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**
** $Id: DecompressBlock.S,v 21.2 92/05/17 03:27:44 chris Exp $
** $Revision: 21.2 $
**
** $Filename: DecompressBlock.S $
** $Author: chris $
** $Date: 92/05/17 03:27:44 $
**
** iff.library/IFFL_DecompressBlock
**
** 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 IFFL_DecompressBlock
SECTION text,CODE
INCLUDE "IffLib.i"
XREF SetError
XDEF DecompressBlockFunc
XREF Compress_NONE
XDEF Decompress_BYTERUN1 ;,Decompress_FIBDELTA
******* iff.library/IFFL_DecompressBlock ************************************
*
* NAME
* IFFL_DecompressBlock -- Decompress a memory block
*
* SYNOPSIS
* result = IFFL_DecompressBlock( source, destination, size, mode )
* A0 A1 D0 D1
*
* ULONG IFFL_DecompressBlock( APTR, APTR, ULONG, ULONG )
*
* FUNCTION
* Decompress the memory block using the appropriate Decompression mode.
* If the Decompressed data would become longer than the unDecompressed,
* an error is returned.
*
* INPUTS
* source - Pointer to data to decompress
* destination - Target address for decompression
* size - Number of _DECOMPRESSED_ data bytes
* mode - Compression mode. Currently, the following modes
* are supported:
*
* IFFL_COMPR_NONE - Vanilla copy
* IFFL_COMPR_BYTERUN1 - CmpByteRun1 (ILBM BODY data)
* IFFL_COMPR_FIBDELTA - Fibonacci Delta (8SVX BODY data)
*
* RESULTS
* Length of uncompressed data or 0 if an error occurred.
* IFFL_IFFError() returns IFFL_ERROR_BADCOMPRESSION if you ask for
* an unsupported compression mode.
*
* SEE ALSO
* IFFL_CompressBlock()
*
*****************************************************************************
DecompressBlockFunc:
subq.l #1,d1
beq.b Decompress_BYTERUN1 ; Modus == 1
bmi Compress_NONE ; Modus == 0
*** Unbekannter Modus --> Error setzen
movem.l a5-a6,-(SP)
movea.l a6,a5 ; A5 : IFFBase für SetError()
moveq.l #IFFL_ERROR_BADCOMPRESSION,d0
bsr SetError ; Setzt auch D0 auf 0
movem.l (SP)+,a5-a6
rts
*****************************************************************************
** CmpByteRun1 dekomprimieren
Decompress_BYTERUN1:
movem.l d0/d2,-(SP)
1$: moveq.l #0,d1
move.b (a0)+,d1 ; D1 : nächstes Kommando-Byte
bmi.b 2$ ; crunched --->
.CopyLoop: move.b (a0)+,(a1)+ ; D1+1 Bytes normal kopieren
subq.l #1,d0 ; DEC length counter
dble d1,.CopyLoop
bra.b 3$ ; --->
2$:
neg.b d1
bmi.b 3$ ; ~$80 (== $80) ist 'NOP'
move.b (a0)+,d2 ; Zu repetierender Wert
.RepLoop: move.b d2,(a1)+
subq.l #1,d0 ; DEC length counter
dble d1,.RepLoop
3$:
tst.l d0 ; Linie fertig ? (Braucht's das tst??)
bgt.b 1$ ; noch nicht ---> Loop
movem.l (SP)+,d0/d2
rts
END
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