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 <stdint.h>
  12 #include <sys/sysctl.h>
  13 #include <sys/time.h>
  14 #include <sys/types.h>
  15 #include <time.h>
  16
  17 #include "base/basictypes.h"
  18 #include "base/logging.h"
  19 #include "base/mac/mach_logging.h"
  20 #include "base/mac/scoped_cftyperef.h"
  21 #include "base/mac/scoped_mach_port.h"
  22 #include "base/numerics/safe_conversions.h"
  23
  24 namespace {
  25
  26 int64_t ComputeCurrentTicks() {
  27 #if defined(OS_IOS)
  28   // On iOS mach_absolute_time stops while the device is sleeping. Instead use
  29   // now - KERN_BOOTTIME to get a time difference that is not impacted by clock
  30   // changes. KERN_BOOTTIME will be updated by the system whenever the system
  31   // clock change.
  32   struct timeval boottime;
  33   int mib[2] = {CTL_KERN, KERN_BOOTTIME};
  34   size_t size = sizeof(boottime);
  35   int kr = sysctl(mib, arraysize(mib), &boottime, &size, NULL, 0);
  36   DCHECK_EQ(KERN_SUCCESS, kr);
  37   base::TimeDelta time_difference = base::Time::Now() -
  38       (base::Time::FromTimeT(boottime.tv_sec) +
  39        base::TimeDelta::FromMicroseconds(boottime.tv_usec));
  40   return time_difference.InMicroseconds();
  41 #else
  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   base::CheckedNumeric<uint64_t> result(
  60       mach_absolute_time() / base::Time::kNanosecondsPerMicrosecond);
  61   result *= timebase_info.numer;
  62   result /= timebase_info.denom;
  63
  64   // Don't bother with the rollover handling that the Windows version does.
  65   // With numer and denom = 1 (the expected case), the 64-bit absolute time
  66   // reported in nanoseconds is enough to last nearly 585 years.
  67   return base::checked_cast<int64_t>(result.ValueOrDie());
  68 #endif  // defined(OS_IOS)
  69 }
  70
  71 int64_t ComputeThreadTicks() {
  72 #if defined(OS_IOS)
  73   NOTREACHED();
  74   return 0;
  75 #else
  76   base::mac::ScopedMachSendRight thread(mach_thread_self());
  77   mach_msg_type_number_t thread_info_count = THREAD_BASIC_INFO_COUNT;
  78   thread_basic_info_data_t thread_info_data;
  79
  80   if (thread.get() == MACH_PORT_NULL) {
  81     DLOG(ERROR) << "Failed to get mach_thread_self()";
  82     return 0;
  83   }
  84
  85   kern_return_t kr = thread_info(
  86       thread,
  87       THREAD_BASIC_INFO,
  88       reinterpret_cast<thread_info_t>(&thread_info_data),
  89       &thread_info_count);
  90   MACH_DCHECK(kr == KERN_SUCCESS, kr) << "thread_info";
  91
  92   base::CheckedNumeric<int64_t> absolute_micros(
  93       thread_info_data.user_time.seconds);
  94   absolute_micros *= base::Time::kMicrosecondsPerSecond;
  95   absolute_micros += thread_info_data.user_time.microseconds;
  96   return absolute_micros.ValueOrDie();
  97 #endif  // defined(OS_IOS)
  98 }
  99
 100 }  // namespace
 101
 102 namespace base {
 103
 104 // The Time routines in this file use Mach and CoreFoundation APIs, since the
 105 // POSIX definition of time_t in Mac OS X wraps around after 2038--and
 106 // there are already cookie expiration dates, etc., past that time out in
 107 // the field.  Using CFDate prevents that problem, and using mach_absolute_time
 108 // for TimeTicks gives us nice high-resolution interval timing.
 109
 110 // Time -----------------------------------------------------------------------
 111
 112 // Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
 113 // The UNIX epoch is 1970-01-01 00:00:00 UTC.
 114 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
 115 // so that our time representations match across all platforms.  See bug 14734.
 116 //   irb(main):010:0> Time.at(0).getutc()
 117 //   => Thu Jan 01 00:00:00 UTC 1970
 118 //   irb(main):011:0> Time.at(-11644473600).getutc()
 119 //   => Mon Jan 01 00:00:00 UTC 1601
 120 static const int64 kWindowsEpochDeltaSeconds = INT64_C(11644473600);
 121
 122 // static
 123 const int64 Time::kWindowsEpochDeltaMicroseconds =
 124     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
 125
 126 // Some functions in time.cc use time_t directly, so we provide an offset
 127 // to convert from time_t (Unix epoch) and internal (Windows epoch).
 128 // static
 129 const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
 130
 131 // static
 132 Time Time::Now() {
 133   return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
 134 }
 135
 136 // static
 137 Time Time::FromCFAbsoluteTime(CFAbsoluteTime t) {
 138   COMPILE_ASSERT(std::numeric_limits<CFAbsoluteTime>::has_infinity,
 139                  numeric_limits_infinity_is_undefined_when_not_has_infinity);
 140   if (t == 0)
 141     return Time();  // Consider 0 as a null Time.
 142   if (t == std::numeric_limits<CFAbsoluteTime>::infinity())
 143     return Max();
 144   return Time(static_cast<int64>(
 145       (t + kCFAbsoluteTimeIntervalSince1970) * kMicrosecondsPerSecond) +
 146       kWindowsEpochDeltaMicroseconds);
 147 }
 148
 149 CFAbsoluteTime Time::ToCFAbsoluteTime() const {
 150   COMPILE_ASSERT(std::numeric_limits<CFAbsoluteTime>::has_infinity,
 151                  numeric_limits_infinity_is_undefined_when_not_has_infinity);
 152   if (is_null())
 153     return 0;  // Consider 0 as a null Time.
 154   if (is_max())
 155     return std::numeric_limits<CFAbsoluteTime>::infinity();
 156   return (static_cast<CFAbsoluteTime>(us_ - kWindowsEpochDeltaMicroseconds) /
 157       kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
 158 }
 159
 160 // static
 161 Time Time::NowFromSystemTime() {
 162   // Just use Now() because Now() returns the system time.
 163   return Now();
 164 }
 165
 166 // static
 167 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
 168   CFGregorianDate date;
 169   date.second = exploded.second +
 170       exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
 171   date.minute = exploded.minute;
 172   date.hour = exploded.hour;
 173   date.day = exploded.day_of_month;
 174   date.month = exploded.month;
 175   date.year = exploded.year;
 176
 177   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
 178       is_local ? CFTimeZoneCopySystem() : NULL);
 179   CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
 180       kCFAbsoluteTimeIntervalSince1970;
 181   return Time(static_cast<int64>(seconds * kMicrosecondsPerSecond) +
 182       kWindowsEpochDeltaMicroseconds);
 183 }
 184
 185 void Time::Explode(bool is_local, Exploded* exploded) const {
 186   // Avoid rounding issues, by only putting the integral number of seconds
 187   // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
 188   int64 microsecond = us_ % kMicrosecondsPerSecond;
 189   if (microsecond < 0)
 190     microsecond += kMicrosecondsPerSecond;
 191   CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) -
 192                            kWindowsEpochDeltaSeconds -
 193                            kCFAbsoluteTimeIntervalSince1970;
 194
 195   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
 196       is_local ? CFTimeZoneCopySystem() : NULL);
 197   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
 198   // 1 = Monday, ..., 7 = Sunday.
 199   int cf_day_of_week = CFAbsoluteTimeGetDayOfWeek(seconds, time_zone);
 200
 201   exploded->year = date.year;
 202   exploded->month = date.month;
 203   exploded->day_of_week = cf_day_of_week % 7;
 204   exploded->day_of_month = date.day;
 205   exploded->hour = date.hour;
 206   exploded->minute = date.minute;
 207   // Make sure seconds are rounded down towards -infinity.
 208   exploded->second = floor(date.second);
 209   // Calculate milliseconds ourselves, since we rounded the |seconds|, making
 210   // sure to round towards -infinity.
 211   exploded->millisecond =
 212       (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond :
 213                            (microsecond - kMicrosecondsPerMillisecond + 1) /
 214                                kMicrosecondsPerMillisecond;
 215 }
 216
 217 // TimeTicks ------------------------------------------------------------------
 218
 219 // static
 220 TimeTicks TimeTicks::Now() {
 221   return TimeTicks(ComputeCurrentTicks());
 222 }
 223
 224 // static
 225 bool TimeTicks::IsHighResolution() {
 226   return true;
 227 }
 228
 229 // static
 230 ThreadTicks ThreadTicks::Now() {
 231   return ThreadTicks(ComputeThreadTicks());
 232 }
 233
 234 // static
 235 TraceTicks TraceTicks::Now() {
 236   return TraceTicks(ComputeCurrentTicks());
 237 }
 238
 239 }  // namespace base