Update Mac implemention of Time to prevent problems with...

base/time_mac.cc

+// 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.c 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 Time::kTimeTToMicrosecondsOffset = GG_INT64_C(0);
+
+// static
+Time Time::Now() {
+  CFAbsoluteTime now =
+      CFAbsoluteTimeGetCurrent() + kCFAbsoluteTimeIntervalSince1970;
+  return Time(static_cast<int64>(now * kMicrosecondsPerSecond));
+}
+
+// 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;
+  if (is_local)
+    time_zone.reset(CFTimeZoneCopySystem());
+  CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
+      kCFAbsoluteTimeIntervalSince1970;
+  return Time(static_cast<int64>(seconds * kMicrosecondsPerSecond));
+}
+
+void Time::Explode(bool is_local, Exploded* exploded) const {
+  CFAbsoluteTime seconds =
+      (static_cast<double>(us_) / kMicrosecondsPerSecond) -
+      kCFAbsoluteTimeIntervalSince1970;
+  
+  scoped_cftyperef<CFTimeZoneRef> time_zone;
+  if (is_local)
+    time_zone.reset(CFTimeZoneCopySystem());
+  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