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*****************************************************************************
** **
** PPDecrunch - Eine Datei PowerPacker-decrunchen auf sich selber **
** **
** Parameter : A0.L : Adresse **
** D0.L : Länge der gecrunchten Daten **
** **
** Resultat : nix **
** **
*****************************************************************************
IDNT PPDecrunch
SECTION text,CODE
INCLUDE "MyExec.i"
XDEF PPDecrunch
PPDecrunch: movem.l d0-d7/a0-a5,-(SP)
lea Efficiency(PC),a5 ; A5: Pointer to efficiency
move.l a0,-(SP) ; Buffer für später
lea PP_SAVEMARGIN(a0),a3 ; A3: Destination
move.l a3,-(SP) ; Quelle für später
move.l (a0)+,-(SP) ; Decrunchte Grösse für später
move.l (a0)+,(a5) ; Efficiency eintragen
lea -8(a0,d0.l),a0 ; A0: Source-Ende
move.l a6,-(SP)
bsr.b Decrunch
movea.l (SP)+,a6
move.l (SP)+,d0 ; Decrunchte Grösse
movea.l (SP)+,a0 ; Quelle
movea.l (SP)+,a1 ; Ziel
jsr meb_CopyMem(a6) ; runterschieben
movem.l (SP)+,d0-d7/a0-a5
rts
Efficiency: dc.l 0
****************************************************************************
* *
* PowerPacker Decrunch assembler subroutine V2.0 (reentrant !) *
* DESTROYS ALL REGISTERS! *
* *
* call as: *
* pp_DecrunchBuffer (endcrun, buffer, &efficiency, coloraddr); *
* with: *
* A0 endcrun : UBYTE * just after last byte of crunched file *
* A3 buffer : UBYTE * to memory block to decrunch in *
* A5 &efficiency: ptr to Longword defining efficiency of crunched file *
* *
* NOTE: *
* Decrunch a few bytes higher (safety margin) than the crunched file *
* to decrunch in the same memory space. (8 bytes suffice) *
* *
****************************************************************************
Decrunch: moveq #3,d6
moveq #7,d7
moveq #1,d5
move.l a3,a2 ; remember start of file
move.l -(a0),d1 ; get file length and empty bits
tst.b d1
beq.b NoEmptyBits
bsr.b ReadBit ; this will always get the next long (D5 = 1)
subq.b #1,d1
lsr.l d1,d5 ; get rid of empty bits
NoEmptyBits:
lsr.l #8,d1
add.l d1,a3 ; a3 = endfile
LoopCheckCrunch:
bsr.b ReadBit ; check if crunch or normal
bcs.b CrunchedBytes
NormalBytes:
moveq #0,d2
Read2BitsRow:
moveq #1,d0
bsr.b ReadD1
add.w d1,d2
cmp.w d6,d1
beq.b Read2BitsRow
ReadNormalByte:
moveq #7,d0
bsr.b ReadD1
move.b d1,-(a3)
dbf d2,ReadNormalByte
cmp.l a3,a2
bcs.b CrunchedBytes
rts
ReadBit:
lsr.l #1,d5 ; this will set X if d5 becomes zero
beq.b GetNextLong
rts
GetNextLong:
move.l -(a0),d5
roxr.l #1,d5 ; X-bit set by lsr above
rts
ReadD1sub:
subq.w #1,d0
ReadD1:
moveq #0,d1
ReadBits:
lsr.l #1,d5 ; this will set X if d5 becomes zero
beq.b GetNext
RotX:
roxl.l #1,d1
dbf d0,ReadBits
rts
GetNext:
move.l -(a0),d5
roxr.l #1,d5 ; X-bit set by lsr above
bra.b RotX
CrunchedBytes:
moveq #1,d0
bsr.b ReadD1 ; read code
moveq #0,d0
move.b 0(a5,d1.w),d0 ; get number of bits of offset
move.w d1,d2 ; d2 = code = length-2
cmp.w d6,d2 ; if d2 = 3 check offset bit and read length
bne.b ReadOffset
bsr.b ReadBit ; read offset bit (long/short)
bcs.b LongBlockOffset
moveq #7,d0
LongBlockOffset:
bsr.b ReadD1sub
move.w d1,d3 ; d3 = offset
Read3BitsRow:
moveq #2,d0
bsr.b ReadD1
add.w d1,d2 ; d2 = length-1
cmp.w d7,d1 ; cmp with #7
beq.b Read3BitsRow
bra.b DecrunchBlock
ReadOffset:
bsr.b ReadD1sub ; read offset
move.w d1,d3 ; d3 = offset
DecrunchBlock:
addq.w #1,d2
DecrunchBlockLoop:
move.b 0(a3,d3.w),-(a3)
dbf d2,DecrunchBlockLoop
EndOfLoop:
cmp.l a3,a2
bcs LoopCheckCrunch
rts
END
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