1*40411Sbostic /*- 2*40411Sbostic * LstNext.c -- 3*40411Sbostic * Return the next node for a list. 4*40411Sbostic * The sequential functions access the list in a slightly different way. 5*40411Sbostic * CurPtr points to their idea of the current node in the list and they 6*40411Sbostic * access the list based on it. Because the list is circular, Lst_Next 7*40411Sbostic * and Lst_Prev will go around the list forever. Lst_IsAtEnd must be 8*40411Sbostic * used to determine when to stop. 9*40411Sbostic * 10*40411Sbostic * Copyright (c) 1988 by University of California Regents 11*40411Sbostic * 12*40411Sbostic * Permission to use, copy, modify, and distribute this 13*40411Sbostic * software and its documentation for any purpose and without 14*40411Sbostic * fee is hereby granted, provided that the above copyright 15*40411Sbostic * notice appears in all copies. Neither the University of California nor 16*40411Sbostic * Adam de Boor makes any representations about the suitability of this 17*40411Sbostic * software for any purpose. It is provided "as is" without 18*40411Sbostic * express or implied warranty. 19*40411Sbostic */ 20*40411Sbostic #ifndef lint 21*40411Sbostic static char *rcsid = 22*40411Sbostic "$Id: lstNext.c,v 1.8 88/11/17 20:53:40 adam Exp $ SPRITE (Berkeley)"; 23*40411Sbostic #endif lint 24*40411Sbostic 25*40411Sbostic #include "lstInt.h" 26*40411Sbostic 27*40411Sbostic /*- 28*40411Sbostic *----------------------------------------------------------------------- 29*40411Sbostic * Lst_Next -- 30*40411Sbostic * Return the next node for the given list. 31*40411Sbostic * 32*40411Sbostic * Results: 33*40411Sbostic * The next node or NILLNODE if the list has yet to be opened. Also 34*40411Sbostic * if the list is non-circular and the end has been reached, NILLNODE 35*40411Sbostic * is returned. 36*40411Sbostic * 37*40411Sbostic * Side Effects: 38*40411Sbostic * the curPtr field is updated. 39*40411Sbostic * 40*40411Sbostic *----------------------------------------------------------------------- 41*40411Sbostic */ 42*40411Sbostic LstNode 43*40411Sbostic Lst_Next (l) 44*40411Sbostic Lst l; 45*40411Sbostic { 46*40411Sbostic register ListNode tln; 47*40411Sbostic register List list = (List)l; 48*40411Sbostic 49*40411Sbostic if ((LstValid (l) == FALSE) || 50*40411Sbostic (list->isOpen == FALSE)) { 51*40411Sbostic return (NILLNODE); 52*40411Sbostic } 53*40411Sbostic 54*40411Sbostic list->prevPtr = list->curPtr; 55*40411Sbostic 56*40411Sbostic if (list->curPtr == NilListNode) { 57*40411Sbostic if (list->atEnd == Unknown) { 58*40411Sbostic /* 59*40411Sbostic * If we're just starting out, atEnd will be Unknown. 60*40411Sbostic * Then we want to start this thing off in the right 61*40411Sbostic * direction -- at the start with atEnd being Middle. 62*40411Sbostic */ 63*40411Sbostic list->curPtr = tln = list->firstPtr; 64*40411Sbostic list->atEnd = Middle; 65*40411Sbostic } else { 66*40411Sbostic tln = NilListNode; 67*40411Sbostic list->atEnd = Tail; 68*40411Sbostic } 69*40411Sbostic } else { 70*40411Sbostic tln = list->curPtr->nextPtr; 71*40411Sbostic list->curPtr = tln; 72*40411Sbostic 73*40411Sbostic if (tln == list->firstPtr || tln == NilListNode) { 74*40411Sbostic /* 75*40411Sbostic * If back at the front, then we've hit the end... 76*40411Sbostic */ 77*40411Sbostic list->atEnd = Tail; 78*40411Sbostic } else { 79*40411Sbostic /* 80*40411Sbostic * Reset to Middle if gone past first. 81*40411Sbostic */ 82*40411Sbostic list->atEnd = Middle; 83*40411Sbostic } 84*40411Sbostic } 85*40411Sbostic 86*40411Sbostic return ((LstNode)tln); 87*40411Sbostic } 88*40411Sbostic 89