[ANNOUNCE] D-Bus 1.0 RC 2 (0.94) released
hp at redhat.com
Sun Oct 15 11:47:08 PDT 2006
Daniel Stone wrote:
> Read until img56.html. Really.
Yes, I've read that before. However, the reality here is that we're
dealing with a low-level untypesafe marshaling API written in C. So,
there is no magic way to make it foolproof.
The route I chose was:
- be 100% consistent as much as possible; the functions
always take &value, not value, rather than varying by
the type of the value
- document how it works
The safer route would be to have append_string, append_int, etc. and
don't have append_basic taking a void*. However, because this is a
low-level API intended to be wrapped, that seems a little bit bloated.
The void* version is probably more convenient for bindings in a lot of
Another safer route would be to have a DBusVariant type in the public
API, but I think that is somewhat bloated also. The variant type would
also have to have either append_* or an append_basic method.
The intent is very much that apps don't use this API, even though
everyone is because the glib bindings need a lot of work, or some people
want to avoid the glib dependency.
Still, that doesn't make it right to shove a a large pure C convenience
binding into libdbus itself. Instead, it makes it right for someone to
do the work on the glib and/or pure C binding. I don't have time but I
would love to see it.
> (After doing this, go back and check out the plain C bindings wrt
> iterators in messages, particularly the part that requires you to hand
> it a _pointer_ to a string, i.e.:
> dbus_message_iter_append(whatever, "this api sucks horribly");
> is broken, whereas:
> argh = strdup("i cannot believe i'm doing this");
> dbus_message_iter_append(whatever, &argh);
> is correct. Obviously.)
The way it works now, you can do things like:
i.e. the void* serves as a simple variant type without introducing
(Obviously the above example of copying message-to-message is
artificial, but copying message-to-some-binding-specific-something is
Code generators can also avoid special cases here; they can just
generate a template like:
instead of having to switch on the TYPE and pick the right thing to do.
The message marshal/unmarshal functions are very much designed to be
used in stubs like this, not in application code. An actual application
binding for C would not expose DBusMessage at all ideally.
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