/* example of single producer and multiple consumers
  
   This differs from prodcons0 in having calls to pthread_yield()
   at points where threads are busy-waiting.  What is the advantage
   of doing this?

 */

#define _XOPEN_SOURCE 500
#define _REENTRANT
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <stdio.h>
#include <values.h>
#include <errno.h>
#include <sched.h>

#define BUF_SIZE 10
int b[BUF_SIZE];
int in = 0, out = 0;

pthread_t consumer;
pthread_t producer;

void * consumer_body (void *arg) {
/* create one unit of data and put it in the buffer
   Assumes arg points to an element of the array id_number,
   identifying the current thread. */
  int tmp;
  int self = *((int *) arg);

  fprintf(stderr, "consumer thread starts\n"); 
  for (;;) {
     /* wait for buffer to fill */
     while (in == out) 
       sched_yield();
     /* take one unit of data from the buffer */
     tmp = b[out];
     out = (out + 1) % BUF_SIZE;     
     /* copy the data to stdout */
     fprintf (stdout, "thread %d: %d\n", self, tmp);
  }
  fprintf(stderr, "consumer thread exits\n"); 
  return NULL;
}

void * producer_body (void * arg) {
/* takes one unit of data from the buffer */
   int i;
   fprintf(stderr, "producer thread starts\n"); 
   for (i = 0; i < MAXINT; i++) {
     /* wait for space in buffer */
     while (((in + 1) % BUF_SIZE) == out)
        sched_yield();
     /* put value i into the buffer */
     b[in] = i;
     in = (in + 1) % BUF_SIZE;     
  }
  return NULL;
}

int main () {
   int result;
   pthread_attr_t attrs;

   /* use default attributes */
   pthread_attr_init (&attrs);

   /* create producer thread */
   if ((result = pthread_create (
          &producer, /* place to store the id of new thread */
          &attrs,
          producer_body,
          NULL))) {
      fprintf (stderr, "pthread_create: %d\n", result);
      exit (-1);
   } 
   fprintf(stderr, "producer thread created\n"); 

   /* create consumer thread */
   if ((result = pthread_create (
       &consumer,
       &attrs,
       consumer_body,
       NULL))) {
     fprintf (stderr, "pthread_create: %d\n", result);
     exit (-1);
   } 
   fprintf(stderr, "consumer threads created\n");

   /* give the other threads a chance to run */
   sleep (10);
   return 0;
}