/* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
/* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

pthread_mutex_t count_mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t condvar = PTHREAD_COND_INITIALIZER;

void * functionCount1();
void * functionCount2();
int count = 0;

#define COUNT_DONE  10
#define COUNT_HALT1  3
#define COUNT_HALT2  6

int main (int argc, const char ** argv)
{
   pthread_t thread1, thread2;

   pthread_create( &thread1, NULL, &functionCount1, NULL);
   pthread_create( &thread2, NULL, &functionCount2, NULL);

   pthread_join( thread1, NULL);
   pthread_join( thread2, NULL);

   printf("Final count: %d\n",count);

   exit(0);
}

void * functionCount1 (void)
{
   for(;;)
   {
      // Lock mutex and then wait for signal to relase mutex
      pthread_mutex_lock(&count_mutex);

      // Wait while functionCount2() operates on count
      // mutex unlocked if condition varialbe in functionCount2() signaled.
      pthread_cond_wait(&condvar, &count_mutex);
      count++;
      printf("Counter value functionCount1: %d\n", count);

      pthread_mutex_unlock(&count_mutex);

      if (count >= COUNT_DONE)
          return NULL;
   }
}

void * functionCount2 (void)
{
    for(;;)
    {
       pthread_mutex_lock(&count_mutex);

       if (count < COUNT_HALT1 || count > COUNT_HALT2)
       {
          // Condition of if statement has been met.
          // Signal to free waiting thread by freeing the mutex.
          // Note: functionCount1() is now permitted to modify "count".
          pthread_cond_signal(&condvar);
       }
       else
       {
          count++;
          printf("Counter value functionCount2: %d\n", count);
       }

       pthread_mutex_unlock(&count_mutex);

       if (count >= COUNT_DONE)
           return NULL;
    }

}