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aplib247b_180_minimal.asm
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aplib247b_180_minimal.asm
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; aPPack decompressor
; original source by dwedit
; very slightly adapted by utopian
; optimized by Metalbrain & Antonio Villena
;247b to 152b optimized by uniabis
;hl = source
;de = dest
depack
init ld a,128
;;cap v1.2 with load address version requires to copy two bytes on top
;ldi
;ldi
apbranch1 ldi
aploop2 ld b,255
aploop call ap_getbit
jr nc,apbranch1
call ap_getbit
jr nc,apbranch2
call ap_getbit
jr nc,apbranch3
ld c,16 ;get an offset
apget4bits call ap_getbit
rl c
jr nc,apget4bits
jr nz,apbranch4
ex de,hl
ld (hl),c ;write a 0
ex de,hl
inc de
jr aploop2
apbranch4 ex af,af'
ld a,e
sub c
ld c,a
sbc a,a
add d
ld b,a
ld a,(bc)
ld (de),a
ex af,af'
inc de
jr aploop2
apbranch3 ex af,af'
ld a,(hl) ;use 7 bit offset, length = 2 or 3
srl a
ret z ;if a zero is found here, it's EOF
inc hl
push hl
ld bc,1
rl c
ld h,255
cpl
ld l,a
push hl
pop ix
apskip3 ex af,af'
apskip4 inc hl
add hl,de
ldir
pop hl
jr aploop
apbranch2 ex af,af'
ld a,b
call ap_getgamma ;use a gamma code * 256 for offset, another gamma code for length
dec c
ex af,af'
add a,c
jr z,ap_r0_gamma
dec a
;do I even need this code?
;bc=bc*256+(hl), lazy 16bit way
cpl
ld b,a
ld a,(hl)
inc hl
cpl
ld c,a
push bc
push bc
pop ix
call ap_getgamma
ex (sp),hl ;bc = len, hl=offs
ex af,af'
ld a,h
cp 255-4
jr nc,apskip2
inc bc
apskip2 inc a
jr nz,apskip3
or l
jp p,apskip3
inc bc
inc bc
jr apskip3
ap_r0_gamma call ap_getgamma ;and a new gamma code for length
push ix
ex (sp),hl
jr apskip4
ap_getgamma ex af,af'
ld bc,1
ap_getgammaloop call ap_getbit
rl c
rl b
call ap_getbit
ret nc
jr ap_getgammaloop
ap_getbit add a,a
ret nz
ld a,(hl)
inc hl
rla
ret