Buffered Transform stream — simple PassThrough stream that also keeps an internal buffer. When a stream is piped into the BufferStream, the internal buffer is written to the new piped stream; after that the BufferStream behaves like a PassThrough.

generate_input.sh

dd if=/dev/zero of=input.txt bs=512k count=50

index.js

var fs = require('fs')
var util = require('util')
var stream = require('stream')

var BufferStream = function (streamOptions) {
  stream.Transform.call(this, streamOptions)
}

util.inherits(BufferStream, stream.Transform)

BufferStream.prototype.pipe = function (destination, options) {
  var res = BufferStream.super_.prototype.pipe.call(this, destination, options)
  if (this.buffer)
    res.write(this.buffer)
  return res
}

BufferStream.prototype._transform = function (chunk, encoding, done) {
  this.buffer = new Buffer(chunk)
  this.push(chunk)
  done()
}

var input = fs.createReadStream('input.txt')
var buffer = new BufferStream()

input.pipe(buffer)
setTimeout(function () {
  buffer.pipe(fs.createWriteStream('output1.txt'))
}, 1)
setTimeout(function () {
  buffer.pipe(fs.createWriteStream('output2.txt'))
}, 50)

nice work

I implement the following based off your code https://gist.github.com/ORESoftware/e733e03334d885c9249b81866ed5b9b9, do you see anything wrong with it?