msgpack5  

A msgpack v5 implementation for node.js, with prototype-based extension points.

This library was built as the data format for JSChan.

Install

npm install msgpack5 --save

Usage

var msgpack = require('msgpack5')() // namespace our extensions
  , assert  = require('assert')
  , a       = new MyType(2, 'a')
  , encode  = msgpack.encode
  , decode  = msgpack.decode

msgpack.register(0x42, MyType, mytipeEncode, mytipeDecode)

console.log(encode({ 'hello': 'world' }).toString('hex'))
// 81a568656c6c6fa5776f726c64
console.log(decode(encode({ 'hello': 'world' })))
// { hello: 'world' }
console.log(encode(a).toString('hex'))
// d5426161
console.log(decode(encode(a)) instanceof MyType)
// true
console.log(decode(encode(a)))
// { value: 'a', size: 2 }

function MyType(size, value) {
  this.value = value
  this.size  = size
}

function mytipeEncode(obj) {
  var buf = new Buffer(obj.size)
  buf.fill(obj.value)
  return buf
}

function mytipeDecode(data) {
  var result = new MyType(data.length, data.toString('utf8', 0, 1))
    , i

  for (i = 0; i < data.length; i++) {
    if (data.readUInt8(0) != data.readUInt8(i)) {
      throw new Error('should all be the same')
    }
  }

  return result
}

API

API

• msgpack()
• msgpack().encode()
• msgpack().decode()
• msgpack().registerEncoder()
• msgpack().registerDecoder()
• msgpack().register()
• msgpack().encoder()
• msgpack().decoder()

msgpack()

Creates a new instance on which you can register new types for being encoded.

encode(object)

Encodes object in msgpack, returns a bl.

decode(buf)

Decodes buf from in msgpack. buf can be a Buffer or a bl instance.

registerEncoder(check(obj), encode(obj))

Register a new custom object type for being automatically encoded. The arguments are:

• check, a function that will be called to check if the passed object should be encoded with the encode function
• encode, a function that will be called to encode an object in binary form; this function must return a Buffer which include the same type for registerDecoder.

registerDecoder(type, decode(buf))

Register a new custom objet type for being automatically decoded. The arguments are:

• type, is a positive integer identificating the type once serialized
• decode, a function that will be called to decode the object from the passed Buffer

register(type, constructor, encode(obj), decode(buf))

Register a new custom objet type for being automatically encoded and decoded. The arguments are:

• type, is a positive integer identificating the type once serialized
• constructor, the function that will be used to match the objects with instanceof
• encode, a function that will be called to encode an object in binary form; this function must return a Buffer that can be deserialized by the decode function
• decode, a function that will be called to decode the object from the passed Buffer

This is just a commodity that calls registerEncoder and registerDecoder internally.

encoder(opts)

Builds a stream in object mode that encodes msgpack. By default it writes an 4 byte length header containing the message length as a UInt32BE. This header can be disabled by passing { header: false } as an option.

decoder(opts)

Builds a stream in object mode that decodes msgpack. By default it expects msgpack to have a 4 byte length header containing the packaged length as a UInt32BE. This header can be disabled by passing { header: false } as an option.

Disclaimer

This library is built fully on JS and on bl to simplify the code. Every improvement that keeps the same API is welcome.

Acknowledgements

This project was kindly sponsored by nearForm.

License

MIT