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optimized ZX0 with eZ80 instructions #647

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19 changes: 11 additions & 8 deletions src/ce/zx0.src
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Original file line number Diff line number Diff line change
Expand Up @@ -15,11 +15,11 @@ _zx0_Decompress:
; -----------------------------------------------------------------------------

dzx0_turbo:
ld bc, -1 ; preserve default offset 1
ld (dzx0t_last_offset+1), bc
inc bc
ld a, $80
jr dzx0t_literals
ld iy, -1 ; preserve default offset 1
lea bc, iy + 2 ; ld bc, 1
scf
jr dzx0t_start

dzx0t_new_offset:
dec bc
dec bc ; prepare negative offset
Expand All @@ -37,14 +37,15 @@ dzx0t_new_offset_skip:
inc hl
rr b ; last offset bit becomes first length bit
rr c
ld (dzx0t_last_offset+1), bc ; preserve new offset
push bc
pop iy ; preserve new offset
ld bc, 1 ; obtain length
call nc, dzx0t_elias
inc bc
dzx0t_copy:
push hl ; preserve source
dzx0t_last_offset:
ld hl, 0 ; restore offset
; dzx0t_last_offset:
lea hl, iy ; restore offset
add hl, de ; calculate destination - offset
ldir ; copy from offset
pop hl ; restore source
Expand All @@ -54,6 +55,7 @@ dzx0t_literals:
inc c ; obtain length
add a, a
jr nz, dzx0t_literals_skip
dzx0t_start:
ld a, (hl) ; load another group of 8 bits
inc hl
rla
Expand All @@ -71,6 +73,7 @@ dzx0t_literals_skip:
dzx0t_last_offset_skip:
call nc, dzx0t_elias
jr dzx0t_copy

dzx0t_elias:
add a, a ; interlaced Elias gamma coding
rl c
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