Gio.PollableOutputStream¶

interface

GPollableOutputStream is implemented by OutputStreams that can be polled for readiness to write. This can be used when interfacing with a non-GIO API that expects UNIX-file-descriptor-style asynchronous I/O rather than GIO-style.

Some classes may implement GPollableOutputStream but have only certain instances of that class be pollable. If PollableOutputStream.can_poll returns false, then the behavior of other GPollableOutputStream methods is undefined.

Methods¶

can_poll¶

def can_poll(self) -> bool

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.

create_source¶

def create_source(self, cancellable: Cancellable | None = ...) -> GLib.Source

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

As with PollableOutputStream.is_writable, it is possible that the stream may not actually be writable even after the source triggers, so you should use PollableOutputStream.write_nonblocking rather than OutputStream.write from the callback.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

Parameters:

cancellable — a Cancellable, or None

is_writable¶

def is_writable(self) -> bool

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 OutputStream.write after this returns True would still block. To guarantee non-blocking behavior, you should always use PollableOutputStream.write_nonblocking, which will return a IOErrorEnum.WOULD_BLOCK error rather than blocking.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

write_nonblocking¶

def write_nonblocking(self, buffer: list[int], cancellable: Cancellable | None = ...) -> int

Attempts to write up to count bytes from buffer to stream, as with OutputStream.write. If stream is not currently writable, this will immediately return IOErrorEnum.WOULD_BLOCK, and you can use PollableOutputStream.create_source to create a GLib.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 IOErrorEnum.WOULD_BLOCK is returned some underlying transports like D/TLS require that you re-send the same buffer and count in the next write call.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

Parameters:

buffer — a buffer to write data from
cancellable — a Cancellable, or None

writev_nonblocking¶

def writev_nonblocking(self, vectors: list[OutputVector], cancellable: Cancellable | None = ...) -> tuple[PollableReturn, int]

Attempts to write the bytes contained in the n_vectors vectors to stream, as with OutputStream.writev. If stream is not currently writable, this will immediately return %G_POLLABLE_RETURN_WOULD_BLOCK, and you can use PollableOutputStream.create_source to create a GLib.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 PollableReturn.WOULD_BLOCK is returned some underlying transports like D/TLS require that you re-send the same vectors and n_vectors in the next write call.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

Parameters:

vectors — the buffer containing the GOutputVectors to write.
cancellable — a Cancellable, or None

Virtual methods¶

do_can_poll¶

def do_can_poll(self) -> bool

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.

do_create_source¶

def do_create_source(self, cancellable: Cancellable | None = ...) -> GLib.Source

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

As with PollableOutputStream.is_writable, it is possible that the stream may not actually be writable even after the source triggers, so you should use PollableOutputStream.write_nonblocking rather than OutputStream.write from the callback.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

Parameters:

cancellable — a Cancellable, or None

do_is_writable¶

def do_is_writable(self) -> bool

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 OutputStream.write after this returns True would still block. To guarantee non-blocking behavior, you should always use PollableOutputStream.write_nonblocking, which will return a IOErrorEnum.WOULD_BLOCK error rather than blocking.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

do_write_nonblocking¶

def do_write_nonblocking(self, buffer: list[int] | None = ...) -> int

Attempts to write up to count bytes from buffer to stream, as with OutputStream.write. If stream is not currently writable, this will immediately return IOErrorEnum.WOULD_BLOCK, and you can use PollableOutputStream.create_source to create a GLib.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 IOErrorEnum.WOULD_BLOCK is returned some underlying transports like D/TLS require that you re-send the same buffer and count in the next write call.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

Parameters:

buffer — a buffer to write data from

do_writev_nonblocking¶

def do_writev_nonblocking(self, vectors: list[OutputVector]) -> tuple[PollableReturn, int]

Attempts to write the bytes contained in the n_vectors vectors to stream, as with OutputStream.writev. If stream is not currently writable, this will immediately return %G_POLLABLE_RETURN_WOULD_BLOCK, and you can use PollableOutputStream.create_source to create a GLib.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 PollableReturn.WOULD_BLOCK is returned some underlying transports like D/TLS require that you re-send the same vectors and n_vectors in the next write call.

The behaviour of this method is undefined if PollableOutputStream.can_poll returns False for stream.

Parameters:

vectors — the buffer containing the GOutputVectors to write.