synchronized_queue.h

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#ifndef SYNCHRONIZED_QUEUE_H_
#define SYNCHRONIZED_QUEUE_H_
 
#include <condition_variable>
#include <mutex>
#include <queue>
#include <utility>
 
struct msg {
        virtual ~msg() {}
};
 
struct msg_quit : public msg {};
 
template<typename T = struct msg *, int max_len = 1>
class synchronized_queue {
public:
        int size()
        {
                std::unique_lock<std::mutex> l(m_lock);
                return m_queue.size();
        }
 
        void push(T const & message)
        {
                std::unique_lock<std::mutex> l(m_lock);
                if (max_len != -1) {
                        m_queue_decremented.wait(l, [this]{return m_queue.size() < (unsigned int) max_len;});
                }
                m_queue.push(message);
                l.unlock();
                m_queue_incremented.notify_one();
        }
 
        void push(T && message)
        {
                std::unique_lock<std::mutex> l(m_lock);
                if (max_len != -1) {
                        m_queue_decremented.wait(l, [this]{return m_queue.size() < (unsigned int) max_len;});
                }
                m_queue.push(std::move(message));
                l.unlock();
                m_queue_incremented.notify_one();
        }
 
        T pop(bool nonblocking = false)
        {
                std::unique_lock<std::mutex> l(m_lock);
                if (m_queue.size() == 0 && nonblocking) {
                        return T();
                }
 
                m_queue_incremented.wait(l, [this]{return m_queue.size() > 0;});
                T ret = std::move(m_queue.front());
                m_queue.pop();
 
                l.unlock();
                m_queue_decremented.notify_one();
                return ret;
        }
 
        template<typename Rep, typename Period>
        bool timed_pop(T& result, std::chrono::duration<Rep, Period> const& timeout)
        {
                std::unique_lock<std::mutex> l(m_lock);
                if (!m_queue_incremented.wait_for(l, timeout, [this]{return m_queue.size() > 0;})) {
                        return false;
                }
                result = std::move(m_queue.front());
                m_queue.pop();
                l.unlock();
                m_queue_decremented.notify_one();
                return true;
        }
 
private:
        std::queue<T>           m_queue;
        std::mutex              m_lock;
        std::condition_variable m_queue_decremented;
        std::condition_variable m_queue_incremented;
};
 
#ifndef NO_EXTERN_MSGQ_MSG
extern template class synchronized_queue<msg *, -1>;
extern template class synchronized_queue<msg *, 1>;
#endif
 
#endif // SYNCHRONIZED_QUEUE_H_