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scoutos / prex-0.9.0 / bsp / drv / lib / queue.c @ 03e9c04a

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/*-
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 * Copyright (c) 2005, Kohsuke Ohtani
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the author nor the names of any co-contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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/*
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 * queue.c - generic queue management library
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 */
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#include <sys/queue.h>
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/*
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 * Insert element at tail of queue
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 */
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void
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enqueue(queue_t head, queue_t item)
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{
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        item->next = head;
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        item->prev = head->prev;
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        item->prev->next = item;
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        head->prev = item;
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}
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/*
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 * Remove and return element of head of queue
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 */
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queue_t
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dequeue(queue_t head)
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{
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        queue_t item;
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        if (head->next == head)
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                return ((queue_t)0);
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        item = head->next;
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        item->next->prev = head;
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        head->next = item->next;
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        return item;
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}
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/*
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 * Insert element after specified element
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 */
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void
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queue_insert(queue_t prev, queue_t item)
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{
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        item->prev = prev;
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        item->next = prev->next;
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        prev->next->prev = item;
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        prev->next = item;
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}
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/*
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 * Remove specified element from queue
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 */
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void
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queue_remove(queue_t item)
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{
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        item->prev->next = item->next;
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        item->next->prev = item->prev;
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}