113 lines
3.0 KiB
C
113 lines
3.0 KiB
C
|
/*
|
||
|
|
* Copyright (C) 2019 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 _UI_INPUT_BLOCKING_QUEUE_H
|
||
|
|
#define _UI_INPUT_BLOCKING_QUEUE_H
|
||
|
|
|
||
|
|
#include "android-base/thread_annotations.h"
|
||
|
|
#include <condition_variable>
|
||
|
|
#include <mutex>
|
||
|
|
#include <vector>
|
||
|
|
|
||
|
|
namespace android {
|
||
|
|
|
||
|
|
/**
|
||
|
|
* A FIFO queue that stores up to <i>capacity</i> objects.
|
||
|
|
* Objects can always be added. Objects are added immediately.
|
||
|
|
* If the queue is full, new objects cannot be added.
|
||
|
|
*
|
||
|
|
* The action of retrieving an object will block until an element is available.
|
||
|
|
*/
|
||
|
|
template <class T>
|
||
|
|
class BlockingQueue {
|
||
|
|
public:
|
||
|
|
BlockingQueue(size_t capacity) : mCapacity(capacity) {
|
||
|
|
mQueue.reserve(mCapacity);
|
||
|
|
};
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Retrieve and remove the oldest object.
|
||
|
|
* Blocks execution while queue is empty.
|
||
|
|
*/
|
||
|
|
T pop() {
|
||
|
|
std::unique_lock lock(mLock);
|
||
|
|
android::base::ScopedLockAssertion assumeLock(mLock);
|
||
|
|
mHasElements.wait(lock, [this]() REQUIRES(mLock) { return !this->mQueue.empty(); });
|
||
|
|
T t = std::move(mQueue.front());
|
||
|
|
mQueue.erase(mQueue.begin());
|
||
|
|
return t;
|
||
|
|
};
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Add a new object to the queue.
|
||
|
|
* Does not block.
|
||
|
|
* Return true if an element was successfully added.
|
||
|
|
* Return false if the queue is full.
|
||
|
|
*/
|
||
|
|
bool push(T&& t) {
|
||
|
|
{
|
||
|
|
std::scoped_lock lock(mLock);
|
||
|
|
if (mQueue.size() == mCapacity) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
mQueue.push_back(std::move(t));
|
||
|
|
}
|
||
|
|
mHasElements.notify_one();
|
||
|
|
return true;
|
||
|
|
};
|
||
|
|
|
||
|
|
void erase(const std::function<bool(const T&)>& lambda) {
|
||
|
|
std::scoped_lock lock(mLock);
|
||
|
|
mQueue.erase(std::remove_if(mQueue.begin(), mQueue.end(),
|
||
|
|
[&lambda](const T& t) { return lambda(t); }), mQueue.end());
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Remove all elements.
|
||
|
|
* Does not block.
|
||
|
|
*/
|
||
|
|
void clear() {
|
||
|
|
std::scoped_lock lock(mLock);
|
||
|
|
mQueue.clear();
|
||
|
|
};
|
||
|
|
|
||
|
|
/**
|
||
|
|
* How many elements are currently stored in the queue.
|
||
|
|
* Primary used for debugging.
|
||
|
|
* Does not block.
|
||
|
|
*/
|
||
|
|
size_t size() {
|
||
|
|
std::scoped_lock lock(mLock);
|
||
|
|
return mQueue.size();
|
||
|
|
}
|
||
|
|
|
||
|
|
private:
|
||
|
|
const size_t mCapacity;
|
||
|
|
/**
|
||
|
|
* Used to signal that mQueue is non-empty.
|
||
|
|
*/
|
||
|
|
std::condition_variable mHasElements;
|
||
|
|
/**
|
||
|
|
* Lock for accessing and waiting on elements.
|
||
|
|
*/
|
||
|
|
std::mutex mLock;
|
||
|
|
std::vector<T> mQueue GUARDED_BY(mLock);
|
||
|
|
};
|
||
|
|
|
||
|
|
|
||
|
|
} // namespace android
|
||
|
|
#endif
|