[cffi-devel] Converting foreign structures with CFFI generic functions

[Liam Healy]

I'm looking for some clarification of the design and intent of some CFFI
definitions. As has been mentioned in another thread, I am working on
incorporating my system Foreign Structures By Value, FSBV, into CFFI.  As a
first step toward that integration, I have been looking at conversion of
objects from CL to foreign and vice versa, with the idea of unifying the
approach to include foreign structures.  My goal is to be as consistent with
the existing CFFI design as I can be.

My understanding is that CFFI's conversion design is expressed in the
generic functions translate-to-foreign, translate-from-foreign, and
free-translated-object, to which applications may add methods, and the
functions convert-to-foreign and convert-from-foreign to permit the user to
make a conversion manually.  At present there are no definitions to convert
foreign structures, and I'd like to add that.  I think my approach should be
to add methods to translate-*-foreign and free-translated-object, or have
defcstruct add the methods when it is expanded.

My thought now is that I should define methods for translate-*-foreign and
free-translated-object dispatching on the foreign-struct-type class.  The
body will call the same method with the structure name, and applications can
define methods eql-specialized on the name.  Does this sound like it will
work correctly with CFFI as it exists now, so that I can then introduce the
libffi interface for the calls to foreign functions?

Thanks,
Liam
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