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z80_unpacker: add backward variant of unpacker + example extended

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This commit is contained in:
Peter Helcmanovsky (Ped)
2022-09-18 00:23:14 +02:00
parent 3c773aca8d
commit b13fa05413
7 changed files with 80 additions and 21 deletions
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77
z80_unpacker/example/example.asm
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@@ -3,7 +3,8 @@
DEVICE ZXSPECTRUM48,$8FFF
ORG $9000
compressed_scr_files: ; border color byte + upkr-packed .scr file
;; forward example data
compressed_scr_files.fwd: ; border color byte + upkr-packed .scr file
DB 1
INCBIN "screens/Grongy - ZX Spectrum (2022).scr.upk"
DB 7
@@ -13,37 +14,87 @@ compressed_scr_files: ; border color byte + upkr-packed .scr file
DB 6
INCBIN "screens/diver - Back to Bjork (2015).scr.upk"
.e:
;; backward example data (unpacker goes from the end of the data!)
compressed_scr_files.rwd.e: EQU $-1 ; the final IX will point one byte ahead of "$" here
INCBIN "screens.reversed/diver - Back to Bjork (2015).scr.upk"
DB 6
INCBIN "screens.reversed/diver - Mercenary 4. The Heaven's Devil (2014) (Forever 2014 Olympic Edition, 1).scr.upk"
DB 0
INCBIN "screens.reversed/Schafft - Poison (2017).scr.upk"
DB 7
INCBIN "screens.reversed/Grongy - ZX Spectrum (2022).scr.upk"
compressed_scr_files.rwd: ; border color byte + upkr-packed .scr file (backward)
DB 1
start:
di
; OPT --zxnext
; nextreg 7,3 ; ZX Next: switch to 28Mhz
ld ix,compressed_scr_files
.slideshow_loop
; nextreg 7,3 ; ZX Next: switch to 28Mhz
;;; FORWARD packed/unpacked data demo
ld ix,compressed_scr_files.fwd
.slideshow_loop.fwd:
; set BORDER for next image
ldi a,(ix) ; fake: ld a,(ix) : inc ix
ld a,(ix)
inc ix
out (254),a
; call unpack of next image directly into VRAM
ld de,$4000 ; target VRAM
ld de,$4000 ; target VRAM
exx
; IX = packed data, DE' = destination ($4000)
; returned IX will point right after the packed data
call upkr.unpack
call fwd.upkr.unpack
; do some busy loop with CPU to delay between images
call delay
; check if all images were displayed, loop around from first one then
ld a,ixl
cp low compressed_scr_files.fwd.e
jr nz,.slideshow_loop.fwd
;;; BACKWARD packed/unpacked data demo
ld ix,compressed_scr_files.rwd
.slideshow_loop.rwd:
; set BORDER for next image
ld a,(ix)
dec ix
out (254),a
; call unpack of next image directly into VRAM
ld de,$5AFF ; target VRAM
exx
; IX = packed data, DE' = destination
; returned IX will point right ahead of the packed data
call rwd.upkr.unpack
; do some busy loop with CPU to delay between images
call delay
; check if all images were displayed, loop around from first one then
ld a,ixl
cp low compressed_scr_files.rwd.e
jr nz,.slideshow_loop.rwd
jr start
delay:
ld bc,$AA00
.delay:
.8 ex (sp),ix
dec c
jr nz,.delay
djnz .delay
; check if all images were displayed, loop around from first one then
ld a,ixl
cp low compressed_scr_files.e
jr z,start
jr .slideshow_loop
ret
; include the depacker library, optionally putting probs array buffer near end of RAM
DEFINE UPKR_PROBS_ORIGIN $FA00 ; if not defined, array will be put after unpack code
INCLUDE "../unpack.asm"
MODULE fwd
INCLUDE "../unpack.asm"
ENDMODULE
MODULE rwd
DEFINE BACKWARDS_UNPACK ; defined to build backwards unpack
; initial IX points at last byte of compressed data
; initial DE' points at last byte of unpacked data
INCLUDE "../unpack.asm"
ENDMODULE
SAVESNA "example.sna",start