index.js
function pipe(dest, options) {
    var settings = options || {}
    var onend = once(onended)

    emitter.on('data', ondata)
    emitter.on('error', onerror)
    emitter.on('end', cleanup)
    emitter.on('close', cleanup)

    // If the `end` option is not supplied, `dest.end()` will be called when the
    // `end` or `close` events are received.  Only `dest.end()` once.
    if (!dest._isStdio && settings.end !== false) {
      emitter.on('end', onend)
    }

    dest.on('error', onerror)
    dest.on('close', cleanup)

    dest.emit('pipe', emitter)

    return dest

    // End destination.
    function onended() {
      if (dest.end) {
        dest.end()
      }
    }

    // Handle data.
    function ondata(chunk) {
      if (dest.writable) {
        dest.write(chunk)
      }
    }

    // Clean listeners.
    function cleanup() {
      emitter.removeListener('data', ondata)
      emitter.removeListener('end', onend)
      emitter.removeListener('error', onerror)
      emitter.removeListener('end', cleanup)
      emitter.removeListener('close', cleanup)

      dest.removeListener('error', onerror)
      dest.removeListener('close', cleanup)
    }

    // Close dangling pipes and handle unheard errors.
    function onerror(err) {
      var handlers = emitter._events.error

      cleanup()

      // Cannot use `listenerCount` in node <= 0.12.
      if (!handlers || handlers.length === 0 || handlers === onerror) {
        throw err // Unhandled stream error in pipe.
      }
    }
  }
function pipe(dest, options) {
    var settings = options || {}
    var onend = once(onended)

    emitter.on('data', ondata)
    emitter.on('error', onerror)
    emitter.on('end', cleanup)
    emitter.on('close', cleanup)

    // If the `end` option is not supplied, `dest.end()` will be called when the
    // `end` or `close` events are received.  Only `dest.end()` once.
    if (!dest._isStdio && settings.end !== false) {
      emitter.on('end', onend)
    }

    dest.on('error', onerror)
    dest.on('close', cleanup)

    dest.emit('pipe', emitter)

    return dest

    // End destination.
    function onended() {
      if (dest.end) {
        dest.end()
      }
    }

    // Handle data.
    function ondata(chunk) {
      if (dest.writable) {
        dest.write(chunk)
      }
    }

    // Clean listeners.
    function cleanup() {
      emitter.removeListener('data', ondata)
      emitter.removeListener('end', onend)
      emitter.removeListener('error', onerror)
      emitter.removeListener('end', cleanup)
      emitter.removeListener('close', cleanup)

      dest.removeListener('error', onerror)
      dest.removeListener('close', cleanup)
    }

    // Close dangling pipes and handle unheard errors.
    function onerror(err) {
      var handlers = emitter._events.error

      cleanup()

      // Cannot use `listenerCount` in node <= 0.12.
      if (!handlers || handlers.length === 0 || handlers === onerror) {
        throw err // Unhandled stream error in pipe.
      }
    }
  }
Pipe the processor into a writable stream.  Basically `Stream#pipe`, but inlined and simplified to keep the bundled size down. See <https://github.com/nodejs/node/blob/master/lib/stream.js#L26>.