Re: [Vala] Creating a binding for a non-glib library and using delegate to map a function pointer

في ح، 13-03-2011 عند 17:54 +0100 ، كتب Luca Dionisi:

Another important point: you shouldn't use has_target=false if the
library you are binding has user_data arguments, so your
FunctionDelegate should be defined as

public delegate void* FunctionDelegate ();

And generally, you should try to avoid using void* if possible. For
example, if it makes sense for your library, you can use a generic

I don't get how this would map a prototype like:
void foobar(void *(*f)(void *), void *user_data);
We have a 'void *(*f)(void *)', it's a callback that only takes a
user_data parameter (which is implicit in vala) and returns a pointer,
at first it would be bound as:

public delegate void* FunctionDelegate ();
public void foobar (FunctionDelegate f);

then, if the type of the return value can be known "at compile time",
i.e. the delegate isn't supposed to return a random pointer, you can
convert this to generics using something like (untested):

public delegate G FunctionDelegate<G> ();
public void foobar<G> (FunctionDelegate<G> f);

To be explicit in real world, I want to make a binding for GNU Pth. In
their header there is:

extern pth_t          pth_spawn(pth_attr_t, void *(*)(void *), void *);
It's better to look at their documentation rather than their header :-)
Otherwise, I think what I said above applies.

You can also take a look at how this is done in the GLib threading API
for inspiration ;-)


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