**
**	$Id: $
**	$Revision: $
**
**	$Filename: DecompressBlock.S $
**	$Author: Christian A. Weber $
**	$Release: $
**	$Date: 92/05/12 22:26:30 $
**
**	iff.library/IFFLib_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	IFFLib_DecompressBlock
		SECTION	text,CODE

		INCLUDE	"IffLib.i"

		XREF	ClearError
		XDEF	DecompressBlockFunc


******* iff.library/IFFLib_DecompressBlock ************************************
*
*    NAME
*	IFFLib_DecompressBlock -- Decompress a memory block
*
*    SYNOPSIS
*	result = IFFLib_DecompressBlock( source, destination, size, mode )
*	                                 A0      A1           D0    D1
*
*	ULONG IFFLib_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 data bytes to decompress
*	mode        - Compression mode. Currently, the following modes
*	              are supported:
*	              $$$
*
*    RESULTS
*	Length of uncompressed data or 0 if an error occurred.
*
*    SEE ALSO
*	IFFLib_CompressBlock()
*
*****************************************************************************

DecompressBlockFunc:
		tst.l	d1		; Modus == 0 ?
		beq.b	Mode_Copy
		subq.l	#1,d1		; Modus == 1 ?
		beq.b	Mode_CmpByteRun1
		moveq.l	#0,d0
		rts

*****************************************************************************
**	Kopiermodus

Mode_Copy:	movem.l	d0/a6,-(SP)
		movea.l	ib_SysBase(a6),a6
		JSRLIB	CopyMem
		movem.l	(SP)+,d0/a6
		rts

*****************************************************************************
**	CmpByteRun1 dekomprimieren

Mode_CmpByteRun1:
		move.l	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 (== $80) ist 'NOP'
		move.b	(a0)+,d2	; Zu repetierender Wert
.RepLoop:	move.b	d2,(a1)+
		subq.l	#1,d0		; DEC ColumnCounter
		dble	d1,.RepLoop
3$:
		tst.l	d0		; Linie fertig ? (Braucht's das tst??)
		bgt.b	1$		; noch nicht ---> Loop

		move.l	(SP)+,d2
		rts

		END