A ReadableStream with a base64 StringDecoder backed by only
one or two bytes would fail to output its partial data before
ending. This fix adds a check to see if the `read` was triggered
by an internal `flow`, and if so, empties any remaining data.
fixes#7914.
Signed-off-by: Fedor Indutny <fedor@indutny.com>
Closes#5860
In streams2, there is an "old mode" for compatibility. Once switched
into this mode, there is no going back.
With this change, there is a "flowing mode" and a "paused mode". If you
add a data listener, then this will start the flow of data. However,
hitting the `pause()` method will switch *back* into a non-flowing mode,
where the `read()` method will pull data out.
Every time `read()` returns a data chunk, it also emits a `data` event.
In this way, a passive data listener can be added, and the stream passed
off to some other reader, for use with progress bars and the like.
There is no API change beyond this added flexibility.
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.
When switching into compatibility mode by setting `data` event listener,
`_read()` method will be called immediately. If method implementation
invokes callback in the same tick - all emitted `data` events will be
discarded, because `data` listener wasn't set yet.