Module: Gio::PollableInputStream

Defined in:


GPollable::InputStream is implemented by #GInputStreams 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.

Instance Method Summary collapse

Instance Method Details


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


  • (TrueClass)

    true if stream is pollable, false if not.

#create_source(cancellable) ⇒ GLib::Source

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

As with g_pollable_input_stream_is_readable(), it is possible that the stream may not actually be readable even after the source triggers, so you should use g_pollable_input_stream_read_nonblocking() rather than g_input_stream_read() from the callback.



  • (GLib::Source)

    a new #GSource


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


  • (TrueClass)

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

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

Attempts to read up to count bytes from stream into buffer, as with g_input_stream_read(). If stream is not currently readable, this will immediately return %G_IO_ERROR_WOULD_BLOCK, and you can use g_pollable_input_stream_create_source() to create a #GSource 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.


  • buffer (Array<Integer>)

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

  • count (Integer)

    the number of bytes you want to read

  • cancellable (Gio::Cancellable)

    a #GCancellable, or nil


  • (Gio::gssize)

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