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/mach_logging.h"
  19 #include "base/mac/scoped_cftyperef.h"
  20 #include "base/mac/scoped_mach_port.h"
  21
  22 namespace {
  23
  24 uint64_t ComputeCurrentTicks() {
  25 #if defined(OS_IOS)
  26   // On iOS mach_absolute_time stops while the device is sleeping. Instead use
  27   // now - KERN_BOOTTIME to get a time difference that is not impacted by clock
  28   // changes. KERN_BOOTTIME will be updated by the system whenever the system
  29   // clock change.
  30   struct timeval boottime;
  31   int mib[2] = {CTL_KERN, KERN_BOOTTIME};
  32   size_t size = sizeof(boottime);
  33   int kr = sysctl(mib, arraysize(mib), &boottime, &size, NULL, 0);
  34   DCHECK_EQ(KERN_SUCCESS, kr);
  35   base::TimeDelta time_difference = base::Time::Now() -
  36       (base::Time::FromTimeT(boottime.tv_sec) +
  37        base::TimeDelta::FromMicroseconds(boottime.tv_usec));
  38   return time_difference.InMicroseconds();
  39 #else
  40   uint64_t absolute_micro;
  41
  42   static mach_timebase_info_data_t timebase_info;
  43   if (timebase_info.denom == 0) {
  44     // Zero-initialization of statics guarantees that denom will be 0 before
  45     // calling mach_timebase_info.  mach_timebase_info will never set denom to
  46     // 0 as that would be invalid, so the zero-check can be used to determine
  47     // whether mach_timebase_info has already been called.  This is
  48     // recommended by Apple's QA1398.
  49     kern_return_t kr = mach_timebase_info(&timebase_info);
  50     MACH_DCHECK(kr == KERN_SUCCESS, kr) << "mach_timebase_info";
  51   }
  52
  53   // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
  54   // with less precision (such as TickCount) just call through to
  55   // mach_absolute_time.
  56
  57   // timebase_info converts absolute time tick units into nanoseconds.  Convert
  58   // to microseconds up front to stave off overflows.
  59   absolute_micro =
  60       mach_absolute_time() / base::Time::kNanosecondsPerMicrosecond *
  61       timebase_info.numer / timebase_info.denom;
  62
  63   // Don't bother with the rollover handling that the Windows version does.
  64   // With numer and denom = 1 (the expected case), the 64-bit absolute time
  65   // reported in nanoseconds is enough to last nearly 585 years.
  66   return absolute_micro;
  67 #endif  // defined(OS_IOS)
  68 }
  69
  70 uint64_t ComputeThreadTicks() {
  71 #if defined(OS_IOS)
  72   NOTREACHED();
  73   return 0;
  74 #else
  75   base::mac::ScopedMachSendRight thread(mach_thread_self());
  76   mach_msg_type_number_t thread_info_count = THREAD_BASIC_INFO_COUNT;
  77   thread_basic_info_data_t thread_info_data;
  78
  79   if (thread.get() == MACH_PORT_NULL) {
  80     DLOG(ERROR) << "Failed to get mach_thread_self()";
  81     return 0;
  82   }
  83
  84   kern_return_t kr = thread_info(
  85       thread,
  86       THREAD_BASIC_INFO,
  87       reinterpret_cast<thread_info_t>(&thread_info_data),
  88       &thread_info_count);
  89   MACH_DCHECK(kr == KERN_SUCCESS, kr) << "thread_info";
  90
  91   return (thread_info_data.user_time.seconds *
  92               base::Time::kMicrosecondsPerSecond) +
  93          thread_info_data.user_time.microseconds;
  94 #endif  // defined(OS_IOS)
  95 }
  96
  97 }  // namespace
  98
  99 namespace base {
 100
 101 // The Time routines in this file use Mach and CoreFoundation APIs, since the
 102 // POSIX definition of time_t in Mac OS X wraps around after 2038--and
 103 // there are already cookie expiration dates, etc., past that time out in
 104 // the field.  Using CFDate prevents that problem, and using mach_absolute_time
 105 // for TimeTicks gives us nice high-resolution interval timing.
 106
 107 // Time -----------------------------------------------------------------------
 108
 109 // Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
 110 // The UNIX epoch is 1970-01-01 00:00:00 UTC.
 111 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
 112 // so that our time representations match across all platforms.  See bug 14734.
 113 //   irb(main):010:0> Time.at(0).getutc()
 114 //   => Thu Jan 01 00:00:00 UTC 1970
 115 //   irb(main):011:0> Time.at(-11644473600).getutc()
 116 //   => Mon Jan 01 00:00:00 UTC 1601
 117 static const int64 kWindowsEpochDeltaSeconds = GG_INT64_C(11644473600);
 118
 119 // static
 120 const int64 Time::kWindowsEpochDeltaMicroseconds =
 121     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
 122
 123 // Some functions in time.cc use time_t directly, so we provide an offset
 124 // to convert from time_t (Unix epoch) and internal (Windows epoch).
 125 // static
 126 const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
 127
 128 // static
 129 Time Time::Now() {
 130   return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
 131 }
 132
 133 // static
 134 Time Time::FromCFAbsoluteTime(CFAbsoluteTime t) {
 135   COMPILE_ASSERT(std::numeric_limits<CFAbsoluteTime>::has_infinity,
 136                  numeric_limits_infinity_is_undefined_when_not_has_infinity);
 137   if (t == 0)
 138     return Time();  // Consider 0 as a null Time.
 139   if (t == std::numeric_limits<CFAbsoluteTime>::infinity())
 140     return Max();
 141   return Time(static_cast<int64>(
 142       (t + kCFAbsoluteTimeIntervalSince1970) * kMicrosecondsPerSecond) +
 143       kWindowsEpochDeltaMicroseconds);
 144 }
 145
 146 CFAbsoluteTime Time::ToCFAbsoluteTime() const {
 147   COMPILE_ASSERT(std::numeric_limits<CFAbsoluteTime>::has_infinity,
 148                  numeric_limits_infinity_is_undefined_when_not_has_infinity);
 149   if (is_null())
 150     return 0;  // Consider 0 as a null Time.
 151   if (is_max())
 152     return std::numeric_limits<CFAbsoluteTime>::infinity();
 153   return (static_cast<CFAbsoluteTime>(us_ - kWindowsEpochDeltaMicroseconds) /
 154       kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
 155 }
 156
 157 // static
 158 Time Time::NowFromSystemTime() {
 159   // Just use Now() because Now() returns the system time.
 160   return Now();
 161 }
 162
 163 // static
 164 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
 165   CFGregorianDate date;
 166   date.second = exploded.second +
 167       exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
 168   date.minute = exploded.minute;
 169   date.hour = exploded.hour;
 170   date.day = exploded.day_of_month;
 171   date.month = exploded.month;
 172   date.year = exploded.year;
 173
 174   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
 175       is_local ? CFTimeZoneCopySystem() : NULL);
 176   CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
 177       kCFAbsoluteTimeIntervalSince1970;
 178   return Time(static_cast<int64>(seconds * kMicrosecondsPerSecond) +
 179       kWindowsEpochDeltaMicroseconds);
 180 }
 181
 182 void Time::Explode(bool is_local, Exploded* exploded) const {
 183   // Avoid rounding issues, by only putting the integral number of seconds
 184   // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
 185   int64 microsecond = us_ % kMicrosecondsPerSecond;
 186   if (microsecond < 0)
 187     microsecond += kMicrosecondsPerSecond;
 188   CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) -
 189                            kWindowsEpochDeltaSeconds -
 190                            kCFAbsoluteTimeIntervalSince1970;
 191
 192   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
 193       is_local ? CFTimeZoneCopySystem() : NULL);
 194   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
 195   // 1 = Monday, ..., 7 = Sunday.
 196   int cf_day_of_week = CFAbsoluteTimeGetDayOfWeek(seconds, time_zone);
 197
 198   exploded->year = date.year;
 199   exploded->month = date.month;
 200   exploded->day_of_week = cf_day_of_week % 7;
 201   exploded->day_of_month = date.day;
 202   exploded->hour = date.hour;
 203   exploded->minute = date.minute;
 204   // Make sure seconds are rounded down towards -infinity.
 205   exploded->second = floor(date.second);
 206   // Calculate milliseconds ourselves, since we rounded the |seconds|, making
 207   // sure to round towards -infinity.
 208   exploded->millisecond =
 209       (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond :
 210                            (microsecond - kMicrosecondsPerMillisecond + 1) /
 211                                kMicrosecondsPerMillisecond;
 212 }
 213
 214 // TimeTicks ------------------------------------------------------------------
 215
 216 // static
 217 TimeTicks TimeTicks::Now() {
 218   return TimeTicks(ComputeCurrentTicks());
 219 }
 220
 221 // static
 222 TimeTicks TimeTicks::HighResNow() {
 223   return Now();
 224 }
 225
 226 // static
 227 bool TimeTicks::IsHighResNowFastAndReliable() {
 228   return true;
 229 }
 230
 231 // static
 232 TimeTicks TimeTicks::ThreadNow() {
 233   return TimeTicks(ComputeThreadTicks());
 234 }
 235
 236 // static
 237 TimeTicks TimeTicks::NowFromSystemTraceTime() {
 238   return HighResNow();
 239 }
 240
 241 }  // namespace base