/*

    File:       TQueue.c

    Contains:   Definition of operations for TQueue, a generic queue datatype

    Copyright:  © 1997-1999 by Apple Computer, Inc., all rights reserved.

*/

#include "TQueue.h"

typedef struct __cElement

{

    TCycle  __itsLink;

    void *  __itsPayload;

} __cElement;

static

__cElement **

__ElementNew(

    void *  inPayload )

{

    __cElement **   __elementNew;

    __elementNew = ( __cElement ** ) CycleNew( sizeof( **__elementNew ) );

    if( __elementNew )

        ( **__elementNew ).__itsPayload = inPayload;

    return( __elementNew );

}

static

TCycle **

__ElementCycle(

    __cElement **   inElement )

{

    return( ( TCycle ** ) inElement );

}

static

void *

__ElementPayload(

    __cElement **   inElement )

{

    return( ( **inElement ).__itsPayload );

}

static

void

__ElementDispose(

    __cElement **   inElement )

{

    CycleDispose( ( TCycle ** ) inElement );

}

extern

void

QueueInitialize(

    TQueue *    inQueue )

{

    if( inQueue )

    {

        inQueue->__itsList = 0;

        inQueue->__itsCount = 0;

    }

}

extern

UInt32

QueueCount(

    const TQueue *      inQueue )

{

    UInt32  queueCount = 0;

    if( inQueue )

        queueCount = inQueue->__itsCount;

    return( queueCount );

}

extern

void *

QueueHead(

    const TQueue *  inQueue )

{

    void *  queueHead = 0;

    if( inQueue  &&  inQueue->__itsList )

        queueHead = __ElementPayload( ( __cElement ** ) CycleNext( inQueue->__itsList ) );

    return( queueHead );

}

extern

void *

QueueEnqueue(

    TQueue *    inQueue,

    void *      inElement )

{

    void *          queueEnqueue = 0;

    __cElement **   theElement;

    if( inQueue  &&  inElement )

    {

        theElement = __ElementNew( inElement );

        if( theElement )

        {

            if( inQueue->__itsList )

                CyclePut( inQueue->__itsList, __ElementCycle( theElement ) );

            inQueue->__itsList = __ElementCycle( theElement );

            inQueue->__itsCount++;

            queueEnqueue = inElement;

        }

    }

    return( queueEnqueue );

}

extern

void *

QueueDequeue(

    TQueue *    inQueue )

{

    void *          queueDequeue = 0;

    __cElement **   theElement;

    if( inQueue  &&  inQueue->__itsList )

    {

        theElement = ( __cElement ** ) CycleGet( inQueue->__itsList );

        queueDequeue = __ElementPayload( theElement );

        __ElementDispose( theElement );

        --inQueue->__itsCount;

        if( !inQueue->__itsCount )

            inQueue->__itsList = 0;

    }

    return( queueDequeue );

}