Gio.PollableOutputStream¶

Implementations:: Gio.ConverterOutputStream, Gio.MemoryOutputStream, Gio.UnixOutputStream

Methods¶

	`can_poll` ()
	`create_source` (cancellable)
	`is_writable` ()
	`write_nonblocking` (buffer, cancellable)
	`writev_nonblocking` (vectors, cancellable)

Virtual Methods¶

	`do_can_poll` ()
	`do_create_source` (cancellable)
	`do_is_writable` ()
	`do_write_nonblocking` (buffer)
	`do_writev_nonblocking` (vectors)

Properties¶

None

Signals¶

None

Fields¶

None

Class Details¶

class Gio.PollableOutputStream¶

Bases:: GObject.GInterface
Structure:: Gio.PollableOutputStreamInterface

GPollableOutputStream is implemented by [class`Gio`.OutputStream]s 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 [method`Gio`.PollableOutputStream.can_poll] returns false, then the behavior of other GPollableOutputStream 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.PollableOutputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other Gio.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.

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 written, or cancellable is triggered or an error occurs. The callback on the source is of the Gio.PollableSourceFunc type.

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

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

New in version 2.28.

is_writable()[source]¶

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

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

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

New in version 2.28.

write_nonblocking(buffer, cancellable)[source]¶

Parameters:

buffer (bytes) – a buffer to write data from
cancellable (Gio.Cancellable or None) – a Gio.Cancellable, or None

Raises:

GLib.Error

Returns:

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

Return type:

int

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

writev_nonblocking(vectors, cancellable)[source]¶

Parameters:

vectors ([Gio.OutputVector]) – the buffer containing the Gio.OutputVectors to write.
cancellable (Gio.Cancellable or None) – a Gio.Cancellable, or None

Raises:

GLib.Error

Returns:

%:obj:Gio.PollableReturn.OK on success, Gio.PollableReturn.WOULD_BLOCK if the stream is not currently writable (and error is *not* set), or Gio.PollableReturn.FAILED if there was an error in which case error will be set.

bytes_written:: location to store the number of bytes that were written to the stream

Return type:

(Gio.PollableReturn, bytes_written: int)

Attempts to write the bytes contained in the n_vectors vectors to self, as with Gio.OutputStream.writev(). If self is not currently writable, this will immediately return %:obj:Gio.PollableReturn.WOULD_BLOCK, and you can use Gio.PollableOutputStream.create_source() to create a GLib.Source that will be triggered when self 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 Gio.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 Gio.PollableOutputStream.can_poll() returns False for self.

New in version 2.60.

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.PollableOutputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other Gio.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.

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 written, or cancellable is triggered or an error occurs. The callback on the source is of the Gio.PollableSourceFunc type.

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

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

New in version 2.28.

do_is_writable() virtual¶

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

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

New in version 2.28.

do_write_nonblocking(buffer) virtual¶

Parameters:: buffer (bytes or None) – a buffer to write data from
Returns:: the number of bytes written, or -1 on error (including Gio.IOErrorEnum.WOULD_BLOCK).
Return type:: int

Attempts to write up to count bytes from buffer to stream, as with Gio.OutputStream.write(). If stream is not currently writable, this will immediately return Gio.IOErrorEnum.WOULD_BLOCK, and you can use Gio.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 Gio.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 Gio.PollableOutputStream.can_poll() returns False for stream.

do_writev_nonblocking(vectors) virtual¶

Parameters:

vectors ([Gio.OutputVector]) – the buffer containing the Gio.OutputVectors to write.

Returns:

%:obj:Gio.PollableReturn.OK on success, Gio.PollableReturn.WOULD_BLOCK if the stream is not currently writable (and error is *not* set), or Gio.PollableReturn.FAILED if there was an error in which case error will be set.

bytes_written:: location to store the number of bytes that were written to the stream

Return type:

(Gio.PollableReturn, bytes_written: int)

Attempts to write the bytes contained in the n_vectors vectors to stream, as with Gio.OutputStream.writev(). If stream is not currently writable, this will immediately return %:obj:Gio.PollableReturn.WOULD_BLOCK, and you can use Gio.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 Gio.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 Gio.PollableOutputStream.can_poll() returns False for stream.

New in version 2.60.