconds up front to stave off overflows.
  56   absolute_micro =
  57       mach_absolute_time() / base::Time::kNanosecondsPerMicrosecond *
  58       timebase_info.numer / timebase_info.denom;
  59
  60   // Don't bother with the rollover handling that the Windows version does.
  61   // With numer and denom = 1 (the expected case), the 64-bit absolute time
  62   // reported in nanoseconds is enough to last nearly 585 years.
  63   return absolute_micro;
  64 #endif  // defined(OS_IOS)
  65 }
  66
  67 }  // namespace
  68
  69 namespace base {
  70
  71 // The Time routines in this file use Mach and CoreFoundation APIs, since the
  72 // POSIX definition of time_t in Mac OS X wraps around after 2038--and
  73 // there are already cookie expiration dates, etc., past that time out in
  74 // the field.  Using CFDate prevents that problem, and using mach_absolute_time
  75 // for TimeTicks gives us nice high-resolution interval timing.
  76
  77 // Time -----------------------------------------------------------------------
  78
  79 // Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
  80 // The UNIX epoch is 1970-01-01 00:00:00 UTC.
  81 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
  82 // so that our time representations match across all platforms.  See bug 14734.
  83 //   irb(main):010:0> Time.at(0).getutc()
  84 //   => Thu Jan 01 00:00:00 UTC 1970
  85 //   irb(main):011:0> Time.at(-11644473600).getutc()
  86 //   => Mon Jan 01 00:00:00 UTC 1601
  87 static const int64 kWindowsEpochDeltaSeconds = GG_INT64_C(11644473600);
  88 static const int64 kWindowsEpochDeltaMilliseconds =
  89     kWindowsEpochDeltaSeconds * Time::kMillisecondsPerSecond;
  90
  91 // static
  92 const int64 Time::kWindowsEpochDeltaMicroseconds =
  93     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
  94
  95 // Some functions in time.cc use time_t directly, so we provide an offset
  96 // to convert from time_t (Unix epoch) and internal (Windows epoch).
  97 // static
  98 const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
  99
 100 // static
 101 Time Time::Now() {
 102   return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
 103 }
 104
 105 // static
 106 Time Time::FromCFAbsoluteTime(CFAbsoluteTime t) {
 107   if (t == 0)
 108     return Time();  // Consider 0 as a null Time.
 109   if (t == std::numeric_limits<CFAbsoluteTime>::max())
 110     return Max();
 111   return Time(static_cast<int64>(
 112       (t + kCFAbsoluteTimeIntervalSince1970) * kMicrosecondsPerSecond) +
 113       kWindowsEpochDeltaMicroseconds);
 114 }
 115
 116 CFAbsoluteTime Time::ToCFAbsoluteTime() const {
 117   if (is_null())
 118     return 0;  // Consider 0 as a null Time.
 119   if (is_max())
 120     return std::numeric_limits<CFAbsoluteTime>::max();
 121   return (static_cast<CFAbsoluteTime>(us_ - kWindowsEpochDeltaMicroseconds) /
 122       kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
 123 }
 124
 125 // static
 126 Time Time::NowFromSystemTime() {
 127   // Just use Now() because Now() returns the system time.
 128   return Now();
 129 }
 130
 131 // static
 132 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
 133   CFGregorianDate date;
 134   date.second = exploded.second +
 135       exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
 136   date.minute = exploded.minute;
 137   date.hour = exploded.hour;
 138   date.day = exploded.day_of_month;
 139   date.month = exploded.month;
 140   date.year = exploded.year;
 141
 142   base::mac::ScopedCFTypeRef<CFTimeZoneRef>
 143       time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
 144   CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
 145       kCFAbsoluteTimeIntervalSince1970;
 146   return Time(static_cast<int64>(seconds * kMicrosecondsPerSecond) +
 147       kWindowsEpochDeltaMicroseconds);
 148 }
 149
 150 void Time::Explode(bool is_local, Exploded* exploded) const {
 151   // Avoid rounding issues, by only putting the integral number of seconds
 152   // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
 153   int64 microsecond = us_ % kMicrosecondsPerSecond;
 154   if (microsecond < 0)
 155     microsecond += kMicrosecondsPerSecond;
 156   CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) -
 157                            kWindowsEpochDeltaSeconds -
 158                            kCFAbsoluteTimeIntervalSince1970;
 159
 160   base::mac::ScopedCFTypeRef<CFTimeZoneRef>
 161       time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
 162   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
 163   // 1 = Monday, ..., 7 = Sunday.
 164   int cf_day_of_week = CFAbsoluteTimeGetDayOfWeek(seconds, time_zone);
 165
 166   exploded->year = date.year;
 167   exploded->month = date.month;
 168   exploded->day_of_week = cf_day_of_week % 7;
 169   exploded->day_of_month = date.day;
 170   exploded->hour = date.hour;
 171   exploded->minute = date.minute;
 172   // Make sure seconds are rounded down towards -infinity.
 173   exploded->second = floor(date.second);
 174   // Calculate milliseconds ourselves, since we rounded the |seconds|, making
 175   // sure to round towards -infinity.
 176   exploded->millisecond =
 177       (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond :
 178                            (microsecond - kMicrosecondsPerMillisecond + 1) /
 179                                kMicrosecondsPerMillisecond;
 180 }
 181
 182 // TimeTicks ------------------------------------------------------------------
 183
 184 // static
 185 TimeTicks TimeTicks::Now() {
 186   return TimeTicks(ComputeCurrentTicks());
 187 }
 188
 189 // static
 190 TimeTicks TimeTicks::HighResNow() {
 191   return Now();
 192 }
 193
 194 // static
 195 TimeTicks TimeTicks::NowFromSystemTraceTime() {
 196   return HighResNow();
 197 }
 198
 199 }  // namespace base