/*****************************************************************************
			
			buffer pool management primitives
			 
******************************************************************************/


/*****************************************************************************
			initialize a buffer pool
******************************************************************************/

int    init_pool (poolptr pp, int pool_length)

{	int i ;
	pp->pool_size=pool_length;
	sema_init(&pp->poolsem,pp->pool_size,USYNC_THREAD,0);
	mutex_init(&pp->poolmut,USYNC_THREAD,0);
	pp->front=&(pp->bufs[0]);
       	for (i=0; i<pp->pool_size - 1; i ++)
		pp->bufs[i].next = &(pp->bufs[i+1]);
	pp->rear=&(pp->bufs[pp->pool_size-1]);
}

/*****************************************************************************
			check a buffer pool
******************************************************************************/


bufptr check_pool(poolptr pp)

{ 	bufptr bp;
	bp=pp->front;
	return(bp);
}


/*****************************************************************************
			get a buffer from a pool
******************************************************************************/

bufptr get_buf(poolptr pp)

{ 	bufptr bp;
	sema_wait(&pp->poolsem);
	mutex_lock(&pp->poolmut);
	bp= pp->front;
	pp->front=bp->next;
	mutex_unlock(&pp->poolmut);	
	return(bp);
}



/*****************************************************************************
			put a buffer to a pool
******************************************************************************/

int put_buf(poolptr pp, bufptr bp)

{	bp->next=NULL;
	mutex_lock(&pp->poolmut);
	pp->rear->next=bp;
	pp->rear=bp;
	if (pp->front==NULL) pp->front=bp;
	mutex_unlock(&pp->poolmut);
	sema_post(&pp->poolsem);
}