LZW compression and decompression by @_sebastienp (not me)

annotated.js

/*

   Copyright (c) 2011 Sebastien P.

   http://twitter.com/_sebastienp

   MIT licensed.

   ---

   LZW compression/decompression attempt for 140byt.es.

   ---

   See http://rosettacode.org/wiki/LZW_compression#JavaScript !

*/

window.LZW = {

    // 163 bytes
    compress: function (
        a, // String to compress
        b, // Placeholder for dictionary size
        c, // Placeholder for dictionary
        d, // Placeholder for iterator
        e, // Placeholder for w
        f, // Placeholder for result
        g, // Placeholder for c
        h // Placeholder for wc
    ) {

        for (b = d = 256, c = {}; d--;)

            c[String.fromCharCode(d)] = d;

        for (f = []; g = a[++d];)
        //for (e = "", f = []; g = a[++d];) // Using this one is 1 byte longer ...

            e = c[h = e ? e + g : g] ? h : (f.push(c[e]), c[h] = b++, g);
            //e = c[h = e + g] ? h : (f.push(c[e]), c[h] = b++, g); // ... but maybe faster ?

        e && f.push(c[e]);

        return f

    },

    // 158 bytes
    decompress: function (
        a, // Array to decompress
        b, // Placeholder for dictionary size
        c, // Placeholder for dictionary
        d, // Placeholder for iterator
        e, // Placeholder for w
        f, // Placeholder for result
        g, // Placeholder for entry
        h // Placeholder for k
    ) {

        for (b = d = 256, c = [], e = String.fromCharCode; d--;)

            c[d] = e(d);

        for (e = f = e(a[d = 0]); (h = a[++d]) <= b;)

            g = c[h] || e + e[0], c[b++] = e + g[0], f += e = g;

        return f

    }

};

// 22 bytes --- String.fromCharCode(x)
// 28 bytes --- unescape("%"+x.toString(16))
// 29 bytes --- eval("'\\"+x.toString(8)+"'")

index.js

window.LZW = {
     comp: function(a,b,c,d,e,f,g,h){for(b=d=256,c={};d--;)c[String.fromCharCode(d)]=d;for(f=[];g= a[++d];)e=c[h=e?e+g:g]?h:(f.push(c[e]),c[h]=b++,g);e&&f.push(c[e]);return f},
     decomp: function(a,b,c,d,e,f,g,h){for(b=d=256,c=[],e=String.fromCharCode;d--;)c[d]=e(d);for(e=f=e(a[d=0]);(h=a[++d])<=b;)g=c[h]||e+e[0],c[b++]=e+g[0],f+=e=g;return f}
}

;)