reedsolomon

reedsolomon.js

reedsolomon.js is an implementation of Reed-Solomon coding method for both encoding and decoding.

This is ported from Zxing open source project written in Java. Almost code is copied from com.google.zxing.common.reedsolomon package.

SYNOPSIS

This library provides only low-level RS coding classes (faithfully imported from original Zxing).

// running on node.js
var rs = require('./reedsolomon.js');

function RS(messageLength, errorCorrectionLength) {
	var dataLength = messageLength - errorCorrectionLength;
	var encoder = new rs.ReedSolomonEncoder(rs.GenericGF.AZTEC_DATA_8());
	var decoder = new rs.ReedSolomonDecoder(rs.GenericGF.AZTEC_DATA_8());
	return {
		dataLength: dataLength,
		messageLength: messageLength,
		errorCorrectionLength: errorCorrectionLength,

		encode : function (message) {
			encoder.encode(message, errorCorrectionLength);
		},

		decode: function (message) {
			decoder.decode(message, errorCorrectionLength);
		}
	};
}

var ec = RS(32, 8);
var message = new Int32Array(ec.messageLength);
for (var i = 0; i < ec.dataLength; i++) message[i] = i;

console.log('raw data');
console.log(Array.prototype.join.call(message));
//=> 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,0,0,0,0,0,0,0,0

ec.encode(message);

console.log('rs coded');
console.log(Array.prototype.join.call(message));
//=> 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,180,183,0,112,111,203,47,126

console.log('corrupted');
for (var i = 0; i < 4; i++) message[ Math.floor(Math.random() * message.length) ] = 0xff;
console.log(Array.prototype.join.call(message));
//=> 0,1,2,3,4,255,6,7,8,9,10,11,12,13,14,15,255,17,18,19,20,21,22,23,255,183,255,112,111,203,47,126

ec.decode(message);

console.log('rs decoded');
console.log(Array.prototype.join.call(message));
//=> 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,180,183,0,112,111,203,47,126

API

See also: http://zxing.github.io/zxing/apidocs/com/google/zxing/common/reedsolomon/package-frame.html