base/time/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/time.h"
   6
   7 #include <CoreFoundation/CFDate.h>
   8 #include <CoreFoundation/CFTimeZone.h>
   9 #include <mach/mach.h>
  10 #include <mach/mach_time.h>
  11 #include <sys/sysctl.h>
  12 #include <sys/time.h>
  13 #include <sys/types.h>
  14 #include <time.h>
  15
  16 #include "base/basictypes.h"
  17 #include "base/logging.h"
  18 #include "base/mac/scoped_cftyperef.h"
  19 #include "base/mac/scoped_mach_port.h"
  20
  21 namespace {
  22
  23 uint64_t ComputeCurrentTicks() {
  24 #if defined(OS_IOS)
  25   // On iOS mach_absolute_time stops while the device is sleeping. Instead use
  26   // now - KERN_BOOTTIME to get a time difference that is not impacted by clock
  27   // changes. KERN_BOOTTIME will be updated by the system whenever the system
  28   // clock change.
  29   struct timeval boottime;
  30   int mib[2] = {CTL_KERN, KERN_BOOTTIME};
  31   size_t size = sizeof(boottime);
  32   int kr = sysctl(mib, arraysize(mib), &boottime, &size, NULL, 0);
  33   DCHECK_EQ(KERN_SUCCESS, kr);
  34   base::TimeDelta time_difference = base::Time::Now() -
  35       (base::Time::FromTimeT(boottime.tv_sec) +
  36        base::TimeDelta::FromMicroseconds(boottime.tv_usec));
  37   return time_difference.InMicroseconds();
  38 #else
  39   uint64_t absolute_micro;
  40
  41   static mach_timebase_info_data_t timebase_info;
  42   if (timebase_info.denom == 0) {
  43     // Zero-initialization of statics guarantees that denom will be 0 before
  44     // calling mach_timebase_info.  mach_timebase_info will never set denom to
  45     // 0 as that would be invalid, so the zero-check can be used to determine
  46     // whether mach_timebase_info has already been called.  This is
  47     // recommended by Apple's QA1398.
  48     kern_return_t kr = mach_timebase_info(&timebase_info);
  49     DCHECK_EQ(KERN_SUCCESS, kr);
  50   }
  51
  52   // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
  53   // with less precision (such as TickCount) just call through to
  54   // mach_absolute_time.
  55
  56   // timebase_info converts absolute time tick units into nanoseconds.  Convert
  57   // to microseconds up front to stave off overflows.
  58   absolute_micro =
  59       mach_absolute_time() / base::Time::kNanosecondsPerMicrosecond *
  60       timebase_info.numer / timebase_info.denom;
  61
  62   // Don't bother with the rollover handling that the Windows version does.
  63   // With numer and denom = 1 (the expected case), the 64-bit absolute time
  64   // reported in nanoseconds is enough to last nearly 585 years.
  65   return absolute_micro;
  66 #endif  // defined(OS_IOS)
  67 }
  68
  69 uint64_t ComputeThreadTicks() {
  70 #if defined(OS_IOS)
  71   NOTREACHED();
  72   return 0;
  73 #else
  74   base::mac::ScopedMachPort thread(mach_thread_self());
  75   mach_msg_type_number_t thread_info_count = THREAD_BASIC_INFO_COUNT;
  76   thread_basic_info_data_t thread_info_data;
  77
  78   if (thread == MACH_PORT_NULL) {
  79     DLOG(ERROR) << "Failed to get mach_thread_self()";
  80     return 0;
  81   }
  82
  83   kern_return_t kr = thread_info(
  84       thread,
  85       THREAD_BASIC_INFO,
  86       reinterpret_cast<thread_info_t>(&thread_info_data),
  87       &thread_info_count);
  88   DCHECK_EQ(KERN_SUCCESS, kr);
  89
  90   return (thread_info_data.user_time.seconds *
  91               base::Time::kMicrosecondsPerSecond) +
  92          thread_info_data.user_time.microseconds;
  93 #endif  // defined(OS_IOS)
  94 }
  95
  96 }  // namespace
  97
  98 namespace base {
  99
 100 // The Time routines in this file use Mach and CoreFoundation APIs, since the
 101 // POSIX definition of time_t in Mac OS X wraps around after 2038--and
 102 // there are already cookie expiration dates, etc., past that time out in
 103 // the field.  Using CFDate prevents that problem, and using mach_absolute_time
 104 // for TimeTicks gives us nice high-resolution interval timing.
 105
 106 // Time -----------------------------------------------------------------------
 107
 108 // Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
 109 // The UNIX epoch is 1970-01-01 00:00:00 UTC.
 110 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
 111 // so that our time representations match across all platforms.  See bug 14734.
 112 //   irb(main):010:0> Time.at(0).getutc()
 113 //   => Thu Jan 01 00:00:00 UTC 1970
 114 //   irb(main):011:0> Time.at(-11644473600).getutc()
 115 //   => Mon Jan 01 00:00:00 UTC 1601
 116 static const int64 kWindowsEpochDeltaSeconds = GG_INT64_C(11644473600);
 117
 118 // static
 119 const int64 Time::kWindowsEpochDeltaMicroseconds =
 120     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
 121
 122 // Some functions in time.cc use time_t directly, so we provide an offset
 123 // to convert from time_t (Unix epoch) and internal (Windows epoch).
 124 // static
 125 const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
 126
 127 // static
 128 Time Time::Now() {
 129   return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
 130 }
 131
 132 // static
 133 Time Time::FromCFAbsoluteTime(CFAbsoluteTime t) {
 134   if (t == 0)
 135     return Time();  // Consider 0 as a null Time.
 136   if (t == std::numeric_limits<CFAbsoluteTime>::max())
 137     return Max();
 138   return Time(static_cast<int64>(
 139       (t + kCFAbsoluteTimeIntervalSince1970) * kMicrosecondsPerSecond) +
 140       kWindowsEpochDeltaMicroseconds);
 141 }
 142
 143 CFAbsoluteTime Time::ToCFAbsoluteTime() const {
 144   if (is_null())
 145     return 0;  // Consider 0 as a null Time.
 146   if (is_max())
 147     return std::numeric_limits<CFAbsoluteTime>::max();
 148   return (static_cast<CFAbsoluteTime>(us_ - kWindowsEpochDeltaMicroseconds) /
 149       kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
 150 }
 151
 152 // static
 153 Time Time::NowFromSystemTime() {
 154   // Just use Now() because Now() returns the system time.
 155   return Now();
 156 }
 157
 158 // static
 159 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
 160   CFGregorianDate date;
 161   date.second = exploded.second +
 162       exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
 163   date.minute = exploded.minute;
 164   date.hour = exploded.hour;
 165   date.day = exploded.day_of_month;
 166   date.month = exploded.month;
 167   date.year = exploded.year;
 168
 169   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
 170       is_local ? CFTimeZoneCopySystem() : NULL);
 171   CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
 172       kCFAbsoluteTimeIntervalSince1970;
 173   return Time(static_cast<int64>(seconds * kMicrosecondsPerSecond) +
 174       kWindowsEpochDeltaMicroseconds);
 175 }
 176
 177 void Time::Explode(bool is_local, Exploded* exploded) const {
 178   // Avoid rounding issues, by only putting the integral number of seconds
 179   // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
 180   int64 microsecond = us_ % kMicrosecondsPerSecond;
 181   if (microsecond < 0)
 182     microsecond += kMicrosecondsPerSecond;
 183   CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) -
 184                            kWindowsEpochDeltaSeconds -
 185                            kCFAbsoluteTimeIntervalSince1970;
 186
 187   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
 188       is_local ? CFTimeZoneCopySystem() : NULL);
 189   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
 190   // 1 = Monday, ..., 7 = Sunday.
 191   int cf_day_of_week = CFAbsoluteTimeGetDayOfWeek(seconds, time_zone);
 192
 193   exploded->year = date.year;
 194   exploded->month = date.month;
 195   exploded->day_of_week = cf_day_of_week % 7;
 196   exploded->day_of_month = date.day;
 197   exploded->hour = date.hour;
 198   exploded->minute = date.minute;
 199   // Make sure seconds are rounded down towards -infinity.
 200   exploded->second = floor(date.second);
 201   // Calculate milliseconds ourselves, since we rounded the |seconds|, making
 202   // sure to round towards -infinity.
 203   exploded->millisecond =
 204       (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond :
 205                            (microsecond - kMicrosecondsPerMillisecond + 1) /
 206                                kMicrosecondsPerMillisecond;
 207 }
 208
 209 // TimeTicks ------------------------------------------------------------------
 210
 211 // static
 212 TimeTicks TimeTicks::Now() {
 213   return TimeTicks(ComputeCurrentTicks());
 214 }
 215
 216 // static
 217 TimeTicks TimeTicks::HighResNow() {
 218   return Now();
 219 }
 220
 221 // static
 222 bool TimeTicks::IsHighResNowFastAndReliable() {
 223   return true;
 224 }
 225
 226 // static
 227 TimeTicks TimeTicks::ThreadNow() {
 228   return TimeTicks(ComputeThreadTicks());
 229 }
 230
 231 // static
 232 TimeTicks TimeTicks::NowFromSystemTraceTime() {
 233   return HighResNow();
 234 }
 235
 236 }  // namespace base