118 lines
3.8 KiB
C
118 lines
3.8 KiB
C
/*
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* Copyright (c) 1988, 1989, 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Adam de Boor.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)lstNext.c 8.1 (Berkeley) 6/6/93
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*/
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#ifndef lint
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#include <sys/cdefs.h>
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__RCSID("$FreeBSD$");
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#endif /* not lint */
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/*-
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* LstNext.c --
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* Return the next node for a list.
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* The sequential functions access the list in a slightly different way.
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* CurPtr points to their idea of the current node in the list and they
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* access the list based on it. Because the list is circular, Lst_Next
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* and Lst_Prev will go around the list forever. Lst_IsAtEnd must be
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* used to determine when to stop.
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*/
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#include "lstInt.h"
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/*-
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*-----------------------------------------------------------------------
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* Lst_Next --
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* Return the next node for the given list.
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*
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* Results:
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* The next node or NULL if the list has yet to be opened. Also
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* if the list is non-circular and the end has been reached, NULL
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* is returned.
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*
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* Side Effects:
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* the curPtr field is updated.
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*
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*-----------------------------------------------------------------------
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*/
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LstNode
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Lst_Next (l)
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Lst l;
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{
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register ListNode tln;
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register List list = (List)l;
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if ((LstValid (l) == FALSE) ||
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(list->isOpen == FALSE)) {
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return (NULL);
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}
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list->prevPtr = list->curPtr;
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if (list->curPtr == NULL) {
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if (list->atEnd == Unknown) {
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/*
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* If we're just starting out, atEnd will be Unknown.
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* Then we want to start this thing off in the right
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* direction -- at the start with atEnd being Middle.
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*/
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list->curPtr = tln = list->firstPtr;
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list->atEnd = Middle;
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} else {
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tln = NULL;
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list->atEnd = Tail;
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}
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} else {
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tln = list->curPtr->nextPtr;
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list->curPtr = tln;
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if (tln == list->firstPtr || tln == NULL) {
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/*
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* If back at the front, then we've hit the end...
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*/
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list->atEnd = Tail;
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} else {
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/*
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* Reset to Middle if gone past first.
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*/
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list->atEnd = Middle;
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}
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}
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return ((LstNode)tln);
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}
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