We're hiring!
*

GLib now has a datagram interface

Philip Withnall avatar

Philip Withnall
October 13, 2015

Share this post:

For those who like their I/O packetised, GLib now has a companion for its GIOStream class — the GDatagramBasedinterface, which we’ve implemented as part of R&D work at Collabora. This is designed to be implemented by any class which does datagram-based I/O. GSocket implements it, essentially as an interface to recvmmsg() and sendmmsg(). The upcoming DTLS support in glib-networking will use it.

How is it shaped? Basically as a GLib-shaped version of recvmmsg() and sendmmsg(), where GInputMessage and GOutputMessage are effectively equivalent to struct mmsghdr, and GInputVector and GOutputVector are equivalent to struct msghdr.

The interface is designed around polling, potentially-blocking I/O. What’s ‘potentially-blocking’ about it? The timeout parameter. Set it to zero for non-blocking behaviour, where the functions will return G_IO_ERROR_WOULD_BLOCK if they would block. Set it negative for blocking behaviour, where the functions will not return until they can do at least some I/O. Set it positive for timeout behaviour, where the functions will block for the given number of microseconds, then return G_IO_ERROR_TIMED_OUT if they managed to perform no I/O.

gint
g_datagram_based_receive_messages (GDatagramBased   *datagram_based,
                                   GInputMessage    *messages,
                                   guint             num_messages,
                                   gint              flags,
                                   gint64            timeout,
                                   GCancellable     *cancellable,
                                   GError          **error);
 
gint
g_datagram_based_send_messages    (GDatagramBased   *datagram_based,
                                   GOutputMessage   *messages,
                                   guint             num_messages,
                                   gint              flags,
                                   gint64            timeout,
                                   GCancellable     *cancellable,
                                   GError          **error);
 
GSource *
g_datagram_based_create_source    (GDatagramBased   *datagram_based,
                                   GIOCondition      condition,
                                   GCancellable     *cancellable);
GIOCondition
g_datagram_based_condition_check  (GDatagramBased   *datagram_based,
                                   GIOCondition      condition);
gboolean
g_datagram_based_condition_wait   (GDatagramBased   *datagram_based,
                                   GIOCondition      condition,
                                   gint64            timeout,
                                   GCancellable     *cancellable,
                                   GError          **error);
 

Currently, the API (particularly GInputMessage and GOutputMessage, due to the way they are used as in-out parameters) doesn’t support introspection. This can be added in future if needed by creating some convenience API for allocating and freeing the message structures as boxed types.

The grand, overarching plan is for this to appear in a libnice version near you, some time soon, exposing the whole of an ICE connection as a GDatagramBased.

If you think the name is bad, tough. It has been bikeshedded enough already.

Related Posts

Related Posts

Comments (0)


Add a Comment






Allowed tags: <b><i><br>Add a new comment:


Latest Blog Posts

Testing Video4Linux2 drivers like a boss

23/05/2019

With virtme, you can run a custom built kernel on top of our running root filesystem. In this post, we explore another example of virtme…

Permissively-licensed MTP device implementation

16/05/2019

Introducing cmtp-responder - a permissively licensed Media Transfer Protocol (MTP) responder implementation which allows embedded devices…

An eBPF overview, part 5: Tracing user processes

14/05/2019

Up until now, talking in-depth about userspace tracing was deliberately avoided because it merits special treatment, hence this part devoted…

CEF on Wayland upstreamed

08/05/2019

After a successful team effort, the patch enabling the Chromium Embedded Framework (CEF) Ozone builds to run with different platform backends,…

An eBPF overview, part 4: Working with embedded systems

06/05/2019

Now that we've studied the mainstream way of developing and using eBPF programs on top of the low-level VM mechanisms, we'll look at projects…

Running Android and Wayland on embedded devices

02/05/2019

A previous post introduced the SPURV Android compatibility layer for Wayland based Linux environment. In this post, we're going to dig into…

Open Since 2005 logo

We use cookies on this website to ensure that you get the best experience. By continuing to use this website you are consenting to the use of these cookies. To find out more please follow this link.

Collabora Ltd © 2005-2019. All rights reserved. Website sitemap.