Gio.PollableInputStream¶

interface

GPollableInputStream is implemented by InputStreams that can be polled for readiness to read. 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 GPollableInputStream but have only certain instances of that class be pollable. If PollableInputStream.can_poll returns false, then the behavior of other GPollableInputStream methods is undefined.

Methods¶

can_poll¶

def can_poll(self) -> bool

Checks if stream is actually pollable. Some classes may implement PollableInputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other PollableInputStream 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 read, or cancellable is triggered or an error occurs. The callback on the source is of the GPollableSourceFunc type.

As with PollableInputStream.is_readable, it is possible that the stream may not actually be readable even after the source triggers, so you should use PollableInputStream.read_nonblocking rather than InputStream.read from the callback.

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

Parameters:

cancellable — a Cancellable, or None

is_readable¶

def is_readable(self) -> bool

Checks if stream can be read.

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

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

read_nonblocking¶

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

Attempts to read up to count bytes from stream into buffer, as with InputStream.read. If stream is not currently readable, this will immediately return IOErrorEnum.WOULD_BLOCK, and you can use PollableInputStream.create_source to create a GLib.Source that will be triggered when stream is readable.

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.

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

Parameters:

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 PollableInputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other PollableInputStream 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 read, or cancellable is triggered or an error occurs. The callback on the source is of the GPollableSourceFunc type.

As with PollableInputStream.is_readable, it is possible that the stream may not actually be readable even after the source triggers, so you should use PollableInputStream.read_nonblocking rather than InputStream.read from the callback.

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

Parameters:

cancellable — a Cancellable, or None

do_is_readable¶

def do_is_readable(self) -> bool

Checks if stream can be read.

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

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

do_read_nonblocking¶

def do_read_nonblocking(self) -> tuple[int, list[int]]

Attempts to read up to count bytes from stream into buffer, as with InputStream.read. If stream is not currently readable, this will immediately return IOErrorEnum.WOULD_BLOCK, and you can use PollableInputStream.create_source to create a GLib.Source that will be triggered when stream is readable.

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.

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