1/*
2 * Copyright (C) 2011, 2012  Internet Systems Consortium, Inc. ("ISC")
3 *
4 * Permission to use, copy, modify, and/or distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
9 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
10 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
11 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
12 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
13 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
14 * PERFORMANCE OF THIS SOFTWARE.
15 */
16
17/* $Id$ */
18
19/*
20 * This is a generic implementation of a two-lock concurrent queue.
21 * There are built-in mutex locks for the head and tail of the queue,
22 * allowing elements to be safely added and removed at the same time.
23 */
24
25#ifndef ISC_QUEUE_H
26#define ISC_QUEUE_H 1
27#include <isc/assertions.h>
28#include <isc/boolean.h>
29#include <isc/mutex.h>
30
31#ifdef ISC_QUEUE_CHECKINIT
32#define ISC_QLINK_INSIST(x) ISC_INSIST(x)
33#else
34#define ISC_QLINK_INSIST(x) (void)0
35#endif
36
37#define ISC_QLINK(type) struct { void *next; isc_boolean_t linked; }
38#define ISC_QLINK_INIT(elt, link) \
39	do { \
40		(elt)->link.next = (void *)(-1); \
41		(elt)->link.linked = ISC_FALSE; \
42	} while (0)
43#define ISC_QLINK_LINKED(elt, link) ((elt)->link.linked)
44
45#define ISC_QUEUE(type) struct { \
46	type headnode; \
47	type *head, *tail; \
48	isc_mutex_t headlock, taillock; \
49}
50
51#define ISC_QUEUE_INIT(queue, link) \
52	do { \
53		isc_mutex_init(&(queue).headlock); \
54		isc_mutex_init(&(queue).taillock); \
55		(queue).head = (void *) &((queue).headnode); \
56		(queue).tail = (void *) &((queue).headnode); \
57		ISC_QLINK_INIT((queue).head, link); \
58	} while (0)
59
60#define ISC_QUEUE_EMPTY(queue) ISC_TF((queue).head == (queue).tail)
61
62#define ISC_QUEUE_DESTROY(queue) \
63	do { \
64		ISC_QLINK_INSIST(ISC_QUEUE_EMPTY(queue)); \
65		isc_mutex_destroy(&(queue).headlock); \
66		isc_mutex_destroy(&(queue).taillock); \
67	} while (0)
68
69#define ISC_QUEUE_PUSH(queue, elt, link) \
70	do { \
71		ISC_QLINK_INSIST(!ISC_QLINK_LINKED(elt, link)); \
72		(elt)->link.next = (void *)(-1); \
73		LOCK(&(queue).taillock); \
74		(queue).tail->link.next = elt; \
75		(queue).tail = elt; \
76		UNLOCK(&(queue).taillock); \
77		(elt)->link.linked = ISC_TRUE; \
78	} while (0)
79
80#define ISC_QUEUE_POP(queue, link, ret) \
81	do { \
82		LOCK(&(queue).headlock); \
83		ret = (queue).head->link.next; \
84		if (ret == (void *)(-1)) { \
85			UNLOCK(&(queue).headlock); \
86			ret = NULL; \
87		} else { \
88			(queue).head->link.next = ret->link.next; \
89			if (ret->link.next == (void *)(-1)) { \
90				LOCK(&(queue).taillock); \
91				(queue).tail = (queue).head; \
92				UNLOCK(&(queue).taillock); \
93			} \
94			UNLOCK(&(queue).headlock); \
95			ret->link.next = (void *)(-1); \
96			ret->link.linked = ISC_FALSE; \
97		} \
98	} while (0)
99
100#endif /* ISC_QUEUE_H */
101