threading object function c++ - c++

Question

i'm having trouble with some threads in my program
I'm new in this thread material
I'm trying to start 2 threads on 2 different object function and it seems that they are not working at the same time (t1 works and t2 dont)..
edit:
the function of t1 works but t2 doesnt work. i checked t2 and t1, on their own they work, but together its like t1 prevents t2 from working
here is the main:
MessagesSender MSM=MessagesSender();
MSM.Push_user("ronik");
MSM.Push_user("ligal");
thread t1(&MessagesSender::DataRead,&MSM);
thread t2(&MessagesSender::DataSend, &MSM);
t1.join();
t2.join();
return 0;
here are is the function of t1:
void MessagesSender::DataRead()
{
ifstream file_read;
ofstream file_delete;
string line;
while (true)
{
file_read.open("data.txt"); // opens the file
mtx.lock(); // locks the use of THOR
while (getline(file_read, line)) // reads to THOR
{
cout << "im reading now" << endl;
this->THOR.push(line);
}
mtx.unlock(); // unlock the use of THOR
file_read.close(); // closes the file for reading
file_delete.open("data.txt", ios::out | ios::trunc);/// opens the file and deletes the content/data
file_delete.close(); // closes the file
cout << "im sleeping now" << endl;
print_THOR();
this_thread::sleep_for(chrono::seconds(30)); // makes the thread sleep for 1 minute
}
}
here is the function of t2:
void MessagesSender::DataSend()
{
ofstream file_send;
file_send.open("output.txt");
set<string>::iterator SEI;
while (true)
{
mtx.lock();
while (!THOR.empty()) // while that prints all the THOR lines
{
for (SEI = ConUsers.begin(); SEI != ConUsers.end(); SEI++) /// to print the users
{
if (THOR.empty())
{
break;
}
string p2(THOR.front());
cout << "im sending now" << endl;
file_send << *SEI << ": " << p2 << endl;
}
}
mtx.unlock();
THOR.push("im empty");
print_THOR();
this_thread::sleep_for(chrono::seconds(30));
}
file_send.close();
}

Answer 1

I believe this may be an issue of buffered streams. You are using the std::cout and calling std::endl. This causes the thread to pause until the data has been written to the console (slow). I've done this before and had the same problem. t2 is getting hung up on the buffered stream, waiting for it to be cleared while t1 has used it. Try replacing your std::endl with regular '\n' then just do a std::cout << std::flush; at the end of your program.