This makes it so that `stream.push(chunk)` is the only way to signal the
end of reading, removing the confusing disparity between the
callback-style _read method, and the fact that most real-world streams
do not have a 1:1 corollation between the "please give me data" event,
and the actual arrival of a chunk of data.
It is still possible, of course, to implement a `CallbackReadable` on
top of this. Simply provide a method like this as the callback:
function readCallback(er, chunk) {
if (er)
stream.emit('error', er);
else
stream.push(chunk);
}
However, *only* fs streams actually would behave in this way, so it
makes not a lot of sense to make TCP, TLS, HTTP, and all the rest have
to bend into this uncomfortable paradigm.
Those values, if passed to the _read() cb, will not signal an EOF. Only
null or undefined will mark the end of data, and trigger the end event.
However, great care must be taken if you are returning an empty string
or buffer! There must be some other thing somewhere that will trigger
a read() call, because there will never be a readable event fired later.
This is in preparation for CryptoStreams being ported to streams2, where
it is safe to simply stop reading, because the crypto cycle process will
cause it to read(0) again at some future date.
isaacs