stream_spec.md

a Stream spec

This document defines the behaviour that a Stream must implement in order to be compatible with Stream#pipe. This is not an official document, but is intended as a guide to produce correct behaviour in user-land streams.

Stream

All streams must emit 'error' if writing to or reading from becomes physically impossible. 'error' implys that the stream has ended.

All streams may emit 'close'. 'close' means that any underlying resources have been disposed of. If a ReadableStream has ended normally, it must not emit 'close' before 'end'.

A Stream must not emit 'error' if the error is recoverable. (that is not in the stream spec)

All streams should implement destroy but a WritableStream must implement destroy.

emit('error')

All streams must emit 'error' when an error that is not recoverable has occurred. If it has become physically impossible to write to or read from the Stream, then emit 'error'.

A WriteableStream may throw an error if write has been called after end. (which should never happen, in correct usage)

otherwise, a stream must never throw an error. (always emit)

WritableStream

A WritableStream must implement methods write, end, and destroy, and writable must be set to true, and must inherit Stream#pipe

write(data)

write must return either true or false. (if false then the writer should pause) If write is called after end, an error may be thrown.

end()

calling end may set writable to false. If the Stream is also readable, it must eventually emit 'end'.

destroy()

Used to dispose of a Stream.

Calling destroy must dispose of any underlying resources. Calling destroy must emit 'close' eventually, once any underlying resources are disposed of.

ReadableStream

A ReadableStream must inherit pipe from Stream, and set readable to true, and must emit zero or more 'data' events, followed by a single end event. A ReadableStream may implement pause and resume methods.

• I will not bother to specify the behaviour of pipe because I am attempting to document what must be done in order for your Stream to be compatible with pipe.

emit('data', data)

A ReadableStream may emit one or more 'data' events. A ReadableStream must not emit emit a 'data' event after it has emitted 'end'

emit('end')

A ReadableStream should emit an 'end' event when it is not going to emit any more 'data' events. 'end' must not be emitted more than once. A ReadableStream may set readable to false after it has emitted the 'end' event.

pause()

A readable Stream may implement the pause method. When pause is called, the stream should attempt to emit 'data' less often. (possibly stopping altogether until resume is called)

resume()

A ReadableStream may implement the resume method. If the Stream has been paused, it may now emit 'data' more often, or commence emitting data if it has stopped all together.

destroy()

A ReadableStream should implement destroy.

Calling destroy must dispose of any underlying resources. Calling destroy must emit 'close' eventually, once any underlying resources are disposed of.

request for comment

thank you in advance!

I've made a few improvements since you forked this. 'star' might be more useful.

Thanks for the update. :)