Listing 8: The Printer Class
#include <iostream>
#include <signal.h>
#include "printer.hpp"

// Constructor
printer::printer()
{
  // Arrange to catch SIGUSR1 using the calcFinished method
  struct sigaction act;
  act.sa_handler = printer::calcFinished;
  sigfillset(&(act.sa_mask));
  sigaction(SIGUSR1, &act, NULL);
}

// Signal handler for catching Calculator completed signal (SIGUSR1)
void printer::calcFinished(int sigNo)
{
  // If the signal is SIGUSR1 just return and let the thread continue
  if (SIGUSR1 == sigNo)
    return;
  
  // Otherwise terminate the thread
  else
    thr_exit(NULL);
}

// Retrieve powers of 2 from the calculator queue and print them
void printer::printPowersOfTwo(calculator *calc)
{

  // Loop continually, until the thread is killed
  while(true)
  {

    // Wait for the data ready signal from the calculator
    mutex_lock(&calc->queueReady);
    cond_wait(&calc->signalQueueReady, &calc->queueReady);  

    // Retrieve and display values from the queue
    while (!calc->power2Queue.empty())
    {
      int data = calc->power2Queue.front();
      calc->power2Queue.pop();
      cout << printerName << ":" << data << endl;
    }

    // Indicate that the queue is now empty
    mutex_unlock(&calc->queueReady);
  }
}