base/time_mac.cc

   1 // Copyright (c) 2011 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/time.h>
  11 #include <time.h>
  12
  13 #include "base/basictypes.h"
  14 #include "base/logging.h"
  15 #include "base/mac/scoped_cftyperef.h"
  16
  17 namespace base {
  18
  19 // The Time routines in this file use Mach and CoreFoundation APIs, since the
  20 // POSIX definition of time_t in Mac OS X wraps around after 2038--and
  21 // there are already cookie expiration dates, etc., past that time out in
  22 // the field.  Using CFDate prevents that problem, and using mach_absolute_time
  23 // for TimeTicks gives us nice high-resolution interval timing.
  24
  25 // Time -----------------------------------------------------------------------
  26
  27 // Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
  28 // The UNIX epoch is 1970-01-01 00:00:00 UTC.
  29 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
  30 // so that our time representations match across all platforms.  See bug 14734.
  31 //   irb(main):010:0> Time.at(0).getutc()
  32 //   => Thu Jan 01 00:00:00 UTC 1970
  33 //   irb(main):011:0> Time.at(-11644473600).getutc()
  34 //   => Mon Jan 01 00:00:00 UTC 1601
  35 static const int64 kWindowsEpochDeltaSeconds = GG_INT64_C(11644473600);
  36 static const int64 kWindowsEpochDeltaMilliseconds =
  37     kWindowsEpochDeltaSeconds * Time::kMillisecondsPerSecond;
  38
  39 // static
  40 const int64 Time::kWindowsEpochDeltaMicroseconds =
  41     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
  42
  43 // Some functions in time.cc use time_t directly, so we provide an offset
  44 // to convert from time_t (Unix epoch) and internal (Windows epoch).
  45 // static
  46 const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
  47
  48 // static
  49 Time Time::Now() {
  50   CFAbsoluteTime now =
  51       CFAbsoluteTimeGetCurrent() + kCFAbsoluteTimeIntervalSince1970;
  52   return Time(static_cast<int64>(now * kMicrosecondsPerSecond) +
  53       kWindowsEpochDeltaMicroseconds);
  54 }
  55
  56 // static
  57 Time Time::NowFromSystemTime() {
  58   // Just use Now() because Now() returns the system time.
  59   return Now();
  60 }
  61
  62 // static
  63 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
  64   CFGregorianDate date;
  65   date.second = exploded.second +
  66       exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
  67   date.minute = exploded.minute;
  68   date.hour = exploded.hour;
  69   date.day = exploded.day_of_month;
  70   date.month = exploded.month;
  71   date.year = exploded.year;
  72
  73   base::mac::ScopedCFTypeRef<CFTimeZoneRef>
  74       time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
  75   CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
  76       kCFAbsoluteTimeIntervalSince1970;
  77   return Time(static_cast<int64>(seconds * kMicrosecondsPerSecond) +
  78       kWindowsEpochDeltaMicroseconds);
  79 }
  80
  81 void Time::Explode(bool is_local, Exploded* exploded) const {
  82   CFAbsoluteTime seconds =
  83       ((static_cast<double>(us_) - kWindowsEpochDeltaMicroseconds) /
  84       kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
  85
  86   base::mac::ScopedCFTypeRef<CFTimeZoneRef>
  87       time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
  88   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
  89
  90   exploded->year = date.year;
  91   exploded->month = date.month;
  92   exploded->day_of_month = date.day;
  93   exploded->hour = date.hour;
  94   exploded->minute = date.minute;
  95   exploded->second = date.second;
  96   exploded->millisecond  =
  97       static_cast<int>(date.second * kMillisecondsPerSecond) %
  98       kMillisecondsPerSecond;
  99 }
 100
 101 // TimeTicks ------------------------------------------------------------------
 102
 103 // static
 104 TimeTicks TimeTicks::Now() {
 105   uint64_t absolute_micro;
 106
 107   static mach_timebase_info_data_t timebase_info;
 108   if (timebase_info.denom == 0) {
 109     // Zero-initialization of statics guarantees that denom will be 0 before
 110     // calling mach_timebase_info.  mach_timebase_info will never set denom to
 111     // 0 as that would be invalid, so the zero-check can be used to determine
 112     // whether mach_timebase_info has already been called.  This is
 113     // recommended by Apple's QA1398.
 114     kern_return_t kr = mach_timebase_info(&timebase_info);
 115     DCHECK_EQ(KERN_SUCCESS, kr);
 116   }
 117
 118   // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
 119   // with less precision (such as TickCount) just call through to
 120   // mach_absolute_time.
 121
 122   // timebase_info converts absolute time tick units into nanoseconds.  Convert
 123   // to microseconds up front to stave off overflows.
 124   absolute_micro = mach_absolute_time() / Time::kNanosecondsPerMicrosecond *
 125                    timebase_info.numer / timebase_info.denom;
 126
 127   // Don't bother with the rollover handling that the Windows version does.
 128   // With numer and denom = 1 (the expected case), the 64-bit absolute time
 129   // reported in nanoseconds is enough to last nearly 585 years.
 130
 131   return TimeTicks(absolute_micro);
 132 }
 133
 134 // static
 135 TimeTicks TimeTicks::HighResNow() {
 136   return Now();
 137 }
 138
 139 }  // namespace base