snapcast/common/queue.h

/***
    This file is part of snapcast
    Copyright (C) 2014-2016  Johannes Pohl

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
***/

#ifndef QUEUE_H
#define QUEUE_H

#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>

template <typename T>
class Queue
{
public:

	T pop()
	{
		std::unique_lock<std::mutex> mlock(mutex_);
		while (queue_.empty())
		{
			cond_.wait(mlock);
		}
		auto val = queue_.front();
		queue_.pop();
		return val;
	}

	T front()
	{
		std::unique_lock<std::mutex> mlock(mutex_);
		while (queue_.empty())
			cond_.wait(mlock);

		return queue_.front();
	}

	bool try_pop(T& item, std::chrono::microseconds timeout)
	{
		std::unique_lock<std::mutex> mlock(mutex_);

		if(!cond_.wait_for(mlock, timeout, [this] { return !queue_.empty(); }))
			return false;

		item = std::move(queue_.front());
		queue_.pop();

		return true;
	}

	bool try_pop(T& item, std::chrono::milliseconds timeout)
	{
		return try_pop(item, std::chrono::duration_cast<std::chrono::microseconds>(timeout));
	}

	void pop(T& item)
	{
		std::unique_lock<std::mutex> mlock(mutex_);
		while (queue_.empty())
		{
			cond_.wait(mlock);
		}
		item = queue_.front();
		queue_.pop();
	}

	void push(const T& item)
	{
		std::unique_lock<std::mutex> mlock(mutex_);
		queue_.push(item);
		mlock.unlock();
		cond_.notify_one();
	}

	void push(T&& item)
	{
		std::unique_lock<std::mutex> mlock(mutex_);
		queue_.push(std::move(item));
		mlock.unlock();
		cond_.notify_one();
	}

	size_t size() const
	{
		std::unique_lock<std::mutex> mlock(mutex_);
		return queue_.size();
	}

	bool empty() const
	{
		return (size() == 0);
	}

	Queue()=default;
	Queue(const Queue&) = delete;            // disable copying
	Queue& operator=(const Queue&) = delete; // disable assignment

private:
	std::queue<T> queue_;
	mutable std::mutex mutex_;
	std::condition_variable cond_;
};


#endif