binary-parse-stream

Painless streaming binary protocol parsers using generators.

Installation

npm install binary-parse-stream

Synchronous

This module uses the exact same generator interface as binary-parse-stream, which presents a synchronous interface to a generator parser.

Usage

const BinaryParseStream = require('binary-parse-stream')
const {One} = BinaryParseStream // -1

BinaryParseStream is a TransformStream that consumes buffers and outputs objects on the other end. It expects your subclass to implement a _parse method that is a generator. When your generator yields a number, it'll be fed a buffer of that length from the input. If it yields -1, it'll be given the value of the first byte instead of a single-byte buffer. When your generator returns, the return value will be pushed to the output side.

Example

The following module parses a protocol that consists of a 32-bit unsigned big-endian type parameter, an unsigned 8-bit length parameter, and a buffer of the specified length. It outputs {type, buf} objects.

class SillyProtocolParseStream extends BinaryParseStream {
  constructor(options) {
    super(options)
    this.count = 0
  }

  *_parse() {
    const type = (yield 4).readUInt32BE(0, true)
    const length = yield -1
    const buf = yield length
    this.count++
    return {type, buf}
  }
}

There is also a shorter syntax for when you don't want to explicitly subclass: BinaryParseStream.extend(function*()).