Paste: initial lzw-compress/uncompress

! Copyright (C) 2009 Doug Coleman.
! See http://factorcode.org/license.txt for BSD license.
USING: accessors assocs io io.encodings.binary
io.streams.byte-array kernel sequences prettyprint vectors
sets math streams.object bitstreams combinators byte-arrays ;
IN: lzw

CONSTANT: clear-code 256
CONSTANT: end-of-information 257

TUPLE: lzw table count omega omega-k output #bits
code old-code ;

ERROR: index-too-big n ;

: lzw-bit-width ( n -- n' )
    {
        { [ dup 510 <= ] [ drop 9 ] }
        { [ dup 1022 <= ] [ drop 10 ] }
        { [ dup 2046 <= ] [ drop 11 ] }
        { [ dup 4094 <= ] [ drop 12 ] }
        [ index-too-big ]
    } cond ;

: lzw-bit-width-compress ( lzw -- n )
    count>> lzw-bit-width ;

: lzw-bit-width-uncompress ( lzw -- n )
    table>> length lzw-bit-width ;

: initial-compress-table ( -- assoc )
    258 iota [ [ 1vector ] keep ] H{ } map>assoc ;

: initial-uncompress-table ( -- seq )
    258 iota [ 1vector ] V{ } map-as ;

: reset-lzw ( lzw -- lzw )
    257 >>count
    V{ } clone >>omega
    V{ } clone >>omega-k
    9 >>#bits ;

: reset-lzw-compress ( lzw -- lzw )
    initial-compress-table >>table
    reset-lzw ;

: reset-lzw-uncompress ( lzw -- lzw )
    initial-uncompress-table >>table
    reset-lzw ;

: <lzw-compress> ( -- obj )
    lzw new
        V{ } clone >>output
        reset-lzw-compress ;

: <lzw-uncompress> ( -- obj )
    lzw new
        V{ } clone >>output
        reset-lzw-uncompress ;

: push-k ( lzw ch -- lzw )
    over omega>> clone [ push ] keep >>omega-k ;

: omega-k-in-table? ( lzw -- ? )
    [ omega-k>> ] [ table>> ] bi key? ;

ERROR: not-in-table ;
: write-output ( lzw -- )
    [
        [ omega>> ] [ table>> ] bi at*
        [ not-in-table ] unless
    ] [ output>> push ] bi ;

: omega-k>omega ( lzw -- lzw )
    dup omega-k>> clone >>omega ;

: new-omega ( lzw -- lzw )
    dup omega-k>> 1 tail* >>omega ;

: add-omega-k ( lzw -- )
    [ [ 1+ ] change-count count>> ]
    [ omega-k>> ]
    [ table>> ] tri set-at ;

: lzw-compress-char ( lzw -- )
    read1 [
        push-k [
            dup omega-k-in-table? [
                omega-k>omega drop
            ] [
                [ write-output ]
                [ add-omega-k ]
                [ new-omega drop ] tri
            ] if
        ] [
            lzw-compress-char
        ] bi
    ] [
        drop
    ] if* ;

: lzw-compress ( byte-array -- seq )
    binary <byte-reader> [
        <lzw-compress> [ lzw-compress-char ] keep output>>
    ] with-input-stream ;

: lookup-old-code ( lzw -- vector )
    [ old-code>> ] [ table>> ] bi nth ;

: lookup-code ( lzw -- vector )
    [ code>> ] [ table>> ] bi nth ;

: code-in-table? ( lzw -- ? )
    [ code>> ] [ table>> length ] bi < ;

: code>old-code ( lzw -- lzw )
    dup code>> >>old-code ;

: write-code ( lzw -- )
    [ lookup-code ] [ output>> ] bi push ;

: add-to-table ( seq lzw -- )
    table>> push ;

: lzw-read ( lzw -- lzw n )
    dup lzw-bit-width-uncompress read ;

DEFER: lzw-uncompress-char
: handle-clear-code ( lzw -- )
    reset-lzw-uncompress
    lzw-read dup end-of-information = [
        2drop ! return
    ] [
        >>code
        [ write-code ]
        [ code>old-code ] bi
        lzw-uncompress-char
    ] if ;

: handle-uncompress-code ( lzw -- lzw )
    dup code-in-table? [
        [ write-code ]
        [
            [
                [ lookup-old-code ]
                [ lookup-code first ] bi suffix
            ] [ add-to-table ] bi
        ] [ code>old-code ] tri
    ] [
        [
            [ lookup-old-code dup first suffix ] keep
            [ output>> push ] [ add-to-table ] 2bi
        ] [ code>old-code ] bi
    ] if ;
    
: lzw-uncompress-char ( lzw -- )
    lzw-read [
        >>code
        dup code>> end-of-information = [
            drop
        ] [
            dup code>> clear-code = [
                handle-clear-code
            ] [
                handle-uncompress-code
                lzw-uncompress-char
            ] if
        ] if
    ] [
        drop ! return
    ] if* ;

: lzw-uncompress ( seq -- byte-array )
    binary <byte-reader> <bitstream-reader> [
        <lzw-uncompress>
        [ lzw-uncompress-char ]
        [ output>> concat >byte-array ] bi
    ] with-input-stream ;