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113 lines
3.0 KiB
113 lines
3.0 KiB
/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _UI_INPUT_BLOCKING_QUEUE_H
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#define _UI_INPUT_BLOCKING_QUEUE_H
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#include "android-base/thread_annotations.h"
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#include <condition_variable>
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#include <mutex>
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#include <vector>
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namespace android {
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/**
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* A FIFO queue that stores up to <i>capacity</i> objects.
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* Objects can always be added. Objects are added immediately.
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* If the queue is full, new objects cannot be added.
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*
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* The action of retrieving an object will block until an element is available.
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*/
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template <class T>
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class BlockingQueue {
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public:
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BlockingQueue(size_t capacity) : mCapacity(capacity) {
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mQueue.reserve(mCapacity);
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};
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/**
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* Retrieve and remove the oldest object.
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* Blocks execution while queue is empty.
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*/
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T pop() {
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std::unique_lock lock(mLock);
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android::base::ScopedLockAssertion assumeLock(mLock);
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mHasElements.wait(lock, [this]() REQUIRES(mLock) { return !this->mQueue.empty(); });
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T t = std::move(mQueue.front());
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mQueue.erase(mQueue.begin());
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return t;
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};
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/**
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* Add a new object to the queue.
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* Does not block.
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* Return true if an element was successfully added.
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* Return false if the queue is full.
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*/
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bool push(T&& t) {
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{
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std::scoped_lock lock(mLock);
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if (mQueue.size() == mCapacity) {
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return false;
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}
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mQueue.push_back(std::move(t));
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}
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mHasElements.notify_one();
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return true;
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};
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void erase(const std::function<bool(const T&)>& lambda) {
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std::scoped_lock lock(mLock);
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mQueue.erase(std::remove_if(mQueue.begin(), mQueue.end(),
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[&lambda](const T& t) { return lambda(t); }), mQueue.end());
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}
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/**
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* Remove all elements.
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* Does not block.
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*/
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void clear() {
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std::scoped_lock lock(mLock);
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mQueue.clear();
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};
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/**
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* How many elements are currently stored in the queue.
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* Primary used for debugging.
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* Does not block.
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*/
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size_t size() {
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std::scoped_lock lock(mLock);
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return mQueue.size();
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}
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private:
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const size_t mCapacity;
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/**
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* Used to signal that mQueue is non-empty.
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*/
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std::condition_variable mHasElements;
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/**
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* Lock for accessing and waiting on elements.
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*/
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std::mutex mLock;
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std::vector<T> mQueue GUARDED_BY(mLock);
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};
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} // namespace android
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#endif
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