binary-message-parser

Binary Message Parser

Puts together size-prefixed binary messages from received bytes. Works with pipes.

Example

const fs     = require('fs');
const Parser = require('binary-message-parser');

const rawData = Buffer.from([0, 0, 0, 8, 0, 0, 0, 5, 0, 0, 0, 8, 0, 1, 0, 0]);

// parser requires header extractor object which determines sizes of messages
// from their header bytes
const parser = new Parser(Parser.HeaderExtractorInt32BE);

// message is a Buffer containing all of the message bytes including header
parser.on('message', message => {
	console.log('message size:', message.readInt32BE(0),
	            'data:', message.readInt32BE(4));
});

parser.on('error', (err, args) => {
	console.log('error:', err, args);
});

// give data to the parser manually
parser.parseBytes(rawData);

// create file and pipe its contents to the parser
const filePath = './test.dat';
fs.writeFileSync(filePath, rawData);
fs.createReadStream(filePath)
	.pipe(parser)
	.on('finish', () => { fs.unlinkSync(filePath); });

Expected output:

message size: 8 data: 5
message size: 8 data: 65536
message size: 8 data: 5
message size: 8 data: 65536

Header Extractor

Header extractor is an object responsible for determining size of the message based on given header bytes.

Header extractors for some POD data types are available:

const Parser = require('binary-message-parser');

Parser.HeaderExtractorInt8
Parser.HeaderExtractorUInt8
Parser.HeaderExtractorInt16LE
Parser.HeaderExtractorUInt16LE
Parser.HeaderExtractorInt16BE
Parser.HeaderExtractorUInt16BE
Parser.HeaderExtractorInt32LE
Parser.HeaderExtractorUInt32LE
Parser.HeaderExtractorInt32BE
Parser.HeaderExtractorUInt32BE

Example of custom header extractor:

var customHeaderExtractor = {
	// number indicating number of bytes header consists of
	headerByteCount     : 6,

	/*
	 * this method returns number of bytes message consists of (including
	 * header bytes)
	 * @param {Buffer} buffer contains header bytes
	 */
	extractMessageSize  : buffer => {
		return buffer.readInt16BE(0) + buffer.readInt32BE(2);
	},

	/*
	 * this method is optional, by default always returns true
	 * returns true if message size is in valid range, false otherwise
	 * when false is returned 'error' event is emitted and parser object is
	 * shutdown (no longer usable).
	 * @param {Number} message size
	 */
	validateMessageSize : size => {
		return size >= headerByteCount;
	},
}

Tests

mocha