/*-
 * LstDeQueue.c --
 *	Remove the node and return its datum from the head of the list
 *
 * Copyright (c) 1988 by University of California Regents
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appears in all copies.  Neither the University of California nor
 * Adam de Boor makes any representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */
#ifndef lint
static char *rcsid =
"$Id: lstDeQueue.c,v 1.5 88/11/17 20:52:11 adam Exp $ SPRITE (Berkeley)";
#endif lint

#include	"lstInt.h"

/*-
 *-----------------------------------------------------------------------
 * Lst_DeQueue --
 *	Remove and return the datum at the head of the given list.
 *
 * Results:
 *	The datum in the node at the head or (ick) NIL if the list
 *	is empty.
 *
 * Side Effects:
 *	The head node is removed from the list.
 *
 *-----------------------------------------------------------------------
 */
ClientData
Lst_DeQueue (l)
    Lst	    	  l;
{
    ClientData	  rd;
    register ListNode	tln;
    
    tln = (ListNode) Lst_First (l);
    if (tln == NilListNode) {
	return ((ClientData) NIL);
    }
    
    rd = tln->datum;
    if (Lst_Remove (l, (LstNode)tln) == FAILURE) {
	return ((ClientData) NIL);
    } else {
	return (rd);
    }
}