from2

Convenience wrapper for ReadableStream, with an API lifted from "from" and "through2"

from2

from2 is a high-level module for creating readable streams that properly handle backpressure.

Convience wrapper for readable-stream's ReadableStream base class, with an API lifted from from and through2.

Where opts are the options to pass on to the ReadableStream constructor, and read(size, next) is called when data is requested from the stream.

  • size is the recommended amount of data (in bytes) to retrieve.
  • next(err) should be called when you're ready to emit more data.

For example, here's a readable stream that emits the contents of a given string:

var from = require('from2')
 
module.exports = fromString
 
function fromString(string) {
  return from(function(sizenext) {
    // if there's no more content 
    // left in the string, close the stream. 
    if (string.length <= 0) return this.push(null)
 
    // Pull in a new chunk of text, 
    // removing it from the string. 
    var chunk = string.slice(0, size)
    string = string.slice(size)
 
    // Emit "chunk" from the stream. 
    next(null, chunk)
  })
}
 
// pipe "hello world" out 
// to stdout. 
fromString('hello world').pipe(process.stdout)

Shorthand for from2({ objectMode: true }, read).

If you're creating similar streams in quick succession you can improve performance by generating a stream constructor that you can reuse instead of creating one-off streams on each call.

Takes the same options as from2, instead returning a constructor which you can use to create new streams.

MIT. See LICENSE.md for details.