osfmk/kern/queue.c

   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  */
  70 void
  71 enqueue_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  */
  84 void
  85 enqueue_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  */
  98 queue_entry_t
  99 dequeue_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  */
 116 queue_entry_t
 117 dequeue_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*/
 138 void
 139 remqueue(
 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  */
 150 void
 151 insque(
 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
 161 void
 162 remque(
 163         register queue_entry_t elt)
 164 {
 165         (elt->next)->prev = elt->prev;
 166         (elt->prev)->next = elt->next;
 167 }
 168
 169 #endif