queue.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 84 行

/****************************************************************************
*
*                            Open Watcom Project
*
*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
*
*  ========================================================================
*
*    This file contains Original Code and/or Modifications of Original
*    Code as defined in and that are subject to the Sybase Open Watcom
*    Public License version 1.0 (the 'License'). You may not use this file
*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
*    ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
*    provided with the Original Code and Modifications, and is also
*    available at www.sybase.com/developer/opensource.
*
*    The Original Code and all software distributed under the License are
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* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
*               DESCRIBE IT HERE!
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****************************************************************************/


#include <stddef.h>
#include "womp.h"
#include "queue.h"
#include "myassert.h"

extern void QInit( qdesc *q ) {
/***************************/
    q->head = NULL;
    q->tail = NULL;
}

extern void QEnqueue( qdesc *q, void *item ) {
/******************************************/
    if( q->head == NULL ) {
        q->head = q->tail = item;
    } else {
/**/    myassert( q->tail != NULL );
        *(void **)q->tail = item;
        q->tail = item;
    }
    *(void**)item = NULL;
}

extern void QJoinQueue( qdesc *dest, qdesc *src ) {
/***********************************************/
    if( dest->head == NULL ) {
        dest->head = src->head;
    } else if( src->head == NULL ) {
        return;
    } else {
/**/    myassert( dest->tail != NULL );
        *((void **)dest->tail) = src->head;
    }
    dest->tail = src->tail;
    *(void **)src->tail = NULL;
}

extern void *QDequeue( qdesc *q ) {
/*******************************/
    void *item;

    if( q->head == NULL ) {
        return( NULL );
    }
    item = q->head;
    q->head = *(void**)item;
    if( q->head == NULL ) {
        q->tail = NULL;
    }
    return( item );
}