95 lines
2.6 KiB
C++
95 lines
2.6 KiB
C++
/* Copyright 2020, Ableton AG, Berlin. All rights reserved.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* If you would like to incorporate Link into a proprietary software application,
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* please contact <link-devs@ableton.com>.
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*/
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#pragma once
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#include <atomic>
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#include <condition_variable>
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#include <freertos/task.h>
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namespace ableton
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{
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namespace platforms
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{
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namespace esp32
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{
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// Utility to signal invocation of a callback on another thread in a lock free manner.
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// The callback is evoked on a thread owned by the instance of this class.
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//
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// A condition variable is used to notify a waiting thread, but only if the required
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// lock can be acquired immediately. If that fails, we fall back on signaling
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// after a timeout. This gives us a guaranteed minimum signaling rate which is defined
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// by the fallbackPeriod parameter.
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template <typename Callback, typename Duration>
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class LockFreeCallbackDispatcher
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{
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public:
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LockFreeCallbackDispatcher(Callback callback, Duration fallbackPeriod)
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: mCallback(std::move(callback))
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, mFallbackPeriod(std::move(fallbackPeriod))
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, mRunning(true)
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{
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xTaskCreate(run, "link", 4096, this, tskIDLE_PRIORITY, &mTaskHandle);
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}
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~LockFreeCallbackDispatcher()
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{
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mRunning = false;
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mCondition.notify_one();
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vTaskDelete(mTaskHandle);
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}
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void invoke()
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{
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if (mMutex.try_lock())
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{
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mCondition.notify_one();
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mMutex.unlock();
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}
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}
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private:
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static void run(void* userData)
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{
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auto dispatcher = static_cast<LockFreeCallbackDispatcher*>(userData);
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while (dispatcher->mRunning.load())
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{
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{
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std::unique_lock<std::mutex> lock(dispatcher->mMutex);
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dispatcher->mCondition.wait_for(lock, dispatcher->mFallbackPeriod);
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}
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dispatcher->mCallback();
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vTaskDelay(1);
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}
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}
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Callback mCallback;
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Duration mFallbackPeriod;
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std::atomic<bool> mRunning;
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std::mutex mMutex;
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std::condition_variable mCondition;
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TaskHandle_t mTaskHandle;
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};
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} // namespace esp32
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} // namespace platforms
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} // namespace ableton
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