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/*
* Copyright 2019 Xilinx Inc.
*
* 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 DEEPHI_RING_QUEUE_HPP_
#define DEEPHI_RING_QUEUE_HPP_
#include <condition_variable>
#include <mutex>
#include <vector>
namespace vitis {
namespace ai {
/**
* A thread safe queue with a size limit.
* When it is full, it will overwrite the earliest element.
*/
template <typename T>
class RingQueue {
public:
explicit RingQueue(std::size_t capacity)
: capacity_(capacity),
buffer_(capacity),
size_(0U),
front_(0U),
rear_(0U) {}
/**
* Return the maxium size of the queue.
*/
std::size_t capacity() const { return capacity_; }
/**
* Return the size of the queue.
*/
std::size_t size() const { return size_; }
/**
* Copy the value to the end of this queue.
*/
void push(const T& new_value) {
std::lock_guard<std::mutex> lock(mtx_);
buffer_[rear_] = new_value;
rear_ = (rear_ + 1) % capacity_;
if (size_ >= capacity_) {
front_ = rear_;
} else {
++size_;
}
}
/**
* Get the first element in the queue and remove it from the queue.
* Return false if the queue is empty
*/
bool pop(T& value) {
std::lock_guard<std::mutex> lock(mtx_);
bool res = false;
if (size_ > 0) {
value = buffer_[front_];
front_ = (front_ + 1) % capacity_;
--size_;
res = true;
}
return res;
}
/**
* Look at the top of the queue. i.e. the element that would be poped.
* Warning: the returned pointer can become dangled
*/
T* pop() {
std::lock_guard<std::mutex> lock(mtx_);
T* res = nullptr;
if (size_ > 0) {
res = &buffer_[front_];
front_ = (front_ + 1) % capacity_;
--size_;
}
return res;
}
/**
* Return the first element in the queue and remove it from the queue.
* Warning: the returned pointer can become dangled
*/
T* top() {
std::lock_guard<std::mutex> lock(mtx_);
T* res = nullptr;
if (size_ > 0) {
res = &buffer_[front_];
}
return res;
}
private:
std::size_t capacity_;
std::vector<T> buffer_;
std::size_t size_;
std::size_t front_;
std::size_t rear_;
mutable std::mutex mtx_;
};
} // namespace ai
} // namespace vitis
#endif
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