2008-06-07 17:24:26

by David Stockwell

[permalink] [raw]
Subject: [Bluez-devel] UPDATE: Retrieving an Array of Strings, that is attached to a G_HASH_TABLE variant

Regarding my question about Retrieving an Array of Strings, attached to a "dict" variant in the new interface (e.g., the Device
interface, UUIDs property), I received the following answer. I have implemented it in my code, and it works (of course).

Just submitting to bluez-devel (a "managed" cross-posting from dbus-devel), so that anybody else developing to the new Bluez DBus
interfaces having similar issues can save time.

DS

----- Original Message -----
From: "Simon McVittie"

On Thu, 05 Jun 2008 at 23:42:00 -0500, David Stockwell wrote:
> (GStrv) gPropValue = (GStrv) g_hash_table_lookup(propTable, "Strings"); // Assume that the "key" is "Strings"

This is wrong - an a{sv} maps to a GHashTable from gchar * to GValue *.

The right way to access it is like this:

GValue *tmp = g_hash_table_lookup (propTable, "Strings");
gchar **gPropValue;

if (G_VALUE_HOLDS (tmp, G_TYPE_STRV))
{
gPropValue = g_value_get_boxed (tmp);
}
else
{
/* caller has done the wrong thing - recover in whatever way you
* think best (but crashing in response to D-Bus messages is never the
* right answer) */
g_debug ("wtf? someone's using the wrong type - ignoring this message");
return;
}

Similarly, if you have a (string|integer|...) value in your dictionary,
it'll actually be a GValue containing a (string|integer|...), and you
have to check with (G_VALUE_HOLDS_STRING|G_VALUE_HOLDS_INT|...) that the
caller gave you the right thing, then call
(g_value_get_string|g_value_get_int|...) to get the actual value.

The functions tp_asv_get_uint32 (etc.) in telepathy-glib/dbus.[ch],
available from <http://telepathy.freedesktop.org/releases/telepathy-glib/> or
<http://darcs.collabora.co.uk/>, illustrate how to use an a{sv} in
dbus-glib code.

Regards,
Simon



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