2012-01-29, 02:41 AM
I was using MegaLZ, and I figured it worth listing how to make it a SUB.
Trivially easy, actually - it's provided as ASM source. There's a windows binary program to compress data. Just call this like a mem copy, with source (packed data) and destination (for unpacked data).
I've used it to pack down screen data, and just unpacked it to the screen - it's slow enough to be visible, so do it with attributes set to invisible, and the user won't notice.
Trivially easy, actually - it's provided as ASM source. There's a windows binary program to compress data. Just call this like a mem copy, with source (packed data) and destination (for unpacked data).
I've used it to pack down screen data, and just unpacked it to the screen - it's slow enough to be visible, so do it with attributes set to invisible, and the user won't notice.
Code:
SUB megaLZDepack (source as uInteger, dest as uInteger)
ASM
LD E,(IX+6)
LD D,(IX+7)
;Z80 depacker for megalz V4 packed files (C) fyrex^mhm
; DESCRIPTION:
;
; Depacker is fully relocatable, not self-modifying,
;it's length is 110 bytes starting from DEC40.
;Register usage: AF,AF',BC,DE,HL. Must be CALL'ed, return is done by RET.
;Provide extra stack location for store 2 bytes (1 word). Depacker does not
;disable or enable interrupts, as well as could be interrupted at any time
;(no f*cking wicked stack usage :).
; USAGE:
;
; - put depacker anywhere you want,
; - put starting address of packed block in HL,
; - put location where you want data to be depacked in DE,
; (much like LDIR command, but without BC)
; - make CALL to depacker (DEC40).
; - enjoy! ;)
; PRECAUTIONS:
;
; Be very careful if packed and depacked blocks coincide somewhere in memory.
;Here are some advices:
;
; 1. put packed block to the highest addresses possible.
; Best if last byte of packed block has address #FFFF.
;
; 2. Leave some gap between ends of packed and depacked block.
; For example, last byte of depacked block at #FF00,
; last byte of packed block at #FFFF.
;
; 3. Place nonpackable data to the end of block.
;
; 4. Always check whether depacking occurs OK and neither corrupts depacked data
; nor hangs computer.
;
;DEC40
LD A,80h
EX AF,AF'
MS: LDI
M0: LD BC,2FFh
M1: EX AF,AF'
M1X: ADD A,A
JR NZ,M2
LD A,(HL)
INC HL
RLA
M2: RL C
JR NC,M1X
EX AF,AF'
DJNZ X2
LD A,2
SRA C
JR C,N1
INC A
INC C
JR Z,N2
LD BC,33Fh
JR M1
X2: DJNZ X3
SRL C
JR C,MS
INC B
JR M1
X6:
ADD A,C
N2:
LD BC,4FFh
JR M1
N1:
INC C
JR NZ,M4
EX AF,AF'
INC B
N5: RR C
JP C, END_DEC40
RL B
ADD A,A
JR NZ,N6
LD A,(HL)
INC HL
RLA
N6: JR NC,N5
EX AF,AF'
ADD A,B
LD B,6
JR M1
X3:
DJNZ X4
LD A,1
JR M3
X4: DJNZ X5
INC C
JR NZ,M4
LD BC,51Fh
JR M1
X5:
DJNZ X6
LD B,C
M4: LD C,(HL)
INC HL
M3: DEC B
PUSH HL
LD L,C
LD H,B
ADD HL,DE
LD C,A
LD B,0
LDIR
POP HL
JR M0
END_DEC40:
END ASM
END SUB