File: time_mac.cc

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/time.h"

#include <CoreFoundation/CFDate.h>
#include <CoreFoundation/CFTimeZone.h>
#include <mach/mach_time.h>
#include <sys/time.h>
#include <time.h>

#include "base/basictypes.h"
#include "base/logging.h"
#include "base/scoped_cftyperef.h"

namespace base {

// The Time routines in this file use Mach and CoreFoundation APIs, since the
// POSIX definition of time_t in Mac OS X wraps around after 2038--and
// there are already cookie expiration dates, etc., past that time out in
// the field.  Using CFDate prevents that problem, and using mach_absolute_time
// for TimeTicks gives us nice high-resolution interval timing.

// Time -----------------------------------------------------------------------

// The internal representation of Time uses a 64-bit microsecond count
// from 1970-01-01 00:00:00 UTC.  Core Foundation uses a double second count
// since 2001-01-01 00:00:00 UTC.

// Some functions in time.cc use time_t directly, so we provide a zero offset
// for them.  The epoch is 1970-01-01 00:00:00 UTC.
// static
const int64_t Time::kTimeTToMicrosecondsOffset = GG_INT64_C(0);

// static
Time Time::Now() {
  CFAbsoluteTime now =
      CFAbsoluteTimeGetCurrent() + kCFAbsoluteTimeIntervalSince1970;
  return Time(static_cast<int64_t>(now * kMicrosecondsPerSecond));
}

// static
Time Time::NowFromSystemTime() {
  // Just use Now() because Now() returns the system time.
  return Now();
}

// static
Time Time::FromExploded(bool is_local, const Exploded& exploded) {
  CFGregorianDate date;
  date.second = exploded.second +
      exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
  date.minute = exploded.minute;
  date.hour = exploded.hour;
  date.day = exploded.day_of_month;
  date.month = exploded.month;
  date.year = exploded.year;

  scoped_cftyperef<CFTimeZoneRef>
      time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
  CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
      kCFAbsoluteTimeIntervalSince1970;
  return Time(static_cast<int64_t>(seconds * kMicrosecondsPerSecond));
}

void Time::Explode(bool is_local, Exploded* exploded) const {
  CFAbsoluteTime seconds =
      (static_cast<double>(us_) / kMicrosecondsPerSecond) -
      kCFAbsoluteTimeIntervalSince1970;

  scoped_cftyperef<CFTimeZoneRef>
      time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
  CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);

  exploded->year = date.year;
  exploded->month = date.month;
  exploded->day_of_month = date.day;
  exploded->hour = date.hour;
  exploded->minute = date.minute;
  exploded->second = date.second;
  exploded->millisecond  =
      static_cast<int>(date.second * kMillisecondsPerSecond) %
      kMillisecondsPerSecond;
}

// TimeTicks ------------------------------------------------------------------

// static
TimeTicks TimeTicks::Now() {
  uint64_t absolute_micro;

  static mach_timebase_info_data_t timebase_info;
  if (timebase_info.denom == 0) {
    // Zero-initialization of statics guarantees that denom will be 0 before
    // calling mach_timebase_info.  mach_timebase_info will never set denom to
    // 0 as that would be invalid, so the zero-check can be used to determine
    // whether mach_timebase_info has already been called.  This is
    // recommended by Apple's QA1398.
    kern_return_t kr = mach_timebase_info(&timebase_info);
    DCHECK(kr == KERN_SUCCESS);
  }

  // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
  // with less precision (such as TickCount) just call through to
  // mach_absolute_time.

  // timebase_info converts absolute time tick units into nanoseconds.  Convert
  // to microseconds up front to stave off overflows.
  absolute_micro = mach_absolute_time() / Time::kNanosecondsPerMicrosecond *
                   timebase_info.numer / timebase_info.denom;

  // Don't bother with the rollover handling that the Windows version does.
  // With numer and denom = 1 (the expected case), the 64-bit absolute time
  // reported in nanoseconds is enough to last nearly 585 years.

  return TimeTicks(absolute_micro);
}

// static
TimeTicks TimeTicks::HighResNow() {
  return Now();
}

}  // namespace base