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In the chapter on the Resource Manager in
Inside Macintosh: More Macintosh Toolbox,
owned resources are explained, but the chapter
does not include a sample of how to actually figure out the resource's base
value. This Technote includes a shortcut in C, Pascal and ASM to
accomplish this task.
This Technote is specifically aimed at those developers who need to know
about a resource's ownership, such as developers working on Desk
Accessories or Control Panels.
[Oct 1 1995]
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A Shortcut for Figuring Out a Resource's Base Value
The function GetResBase takes the driver number and returns
the ID of the first resource owned by that driver.
This is according to the private resource numbering convention
documented in the Resource Manager chapter on page 1-48 of
Inside Macintosh: More Macintosh Toolbox.
In C, you can use this macro:
#define GetResBase(id) (0xC000 | (((-(id)) - 1) << 5))
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and in Pascal, you can use this function:
function GetResBase(resID: integer):integer;
begin
GetResBase := BOR($C000, BSL(longint(((-resID)-1)),5));
end;
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and for those who still program in 68k asm, you can use this function:
;FUNCTION GetResBase(driverNumber: INTEGER): INTEGER;
;
GetResBase FUNC
MOVE.L (SP)+,A0 ; Get return address
MOVE.W (SP)+,D0 ; Get driver number
NOT.W D0 ; Change to unit number
ASL.W #5,D0 ; Move it over in the word
ORI.W #$C000,D0 ; Add the magic bits
MOVE.W D0,(SP) ; Return function result
JMP (A0) ; and return
END
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References
Inside Macintosh: More Macintosh Toolbox, The Resource Manager, 1-48
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Change History
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01-May-1986
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Originally written.
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01-October-1995
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Revised to include Pascal and C
versions of the shortcut.
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Downloadables
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Acrobat version of this Note (52K)
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