1/******************************************************************************
2 *
3 * Copyright (C) 2002 Jason Evans <jasone@FreeBSD.org>.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice(s), this list of conditions and the following disclaimer
11 *    unmodified other than the allowable addition of one or more
12 *    copyright notices.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice(s), this list of conditions and the following disclaimer in
15 *    the documentation and/or other materials provided with the
16 *    distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
25 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
26 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
27 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
28 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 ******************************************************************************/
31
32#ifndef QR_H_
33#define	QR_H_
34
35#include <sys/cdefs.h>
36__FBSDID("$FreeBSD$");
37
38/* Ring definitions. */
39#define qr(a_type)							\
40struct {								\
41	a_type	*qre_next;						\
42	a_type	*qre_prev;						\
43}
44
45/* Ring functions. */
46#define qr_new(a_qr, a_field) do {					\
47	(a_qr)->a_field.qre_next = (a_qr);				\
48	(a_qr)->a_field.qre_prev = (a_qr);				\
49} while (0)
50
51#define qr_next(a_qr, a_field) ((a_qr)->a_field.qre_next)
52
53#define qr_prev(a_qr, a_field) ((a_qr)->a_field.qre_prev)
54
55#define qr_before_insert(a_qrelm, a_qr, a_field) do {			\
56	(a_qr)->a_field.qre_prev = (a_qrelm)->a_field.qre_prev;		\
57	(a_qr)->a_field.qre_next = (a_qrelm);				\
58	(a_qr)->a_field.qre_prev->a_field.qre_next = (a_qr);		\
59	(a_qrelm)->a_field.qre_prev = (a_qr);				\
60} while (0)
61
62#define qr_after_insert(a_qrelm, a_qr, a_field)				\
63    do									\
64    {									\
65	(a_qr)->a_field.qre_next = (a_qrelm)->a_field.qre_next;		\
66	(a_qr)->a_field.qre_prev = (a_qrelm);				\
67	(a_qr)->a_field.qre_next->a_field.qre_prev = (a_qr);		\
68	(a_qrelm)->a_field.qre_next = (a_qr);				\
69    } while (0)
70
71#define qr_meld(a_qr_a, a_qr_b, a_field) do {				\
72	void *t;							\
73	(a_qr_a)->a_field.qre_prev->a_field.qre_next = (a_qr_b);	\
74	(a_qr_b)->a_field.qre_prev->a_field.qre_next = (a_qr_a);	\
75	t = (a_qr_a)->a_field.qre_prev;					\
76	(a_qr_a)->a_field.qre_prev = (a_qr_b)->a_field.qre_prev;	\
77	(a_qr_b)->a_field.qre_prev = t;					\
78} while (0)
79
80/* qr_meld() and qr_split() are functionally equivalent, so there's no need to
81 * have two copies of the code. */
82#define qr_split(a_qr_a, a_qr_b, a_field)				\
83	qr_meld((a_qr_a), (a_qr_b), a_field)
84
85#define qr_remove(a_qr, a_field) do {					\
86	(a_qr)->a_field.qre_prev->a_field.qre_next			\
87	    = (a_qr)->a_field.qre_next;					\
88	(a_qr)->a_field.qre_next->a_field.qre_prev			\
89	    = (a_qr)->a_field.qre_prev;					\
90	(a_qr)->a_field.qre_next = (a_qr);				\
91	(a_qr)->a_field.qre_prev = (a_qr);				\
92} while (0)
93
94#define qr_foreach(var, a_qr, a_field)					\
95	for ((var) = (a_qr);						\
96	    (var) != NULL;						\
97	    (var) = (((var)->a_field.qre_next != (a_qr))		\
98	    ? (var)->a_field.qre_next : NULL))
99
100#define qr_reverse_foreach(var, a_qr, a_field)				\
101	for ((var) = ((a_qr) != NULL) ? qr_prev(a_qr, a_field) : NULL;	\
102	    (var) != NULL;						\
103	    (var) = (((var) != (a_qr))					\
104	    ? (var)->a_field.qre_prev : NULL))
105
106#endif /* QR_H_ */
107