usr/src/usr.bin/make/lst.lib/lstIsAtEnd.c

/*
 * Copyright (c) 1988, 1989, 1990 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 are permitted
 * provided that: (1) source distributions retain this entire copyright
 * notice and comment, and (2) distributions including binaries display
 * the following acknowledgement:  ``This product includes software
 * developed by the University of California, Berkeley and its contributors''
 * in the documentation or other materials provided with the distribution
 * and in all advertising materials mentioning features or use of this
 * software. 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char sccsid[] = "@(#)lstIsAtEnd.c        5.3 (Berkeley) 6/1/90";
#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));
}