Filter Frame Stream

Overview

Filter data frames from a stream of buffers by a head marker and optional tail—or trailing—marker, keeping these bytes intact in the returned chunks. This is useful when splitting up a stream of data with embedded frames used by some protocols (especially useful for variable length frame protocols), or even for extracting other data, such as JPEG images.

Installation

npm install --save filter-frame-stream

Usage

To filter the frame buffers you desire, provide your frame start/head and end/tail as arguments, along with an optional encoding. The arguments are as follows:

filterFrame(start, end, enc)

If not provided, start will default to 0x00. Without specifying an end value (or if end is set to false) the buffers will include everything up until the next occurrence of the start delimiter/marker.

Both start and end may be either a string or buffer. If not provided, enc will default to utf8, although any node-compatible encoding works.

The following is a silly example of how you would filter all websocket frames:

const filterFrame = require('filter-frame-stream')

process.stdin
  .pipe(filterFrame(Buffer.from('00', 'FF', 'hex')))
  .pipe(process.stdout)

For more examples, see the tests.

License

ISC, see LICENSE for details.