Module: Gio::PollableOutputStream

Defined in:
(unknown)

Overview

GPollable::OutputStream is implemented by #GOutputStreams 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.

Instance Method Summary collapse

Instance Method Details

#can_poll ⇒ TrueClass

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

Returns:

  • (TrueClass) —

    true if stream is pollable, false if not.

#create_source(cancellable) ⇒ GLib::Source

Creates a #GSource that triggers when stream can be written, or cancellable is triggered or an error occurs. The callback on the source is of the GPollable::SourceFunc type.

As with g_pollable_output_stream_is_writable(), it is possible that the stream may not actually be writable even after the source triggers, so you should use g_pollable_output_stream_write_nonblocking() rather than g_output_stream_write() from the callback.

Parameters:

Returns:

  • (GLib::Source) —

    a new #GSource

#is_writable ⇒ TrueClass

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 g_output_stream_write() after this returns true would still block. To guarantee non-blocking behavior, you should always use g_pollable_output_stream_write_nonblocking(), which will return a %G_IO_ERROR_WOULD_BLOCK error rather than blocking.

Returns:

  • (TrueClass) —

    true if stream is writable, false if not. If an error has occurred on stream, this will result in g_pollable_output_stream_is_writable() returning true, and the next attempt to write will return the error.

#write_nonblocking(buffer, count, cancellable) ⇒ Gio::gssize

Attempts to write up to count bytes from buffer to stream, as with g_output_stream_write(). If stream is not currently writable, this will immediately return %G_IO_ERROR_WOULD_BLOCK, and you can use g_pollable_output_stream_create_source() to create a #GSource 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 %G_IO_ERROR_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.

Parameters:

  • buffer (Array<Integer>) —

    a buffer to write data from

  • count (Integer) —

    the number of bytes you want to write

  • cancellable (Gio::Cancellable) —

    a #GCancellable, or nil

Returns:

  • (Gio::gssize) —

    the number of bytes written, or -1 on error (including %G_IO_ERROR_WOULD_BLOCK).

#writev_nonblocking(vectors, n_vectors, bytes_written, cancellable) ⇒ Gio::PollableReturn

Attempts to write the bytes contained in the n_vectors vectors to stream, as with g_output_stream_writev(). If stream is not currently writable, this will immediately return %G_POLLABLE_RETURN_WOULD_BLOCK, and you can use g_pollable_output_stream_create_source() to create a #GSource 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 %G_POLLABLE_RETURN_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. if the stream is not currently writable (and error is not set), or %G_POLLABLE_RETURN_FAILED if there was an error in which case error will be set.

Parameters:

  • vectors (Array<Gio::OutputVector>) —

    the buffer containing the GOutput::Vectors to write.

  • n_vectors (Integer) —

    the number of vectors to write

  • bytes_written (Integer) —

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

  • cancellable (Gio::Cancellable) —

    a #GCancellable, or nil

Returns: