readable-to-readable

readable-to-readable

ReadableToReadable forwards the data of another Readable. This can be useful if a Readable must be wrapped into another Readable.

Usage

The package exports the ReadableToReadable class. It can be imported like this:

const ReadableToReadable = require('readable-to-readable')

ReadableToReadable (input, { map, ... })

The ReadableToReadable class can be used as a base class to create the new Readable. The constructor must be called with the input stream as the first parameter. The following optional options can be given as the second argument:

• end: Close the instance at the end of the input stream. (default: false)
• map: A function that translates the incoming chunks.
• others: Any other arguments will be forwarded to the Readable constructor.

ReadableToReadable.readFrom (input, { map })

The readFrom function returns a read function for Readable instances. It will forward the chunks from the given input Readable. The function can be useful to create more customized instances of Readable. The following optional options can be given as the second argument:

• end: Close the output stream at the end of the input stream. (default: false)
• map: A function that translates the incoming chunks.

The function returns true when the end of the input stream is reached and false for the case that the readable buffer is full.

Example

Two streams are created in this example. Data is pushed to the input stream and read from the output stream. The output stream is a ReadableToReadable that takes care of forwarding and also translated the string to upper case. Once the data passed the two streams, it's written to the console. This is done until the output is finished.

const { promisify } = require('util')
const { finished, Readable } = require('readable-stream')
const ReadableToReadable = require('..')

async function main () {
  // just a plain Readable to push some data
  const input = new Readable({
    read: () => {}
  })

  // in the output stream we forward the data from input whenever .read is called
  const output = new ReadableToReadable(input, {
    map: chunk => chunk.toString().toUpperCase()
  })

  // add some data and close the stream
  input.push('a')
  input.push('b')
  input.push('c')
  input.push(null)

  // write each chunk to the console
  output.on('data', chunk => console.log(chunk.toString()))

  // wait till the end event of output was emitted
  await promisify(finished)(output)
}

main()