/*

    File:       UserChkGestaltFunction.c

    Contains:   Use as a alternate means of identifying whether a Gestalt selector

                is available.  The CheckGestalt clause requires the scriptor to enter

                all valid Gestalt selector results.  This poses a future compatibility

                problem in that one would like to simply know that a gestalt selector

                exists and not have to worry about matching the result in order to pass

                the clause.  This user function simply requires that the scriptor pass in 

                the gestalt selector to check for.  A true result is returned if the selector

                is found, false otherwise or if the Gestalt trap was not available.

    Written by: Rich Kubota 

    Copyright:  Copyright © 1988-1999 by Apple Computer, Inc., All Rights Reserved.

                You may incorporate this Apple sample source code into your program(s) without

                restriction. This Apple sample source code has been provided "AS IS" and the

                responsibility for its operation is yours. You are not permitted to redistribute

                this Apple sample source code as "Apple sample source code" after having made

                changes. If you're going to re-distribute the source, we require that you make

                it clear in the source that the code was descended from Apple sample source

                code, but that you've made changes.

    Change History (most recent first):

                8/18/1999   Karl Groethe    Updated for Metrowerks Codewarror Pro 2.1

*/

#if 0

c -b UserChkGestaltFunction.c

Link -ra =resPurgeable -rt infn=1002 -rn -m USERCHKGESTALTFUNCTION -t rsrc -c RSED ¶

        UserChkGestaltFunction.c.o ¶

        "{Libraries}"Interface.o ¶

        -o UserChkGestaltFunction.rsrc

#endif

#include <Types.h>

#include <Traps.h>

#include <OSUtils.h>

#include <GestaltEqu.h>

#include <Patches.h>

#include "UserChkGestaltFunction.h"

/******************  function prototypes  *********************/

short       NumToolboxTraps(void);

TrapType    GetTrapType(unsigned short theTrap);

Boolean     TrapAvailable(unsigned short theTrap);

/**************************************************************/

pascal Boolean UserChkGestaltFunction(short targetVRefNum, long blessedID, long selector)

{

#pragma unused (blessedID, targetVRefNum)

    OSErr   err;

    long    result;

    if (TrapAvailable(_Gestalt))        // check whether the Gestalt trap is available

    {

        err = Gestalt((OSType)selector, &result);   // pass the selector to the Gestalt call

        return (err == noErr);      // return result

    }

    else

        return false;               // gestalt not found, return false

}

/******** The following code is from IM VI *******/

short NumToolboxTraps(void)

{   

    if (NGetTrapAddress(_InitGraf, ToolTrap) == 

        NGetTrapAddress(0xAA6E, ToolTrap))

        return(0x200);

    else

        return(0x400);

}

#define TrapMask    0x0800

TrapType GetTrapType(unsigned short theTrap)

{

    if (theTrap & TrapMask)

        return (ToolTrap);

    else

        return (OSTrap);

}

Boolean TrapAvailable(unsigned short theTrap)

{

    TrapType    theType;

    theType = GetTrapType(theTrap);

    if (theType == ToolTrap) {

        theTrap &= 0x07FF;

        if (theTrap >= NumToolboxTraps())

            theTrap = _Unimplemented;

    }

    return (NGetTrapAddress(theTrap, theType) != 

            NGetTrapAddress(_Unimplemented, ToolTrap));

}