/*
	shmwriter is  part of the CopyFile.
	It is the child process that writes the buffers into stdout.

*/

#include "def.h"

BUFFER		 *buf[2];
int	shmid[2];
int semaphore =0;  /* it allows me to turn on and off the use of semaphores*/

int emptybuf_sem, fullbuf_sem;

main()
{
	int i;
/* 
   get the shared memory segments and attach it
   the parent must have already created it
*/

	for (i = 0; i < 2; i++) {
		if ( (shmid[i] = shmget(SHMKEY + i, sizeof(BUFFER), 0 )) < 0)
			printf("server: can't get shared memory %d", i);
		if ( (buf[i] = (BUFFER *) shmat(shmid[i], (char *) 0, 0))
							== (BUFFER *) -1)
			printf("server: can't attach shared memory %d", i);
	}
/*
   open the two semaphores.
   The parent must have already created it
*/


	if ( (fullbuf_sem = sem_open(SEMKEY1)) < 0)
		printf("server: can't open full  semaphore");
	if ( (emptybuf_sem = sem_open(SEMKEY2)) < 0)
		printf("server: can't create empty semaphore");

	writer();

	/*
	 * Detach and remove the shared memory segments and
	 * close the semaphores.
	 */

	for (i = 0; i < 2; i++) {
		if (shmdt(buf[i]) < 0)
			printf("client: can't detach shared memory ");
		if (shmctl(shmid[i], IPC_RMID, (struct shmid_ds *) 0) < 0)
			printf("client: can't remove shared memory ");
	}

	/*	sem_close(fullbuf_sem);
	sem_close(emptybuf_sem);*/
	sem_rm(fullbuf_sem);
	sem_rm(emptybuf_sem);	
	exit(0);
}
    
writer()
{
	int i=0;
	while (1) {
	  if (semaphore)
	    sem_wait(fullbuf_sem);
	  printf("buff length =%d\n",buf[i]->size);fflush(stdout);
	  
	  write(1, buf[i]->data, buf[i]->size);
	  
	  if (buf[i]->size<=0)
	    return;
	  if (semaphore)
	    sem_signal(emptybuf_sem);
	  i ^= 1;
        }
}