diff --git a/asm/z80/unlzsa_small_v1.asm b/asm/z80/unlzsa_small_v1.asm new file mode 100755 index 0000000..097b92d --- /dev/null +++ b/asm/z80/unlzsa_small_v1.asm @@ -0,0 +1,62 @@ +; +; Size-optimized LZSA decompressor by spke (v.1 19/04/2019, 81 bytes) +; +; The data must be comressed using the command line compressor by Emmanuel Marty +; The compression is done as follows: +; +; lzsa.exe -r +; +; where option -r asks for the generation of raw (frame-less) data. +; +; The decompression is done in the standard way: +; +; ld hl,CompressedData +; ld de,WhereToDecompress +; call DecompressLZSA +; +; Of course, LZSA compression algorithm is (c) 2019 Emmanuel Marty, +; see https://github.com/emmanuel-marty/lzsa for more information +; +; Drop me an email if you have any comments/ideas/suggestions: zxintrospec@gmail.com +; + +@DecompressLZSA: + ld b,0 + +ReadToken: ; first a byte token "O|LLL|MMMM" is read from the stream, + ; where LLL is the number of literals and MMMM is + ; a length of the match that follows after the literals + ld a,(hl) : exa : ld a,(hl) : inc hl + and #70 : jr z,NoLiterals + + rrca : rrca : rrca : rrca ; LLL<7 means 0..6 literals... + cp #07 : call z,ReadLongBA ; LLL=7 means 7+ literals... + + ld c,a : ldir + + ; next we read the first byte of the offset +NoLiterals: push de : ld e,(hl) : inc hl : ld d,b + ; the top bit of token is set if the offset contains two bytes + exa : or a : jp p,ShortOffset + +LongOffset: ld d,(hl) : inc hl + +ShortOffset: and #0F : add 3 : cp 15+3 : call z,ReadLongBA + + ld c,a + ex (sp),hl : push hl ; BC = len, DE = offset, HL = dest, SP ->[dest,src] + scf : sbc hl,de : pop de ; BC = len, DE = dest, HL = dest-offset, SP->[src] + ldir : pop hl ; BC = 0, DE = dest, HL = src + jr ReadToken + +ReadLongBA: ld c,(hl) : inc hl + add c : jr nc,$+3 : inc b + inc c : jr z,.Code255 + inc c : ret nz + +.Code254 add (hl) : inc hl : ret nc : inc b : ret + +.Code255 ld c,(hl) : inc hl : ld b,(hl) : inc hl + + ld a,b : or c : ld a,c : ret nz + pop de : pop de : ret