Memory-managed wrapper type.

A convenience alias for Nothing :: Maybe PollableOutputStream.

Type class for types which can be safely cast to PollableOutputStream, for instance with toPollableOutputStream.

Cast to PollableOutputStream, for types for which this is known to be safe. For general casts, use castTo.

Checks if stream is actually pollable. Some classes may implement PollableOutputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other PollableOutputStream methods is undefined.

For any given stream, the value returned by this method is constant; a stream cannot switch from pollable to non-pollable or vice versa.

Since: 2.28

Creates a Source that triggers when stream can be written, or cancellable is triggered or an error occurs. The callback on the source is of the PollableSourceFunc type.

As with pollableOutputStreamIsWritable, it is possible that the stream may not actually be writable even after the source triggers, so you should use pollableOutputStreamWriteNonblocking rather than outputStreamWrite from the callback.

Since: 2.28

Checks if stream can be written.

Note that some stream types may not be able to implement this 100% reliably, and it is possible that a call to outputStreamWrite after this returns True would still block. To guarantee non-blocking behavior, you should always use pollableOutputStreamWriteNonblocking, which will return a IOErrorEnumWouldBlock error rather than blocking.

Since: 2.28

Attempts to write up to count bytes from buffer to stream, as with outputStreamWrite. If stream is not currently writable, this will immediately return IOErrorEnumWouldBlock, and you can use pollableOutputStreamCreateSource to create a Source that will be triggered when stream is writable.

Note that since this method never blocks, you cannot actually use cancellable to cancel it. However, it will return an error if cancellable has already been cancelled when you call, which may happen if you call this method after a source triggers due to having been cancelled.

Also note that if IOErrorEnumWouldBlock is returned some underlying transports like D/TLS require that you re-send the same buffer and count in the next write call.

Attempts to write the bytes contained in the nVectors vectors to stream, as with outputStreamWritev. If stream is not currently writable, this will immediately return %gPOLLABLERETURNWOULDBLOCK, and you can use pollableOutputStreamCreateSource to create a Source that will be triggered when stream is writable. error will *not* be set in that case.

Note that since this method never blocks, you cannot actually use cancellable to cancel it. However, it will return an error if cancellable has already been cancelled when you call, which may happen if you call this method after a source triggers due to having been cancelled.

Also note that if PollableReturnWouldBlock is returned some underlying transports like D/TLS require that you re-send the same vectors and nVectors in the next write call.

Since: 2.60