Gio.PollableInputStream¶

Implementations:: Gio.ConverterInputStream, Gio.MemoryInputStream, Gio.UnixInputStream

Methods¶

	`can_poll` ()
	`create_source` (cancellable)
	`is_readable` ()
	`read_nonblocking` (cancellable)

Virtual Methods¶

	`do_can_poll` ()
	`do_create_source` (cancellable)
	`do_is_readable` ()
	`do_read_nonblocking` ()

Properties¶

None

Signals¶

None

Fields¶

None

Class Details¶

class Gio.PollableInputStream¶

Bases:: GObject.GInterface
Structure:: Gio.PollableInputStreamInterface

Gio.PollableInputStream is implemented by Gio.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 Gio.PollableInputStream but have only certain instances of that class be pollable. If Gio.PollableInputStream.can_poll() returns False, then the behavior of other Gio.PollableInputStream methods is undefined.

New in version 2.28.

can_poll()[source]¶

Returns:: True if self is pollable, False if not.
Return type:: bool

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

New in version 2.28.

create_source(cancellable)[source]¶

Parameters:: cancellable (Gio.Cancellable or None) – a Gio.Cancellable, or None
Returns:: a new GLib.Source
Return type:: GLib.Source

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

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

The behaviour of this method is undefined if Gio.PollableInputStream.can_poll() returns False for self.

New in version 2.28.

is_readable()[source]¶

Returns:: True if self is readable, False if not. If an error has occurred on self, this will result in Gio.PollableInputStream.is_readable() returning True, and the next attempt to read will return the error.
Return type:: bool

Checks if self 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 Gio.InputStream.read() after this returns True would still block. To guarantee non-blocking behavior, you should always use Gio.PollableInputStream.read_nonblocking(), which will return a Gio.IOErrorEnum.WOULD_BLOCK error rather than blocking.

The behaviour of this method is undefined if Gio.PollableInputStream.can_poll() returns False for self.

New in version 2.28.

read_nonblocking(cancellable)[source]¶

Parameters:

cancellable (Gio.Cancellable or None) – a Gio.Cancellable, or None

Raises:

GLib.Error

Returns:

the number of bytes read, or -1 on error (including Gio.IOErrorEnum.WOULD_BLOCK).

buffer:: a buffer to read data into (which should be at least count bytes long).

Return type:

(int, buffer: bytes)

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

do_can_poll() virtual¶

Returns:: True if stream is pollable, False if not.
Return type:: bool

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

New in version 2.28.

do_create_source(cancellable) virtual¶

Parameters:: cancellable (Gio.Cancellable or None) – a Gio.Cancellable, or None
Returns:: a new GLib.Source
Return type:: 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 Gio.PollableSourceFunc type.

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

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

New in version 2.28.

do_is_readable() virtual¶

Returns:: True if stream is readable, False if not. If an error has occurred on stream, this will result in Gio.PollableInputStream.is_readable() returning True, and the next attempt to read will return the error.
Return type:: 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 Gio.InputStream.read() after this returns True would still block. To guarantee non-blocking behavior, you should always use Gio.PollableInputStream.read_nonblocking(), which will return a Gio.IOErrorEnum.WOULD_BLOCK error rather than blocking.

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

New in version 2.28.

do_read_nonblocking() virtual¶

Returns:

the number of bytes read, or -1 on error (including Gio.IOErrorEnum.WOULD_BLOCK).

buffer:: a buffer to read data into (which should be at least count bytes long).

Return type:

(int, buffer: bytes)

Attempts to read up to count bytes from stream into buffer, as with Gio.InputStream.read(). If stream is not currently readable, this will immediately return Gio.IOErrorEnum.WOULD_BLOCK, and you can use Gio.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 Gio.PollableInputStream.can_poll() returns False for stream.