xref: /illumos-gate/usr/src/cmd/fm/fmd/common/fmd_list.c (revision 7c478bd9)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 /*
30  * Embedded Linked Lists
31  *
32  * Simple doubly-linked list implementation.  This implementation assumes that
33  * each list element contains an embedded fmd_list_t (previous and next
34  * pointers), which is typically the first member of the element struct.
35  * An additional fmd_list_t is used to store the head (l_next) and tail
36  * (l_prev) pointers.  The current head and tail list elements have their
37  * previous and next pointers set to NULL, respectively.
38  *
39  * NOTE: The embeddable list code in this file intentionally provides no
40  * locking of any kind.  The implementation of any list in fmd must provide
41  * an appropriate locking strategy to protect the list or to protect access
42  * to the embedded fmd_list_t inside of each list element to avoid corruption.
43  * Refer to comments in the source files that use fmd_list_t for lock details.
44  */
45 
46 #include <fmd_subr.h>
47 #include <fmd_list.h>
48 
49 void
fmd_list_append(fmd_list_t * lp,void * new)50 fmd_list_append(fmd_list_t *lp, void *new)
51 {
52 	fmd_list_t *p = lp->l_prev;	/* p = tail list element */
53 	fmd_list_t *q = new;		/* q = new list element */
54 
55 	lp->l_prev = q;
56 	q->l_prev = p;
57 	q->l_next = NULL;
58 
59 	if (p != NULL) {
60 		ASSERT(p->l_next == NULL);
61 		p->l_next = q;
62 	} else {
63 		ASSERT(lp->l_next == NULL);
64 		lp->l_next = q;
65 	}
66 }
67 
68 void
fmd_list_prepend(fmd_list_t * lp,void * new)69 fmd_list_prepend(fmd_list_t *lp, void *new)
70 {
71 	fmd_list_t *p = new;		/* p = new list element */
72 	fmd_list_t *q = lp->l_next;	/* q = head list element */
73 
74 	lp->l_next = p;
75 	p->l_prev = NULL;
76 	p->l_next = q;
77 
78 	if (q != NULL) {
79 		ASSERT(q->l_prev == NULL);
80 		q->l_prev = p;
81 	} else {
82 		ASSERT(lp->l_prev == NULL);
83 		lp->l_prev = p;
84 	}
85 }
86 
87 void
fmd_list_insert_before(fmd_list_t * lp,void * before_me,void * new)88 fmd_list_insert_before(fmd_list_t *lp, void *before_me, void *new)
89 {
90 	fmd_list_t *p = before_me;
91 	fmd_list_t *q = new;
92 
93 	if (p == NULL || p->l_prev == NULL) {
94 		fmd_list_prepend(lp, new);
95 		return;
96 	}
97 
98 	q->l_prev = p->l_prev;
99 	q->l_next = p;
100 	p->l_prev = q;
101 	q->l_prev->l_next = q;
102 }
103 
104 void
fmd_list_insert_after(fmd_list_t * lp,void * after_me,void * new)105 fmd_list_insert_after(fmd_list_t *lp, void *after_me, void *new)
106 {
107 	fmd_list_t *p = after_me;
108 	fmd_list_t *q = new;
109 
110 	if (p == NULL || p->l_next == NULL) {
111 		fmd_list_append(lp, new);
112 		return;
113 	}
114 
115 	q->l_next = p->l_next;
116 	q->l_prev = p;
117 	p->l_next = q;
118 	q->l_next->l_prev = q;
119 }
120 
121 void
fmd_list_delete(fmd_list_t * lp,void * existing)122 fmd_list_delete(fmd_list_t *lp, void *existing)
123 {
124 	fmd_list_t *p = existing;
125 
126 	if (p->l_prev != NULL)
127 		p->l_prev->l_next = p->l_next;
128 	else
129 		lp->l_next = p->l_next;
130 
131 	if (p->l_next != NULL)
132 		p->l_next->l_prev = p->l_prev;
133 	else
134 		lp->l_prev = p->l_prev;
135 }
136