/* ---------------------------------------------------------------- */
/* pingpong.c:                                                      */
/*   This program forces an alternating execution of two threads.   */
/* ---------------------------------------------------------------- */

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

#include  "mtuThread.h"

void  Ping(int);                        /* thread prototypes        */
void  Pong(int);

SEM_t StopPing, StopPong;
int   Count;

/* ---------------------------------------------------------------- */
/* Ping():                                                          */
/*   Function Ping()                                                */
/* ---------------------------------------------------------------- */

void  Ping(int  ID)
{
     while (1) {                        /* loop forever             */
          SEMAPHORE_WAIT(StopPing);     /* stop until released      */
               printf("Ping-");         /* print Ping-              */
          SEMAPHORE_SIGNAL(StopPong);   /* release Pong             */
     }

     THREAD_EXIT();
}

/* ---------------------------------------------------------------- */
/* Pong():                                                          */
/*   Function Pong()                                                */
/* ---------------------------------------------------------------- */

void  Pong(int  ID)
{
     do {                               /* loop for 'Count' times   */
          SEMAPHORE_WAIT(StopPong);     /* stop until released      */
               printf("Pong\n");        /* append Pong to Ping-     */
          SEMAPHORE_SIGNAL(StopPing);   /* release Ping             */
          Count--;
     } while (Count > 0);               /* done if Count = 0        */

     THREAD_EXIT();
}

/* ---------------------------------------------------------------- */
/*                        The main program                          */
/* ---------------------------------------------------------------- */
int  main(int argc, char *argv[])
{
     THREAD_t  THREAD_Ping, THREAD_Pong;

     Count = 10;
     if (argc != 2) {
          printf("Use %s #-of-iterations\n", argv[0]);
          printf("No. of iterations is set to %d\n", Count);
     }
     else 
          Count = abs(atoi(argv[1]));

     StopPing = SEMAPHORE_INIT(1);      /* Ping goes first          */
     StopPong = SEMAPHORE_INIT(0);      /* Pong stops until informed*/

     THREAD_Ping = THREAD_CREATE(Ping, THREAD_SIZE, THREAD_NORMAL, 
				 1, (char **) 0);
     THREAD_Pong = THREAD_CREATE(Pong, THREAD_SIZE, THREAD_NORMAL, 
				 2, (char **) 0);

     THREAD_JOIN(THREAD_Pong);          /* can only join Pong()     */

     return 0;
}