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[] = "@(#)lstRemove.c	5.2 (Berkeley) 03/11/90";
23 #endif /* not lint */
24 
25 /*-
26  * LstRemove.c --
27  *	Remove an element from a list
28  */
29 
30 #include	"lstInt.h"
31 
32 /*-
33  *-----------------------------------------------------------------------
34  * Lst_Remove --
35  *	Remove the given node from the given list.
36  *
37  * Results:
38  *	SUCCESS or FAILURE.
39  *
40  * Side Effects:
41  *	The list's firstPtr will be set to NilListNode if ln is the last
42  *	node on the list. firsPtr and lastPtr will be altered if ln is
43  *	either the first or last node, respectively, on the list.
44  *
45  *-----------------------------------------------------------------------
46  */
47 ReturnStatus
48 Lst_Remove (l, ln)
49     Lst	    	  	l;
50     LstNode	  	ln;
51 {
52     register List 	list = (List) l;
53     register ListNode	lNode = (ListNode) ln;
54 
55     if (!LstValid (l) ||
56 	!LstNodeValid (ln, l)) {
57 	    return (FAILURE);
58     }
59 
60     /*
61      * unlink it from the list
62      */
63     if (lNode->nextPtr != NilListNode) {
64 	lNode->nextPtr->prevPtr = lNode->prevPtr;
65     }
66     if (lNode->prevPtr != NilListNode) {
67 	lNode->prevPtr->nextPtr = lNode->nextPtr;
68     }
69 
70     /*
71      * if either the firstPtr or lastPtr of the list point to this node,
72      * adjust them accordingly
73      */
74     if (list->firstPtr == lNode) {
75 	list->firstPtr = lNode->nextPtr;
76     }
77     if (list->lastPtr == lNode) {
78 	list->lastPtr = lNode->prevPtr;
79     }
80 
81     /*
82      * Sequential access stuff. If the node we're removing is the current
83      * node in the list, reset the current node to the previous one. If the
84      * previous one was non-existent (prevPtr == NilListNode), we set the
85      * end to be Unknown, since it is.
86      */
87     if (list->isOpen && (list->curPtr == lNode)) {
88 	list->curPtr = list->prevPtr;
89 	if (list->curPtr == NilListNode) {
90 	    list->atEnd = Unknown;
91 	}
92     }
93 
94     /*
95      * the only way firstPtr can still point to ln is if ln is the last
96      * node on the list (the list is circular, so lNode->nextptr == lNode in
97      * this case). The list is, therefore, empty and is marked as such
98      */
99     if (list->firstPtr == lNode) {
100 	list->firstPtr = NilListNode;
101     }
102 
103     /*
104      * note that the datum is unmolested. The caller must free it as
105      * necessary and as expected.
106      */
107     if (lNode->useCount == 0) {
108 	free ((Address)ln);
109     } else {
110 	lNode->flags |= LN_DELETED;
111     }
112 
113     return (SUCCESS);
114 }
115 
116