A2osX/LIB/LIBPAK.S.LZ.txt

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NEW
2018-11-17 17:17:13 +00:00
PREFIX
AUTO 4,1
.LIST OFF
*--------------------------------------
* Sliding Window = 4096
*--------------------------------------
WSIZE .EQ 4096 power of 2
*--------------------------------------
* Output BITSTREAM :
* 0 : Lit (8)
* 1 : Copy, L (4), P.HI (4), P.LO (8)
*--------------------------------------
Pak.LZ jsr Pak.In.Init Init SrcPtr,SrcCnt
jsr Pak.Out.Init
* future optimization, make P grows from 2 to 12 while increasing W size
* lda #2 Ptr width starts at 2 bits
* sta Pak.LZ.PWidth
* lda #%00000011 Ptr Mask Starts at %000000000011
* sta Pak.LZ.PMaskLO
* stz Pak.LZ.PMaskHI
lda #$ff
sta Pak.LZ.WCnt
sta Pak.LZ.WCnt+1 WCnt=!0
.1 jsr Pak.In.GetRH Z if EOF
beq .80
cmp #3
bcc .8 no more than 2 bytes left....store
cmp #19 more than 18 bytes left, limit to 18
bcc .2
lda #18
.2 tax X = Read ahead max size
lda ZPSrcPtr make ZPSrcWPtr=ZPSrcPtr
sta ZPSrcWPtr
lda ZPSrcPtr
sta ZPSrcWPtr
lda Pak.LZ.WCnt
sta ZPCnt
lda Pak.LZ.WCnt+1
sta ZPCnt+1
stz Pak.LZ.BestLen
.3 inc ZPCnt
bne .4
inc ZPCnt+1
beq .7 reached begining of window....store
lda ZPSrcWPtr make ZPSrcWPtr-=1
sec
sbc #1
sta ZPSrcWPtr
bcs .4
dec ZPSrcWPtr+1
.4 ldy #0
phx save Read ahead max size
.5 lda (ZPSrcPtr),y Try to find a match
cmp (ZPSrcWPtr),y
bne .6
iny
dex don't exceed 18 or Src Buffer
bne .5
.6 plx get back Read ahead max size
cpy #3 matched a least 3 chars ?
bcc .3 no....try one char back in Wnd
cpy Pak.LZ.BestLen better than last match ?
bcc .3 no....try one char back in Wnd
sty Pak.LZ.BestLen
lda ZPSrcWPtr
sta Pak.LZ.BestPtr
lda ZPSrcWPtr+1
sta Pak.LZ.BestPtr+1
bra .3
.7 lda Pak.LZ.BestLen do we match something ?
beq .8
lda Pak.LZ.BestPtr
sec
sbc ZPSrcPtr
sta Pak.LZ.BestPtr
lda Pak.LZ.BestPtr+1
sbc ZPSrcPtr+1
sta Pak.LZ.BestPtr+1
tya get len
dec Adjust range 0-15
dec
dec
ora Pak.LZ.BestPtr+1 merge with P.HI
sec
jsr Pak.Out.PutCA Put 9 bits 1+LLLL+PPPP
bcs .99
lda Pak.LZ.BestPtr Put 8 bits pppppppp
jsr Pak.Out.PutA
bcs .99
tya
bra .81
.8 lda (ZPSrcPtr)
clc
jsr Pak.Out.PutCA Put 9 bits 0+xxxxxxxx
bcs .99
lda #1
.81 jsr Pak.In.MoveFWA
tya
jsr LZ.MoveWndY
bra .3
bra .71
.80 clc
.99 rts
*--------------------------------------
Unpak.LZ
clc
rts
*--------------------------------------
LZ.MoveWndY tya
sec
sbc Pak.LZ.WCnt
tax
lda #0
sbc Pak.LZ.WCnt+1
cpx #WSIZE^$FF
sbc /WSIZE^$FF
bcs .1
ldx #WSIZE^$FF
lda /WSIZE^$FF
.1 stx Pak.LZ.WCnt
sta Pak.LZ.WCnt+1
rts
*--------------------------------------
MAN
2018-11-17 17:17:13 +00:00
SAVE USR/SRC/LIB/LIBPAK.S.LZ
ASM