1 /* 2 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Adam de Boor. 7 * 8 * Redistribution and use in source and binary forms are permitted 9 * provided that the above copyright notice and this paragraph are 10 * duplicated in all such forms and that any documentation, 11 * advertising materials, and other materials related to such 12 * distribution and use acknowledge that the software was developed 13 * by the University of California, Berkeley. The name of the 14 * University may not be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 19 */ 20 21 #ifndef lint 22 static char sccsid[] = "@(#)lstSetCirc.c 5.2 (Berkeley) 03/11/90"; 23 #endif /* not lint */ 24 25 /*- 26 * listSetCirc.c -- 27 * Change the library's notion of the circularity of a list. 28 */ 29 30 #include "lstInt.h" 31 32 /* 33 *------------------------------------------------------------ 34 * Lst_SetCirc -- 35 * change the circularity of a list 36 * 37 * Results: 38 * none 39 * 40 * Side Effects: 41 * The circularity of the list is set appropriately. The head and 42 * tail of the list will be linked or unlinked as necessary 43 *------------------------------------------------------------ 44 */ 45 void 46 Lst_SetCirc (l, circ) 47 Lst l; 48 Boolean circ; 49 { 50 register List list = (List) l; 51 52 /* 53 * if this isn't a change, do nothing. 54 */ 55 if ((list->isCirc && circ) || (!list->isCirc && !circ)) { 56 return; 57 } 58 list->isCirc = circ; 59 60 if (LstIsEmpty (l)) { 61 return; 62 } 63 64 if (circ) { 65 list->firstPtr->prevPtr = list->lastPtr; 66 list->lastPtr->nextPtr = list->firstPtr; 67 } else { 68 list->firstPtr->prevPtr = NilListNode; 69 list->lastPtr->nextPtr = NilListNode; 70 } 71 } 72