Question

I just simply get packets from network, and Enqueue them in one thread and then consume this packets (Dequeue) in an other thread.

So i decide to use boost library to make a shared queue based on
https://www.quantnet.com/cplusplus-multithreading-boost/

template <typename T>
class SynchronisedQueue
{
private:
    std::queue<T> m_queue;  // Use STL queue to store data
    boost::mutex m_mutex;   // The mutex to synchronise on
    boost::condition_variable m_cond;// The condition to wait for

public:

    // Add data to the queue and notify others
    void Enqueue(const T& data)
    {
        // Acquire lock on the queue
        boost::unique_lock<boost::mutex> lock(m_mutex);

        // Add the data to the queue
        m_queue.push(data);

        // Notify others that data is ready
        m_cond.notify_one();

    } // Lock is automatically released here

    // Get data from the queue. Wait for data if not available
    T Dequeue()
    {

        // Acquire lock on the queue
        boost::unique_lock<boost::mutex> lock(m_mutex);

        // When there is no data, wait till someone fills it.
        // Lock is automatically released in the wait and obtained 
        // again after the wait
        while (m_queue.size()==0) m_cond.wait(lock);

        // Retrieve the data from the queue
        T result=m_queue.front(); m_queue.pop();
        return result;

    } // Lock is automatically released here
};

The problem is , while not getting any data, Dequeue() method
blocks my consumer thread, and when i want to terminate consumer
thread i can not able to end it or stop it sometimes.

What is the suggested way to end blocking of Dequeue(), so that i can safely terminate the thread that consume packets?
Any ideas suggestions?

PS: The site https://www.quantnet.com/cplusplus-multithreading-boost/ use “boost::this_thread::interruption_point();” for stopping consumer thread … Because of my legacy code structure this is not possible for me…

Based on Answer I update Shared Queue like this:

#include <queue>
 #include <boost/thread.hpp>  

template <typename T>
class SynchronisedQueue
{
public:

    SynchronisedQueue()
    {
        RequestToEnd = false;  
        EnqueueData = true;
    }
    void Enqueue(const T& data)
    {
        boost::unique_lock<boost::mutex> lock(m_mutex);

        if(EnqueueData)
        {
            m_queue.push(data);
            m_cond.notify_one();
        }

    } 


    bool TryDequeue(T& result)
    {
        boost::unique_lock<boost::mutex> lock(m_mutex);

        while (m_queue.empty() && (! RequestToEnd)) 
        { 
            m_cond.wait(lock);
        }

        if( RequestToEnd )
        {
             DoEndActions();
             return false;
        }

        result= m_queue.front(); m_queue.pop();

        return true;
    }

    void StopQueue()
    {
        RequestToEnd =  true;
        Enqueue(NULL);        
    }

    int Size()
    {
        boost::unique_lock<boost::mutex> lock(m_mutex);
        return m_queue.size();

    }

private:

    void DoEndActions()
    {
        EnqueueData = false;

        while (!m_queue.empty())  
        {
            m_queue.pop();
        }
    }



    std::queue<T> m_queue;              // Use STL queue to store data
    boost::mutex m_mutex;               // The mutex to synchronise on
    boost::condition_variable m_cond;            // The condition to wait for

    bool RequestToEnd;
    bool EnqueueData;
};

And Here is my Test Drive:

#include <iostream>
#include <string>

#include "SynchronisedQueue.h"

using namespace std;

SynchronisedQueue<int> MyQueue;

void InsertToQueue()
{
    int i= 0;

    while(true)
    {
        MyQueue.Enqueue(++i);
    }

}

void ConsumeFromQueue()
{
    while(true)
    {
        int number;

        cout << "Now try to dequeue" << endl;

        bool success = MyQueue.TryDequeue(number);

        if(success)
        {

            cout << "value is " << number << endl;

        }

        else
        {
            cout << " queue is stopped" << endl;
            break;

        }
    }


    cout << "Que size is : " << MyQueue.Size() <<  endl;
}



int main()
{

    cout << "Test Started" << endl;

    boost::thread startInsertIntoQueue = boost::thread(InsertToQueue);
    boost::thread consumeFromQueue = boost::thread(ConsumeFromQueue);

    boost::this_thread::sleep(boost::posix_time::seconds(5)); //After 5 seconds

    MyQueue.StopQueue();

    int endMain;

    cin >> endMain;


    return 0;
}

For now it seems to work…Based on new suggestions:

i change Stop Method as:

void StopQueue()
    {
        boost::unique_lock<boost::mutex> lock(m_mutex);
        RequestToEnd =  true;
        m_cond.notify_one();          
    }

Answer 1

2 easy solutions to let the thread end:

1. send an end message on the queue.

2. add another condition to the condition variable to command to end

   while(queue.empty() && (! RequestToEnd)) m_cond.wait(lock);
   if (RequestToEnd) { doEndActions(); }
   else { T result=m_queue.front(); m_queue.pop(); return result; }