reedsolomon

reedsolomon.js
==============

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

This is ported from [Zxing][1] open source project written in Java. Almost code is copied from [com.google.zxing.common.reedsolomon package][2].

[1]: https://github.com/zxing/zxing
[2]: https://github.com/zxing/zxing/tree/master/core/src/main/java/com/google/zxing/common/reedsolomon

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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

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