lstisatend.c

早期freebsd实现

/*
 * Copyright (c) 1988, 1989, 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)lstIsAtEnd.c	8.1 (Berkeley) 6/6/93";
#endif /* not lint */

/*-
 * LstIsAtEnd.c --
 *	Tell if the current node is at the end of the list.
 *	The sequential functions access the list in a slightly different way.
 *	CurPtr points to their idea of the current node in the list and they
 *	access the list based on it. Because the list is circular, Lst_Next
 *	and Lst_Prev will go around the list forever. Lst_IsAtEnd must be
 *	used to determine when to stop.
 */

#include	"lstInt.h"

/*-
 *-----------------------------------------------------------------------
 * Lst_IsAtEnd --
 *	Return true if have reached the end of the given list.
 *
 * Results:
 *	TRUE if at the end of the list (this includes the list not being
 *	open or being invalid) or FALSE if not. We return TRUE if the list
 *	is invalid or unopend so as to cause the caller to exit its loop
 *	asap, the assumption being that the loop is of the form
 *	    while (!Lst_IsAtEnd (l)) {
 *	    	  ...
 *	    }
 *
 * Side Effects:
 *	None.
 *
 *-----------------------------------------------------------------------
 */
Boolean
Lst_IsAtEnd (l)
    Lst	    l;
{
    register List list = (List) l;

    return (!LstValid (l) || !list->isOpen ||
	    (list->atEnd == Head) || (list->atEnd == Tail));
}