1/*
2 * Copyright (c) 2000-2009 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28/*
29 * @OSF_COPYRIGHT@
30 */
31/*
32 * Mach Operating System
33 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
34 * All Rights Reserved.
35 *
36 * Permission to use, copy, modify and distribute this software and its
37 * documentation is hereby granted, provided that both the copyright
38 * notice and this permission notice appear in all copies of the
39 * software, derivative works or modified versions, and any portions
40 * thereof, and that both notices appear in supporting documentation.
41 *
42 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
43 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
44 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
45 *
46 * Carnegie Mellon requests users of this software to return to
47 *
48 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
49 *  School of Computer Science
50 *  Carnegie Mellon University
51 *  Pittsburgh PA 15213-3890
52 *
53 * any improvements or extensions that they make and grant Carnegie Mellon
54 * the rights to redistribute these changes.
55 */
56/*
57 */
58
59/*
60 *	Routines to implement queue package.
61 */
62
63#include <kern/queue.h>
64
65#if	!defined(__GNUC__)
66
67/*
68 *	Insert element at head of queue.
69 */
70void
71enqueue_head(
72	register queue_t	que,
73	register queue_entry_t	elt)
74{
75	elt->next = que->next;
76	elt->prev = que;
77	elt->next->prev = elt;
78	que->next = elt;
79}
80
81/*
82 *	Insert element at tail of queue.
83 */
84void
85enqueue_tail(
86	register queue_t	que,
87	register queue_entry_t	elt)
88{
89	elt->next = que;
90	elt->prev = que->prev;
91	elt->prev->next = elt;
92	que->prev = elt;
93}
94
95/*
96 *	Remove and return element at head of queue.
97 */
98queue_entry_t
99dequeue_head(
100	register queue_t	que)
101{
102	register queue_entry_t	elt;
103
104	if (que->next == que)
105		return((queue_entry_t)0);
106
107	elt = que->next;
108	elt->next->prev = que;
109	que->next = elt->next;
110	return(elt);
111}
112
113/*
114 *	Remove and return element at tail of queue.
115 */
116queue_entry_t
117dequeue_tail(
118	register queue_t	que)
119{
120	register queue_entry_t	elt;
121
122	if (que->prev == que)
123		return((queue_entry_t)0);
124
125	elt = que->prev;
126	elt->prev->next = que;
127	que->prev = elt->prev;
128	return(elt);
129}
130
131/*
132 *	Remove arbitrary element from queue.
133 *	Does not check whether element is on a queue - the world
134 *	will go haywire if it isn't.
135 */
136
137/*ARGSUSED*/
138void
139remqueue(
140	register queue_entry_t	elt)
141{
142	elt->next->prev = elt->prev;
143	elt->prev->next = elt->next;
144}
145
146/*
147 *	Routines to directly imitate the VAX hardware queue
148 *	package.
149 */
150void
151insque(
152	register queue_entry_t	entry,
153	register queue_entry_t	pred)
154{
155	entry->next = pred->next;
156	entry->prev = pred;
157	(pred->next)->prev = entry;
158	pred->next = entry;
159}
160
161void
162remque(
163	register queue_entry_t elt)
164{
165	(elt->next)->prev = elt->prev;
166	(elt->prev)->next = elt->next;
167}
168
169#endif
170