[cffi-devel] Branch: New Type Translator Interface

[James Bielman]

Hi all,

I've done yet-another rewrite of the type translator interface.  It does
everything through generic functions at run-time, which allows us to
specialize on both the Lisp object being converted, and the foreign type
we are converting to.

DEFINE-TYPE-TRANSLATOR is gone---instead you simply specialize the
generic functions as needed.  For example (taken from
examples/gettimeofday.lisp):

   ;; A NULL-POINTER is a :POINTER that must always be NULL.
   (defctype null-pointer :pointer)

   ;; Translator that ensures VALUE is a null pointer.  NIL is
   ;; also converted to a null pointer for convenience.
   (defmethod translate-to-foreign (value type (name (eql 'null-pointer)))
     (declare (ignore type name))
     (cond 
       ((null value) (null-pointer))
       ((null-pointer-p value) value)
       (t (error "~A is not a null pointer." value))))

This method on TRANSLATE-TO-FOREIGN replaces the :TO-C case of
DEFINE-TYPE-TRANSLATOR.  Specializing the other GFs is similar---I've
also added a FREE-TRANSLATED-OBJECT generic function.

There isn't yet a mechanism for optimizing the case where we are
converting a Lisp object to a C object with dynamic extent---I will add
this next, with some sort of compiler-macro-like interface.

The branch can be downloaded via:

   darcs get http://slacknet.com/~jamesjb/cffi-new-translators

Please give it a spin and let me know what you think!  Documentation
updates coming soon...

James