[A83] Re: Compression algorithms-link


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[A83] Re: Compression algorithms-link




Sorry for the second email, I was a bit too quick with the previous one: can
anybody explain me how the 'Huffman library' should be put in the source
file? I mean, I've can get a fully compiled Huffman tree et all, but I don't
know what input format this routine wants...

With dear regards,
Frank Schoep

-----Oorspronkelijk bericht-----
Van: Henk Poley <HPoley@DDS.nl>
Aan: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
Datum: maandag 29 oktober 2001 8:28
Onderwerp: [A83] Re: Compression algorithms-link


>
>> Van: Frank Schoep <dsfs98@concepts.nl>
>>
>> Is there a decent implementation of a Huffman decompression routine on
>the
>> TI83 (+) and if so, is there any documentation for it? I have already
>> written a fairly good Huffman compression routine.
>
>Strange, I only found decompression routines, where did you find the
>Z80-huffman-compressor?
>
>; ------------------------------> HUFFEXTR.H
><------------------------------
>;
>; Huffman Decompression by Jimmy Mårdell
>;
>; 'Odd address' bug fixed by Florent Dhordain 02/07/98 DDMMYY
>;
>; 'More than 42 files' bug fixed by James Vernon 26/10/2000 DDMMYYYY
>;
>; If you make any changes to the source, please tell us what and why.
>; And you are NOT allowed to distribute a modified source, nor the
>; compiled version of it. Any changes should be made for personal use only.
>;
>; Please notify changes to :
>; Jimmy Mårdell      <mja@algonet.se>
>; Florent Dhordain   <flo.dh@usa.net>
>;
>; ------------------------------> HUFFEXTR.H
><------------------------------
>
>; ld hl,DataFile                 ; (HL) = Start of compressed data file
>; ld ix,gbuf                     ; (IX) = 1024 bytes for Huffman Library
>; ld a,(Level)
>; ld b,a                         ; B = File to extract from data file
>; call HuffExtr                  ; Extract level to temp level storage
>
>;
>
>HuffExtr:
> push de
> push de
> push hl
> inc hl
> ld a,(hl)
> cp 1
> jr nz,MultiFile
> ld b,0
>MultiFile:
> push bc
> inc hl
> ld d,(hl)
> inc hl
> ld e,(hl)              ; DE = noDifChars
> inc hl
> push hl
>; -- James -- ;
> ld l,a
> ld h,0                 ; HL = A
> add hl,hl              ; HL = 2A
> ld b,h
> ld c,l                 ; BC = 2A
> add hl,hl              ; HL = 4A
> add hl,bc              ; HL = 6A
> ld b,h
> ld c,l                 ; BC = 6A
> pop hl
> push hl
>; -- James -- ;
>; add a,a
>; ld c,a
>; add a,a
>; add a,c
>; ld b,0
>; ld c,a
> add hl,bc              ; HL -> chars
> ld b,e
> dec b                  ; B = noDifChars-1
> push hl
> add hl,de
> pop de                 ; DE -> chars, HL -> tree, IX -> treeaddr
> ld (treeaddr),ix
> ld a,1
>UncrunchTree:
> ld c,a
> and (hl)
> jr z,NoBranch
> push ix
> inc ix
> inc ix
>NextTreeBit:
> ld a,c
> rlca
> jr nc,UncrunchTree
> inc hl
> jr UncrunchTree
>NoBranch:
> ld a,(de)
> inc de
> ld (ix),0
> ld (ix+1),a
> inc ix
> inc ix
> ld a,b
> or a
> jr z,TreeBuilt
> ex (sp),hl
> push de
> push ix
> pop de
>;
> ld (hl),d
> inc hl
> ld (hl),e              ; MSB 1st order
>;
> pop de
> ex (sp),hl
> inc sp
> inc sp
> dec b
> jr NextTreeBit
>TreeBuilt:
> pop ix                 ; IX -> fileInfo
> pop af                 ; A = file no
>; -- James -- ;
> ld l,a
> ld h,0                 ; HL = A
> add hl,hl              ; HL = 2A
> ld b,h
> ld c,l                 ; BC = 2A
> add hl,hl              ; HL = 4A
> add hl,bc              ; HL = 6A
> ld b,h
> ld c,l                 ; BC = 6A
>; -- James -- ;
> pop hl                 ; HL -> noFiles
>; add a,a
>; ld c,a
>; add a,a
>; add a,c
>; ld b,0
>; ld c,a
> add ix,bc              ; IX -> fileInfo[file no]
> ld d,(ix)
> ld e,(ix+1)
> add hl,de              ; HL -> data
> ld b,(ix+3)            ; B = start bit
> ld a,1
>Shift:
> rlca
> djnz Shift
> ld c,a                ; C = start bit vlaue
> ld d,(ix+4)
> ld e,(ix+5)           ; DE = length of uncompressed data
> pop ix                ; HL -> Data, C = bitval, DE = length, IX -> Storage
>UncrunchData:
> push de
> ld de,(treeaddr)
>CheckTree:
> ld a,(de)              ; cause of this, we need to store in MSB 1st order
> or a
> jr z,EndOfBranch
> ld a,c
> and (hl)
> jr nz,RightBranch
> inc de
> inc de
> jr NextDataBit
>RightBranch:
> ex de,hl
>;
> ld a, (hl)
> inc hl
> ld l, (hl)
> ld h, a                ; H = (HL), L = (HL+1) : MSB 1st order
>;
> ex de,hl
>NextDataBit:
> rlc c
> jr nc,CheckTree
> inc hl
> jr CheckTree
>EndOfBranch:
> inc de
> ld a,(de)
> ld (ix),a
> inc ix
> pop de
> dec de
> ld a,d
> or e
> jr nz,UncrunchData
> pop de
> ret
>
>treeaddr:
> .dw 0
>
>.end
>
>
>