string objectMode

gistfile1.coffee

{Readable,Transform} = require 'stream'
crypto = require 'crypto'

report = (stream) ->
  int = setInterval ->
    console.log "#{stream.constructor.name}(#{stream._writableState?.length or ''} #{stream._readableState?.length or ''})"
  , 1000
  stream.on 'end', -> clearInterval int

# generates a bunch of strings
class DataGenerator extends Readable
  constructor: (@bytes) ->
    # objectMode incorrectly set to true on the readable side
    super objectMode: true
    @generated = 0
    report @

  _read: () ->
    buf = crypto.randomBytes(Math.min(256, @bytes-@generated))
    @generated += buf.length
    @push buf.toString('base64')
    console.log 'bytes generated:', @generated
    if @bytes == @generated
      console.log 'done generating bytes'
      @push null

# extremely slow consumer of strings, incorrectly configured to be objectMode: true
class SlowDataTransformer extends Transform
  constructor: ->
    super objectMode: true
    report @

  _transform: (chunk, encoding, cb) ->
    setTimeout () ->
      cb null, 1
    , 100000

new DataGenerator(100000) # 100k
.pipe(new SlowDataTransformer())
.on('data', console.log)
.on('end', -> console.log 'done')

output.txt

bytes generated: 256
bytes generated: 512
bytes generated: 768
bytes generated: 1024
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bytes generated: 99840
bytes generated: 100000
done generating bytes
SlowDataTransformer(391 )
SlowDataTransformer(391 )
^C