1 files changed, 80 insertions, 0 deletions
diff --git a/src/mongo/util/background_thread_clock_source.cpp b/src/mongo/util/background_thread_clock_source.cpp
new file mode 100644
index 00000000000..96dececff9c
--- /dev/null
+++ b/src/mongo/util/background_thread_clock_source.cpp
@@ -0,0 +1,80 @@
+/**
+ *    Copyright (C) 2016 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/util/background_thread_clock_source.h"
+
+#include <chrono>
+#include <thread>
+
+#include "mongo/stdx/memory.h"
+#include "mongo/stdx/thread.h"
+#include "mongo/util/time_support.h"
+
+namespace mongo {
+
+BackgroundThreadClockSource::BackgroundThreadClockSource(std::unique_ptr<ClockSource> clockSource,
+                                                         Milliseconds granularity)
+    : _clockSource(std::move(clockSource)), _granularity(granularity), _shutdownTimer(false) {
+    _updateCurrent();
+    _startTimerThread();
+}
+
+BackgroundThreadClockSource::~BackgroundThreadClockSource() {
+    {
+        stdx::unique_lock<stdx::mutex> lock(_mutex);
+        _shutdownTimer = true;
+        _condition.notify_one();
+    }
+
+    _timer.join();
+}
+
+Date_t BackgroundThreadClockSource::now() {
+    return Date_t::fromMillisSinceEpoch(_current.load());
+}
+
+void BackgroundThreadClockSource::_startTimerThread() {
+    // Start the background thread that repeatedly sleeps for the specified duration of milliseconds
+    // and wakes up to store the current time.
+    _timer = stdx::thread([&]() {
+        stdx::unique_lock<stdx::mutex> lock(_mutex);
+        while (!_shutdownTimer) {
+            if (_condition.wait_for(lock, _granularity) == stdx::cv_status::timeout) {
+                _updateCurrent();
+            }
+        }
+    });
+}
+
+void BackgroundThreadClockSource::_updateCurrent() {
+    _current.store(_clockSource->now().toMillisSinceEpoch());
+}
+
+}  // namespace mongo