1 /*-
2  * LstRemove.c --
3  *	Remove an element from a list
4  *
5  * Copyright (c) 1988 by University of California Regents
6  *
7  * Permission to use, copy, modify, and distribute this
8  * software and its documentation for any purpose and without
9  * fee is hereby granted, provided that the above copyright
10  * notice appears in all copies.  Neither the University of California nor
11  * Adam de Boor makes any representations about the suitability of this
12  * software for any purpose.  It is provided "as is" without
13  * express or implied warranty.
14  */
15 #ifndef lint
16 static char *rcsid =
17 "$Id: lstRemove.c,v 1.7 89/06/13 15:01:51 adam Exp $ SPRITE (Berkeley)";
18 #endif lint
19 
20 #include	"lstInt.h"
21 
22 /*-
23  *-----------------------------------------------------------------------
24  * Lst_Remove --
25  *	Remove the given node from the given list.
26  *
27  * Results:
28  *	SUCCESS or FAILURE.
29  *
30  * Side Effects:
31  *	The list's firstPtr will be set to NilListNode if ln is the last
32  *	node on the list. firsPtr and lastPtr will be altered if ln is
33  *	either the first or last node, respectively, on the list.
34  *
35  *-----------------------------------------------------------------------
36  */
37 ReturnStatus
38 Lst_Remove (l, ln)
39     Lst	    	  	l;
40     LstNode	  	ln;
41 {
42     register List 	list = (List) l;
43     register ListNode	lNode = (ListNode) ln;
44 
45     if (!LstValid (l) ||
46 	!LstNodeValid (ln, l)) {
47 	    return (FAILURE);
48     }
49 
50     /*
51      * unlink it from the list
52      */
53     if (lNode->nextPtr != NilListNode) {
54 	lNode->nextPtr->prevPtr = lNode->prevPtr;
55     }
56     if (lNode->prevPtr != NilListNode) {
57 	lNode->prevPtr->nextPtr = lNode->nextPtr;
58     }
59 
60     /*
61      * if either the firstPtr or lastPtr of the list point to this node,
62      * adjust them accordingly
63      */
64     if (list->firstPtr == lNode) {
65 	list->firstPtr = lNode->nextPtr;
66     }
67     if (list->lastPtr == lNode) {
68 	list->lastPtr = lNode->prevPtr;
69     }
70 
71     /*
72      * Sequential access stuff. If the node we're removing is the current
73      * node in the list, reset the current node to the previous one. If the
74      * previous one was non-existent (prevPtr == NilListNode), we set the
75      * end to be Unknown, since it is.
76      */
77     if (list->isOpen && (list->curPtr == lNode)) {
78 	list->curPtr = list->prevPtr;
79 	if (list->curPtr == NilListNode) {
80 	    list->atEnd = Unknown;
81 	}
82     }
83 
84     /*
85      * the only way firstPtr can still point to ln is if ln is the last
86      * node on the list (the list is circular, so lNode->nextptr == lNode in
87      * this case). The list is, therefore, empty and is marked as such
88      */
89     if (list->firstPtr == lNode) {
90 	list->firstPtr = NilListNode;
91     }
92 
93     /*
94      * note that the datum is unmolested. The caller must free it as
95      * necessary and as expected.
96      */
97     if (lNode->useCount == 0) {
98 	free ((Address)ln);
99     } else {
100 	lNode->flags |= LN_DELETED;
101     }
102 
103     return (SUCCESS);
104 }
105 
106