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Diffstat (limited to 'lst.lib/lstNext.c')
| -rw-r--r-- | lst.lib/lstNext.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/lst.lib/lstNext.c b/lst.lib/lstNext.c new file mode 100644 index 0000000..5c2e0ee --- /dev/null +++ b/lst.lib/lstNext.c @@ -0,0 +1,120 @@ +/* $NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $ */ + +/* + * 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. 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 MAKE_NATIVE +static char rcsid[] = "$NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $"; +#else +#include <sys/cdefs.h> +#ifndef lint +#if 0 +static char sccsid[] = "@(#)lstNext.c 8.1 (Berkeley) 6/6/93"; +#else +__RCSID("$NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $"); +#endif +#endif /* not lint */ +#endif + +/*- + * LstNext.c -- + * Return the next node for a 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_Next -- + * Return the next node for the given list. + * + * Results: + * The next node or NULL if the list has yet to be opened. Also + * if the list is non-circular and the end has been reached, NULL + * is returned. + * + * Side Effects: + * the curPtr field is updated. + * + *----------------------------------------------------------------------- + */ +LstNode +Lst_Next(Lst l) +{ + ListNode tln; + List list = l; + + if ((LstValid (l) == FALSE) || + (list->isOpen == FALSE)) { + return NULL; + } + + list->prevPtr = list->curPtr; + + if (list->curPtr == NULL) { + if (list->atEnd == Unknown) { + /* + * If we're just starting out, atEnd will be Unknown. + * Then we want to start this thing off in the right + * direction -- at the start with atEnd being Middle. + */ + list->curPtr = tln = list->firstPtr; + list->atEnd = Middle; + } else { + tln = NULL; + list->atEnd = Tail; + } + } else { + tln = list->curPtr->nextPtr; + list->curPtr = tln; + + if (tln == list->firstPtr || tln == NULL) { + /* + * If back at the front, then we've hit the end... + */ + list->atEnd = Tail; + } else { + /* + * Reset to Middle if gone past first. + */ + list->atEnd = Middle; + } + } + + return (tln); +} + |