concurrent_queue.h

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// Aleth: Ethereum C++ client, tools and libraries.
// Copyright 2018 Aleth Authors.
// Licensed under the GNU General Public License, Version 3.
 
#pragma once
 
#include "Exceptions.h"
 
#include <condition_variable>
#include <mutex>
#include <queue>
#include <utility>
 
namespace dev
{
template <typename _T, typename _QueueT = std::queue<_T>>
class concurrent_queue
{
public:
    template <typename _U>
    void push(_U&& _elem)
    {
        {
            std::lock_guard<decltype(x_mutex)> guard{x_mutex};
            m_queue.push(std::forward<_U>(_elem));
        }
        m_cv.notify_one();
    }
 
    _T pop()
    {
        std::unique_lock<std::mutex> lock{ x_mutex };
        m_cv.wait(lock, [this] { return !m_queue.empty(); });
        auto item = std::move(m_queue.front());
        m_queue.pop();
        return item;
    }
 
    _T pop(std::chrono::milliseconds const& _waitDuration)
    {
        std::unique_lock<std::mutex> lock{x_mutex};
        if (!m_cv.wait_for(lock, _waitDuration, [this] { return !m_queue.empty(); }))
            BOOST_THROW_EXCEPTION(WaitTimeout());
 
        auto item = std::move(m_queue.front());
        m_queue.pop();
        return item;
    }
 
private:
    _QueueT m_queue;
    std::mutex x_mutex;
    std::condition_variable m_cv;
};
 
}  // namespace dev