/**
 * Starting point code from:
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Seventh Edition
 * Copyright John Wiley & Sons - 2005.
 * Implements pthread based producer/consumer solution using semaphores.
 *
 */

/* Modified by Krishna Sivalingam - Feb. 2006 */

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

#define BUFFER_SIZE 10
typedef struct 
{
  int pc_buffer[BUFFER_SIZE];
  int in;
  int out;
} my_buffer;

my_buffer Buffer1;		/* Data Shared by threads. */
sem_t full, empty, mutex;
 
void *producer(); /* the thread */
void *consumer(); /* the thread */

int main(int argc, char *argv[])
{
  pthread_t tid1, tid2; /* the thread identifier */
  pthread_attr_t attr; /* set of attributes for the thread */

  sem_init(&full, 0, 0);
  sem_init(&empty, 0, BUFFER_SIZE);
  sem_init(&mutex, 0, 1);
  
  /* get the default attributes */
  pthread_attr_init(&attr);

  /* create the threads */
  pthread_create(&tid1,&attr,producer, NULL);
  pthread_create(&tid2,&attr,consumer, NULL);

  /* now wait for threads to exit */
  pthread_join(tid1,NULL);

  pthread_join(tid2,NULL);

}

/**
 * Producer thread
 */
void *producer(void *param) 
{
  int i, err;
  
  srandom(10000);		/* Initialize random seed. */

  for (i = 0; i < 20; i++) 
    {

      sleep(random() % 2);		/* Sleep for random time. */ 


      sem_wait(&empty);
      sem_wait(&mutex); 

      /* Add item to buffer */
      Buffer1.pc_buffer[Buffer1.in] = (int) random() % 1000;  

      fprintf(stdout," Item %d produced: %d\n", i,
      Buffer1.pc_buffer[Buffer1.in]); 

      /* Update in pointer. */
      Buffer1.in = (Buffer1.in + 1) % BUFFER_SIZE;
      sem_post(&mutex);
      sem_post(&full);
      
    } /* End for; produces 20 items */

  pthread_exit(0);
}

/**
 * Consumer thread
 */
void *consumer(void *param) 
{

  int i, err;

  for (i = 0; i < 20; i++) 
    {

      sem_wait(&full);
      sem_wait(&mutex); 

      fprintf(stdout," \t\t\tItem %d consumed: %d\n", i,
		  Buffer1.pc_buffer[Buffer1.out]);
	  
      /* Update out pointer. */
      Buffer1.out = (Buffer1.out + 1) % BUFFER_SIZE;

      sleep(random() % 2);		/* Sleep for random time. */ 
      sem_post(&mutex);
      sem_post(&empty);
      
    } /* End for; consumes 20 items */
  
  pthread_exit(0);
}