Modernize TimeCheck
This replaces the usage of Thread, Mutex, Condition and KeyedVector
with their std:: counterparts.
We're also extracting the time thread from TimeCheck and adding a unit
test.
The logic in TimerThread now is easier to follow and it is more
evident that tasks would never be executed before their deadline
arrived. In the original code, this wasn't obvious.
Test: atest libmediautils_test
Bug: 188748333
Change-Id: Iac887e7d6e6758c0a0e5c56695e9671082e64b09
diff --git a/media/utils/include/mediautils/TimerThread.h b/media/utils/include/mediautils/TimerThread.h
new file mode 100644
index 0000000..cf457b8
--- /dev/null
+++ b/media/utils/include/mediautils/TimerThread.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <condition_variable>
+#include <functional>
+#include <map>
+#include <mutex>
+#include <thread>
+
+#include <android-base/thread_annotations.h>
+
+namespace android {
+
+/**
+ * A thread for deferred execution of tasks, with cancellation.
+ */
+class TimerThread {
+ public:
+ using Handle = std::chrono::steady_clock::time_point;
+
+ TimerThread();
+ ~TimerThread();
+
+ /**
+ * Schedule a task to be executed in the future (`timeout` duration from now).
+ * Returns a handle that can be used for cancellation.
+ */
+ template <typename R, typename P>
+ Handle scheduleTask(std::function<void()>&& func, std::chrono::duration<R, P> timeout) {
+ auto deadline = std::chrono::steady_clock::now() + std::chrono::milliseconds(timeout);
+ return scheduleTaskAtDeadline(std::move(func), deadline);
+ }
+
+ /**
+ * Cancel a task, previously scheduled with scheduleTask().
+ * If the task has already executed, this is a no-op.
+ */
+ void cancelTask(Handle handle);
+
+ private:
+ using TimePoint = std::chrono::steady_clock::time_point;
+
+ std::condition_variable mCond;
+ std::mutex mMutex;
+ std::thread mThread;
+ std::map<TimePoint, std::function<void()>> mMonitorRequests GUARDED_BY(mMutex);
+ bool mShouldExit GUARDED_BY(mMutex) = false;
+
+ void threadFunc();
+ Handle scheduleTaskAtDeadline(std::function<void()>&& func, TimePoint deadline);
+};
+
+} // namespace android