stream-limiter

A PassThrough stream that stops streaming after the specified number of bytes has been passed.

Does not support objectMode.

Setup

npm install stream-limiter

Implementation details

Always count bytes and not characters, even if it is inserted into the chain of text streams.

Please note, that for text streams some characters can take more then one byte and thus can be cut off in the middle at the end of the resulting stream. This is an intentional behavior, as the exact byte size is considered to be more important here.

Usage

const StreamLimiter = require('stream-limiter')
const { Readable } = require('stream') // or: require('readable-stream')

// Sample readable stream of 8 bytes.
// The bytes might (but not have to) be interpreted as 8 ascii chars:
//  'M', 'a', 'r', 's', 'h', 'a', 'l', 'l'
const rs = new Readable()
rs.push(Buffer.from([77, 97, 114, 115, 104, 97, 108, 108]))
rs.push(null)

// limiter PassThrough stream with maxBytes = 7
const sl = StreamLimiter(7)

// pipe through it
rs.pipe(sl).pipe(process.stdout)
// output > Marshal     (without last 'l')

// An implicit conversion to chars took place while
// printing output in the terminal window, but basically
// we have [77, 97, 114, 115, 104, 97, 108] bytes sequence
// at the readable end of 'sl' stream here.

The only constructor parameter is the maxBytes - number of bytes allowed to pass through the stream.

This can be any number, including +Infinity. Numbers less then 1 (e.g. 0, 0.99, -5, -Infinity) are treated as zero bytes limit, thus the stream will end (and emit the 'finish' event) immediately after the streaming has begun.

Any other value (like NaN, or of any type other then Number) will be interpreted as +Infinity and act as if there is no limit.

Dependencies

For a "stable streams base, regardless of what version of Node you are using" we use readable-stream standalone stream module instead of Node core implementation (read elaboration on this here).