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**
** $Id: $
** $Revision: $
**
** $Filename: FindChunk.S $
** $Author: Christian A. Weber $
** $Release: 19.1 $
** $Date: 92/05/11 21:11:27 $
**
** iff.library/IFFLib_FindChunk
**
** COPYRIGHT (C) 1987-1992 BY CHRISTIAN A. WEBER, BRUGGERWEG 2,
** CH-8037 ZUERICH, SWITZERLAND. ALL RIGHTS RESERVED. NO PART
** OF THIS SOFTWARE MAY BE COPIED, REPRODUCED, OR TRANSMITTED
** IN ANY FORM OR BY ANY MEANS, WITHOUT THE PRIOR WRITTEN PER-
** MISSION OF THE AUTHOR. USE AT YOUR OWN RISK.
**
IDNT IFFLib_FindChunk
SECTION text,CODE
INCLUDE "IffLib.i"
XDEF FindChunkFunc
******* iff.library/IFFLib_FindChunk ****************************************
*
* NAME
* IFFLib_FindChunk -- find an IFF-chunk
*
* SYNOPSIS
* chunk = IFFLib_FindChunk( ifffile, chunkname )
* D0 A1 D0
*
* APTR IFFLib_FindChunk( IFFFILE, ULONG )
*
* FUNCTION
* Find a specific chunk in an IFF file
*
* INPUTS
* ifffile - pointer to a FORM, normally the result of OpenIFF()
* chunkname - 4 characters packed ASCII ('BODY', 'VHDR' ...)
* if chunkname is 0, FindChunk() returns a pointer to the
* first byte after the end of the current FORM. This can
* be used byANIM readers for jumping from FORM to FORM.
*
* RESULTS
* Pointer to the beginning of the chunk (that means to the chunk
* name itself, followed by the chunk size); zero if chunk not found
*
* BUGS
* none known
*
* SEE ALSO
* IFFLib_GetBMHD(), IFFLib_GetColorTab()
*
*****************************************************************************
FindChunkFunc: movea.l 4(a1),a0 ; FORM-Länge
addq.l #8,a1 ; FORM.... überspringen
adda.l a1,a0 ; A0 zeigt jetzt ans Ende
addq.l #4,a1 ; FORM-Typ überspringen
tst.l d0 ; Chunk-ID == 0 ?
bne.s 1$ ; nein --->
movea.l a0,a1 ; Sonst Ende des FORMs
bra.s 99$ ; zurückgeben
1$: cmp.l (a1),d0 ; Chunk gefunden ?
beq.s 99$ ; ja!
move.l 4(a1),d1 ; Länge dieses Chunks
addq.l #1,d1 ; auf WORD ...
bclr #0,d1 ; ... aufrunden
lea 8(a1,d1.l),a1 ; Name & Länge dazu und zu A1 dazu
cmpa.l a0,a1 ; FORM-Ende erreicht ?
bcs.s 1$ ; noch nicht --->
suba.l a1,a1 ; Code für "nicht gefunden"
99$:
move.l a1,d0 ; Resultat nach D0, set/reset Z-Flag
rts
END
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