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      1 // Copyright (c) 2008 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(kr == KERN_SUCCESS);
    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
    140