msgpack5

A msgpack v5 implementation for node.js and the browser, with extension point support.

Install

npm install msgpack5 --save

Usage

var msgpack = require('msgpack5')() // namespace our extensions
  , 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
}

In the Browser

This library is compatible with Browserify.

If you want to use standalone, grab the file in the dist folder of this repo, and use in your own HTML page, the module will expose a msgpack5 global.

<script type="text/javascript"
        src="./msgpack5.min.js">
</script>

To build

	npm run build

msgpack(options(obj))

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

options:

forceFloat64, a boolean to that forces all floats to be encoded as 64-bits floats. Defaults to false.
compatibilityMode, a boolean that enables "compatibility mode" which doesn't use str 8 format. Defaults to false.

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.

In order to support a stream interface, a user must pass in a bl instance.

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

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))

type, is a greater than zero 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))

type, is a greater than zero 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()

Builds a stream in object mode that encodes msgpack.

decoder()

Builds a stream in object mode that decodes msgpack.

LevelUp Support

msgpack5 can be used as a LevelUp valueEncoding straight away:

var level = require('level')
  , pack  = msgpack()
  , db    = level('foo', {
      valueEncoding: pack
    })
  , obj   = { my: 'obj' }

db.put('hello', obj, function(err) {
  db.get('hello', function(err, result) {
    console.log(result)
    db.close()
  })
})

Related projects

msgpack5rpc: An implementation of the msgpack-rpc spec on top of this library.

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.

This library was originally built as the data format for JSChan.

License

MIT

cheddar-lang/msgpack5