/* =================================================================
   Reader/writer
   ================================================================= */

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

#define N   1000000
#define MAX 10

int nItems = 0;     // Number of items in buffer
int buf[MAX];
int writePtr, readPtr;

pthread_mutex_t  mutex;  // Protect nItems
pthread_mutex_t  Wr;     // Used to block writer
pthread_mutex_t  Rd;     // Used to block reader


void *writer(void *arg)
{
   int i, x, sum;

   sum = 0;

   for ( i = 0; i < N; i++ )
   {
      x = rand()%100;               // Produce an item

      sum += x;

      pthread_mutex_lock(&mutex);   // Block writer

      if ( nItems == MAX )
      {
	  // Buffer is full
          pthread_mutex_lock(&Wr); // Block writer
                                   // Redaer must unblock it !
      }

      buf[writePtr] = x;             // Put x in buffer      
      writePtr = (writePtr+1) % N; 

      if ( 
         UNBLOCK reader;     
   }
}



/* =======================
   MAIN
   ======================= */

int main(int argc, char *argv[])
{
   int i, num_threads;
   pthread_t tid[100];	/* Thread ID used for thread_join() */
   int param[100];	/* used to store parameters for threads */
   pthread_attr_t attr;    

   pthread_attr_init(&attr);         
   
   /* -----
      Check command line
      ----- */
   if ( argc != 2 )
   {
      cout << "Usage: " << argv[0] << " Num_Threads" << endl;
      exit(1);
   }

   /* -----
      Get number of intervals and number of threads
      ----- */
   num_threads = atoi(argv[1]);

   /* ------
      Create threads
      ------ */
   for (i = 0; i < num_threads; i = i + 1)
   {
      param[i] = 1001 + i;

      if ( pthread_create(&tid[i], &attr, worker, &param[i]) )
      {
	 cout << "Cannot create thread" << endl;
	 exit(1);
      }
   }

   for (i = 0; i < num_threads; i = i + 1)
      pthread_join(tid[i], NULL);
}