/*************************************************************************
	> File Name: message_queue.cpp
	> Author: SongTL
	> Mail: songtianlun@comleader.com.cn 
	> Created Time: 2020年07月21日 星期二 16时19分21秒
 ************************************************************************/
# ifndef MSGQUEUE_H
# define MSGQUEUE_H
 
#include <iostream>
#include <cstdlib>
#include <unistd.h> // usleep
#include <fcntl.h>  // threads
#include <pthread.h>
#include <string>   // messages
#include <queue>    // the message queue
 
using namespace std;
 
pthread_mutex_t msgmutex = PTHREAD_MUTEX_INITIALIZER;
 
queue <string> msgq;
 
void *msgreceiver(void *arg)
{
    long qsize;
    string nextmsg;
    while (true)
    {
        if (msgq.empty())
        {
            usleep(10000); // sleep 0.01 sec before trying again
            continue;
        }
 
        // we end up here because there was something in the msg queue
        pthread_mutex_lock( & msgmutex);
        qsize = msgq.size();
        if (qsize > 5)
            cout << "Queue size: " << qsize << endl;
        nextmsg = msgq.front(); // get next message in queue
        msgq.pop(); // remove it from the queue
        pthread_mutex_unlock( & msgmutex);
 
        cout << "Processing value " << nextmsg << endl;
        usleep(2000000);
    }
    pthread_exit((void * )0);
} // msgreceiver()
 
 void *msgtransmitter(void *arg)
 {
    string nextmsg;
    while (true)
    {
        cin >> nextmsg;
        pthread_mutex_lock( & msgmutex);
        msgq.push(nextmsg); // push message onto the queue
        pthread_mutex_unlock( & msgmutex);
    }
    pthread_exit((void * )0);
 } // msgtransmitter()
 
 int main()
 {
    pthread_t thr;
 
    // Create threads
    if (pthread_create( & thr, NULL, msgreceiver, NULL) ||
            pthread_create( & thr, NULL, msgtransmitter, NULL))
    {
        cout << " cannot make thread\n";
        exit(1);
    }
 
    /*
     * At this point the main thread can perform its actions or end
     */
    cout << "** Main thread ends **\n";
    pthread_exit((void * )0);
 
}
 
 # endif // MSGQUEUE_H