LzwCompression.java

package ie.flax.flaxengine.client;

public class LzwCompression {


	public static native String compress(String s) /*-{
		var dict = {};
	    var data = (s + "").split("");
	    var out = [];
	    var currChar;
	    var phrase = data[0];
	    var code = 256;
	    for (var i=1; i<data.length; i++) {
	        currChar=data[i];
	        if (dict[phrase + currChar] != null) {
	            phrase += currChar;
	        }
	        else {
	            out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
	            dict[phrase + currChar] = code;
	            code++;
	            phrase=currChar;
	        }
	    }
	    out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
	    for (var i=0; i<out.length; i++) {
	        out[i] = String.fromCharCode(out[i]);
	    }
	    return out.join("");
	}-*/;
	
	public static native String decompress(String s) /*-{
	
		 var dict = {};
	    var data = (s + "").split("");
	    var currChar = data[0];
	    var oldPhrase = currChar;
	    var out = [currChar];
	    var code = 256;
	    var phrase;
	    for (var i=1; i<data.length; i++) {
	        var currCode = data[i].charCodeAt(0);
	        if (currCode < 256) {
	            phrase = data[i];
	        }
	        else {
	           phrase = dict[currCode] ? dict[currCode] : (oldPhrase + currChar);
	        }
	        out.push(phrase);
	        currChar = phrase.charAt(0);
	        dict[code] = oldPhrase + currChar;
	        code++;
	        oldPhrase = phrase;
	    }
	    return out.join("");
    
	}-*/;
}