#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>


#define SIZE 10
#define KEY  0x123456
#define PERMS IPC_CREAT | 0600

struct misDatos {
   int cin;     // Input position in buffer
   int cout;    // Output position in buffer
   int counter; // Items in buffer
   char buffer[ SIZE ]; // buffer
};


int main( int argc, char ** argv ) {

   int id;
   struct misDatos * x;
   int size = sizeof( struct misDatos );

   srandom( time( NULL ) );

   id = shmget( KEY, size, PERMS );
   x = (struct misDatos *) shmat( id, NULL, 0 );
   x->cin = 0;
   x->cout = 0;
   x->counter = 0;
   if ( fork() ) {
      consumer( x );
   } else {
      producer( x );
   }

   shmctl( id, IPC_RMID, NULL );

}


int producer( struct misDatos * p ) {

   int i, j;
   int t;

   for ( i = 0; i < 23; i++ ) {
       sleep( random()  % 2 );
       while ( p->counter >= SIZE ) {
          printf( "productor esperando por espacio en el buffer ...\n" );
          sleep( random()  % 2 );
       }
       p->buffer[ p->cin++ ] = 'A' + i;
       p->cin %= SIZE;
       p->counter++;
       printf( "item producido [%c] counter = %d \n", 'A' +  i, p->counter );
   }
   exit( 0 );
}


int consumer( struct misDatos * c ) {

   int i, j;
   int t;

   for ( i = 0; i < 23; i++ ) {
       sleep( random() % 5 );
       while ( c->counter <= 0 ) {
          printf( "consumidor esperando por datos ...\n" );
       }

       printf( "Item consumido = %c \n", c->buffer[ c->cout++ ] );
       c->cout %= SIZE;
       c->counter--;
   }
}