queue.pc

无线网络仿真工具Glomosim2.03

/*
 * GloMoSim is COPYRIGHTED software.  Release 2.02 of GloMoSim is available 
 * at no cost to educational users only.
 *
 * Commercial use of this software requires a separate license.  No cost,
 * evaluation licenses are available for such purposes; please contact
 * [e-mail]
 *
 * By obtaining copies of this and any other files that comprise GloMoSim2.02,
 * you, the Licensee, agree to abide by the following conditions and
 * understandings with respect to the copyrighted software:
 *
 * 1.Permission to use, copy, and modify this software and its documentation
 *   for education and non-commercial research purposes only is hereby granted
 *   to Licensee, provided that the copyright notice, the original author's
 *   names and unit identification, and this permission notice appear on all
 *   such copies, and that no charge be made for such copies. Any entity
 *   desiring permission to use this software for any commercial or
 *   non-educational research purposes should contact: 
 *
 *   Professor Rajive Bagrodia 
 *   University of California, Los Angeles 
 *   Department of Computer Science 
 *   Box 951596 
 *   3532 Boelter Hall 
 *   Los Angeles, CA 90095-1596 
 *   [e-mail]
 *
 * 2.NO REPRESENTATIONS ARE MADE ABOUT THE SUITABILITY OF THE SOFTWARE FOR ANY
 *   PURPOSE. IT IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY.
 *
 * 3.Neither the software developers, the Parallel Computing Lab, UCLA, or any
 *   affiliate of the UC system shall be liable for any damages suffered by
 *   Licensee from the use of this software.
 */

// Use the latest version of Parsec if this line causes a compiler error.
/*
 * $Id: queue.pc,v 1.7 1999/12/08 17:04:07 jmartin Exp $
 *
 * Queueing functions used by the framework for
 * buffering messages.
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>

#include "main.h"
#include "queue.h"


        
/*
 * FUNCTION     GLOMO_MessageEnqueue
 * PURPOSE      Function called by user to insert message into the queue.
 *
 * Parameters:
 *    inQueue:    the queue in which the item is to be inserted
 *    inMsg:      the message being enqueued
 *    insertPos:  the position where the item will be inserted
 */
void GLOMO_MessageEnqueue(Queue *inQueue, int insertPos,
                          void *inMsg)
{
    int i;
    int msgSize = 0;
    QueueItem *insertItem = NULL;

    if (inQueue->freeListPtr == NULL) {
        insertItem = (QueueItem *) pc_malloc(sizeof(QueueItem));
    } else {
        insertItem = inQueue->freeListPtr;
        inQueue->freeListPtr = inQueue->freeListPtr->next;
    }
    
    assert(insertItem != NULL);
    insertItem->item = inMsg;


    /*
     * If the number of items in queue is 0,
     * then the item being inserted is the first
     * as well as last item.
     */
    if (inQueue->itemsInQueue == 0) {
        insertItem->prev = NULL;
        insertItem->next = NULL;

        inQueue->first = insertItem;
        inQueue->last = insertItem;
    }

    /*
     * If we are inserting at the end set the "next" field of the current
     * last item and "prev" field of the inserted item.
     * Point the "last" field of queue to the inserted item.
     */
    else if (insertPos == QUEUE_INSERT_END) {
        assert(inQueue->itemsInQueue > 0);
        insertItem->prev = inQueue->last;
        insertItem->next = NULL;

        inQueue->last->next = insertItem;
        inQueue->last = insertItem;
    }

    /*
     * If we are inserting at the front set the "prev" field of the current
     * first item and "next" field of the inserted item.
     * Point the "first" field of queue to the inserted item.
     */
    else if (insertPos == QUEUE_INSERT_FRONT) {
        assert(inQueue->itemsInQueue > 0);
        insertItem->prev = NULL;
        insertItem->next = inQueue->first;

        inQueue->first->prev = insertItem;
        inQueue->first = insertItem;
    }
    else {
        fprintf(stderr, "GLOMO Error: Unknown queue insert position %ld.\n",
                insertPos);
        assert(FALSE);
    }

    /*
     * Increase the count of the number of items in the queue.
     */
    inQueue->itemsInQueue++;
}



/*
 * FUNCTION      GLOMO_MessageDequeue
 * PURPOSE       Function called by user to remove message from queue.
 *
 * Parameters:
 *    outQueue:   the queue from which item is dequeued
 *
 * The actual message is returned. If there are no meessages
 * currently stored in the queue NULL is returned back.
 */
void* GLOMO_MessageDequeue(Queue *outQueue)
{
    QueueItem *outItem;
    int i;

    /*
     * Remove message from queue.
     */
    /*
     * If no items in queue, return NULL.
     */
    if (outQueue->itemsInQueue == 0) {
        return NULL;
    }


    /*
     * If there is just one item in queue, remove it
     * and set "first" and "last" of queue to NULL.
     */
    if (outQueue->itemsInQueue == 1) {
        outItem = outQueue->first;
        outQueue->first = NULL;
        outQueue->last = NULL;
        outQueue->itemsInQueue--;
    }

    /*
     * Remove item. Set "first" of queue to "next" of
     * item being removed.
     */
    else {
        outItem = outQueue->first;
        outQueue->first = outItem->next;
        outQueue->first->prev = NULL;
        outQueue->itemsInQueue--;
    }

    outItem->next = outQueue->freeListPtr;
    outQueue->freeListPtr = outItem;
    
    return outItem->item;
}