@vweevers/length-prefixed-stream

length-prefixed-stream

Streaming equivalent of length-prefixed-message. This module allow you to send Buffers with a varint length prefix to ensure that they will arrive unpartioned. A fork of mafintosh/length-prefixed-stream (2.0.0) that upgraded readable-stream from 3 to 4.

Install

With npm do:

npm i @vweevers/length-prefixed-stream

Usage

const lpstream = require('@vweevers/length-prefixed-stream')

const encode = lpstream.encode() // create an encode stream to send data
const decode = lpstream.decode() // create an decode stream to receive data

encode.write('hello world') // send "hello world"

decode.on('data', function(data) {
  console.log(data.toString()) // will always print "hello world"
})

encode.pipe(decode) // for testing just pipe to our selves

Encoding format

This library encodes each chunks as follows:

<length-of-chunk-1> <chunk-1> <length-of-chunk-2> <chunk-2> …

The length of the following chunk is encoded using varint, which follows the protobuf-style varint encoding.

As an example, we're going to encode two ASCII chunks:

1st chunk:
68 65 79                            hey
2nd chunk:
68 65 6c 6c 6f 20 77 6f 72 6c 64    hello world

Encoded using length-prefixed-stream, they look like this:

03                                  varint-encoded length of 1st chunk
68 65 79                            1st chunk (3 bytes)
0b                                  varint-encoded length ()of 2nd chunk
68 65 6c 6c 6f 20 77 6f 72 6c 64    2nd chunk (11 bytes)

API

transformStream = lpstream.encode()

Creates a new encoder transform stream.

transformStream = lpstream.decode()

Creates a new decoder transform stream.

License

MIT