base: export GetBuildTime

A need for the function came up in another context so this change exposes it
from base/.

BUG=none
TEST=base_unittests


Review URL: http://codereview.chromium.org/8510027

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@109638 0039d316-1c4b-4281-b951-d872f2087c98

base/base.gyp

@@ -123,6 +123,7 @@
         'bind_unittest.cc',
         'bind_unittest.nc',
         'bits_unittest.cc',
+        'build_time_unittest.cc',
         'callback_unittest.cc',
         'callback_unittest.nc',
         'command_line_unittest.cc',

base/base.gypi

@@ -56,6 +56,8 @@
           'bind_internal.h',
           'bind_internal_win.h',
           'bits.h',
+          'build_time.cc',
+          'build_time.h',
           'callback.h',
           'callback_internal.cc',
           'callback_internal.h',

base/build_time.cc

+// Copyright (c) 2011 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/build_time.h"
+
+#include "base/logging.h"
+#include "base/time.h"
+
+namespace base {
+
+Time GetBuildTime() {
+  Time integral_build_time;
+  // The format of __DATE__ and __TIME__ is specified by the ANSI C Standard,
+  // section 6.8.8.
+  //
+  // __DATE__ is exactly "Mmm DD YYYY".
+  // __TIME__ is exactly "hh:mm:ss".
+  const char kDateTime[] = __DATE__ " " __TIME__ " PST";
+  bool result = Time::FromString(kDateTime, &integral_build_time);
+  DCHECK(result);
+  return integral_build_time;
+}
+
+}  // namespace base

base/build_time.h

+// Copyright (c) 2011 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.
+
+#ifndef BASE_BUILD_TIME_
+#define BASE_BUILD_TIME_
+#pragma once
+
+#include "base/base_export.h"
+#include "base/time.h"
+
+namespace base {
+
+// GetBuildTime returns the time at which the current binary was built.
+//
+// This uses the __DATE__ and __TIME__ macros, which don't trigger a rebuild
+// when they change. However, official builds will always be rebuilt from
+// scratch.
+//
+// Also, since __TIME__ doesn't include a timezone, this value should only be
+// considered accurate to a day.
+Time BASE_EXPORT GetBuildTime();
+
+}  // namespace base
+
+#endif  // BASE_BUILD_TIME_

base/build_time_unittest.cc

+// Copyright (c) 2011 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/build_time.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(BuildTime, DateLooksValid) {
+  char build_date[] = __DATE__;
+
+  EXPECT_EQ(11u, strlen(build_date));
+  EXPECT_EQ(' ', build_date[3]);
+  EXPECT_EQ(' ', build_date[6]);
+}
+
+TEST(BuildTime, TimeLooksValid) {
+  char build_time[] = __TIME__;
+
+  EXPECT_EQ(8u, strlen(build_time));
+  EXPECT_EQ(':', build_time[2]);
+  EXPECT_EQ(':', build_time[5]);
+}
+
+TEST(BuildTime, DoesntCrash) {
+  // Since __DATE__ isn't updated unless one does a clobber build, we can't
+  // really test the value returned by it, except to check that it doesn't
+  // crash.
+  base::GetBuildTime();
+}

base/metrics/field_trial.cc

@@ -4,11 +4,12 @@
 
 #include "base/metrics/field_trial.h"
 
+#include "base/build_time.h"
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/sha1.h"
-#include "base/string_util.h"
 #include "base/stringprintf.h"
+#include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 
 namespace base {
@@ -153,15 +154,6 @@ void FieldTrial::EnableBenchmarking() {
 
 FieldTrial::~FieldTrial() {}
 
-// static
-Time FieldTrial::GetBuildTime() {
-  Time integral_build_time;
-  const char* kDateTime = __DATE__ " " __TIME__;
-  bool result = Time::FromString(kDateTime, &integral_build_time);
-  DCHECK(result);
-  return integral_build_time;
-}
-
 // static
 double FieldTrial::HashClientId(const std::string& client_id,
                                 const std::string& trial_name) {

base/metrics/field_trial.h

@@ -184,9 +184,6 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   // Returns the group_name. A winner need not have been chosen.
   std::string group_name_internal() const { return group_name_; }
 
-  // Get build time.
-  static Time GetBuildTime();
-
   // Calculates a uniformly-distributed double between [0.0, 1.0) given
   // a |client_id| and a |trial_name| (the latter is used as salt to avoid
   // separate one-time randomized trials from all having the same results).