Node Split Lines Transform Stream

line-splitter.js

var strDec = require('string_decoder');
var StringDecoder = strDec.StringDecoder;
var stream = require('stream');
var Transform = stream.Transform;
var util = require('util');

function LineSplitter(options) {
	if (!(this instanceof LineSplitter)) {
		return new LineSplitter(options);
	}
	options || (options = {});
	options.readableObjectMode = true;
	Transform.call(this, options);
	var state = this._writableState;
	this._decoder = new StringDecoder(state.defaultEncoding);
	this._lineBuffer = '';
	this._eol = options.eol || '\n';
}
util.inherits(LineSplitter, Transform);

LineSplitter.prototype._transform = function(chunk, encoding, callback) {
	if (encoding === 'buffer') {
		chunk = this._decoder.write(chunk);
	}
	this._readChunk(chunk);
	callback();
};

LineSplitter.prototype._readChunk = function(chunk) {
	var chunk = this._lineBuffer + chunk;
	var eol = this._eol;
	var eolSize = eol.length;
	var eolIndex;
	while (-1 !== (eolIndex = chunk.indexOf(eol))) {
		var line = chunk.substr(0, eolIndex);
		chunk = chunk.substr(eolIndex + eolSize);
		this.push(line);
	}
	this._lineBuffer = chunk;
};

LineSplitter.prototype._flush = function() {
	this._readChunk(this._decoder.end());
	var lastLine = this._lineBuffer;
	this._lineBuffer = null;
	if (lastLine.length) {
		this.push(lastLine);
	}
};