Fix POSIX and Mac Time::Explode().

Also add a test for the case that failed.

BUG=109437,109465

Review URL: http://codereview.chromium.org/9124016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@116969 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 171 insertions, 14 deletions

diff --git a/base/time_mac.cc b/base/time_mac.cc
index 25cf037..da17e28 100644
--- a/base/time_mac.cc
+++ b/base/time_mac.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -79,23 +79,35 @@ Time Time::FromExploded(bool is_local, const Exploded& exploded) {
 }
 
 void Time::Explode(bool is_local, Exploded* exploded) const {
-  CFAbsoluteTime seconds =
-      ((static_cast<double>(us_) - kWindowsEpochDeltaMicroseconds) /
-      kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
+  // Avoid rounding issues, by only putting the integral number of seconds
+  // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
+  int64 microsecond = us_ % kMicrosecondsPerSecond;
+  if (microsecond < 0)
+    microsecond += kMicrosecondsPerSecond;
+  CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) -
+                           kWindowsEpochDeltaSeconds -
+                           kCFAbsoluteTimeIntervalSince1970;
 
   base::mac::ScopedCFTypeRef<CFTimeZoneRef>
       time_zone(is_local ? CFTimeZoneCopySystem() : NULL);
   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
+  // 1 = Monday, ..., 7 = Sunday.
+  int cf_day_of_week = CFAbsoluteTimeGetDayOfWeek(seconds, time_zone);
 
   exploded->year = date.year;
   exploded->month = date.month;
+  exploded->day_of_week = (cf_day_of_week == 7) ? 0 : cf_day_of_week - 1;
   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;
+  // Make sure seconds are rounded down towards -infinity.
+  exploded->second = floor(date.second);
+  // Calculate milliseconds ourselves, since we rounded the |seconds|, making
+  // sure to round towards -infinity.
+  exploded->millisecond =
+      (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond :
+                           (microsecond - kMicrosecondsPerMillisecond + 1) /
+                               kMicrosecondsPerMillisecond;
 }
 
 // TimeTicks ------------------------------------------------------------------
diff --git a/base/time_posix.cc b/base/time_posix.cc
index 79a0b94..be99971 100644
--- a/base/time_posix.cc
+++ b/base/time_posix.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -86,9 +86,27 @@ void Time::Explode(bool is_local, Exploded* exploded) const {
   // Time stores times with microsecond resolution, but Exploded only carries
   // millisecond resolution, so begin by being lossy.  Adjust from Windows
   // epoch (1601) to Unix epoch (1970);
-  int64 milliseconds = (us_ - kWindowsEpochDeltaMicroseconds) /
-      kMicrosecondsPerMillisecond;
-  time_t seconds = milliseconds / kMillisecondsPerSecond;
+  int64 microseconds = us_ - kWindowsEpochDeltaMicroseconds;
+  // The following values are all rounded towards -infinity.
+  int64 milliseconds;  // Milliseconds since epoch.
+  time_t seconds;  // Seconds since epoch.
+  int millisecond;  // Exploded millisecond value (0-999).
+  if (microseconds >= 0) {
+    // Rounding towards -infinity <=> rounding towards 0, in this case.
+    milliseconds = microseconds / kMicrosecondsPerMillisecond;
+    seconds = milliseconds / kMillisecondsPerSecond;
+    millisecond = milliseconds % kMillisecondsPerSecond;
+  } else {
+    // Round these *down* (towards -infinity).
+    milliseconds = (microseconds - kMicrosecondsPerMillisecond + 1) /
+                   kMicrosecondsPerMillisecond;
+    seconds = (milliseconds - kMillisecondsPerSecond + 1) /
+              kMillisecondsPerSecond;
+    // Make this nonnegative (and between 0 and 999 inclusive).
+    millisecond = milliseconds % kMillisecondsPerSecond;
+    if (millisecond < 0)
+      millisecond += kMillisecondsPerSecond;
+  }
 
   struct tm timestruct;
   if (is_local)
@@ -103,7 +121,7 @@ void Time::Explode(bool is_local, Exploded* exploded) const {
   exploded->hour         = timestruct.tm_hour;
   exploded->minute       = timestruct.tm_min;
   exploded->second       = timestruct.tm_sec;
-  exploded->millisecond  = milliseconds % kMillisecondsPerSecond;
+  exploded->millisecond  = millisecond;
 }
 
 // static
diff --git a/base/time_unittest.cc b/base/time_unittest.cc
index 261b831..b81ef44 100644
--- a/base/time_unittest.cc
+++ b/base/time_unittest.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -308,6 +308,133 @@ TEST_F(TimeTest, ParseTimeTestInvalidString) {
   EXPECT_FALSE(Time::FromString("Monday morning 2000", &parsed_time));
 }
 
+TEST_F(TimeTest, ExplodeBeforeUnixEpoch) {
+  static const int kUnixEpochYear = 1970;  // In case this changes (ha!).
+  Time t;
+  Time::Exploded exploded;
+
+  t = Time::UnixEpoch() - TimeDelta::FromMicroseconds(1);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1969-12-31 23:59:59 999 milliseconds (and 999 microseconds).
+  EXPECT_EQ(kUnixEpochYear - 1, exploded.year);
+  EXPECT_EQ(12, exploded.month);
+  EXPECT_EQ(31, exploded.day_of_month);
+  EXPECT_EQ(23, exploded.hour);
+  EXPECT_EQ(59, exploded.minute);
+  EXPECT_EQ(59, exploded.second);
+  EXPECT_EQ(999, exploded.millisecond);
+
+  t = Time::UnixEpoch() - TimeDelta::FromMicroseconds(1000);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1969-12-31 23:59:59 999 milliseconds.
+  EXPECT_EQ(kUnixEpochYear - 1, exploded.year);
+  EXPECT_EQ(12, exploded.month);
+  EXPECT_EQ(31, exploded.day_of_month);
+  EXPECT_EQ(23, exploded.hour);
+  EXPECT_EQ(59, exploded.minute);
+  EXPECT_EQ(59, exploded.second);
+  EXPECT_EQ(999, exploded.millisecond);
+
+  t = Time::UnixEpoch() - TimeDelta::FromMicroseconds(1001);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1969-12-31 23:59:59 998 milliseconds (and 999 microseconds).
+  EXPECT_EQ(kUnixEpochYear - 1, exploded.year);
+  EXPECT_EQ(12, exploded.month);
+  EXPECT_EQ(31, exploded.day_of_month);
+  EXPECT_EQ(23, exploded.hour);
+  EXPECT_EQ(59, exploded.minute);
+  EXPECT_EQ(59, exploded.second);
+  EXPECT_EQ(998, exploded.millisecond);
+
+  t = Time::UnixEpoch() - TimeDelta::FromMilliseconds(1000);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1969-12-31 23:59:59.
+  EXPECT_EQ(kUnixEpochYear - 1, exploded.year);
+  EXPECT_EQ(12, exploded.month);
+  EXPECT_EQ(31, exploded.day_of_month);
+  EXPECT_EQ(23, exploded.hour);
+  EXPECT_EQ(59, exploded.minute);
+  EXPECT_EQ(59, exploded.second);
+  EXPECT_EQ(0, exploded.millisecond);
+
+  t = Time::UnixEpoch() - TimeDelta::FromMilliseconds(1001);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1969-12-31 23:59:58 999 milliseconds.
+  EXPECT_EQ(kUnixEpochYear - 1, exploded.year);
+  EXPECT_EQ(12, exploded.month);
+  EXPECT_EQ(31, exploded.day_of_month);
+  EXPECT_EQ(23, exploded.hour);
+  EXPECT_EQ(59, exploded.minute);
+  EXPECT_EQ(58, exploded.second);
+  EXPECT_EQ(999, exploded.millisecond);
+
+  // Make sure we still handle at/after Unix epoch correctly.
+  t = Time::UnixEpoch();
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1970-12-31 00:00:00 0 milliseconds.
+  EXPECT_EQ(kUnixEpochYear, exploded.year);
+  EXPECT_EQ(1, exploded.month);
+  EXPECT_EQ(1, exploded.day_of_month);
+  EXPECT_EQ(0, exploded.hour);
+  EXPECT_EQ(0, exploded.minute);
+  EXPECT_EQ(0, exploded.second);
+  EXPECT_EQ(0, exploded.millisecond);
+
+  t = Time::UnixEpoch() + TimeDelta::FromMicroseconds(1);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1970-01-01 00:00:00 0 milliseconds (and 1 microsecond).
+  EXPECT_EQ(kUnixEpochYear, exploded.year);
+  EXPECT_EQ(1, exploded.month);
+  EXPECT_EQ(1, exploded.day_of_month);
+  EXPECT_EQ(0, exploded.hour);
+  EXPECT_EQ(0, exploded.minute);
+  EXPECT_EQ(0, exploded.second);
+  EXPECT_EQ(0, exploded.millisecond);
+
+  t = Time::UnixEpoch() + TimeDelta::FromMicroseconds(1000);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1970-01-01 00:00:00 1 millisecond.
+  EXPECT_EQ(kUnixEpochYear, exploded.year);
+  EXPECT_EQ(1, exploded.month);
+  EXPECT_EQ(1, exploded.day_of_month);
+  EXPECT_EQ(0, exploded.hour);
+  EXPECT_EQ(0, exploded.minute);
+  EXPECT_EQ(0, exploded.second);
+  EXPECT_EQ(1, exploded.millisecond);
+
+  t = Time::UnixEpoch() + TimeDelta::FromMilliseconds(1000);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1970-01-01 00:00:01.
+  EXPECT_EQ(kUnixEpochYear, exploded.year);
+  EXPECT_EQ(1, exploded.month);
+  EXPECT_EQ(1, exploded.day_of_month);
+  EXPECT_EQ(0, exploded.hour);
+  EXPECT_EQ(0, exploded.minute);
+  EXPECT_EQ(1, exploded.second);
+  EXPECT_EQ(0, exploded.millisecond);
+
+  t = Time::UnixEpoch() + TimeDelta::FromMilliseconds(1001);
+  t.UTCExplode(&exploded);
+  EXPECT_TRUE(exploded.HasValidValues());
+  // Should be 1970-01-01 00:00:01 1 millisecond.
+  EXPECT_EQ(kUnixEpochYear, exploded.year);
+  EXPECT_EQ(1, exploded.month);
+  EXPECT_EQ(1, exploded.day_of_month);
+  EXPECT_EQ(0, exploded.hour);
+  EXPECT_EQ(0, exploded.minute);
+  EXPECT_EQ(1, exploded.second);
+  EXPECT_EQ(1, exploded.millisecond);
+}
+
 TEST(TimeTicks, Deltas) {
   for (int index = 0; index < 50; index++) {
     TimeTicks ticks_start = TimeTicks::Now();