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/*
* 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.
*/
#ifndef android_hardware_automotive_vehicle_aidl_impl_vhal_include_RecurrentTimer_H_
#define android_hardware_automotive_vehicle_aidl_impl_vhal_include_RecurrentTimer_H_
#include <android-base/thread_annotations.h>
#include <memory>
#include <mutex>
#include <queue>
#include <thread>
#include <unordered_map>
#include <vector>
namespace android {
namespace hardware {
namespace automotive {
namespace vehicle {
// A thread-safe recurrent timer.
class RecurrentTimer final {
public:
// The class for the function that would be called recurrently.
using Callback = std::function<void()>;
RecurrentTimer();
~RecurrentTimer();
// Registers a recurrent callback for a given interval.
// Registering the same callback twice will override the interval provided before.
void registerTimerCallback(int64_t intervalInNano, std::shared_ptr<Callback> callback);
// Unregisters a previously registered recurrent callback.
void unregisterTimerCallback(std::shared_ptr<Callback> callback);
private:
// friend class for unit testing.
friend class RecurrentTimerTest;
struct CallbackInfo {
std::shared_ptr<Callback> callback;
int64_t interval;
int64_t nextTime;
// A flag to indicate whether this CallbackInfo is already outdated and should be ignored.
// The reason we need this flag is because we cannot easily remove an element from a heap.
bool outdated = false;
static bool cmp(const std::unique_ptr<CallbackInfo>& lhs,
const std::unique_ptr<CallbackInfo>& rhs);
};
std::mutex mLock;
std::thread mThread;
std::condition_variable mCond;
bool mStopRequested GUARDED_BY(mLock) = false;
// A map to map each callback to its current active CallbackInfo in the mCallbackQueue.
std::unordered_map<std::shared_ptr<Callback>, CallbackInfo*> mCallbacks GUARDED_BY(mLock);
// A min-heap sorted by nextTime. Note that because we cannot remove arbitrary element from the
// heap, a single Callback can have multiple entries in this queue, all but one should be valid.
// The rest should be mark as outdated. The valid one is one stored in mCallbacks.
std::vector<std::unique_ptr<CallbackInfo>> mCallbackQueue GUARDED_BY(mLock);
void loop();
// Mark the callbackInfo as outdated and should be ignored when popped from the heap.
void markOutdatedLocked(CallbackInfo* callback) REQUIRES(mLock);
// Remove all outdated callbackInfos from the top of the heap. This function must be called
// each time we might introduce outdated elements to the top. We must make sure the heap is
// always valid from the top.
void removeInvalidCallbackLocked() REQUIRES(mLock);
// Gets the next calblack to run (must be valid) from the heap, update its nextTime and put
// it back to the heap.
std::shared_ptr<Callback> getNextCallbackLocked(int64_t now) REQUIRES(mLock);
};
} // namespace vehicle
} // namespace automotive
} // namespace hardware
} // namespace android
#endif // android_hardware_automotive_vehicle_aidl_impl_vhal_include_RecurrentTimer_H_
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