allwpilib/src/support/ConcurrentQueue.h

//
// Copyright (c) 2013 Juan Palacios juan.palacios.puyana@gmail.com
// Subject to the BSD 2-Clause License
// - see < http://opensource.org/licenses/BSD-2-Clause>
//

#ifndef CONCURRENT_QUEUE_
#define CONCURRENT_QUEUE_

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

template <typename T>
class ConcurrentQueue
{
public:
    T pop() 
    {
        std::unique_lock<std::mutex> mlock(mutex_);
        while (queue_.empty())
        {
            cond_.wait(mlock);
        }
        auto item = std::move(queue_.front());
        queue_.pop();
        return item;
    }

    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();
    }

    ConcurrentQueue() = default;
    ConcurrentQueue(const ConcurrentQueue&) = delete;
    ConcurrentQueue& operator=(const ConcurrentQueue&) = delete;
  
private:
    std::queue<T> queue_;
    std::mutex mutex_;
    std::condition_variable cond_;
};

#endif