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Annotation of prex-old/sys/lib/queue.c, Revision 1.1.1.1

1.1       nbrk        1: /*-
                      2:  * Copyright (c) 2005, Kohsuke Ohtani
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms, with or without
                      6:  * modification, are permitted provided that the following conditions
                      7:  * are met:
                      8:  * 1. Redistributions of source code must retain the above copyright
                      9:  *    notice, this list of conditions and the following disclaimer.
                     10:  * 2. Redistributions in binary form must reproduce the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer in the
                     12:  *    documentation and/or other materials provided with the distribution.
                     13:  * 3. Neither the name of the author nor the names of any co-contributors
                     14:  *    may be used to endorse or promote products derived from this software
                     15:  *    without specific prior written permission.
                     16:  *
                     17:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
                     21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     27:  * SUCH DAMAGE.
                     28:  */
                     29:
                     30: /*
                     31:  * queue.c - generic queue management library
                     32:  */
                     33:
                     34: #include <queue.h>
                     35:
                     36: /*
                     37:  * Insert element at tail of queue
                     38:  */
                     39: void
                     40: enqueue(queue_t head, queue_t item)
                     41: {
                     42:        item->next = head;
                     43:        item->prev = head->prev;
                     44:        item->prev->next = item;
                     45:        head->prev = item;
                     46: }
                     47:
                     48: /*
                     49:  * Remove and return element of head of queue
                     50:  */
                     51: queue_t
                     52: dequeue(queue_t head)
                     53: {
                     54:        queue_t item;
                     55:
                     56:        if (head->next == head)
                     57:                return ((queue_t)0);
                     58:        item = head->next;
                     59:        item->next->prev = head;
                     60:        head->next = item->next;
                     61:        return item;
                     62: }
                     63:
                     64: /*
                     65:  * Insert element after specified element
                     66:  */
                     67: void
                     68: queue_insert(queue_t prev, queue_t item)
                     69: {
                     70:        item->prev = prev;
                     71:        item->next = prev->next;
                     72:        prev->next->prev = item;
                     73:        prev->next = item;
                     74: }
                     75:
                     76: /*
                     77:  * Remove specified element from queue
                     78:  */
                     79: void
                     80: queue_remove(queue_t item)
                     81: {
                     82:        item->prev->next = item->next;
                     83:        item->next->prev = item->prev;
                     84: }