1 /* $NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1989, 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Adam de Boor. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #ifndef MAKE_NATIVE 36 static char rcsid[] = "$NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $"; 37 #else 38 #include <sys/cdefs.h> 39 #ifndef lint 40 #if 0 41 static char sccsid[] = "@(#)lstNext.c 8.1 (Berkeley) 6/6/93"; 42 #else 43 __RCSID("$NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $"); 44 #endif 45 #endif /* not lint */ 46 #endif 47 48 /*- 49 * LstNext.c -- 50 * Return the next node for a list. 51 * The sequential functions access the list in a slightly different way. 52 * CurPtr points to their idea of the current node in the list and they 53 * access the list based on it. Because the list is circular, Lst_Next 54 * and Lst_Prev will go around the list forever. Lst_IsAtEnd must be 55 * used to determine when to stop. 56 */ 57 58 #include "lstInt.h" 59 60 /*- 61 *----------------------------------------------------------------------- 62 * Lst_Next -- 63 * Return the next node for the given list. 64 * 65 * Results: 66 * The next node or NULL if the list has yet to be opened. Also 67 * if the list is non-circular and the end has been reached, NULL 68 * is returned. 69 * 70 * Side Effects: 71 * the curPtr field is updated. 72 * 73 *----------------------------------------------------------------------- 74 */ 75 LstNode 76 Lst_Next(Lst l) 77 { 78 ListNode tln; 79 List list = l; 80 81 if ((LstValid (l) == FALSE) || 82 (list->isOpen == FALSE)) { 83 return NULL; 84 } 85 86 list->prevPtr = list->curPtr; 87 88 if (list->curPtr == NULL) { 89 if (list->atEnd == Unknown) { 90 /* 91 * If we're just starting out, atEnd will be Unknown. 92 * Then we want to start this thing off in the right 93 * direction -- at the start with atEnd being Middle. 94 */ 95 list->curPtr = tln = list->firstPtr; 96 list->atEnd = Middle; 97 } else { 98 tln = NULL; 99 list->atEnd = Tail; 100 } 101 } else { 102 tln = list->curPtr->nextPtr; 103 list->curPtr = tln; 104 105 if (tln == list->firstPtr || tln == NULL) { 106 /* 107 * If back at the front, then we've hit the end... 108 */ 109 list->atEnd = Tail; 110 } else { 111 /* 112 * Reset to Middle if gone past first. 113 */ 114 list->atEnd = Middle; 115 } 116 } 117 118 return (tln); 119 } 120 121