X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/clg/blobdiff_plain/e2ebafb115b201d38b16f2ee7064b8514ea6b2e3..a7d19b2a6d3e11b28842476b80ef68d81fb6b8ac:/glib/proxy.lisp

diff --git a/glib/proxy.lisp b/glib/proxy.lisp
index 927e539..1ca8fe5 100644
--- a/glib/proxy.lisp
+++ b/glib/proxy.lisp
@@ -20,7 +20,7 @@
 ;; TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 ;; SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-;; $Id: proxy.lisp,v 1.23 2006-02-02 22:35:14 espen Exp $
+;; $Id: proxy.lisp,v 1.36 2006-02-26 15:30:01 espen Exp $
 
 (in-package "GLIB")
 
@@ -43,10 +43,10 @@   (defclass effective-virtual-slot-definition (standard-effective-slot-definitio
      (boundp :reader slot-definition-boundp :initarg :boundp)))
 
   (defclass direct-special-slot-definition (standard-direct-slot-definition)
-    ())
+    ((special :initarg :special :accessor slot-definition-special)))
   
   (defclass effective-special-slot-definition (standard-effective-slot-definition)
-    ()))
+    ((special :initarg :special :accessor slot-definition-special))))
 
 (defvar *unbound-marker* (gensym "UNBOUND-MARKER-"))
 
@@ -59,23 +59,22 @@ (defun most-specific-slot-value (instances slot &optional (default *unbound-mark
 	(slot-value object slot)
       default)))
 
-(defmethod initialize-instance ((slotd effective-special-slot-definition) &rest initargs)
-  (declare (ignore initargs))
-  (call-next-method)
-  (setf (slot-value slotd 'allocation) :instance))
-
 
 (defmethod direct-slot-definition-class ((class virtual-slots-class) &rest initargs)
-  (case (getf initargs :allocation)
-    (:virtual (find-class 'direct-virtual-slot-definition))
-    (:special (find-class 'direct-special-slot-definition))
-    (t (call-next-method))))
+  (cond
+   ((eq (getf initargs :allocation) :virtual)
+    (find-class 'direct-virtual-slot-definition))
+   ((getf initargs :special)
+    (find-class 'direct-special-slot-definition))
+   (t (call-next-method))))
 
 (defmethod effective-slot-definition-class ((class virtual-slots-class) &rest initargs)
-  (case (getf initargs :allocation)
-    (:virtual (find-class 'effective-virtual-slot-definition))
-    (:special (find-class 'effective-special-slot-definition))
-    (t (call-next-method))))
+  (cond
+   ((eq (getf initargs :allocation) :virtual)
+    (find-class 'effective-virtual-slot-definition))
+   ((getf initargs :special)
+    (find-class 'effective-special-slot-definition))
+   (t (call-next-method))))
 
 
 (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-definition))
@@ -84,7 +83,7 @@ (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-def
        (slot-value slotd 'reader-function)
        #'(lambda (object)
 	   (declare (ignore object))
-	   (error "Can't read slot: ~A" (slot-definition-name slotd)))
+	   (error "Slot is not readable: ~A" (slot-definition-name slotd)))
        (slot-value slotd 'boundp-function)
        #'(lambda (object) (declare (ignore object)) nil))
 
@@ -103,7 +102,7 @@ (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-def
 			      (setq reader
 			       (mkbinding getter 
 				(slot-definition-type slotd) 'pointer)))
-			    (funcall reader (proxy-location object))))))))))
+			    (funcall reader (foreign-location object))))))))))
 
       (setf 
        (slot-value slotd 'boundp-function)
@@ -124,12 +123,15 @@ (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-def
 			     (setq reader
 			      (mkbinding boundp
 			       (slot-definition-type slotd) 'pointer)))
-			   (funcall reader (proxy-location object))))))))
-	((multiple-value-bind (unbound-p unbound-value)
-	     (unbound-value (slot-definition-type slotd))
-	   (when unbound-p
-	     #'(lambda (object)
-		 (not (eq (funcall getter-function object) unbound-value))))))
+			   (funcall reader (foreign-location object))))))))
+	((let ((unbound-value-method
+		(find-applicable-type-method 'unbound-value 
+		 (slot-definition-type slotd) nil)))
+	   (when unbound-value-method
+	     (let ((unbound-value 
+		    (funcall unbound-value-method (slot-definition-type slotd))))
+	       #'(lambda (object)
+		   (not (eq (funcall getter-function object) unbound-value)))))))
 	(#'(lambda (object) (declare (ignore object)) t))))
 
       (setf
@@ -149,10 +151,13 @@ (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-def
 	       (and
 		(funcall boundp-function object)
 		(funcall getter-function object)))))
-	((multiple-value-bind (unbound-p unbound-value)
-	     (unbound-value (slot-definition-type slotd))
-	   (let ((slot-name (slot-definition-name slotd)))
-	     (when unbound-p
+	((let ((unbound-value-method
+		(find-applicable-type-method 'unbound-value 
+		 (slot-definition-type slotd) nil)))
+	   (when unbound-value-method
+	     (let ((unbound-value 
+		    (funcall unbound-value-method (slot-definition-type slotd)))
+		   (slot-name (slot-definition-name slotd)))
 	       #'(lambda (object)
 		   (let ((value (funcall getter-function object)))
 		     (if (eq value unbound-value)
@@ -163,9 +168,9 @@ (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-def
   (setf 
    (slot-value slotd 'writer-function)
    (if (not (slot-boundp slotd 'setter))
-       #'(lambda (object)
-	   (declare (ignore object))
-	   (error "Can't set slot: ~A" (slot-definition-name slotd)))
+       #'(lambda (value object)
+	   (declare (ignore value object))
+	   (error "Slot is not writable: ~A" (slot-definition-name slotd)))
      (with-slots (setter) slotd
        (etypecase setter
 	 (function setter)
@@ -181,9 +186,9 @@ (defmethod initialize-internal-slot-functions ((slotd effective-virtual-slot-def
 		   (setq writer
 		    (mkbinding setter 'nil 'pointer 
 		     (slot-definition-type slotd))))
-		 (funcall writer (proxy-location object) value)))))))))
+		 (funcall writer (foreign-location object) value)))))))))
 
-  (initialize-internal-slot-gfs (slot-definition-name slotd)))
+  #-sbcl>=0.9.8(initialize-internal-slot-gfs (slot-definition-name slotd)))
 
 
 
@@ -191,22 +196,29 @@ (defmethod compute-slot-accessor-info ((slotd effective-virtual-slot-definition)
   nil)
 
 (defmethod compute-effective-slot-definition-initargs ((class virtual-slots-class) direct-slotds)
-  (if (typep (first direct-slotds) 'direct-virtual-slot-definition)
-      (let ((initargs ()))
-	(let ((getter (most-specific-slot-value direct-slotds 'getter)))
-	  (unless (eq getter *unbound-marker*)
-	    (setf (getf initargs :getter) getter)))
-	(let ((setter (most-specific-slot-value direct-slotds 'setter)))
-	  (unless (eq setter *unbound-marker*)
-	    (setf (getf initargs :setter) setter)))
-	(let ((unbound (most-specific-slot-value direct-slotds 'unbound)))
-	  (unless (eq unbound *unbound-marker*)
-	    (setf (getf initargs :unbound) unbound)))
-	(let ((boundp (most-specific-slot-value direct-slotds 'boundp)))
-	  (unless (eq boundp *unbound-marker*)
-	    (setf (getf initargs :boundp) boundp)))
-	(nconc initargs (call-next-method)))
-    (call-next-method)))
+  (typecase (first direct-slotds)
+    (direct-virtual-slot-definition
+     (let ((initargs ()))
+       (let ((getter (most-specific-slot-value direct-slotds 'getter)))
+	 (unless (eq getter *unbound-marker*)
+	   (setf (getf initargs :getter) getter)))
+       (let ((setter (most-specific-slot-value direct-slotds 'setter)))
+	 (unless (eq setter *unbound-marker*)
+	   (setf (getf initargs :setter) setter)))
+       (let ((unbound (most-specific-slot-value direct-slotds 'unbound)))
+	 (unless (eq unbound *unbound-marker*)
+	   (setf (getf initargs :unbound) unbound)))
+       (let ((boundp (most-specific-slot-value direct-slotds 'boundp)))
+	 (unless (eq boundp *unbound-marker*)
+	   (setf (getf initargs :boundp) boundp)))
+       ;; Need this to prevent type expansion in SBCL >= 0.9.8
+       (let ((type (most-specific-slot-value direct-slotds 'type)))
+	 (unless (eq type *unbound-marker*)
+	   (setf (getf initargs :type) type)))
+       (nconc initargs (call-next-method))))
+    (direct-special-slot-definition
+     (append '(:special t) (call-next-method)))
+    (t (call-next-method))))
 
 
 (defmethod slot-value-using-class
@@ -232,14 +244,22 @@ (defmethod validate-superclass
   t)
 
 
+(defmethod slot-definition-special ((slotd standard-direct-slot-definition))
+  (declare (ignore slotd))
+  nil)
+
+(defmethod slot-definition-special ((slotd standard-effective-slot-definition))
+  (declare (ignore slotd))
+  nil)
+
+
 ;;;; Proxy cache
 
-(internal *instance-cache*)
 (defvar *instance-cache* (make-hash-table :test #'eql))
 
 (defun cache-instance (instance &optional (weak-ref t))
   (setf
-   (gethash (sap-int (proxy-location instance)) *instance-cache*)
+   (gethash (sap-int (foreign-location instance)) *instance-cache*)
    (if weak-ref
        (make-weak-pointer instance)
      instance)))
@@ -266,17 +286,50 @@ (defun list-cached-instances ()
 	     *instance-cache*)
     instances))
 			
+;; Instances that gets invalidated tend to be short lived, but created
+;; in large numbers. So we're keeping them in a hash table to be able
+;; to reuse them (and thus reduce consing)
+(defvar *invalidated-instance-cache* (make-hash-table :test #'eql))
+
+(defun cache-invalidated-instance (instance)
+  (push instance
+   (gethash (class-of instance) *invalidated-instance-cache*)))
+
+(defun find-invalidated-instance (class)
+  (when (gethash class *invalidated-instance-cache*)
+    (pop (gethash class *invalidated-instance-cache*))))
+
+(defun list-invalidated-instances ()
+  (let ((instances ()))
+    (maphash #'(lambda (location ref)
+		 (declare (ignore location))
+		 (push ref instances))
+	     *invalidated-instance-cache*)
+    instances))
+
 
 
 ;;;; Proxy for alien instances
 
+;; TODO: add a ref-counted-proxy subclass
 (defclass proxy ()
-  ((location :allocation :special :reader proxy-location :type system-area-pointer))
+  ((location :special t :type pointer))
   (:metaclass virtual-slots-class))
 
 (defgeneric instance-finalizer (object))
 (defgeneric reference-foreign (class location))
 (defgeneric unreference-foreign (class location))
+(defgeneric invalidate-instance (object))
+(defgeneric allocate-foreign (object &key &allow-other-keys))
+
+(defun foreign-location (instance)
+  (slot-value instance 'location))
+
+(defun (setf foreign-location) (location instance)
+  (setf (slot-value instance 'location) location))
+
+(defun proxy-valid-p (instance)
+  (slot-boundp instance 'location))
 
 (defmethod reference-foreign ((name symbol) location)
   (reference-foreign (find-class name) location))
@@ -286,28 +339,25 @@ (defmethod unreference-foreign ((name symbol) location)
 
 (defmethod unreference-foreign :around ((class class) location)
   (unless (null-pointer-p location)
-;;     (format t "Unreferencing ~A at ~A" (class-name class) location)
-;;     (finish-output *standard-output*)
-    (call-next-method)
-;;     (write-line " done")
-;;     (finish-output *standard-output*)
-    ))
+    (call-next-method)))
 
 (defmethod print-object ((instance proxy) stream)
   (print-unreadable-object (instance stream :type t :identity nil)
-    (when (slot-boundp instance 'location)
-      (format stream "at 0x~X" (sap-int (proxy-location instance))))))
-
-(defmethod initialize-instance :around ((instance proxy) &key location)
-  (if location
-      (setf (slot-value instance 'location) location)      
-    (call-next-method))
-  (cache-instance instance)
-  (finalize instance (instance-finalizer instance))
-  instance)
+    (if (slot-boundp instance 'location)
+	(format stream "at 0x~X" (sap-int (foreign-location instance)))
+      (write-string "at <unbound>" stream))))
+
+(defmethod initialize-instance :around ((instance proxy) &rest initargs &key &allow-other-keys) 
+  (setf  
+   (foreign-location instance)
+   (apply #'allocate-foreign instance initargs))
+  (prog1
+      (call-next-method)
+    (cache-instance instance)
+    (finalize instance (instance-finalizer instance))))
 
 (defmethod instance-finalizer ((instance proxy))
-  (let ((location (proxy-location instance))
+  (let ((location (foreign-location instance))
 	(class (class-of instance)))    
 ;;     (unless (find-method #'unreference-foreign nil (list (class-of class) t) nil)
 ;;       (error "No matching method for UNREFERENCE-INSTANCE when called with class ~A" class))
@@ -315,6 +365,14 @@ (defmethod instance-finalizer ((instance proxy))
 	(remove-cached-instance location)
 	(unreference-foreign class location))))
 
+;; Any reference to the foreign object the instance may have held
+;; should be released before this method is invoked
+(defmethod invalidate-instance ((instance proxy))
+  (remove-cached-instance (foreign-location instance))
+  (slot-makunbound instance 'location)
+  (cancel-finalization instance)
+  (cache-invalidated-instance instance))
+
 
 ;;;; Metaclass used for subclasses of proxy
 
@@ -324,11 +382,11 @@ (defgeneric direct-proxy-superclass (class))
 
 (eval-when (:compile-toplevel :load-toplevel :execute)
   (defclass proxy-class (virtual-slots-class)
-    ((size :reader proxy-instance-size)))
+    ((size :reader foreign-size)))
 
   (defclass direct-alien-slot-definition (direct-virtual-slot-definition)
-    ((allocation :initform :alien)
-     (offset :reader slot-definition-offset :initarg :offset)))
+    ((offset :reader slot-definition-offset :initarg :offset))
+    (:default-initargs :allocation :alien))
   
   (defclass effective-alien-slot-definition (effective-virtual-slot-definition)
     ((offset :reader slot-definition-offset :initarg :offset)))
@@ -350,7 +408,7 @@   (defmethod shared-initialize ((class proxy-class) names &key size)
     (cond
       (size (setf (slot-value class 'size) (first size)))
       ((slot-boundp class 'size) (slot-makunbound class 'size))))
-  
+
   (defmethod direct-slot-definition-class ((class proxy-class) &rest initargs)
     (case (getf initargs :allocation)
       (:alien (find-class 'direct-alien-slot-definition))
@@ -363,7 +421,7 @@   (defmethod effective-slot-definition-class ((class proxy-class) &rest initargs
   
   
   (defmethod compute-effective-slot-definition-initargs ((class proxy-class) direct-slotds)
-    (if (eq (most-specific-slot-value direct-slotds 'allocation) :alien)
+    (if (eq (slot-definition-allocation (first direct-slotds)) :alien)
 	(nconc 
 	 (list :offset (most-specific-slot-value direct-slotds 'offset))
 	 (call-next-method))
@@ -378,7 +436,7 @@   (defmethod initialize-internal-slot-functions ((slotd effective-alien-slot-def
 	    (setf 
 	     (slot-value slotd 'getter)
 	     #'(lambda (object)
-		 (funcall reader (proxy-location object) offset)))))
+		 (funcall reader (foreign-location object) offset)))))
 
 	(unless (slot-boundp slotd 'setter)
 	  (let ((writer (writer-function type))
@@ -386,155 +444,172 @@   (defmethod initialize-internal-slot-functions ((slotd effective-alien-slot-def
 	    (setf 
 	     (slot-value slotd 'setter)
 	     #'(lambda (value object)
-		 (let ((location (proxy-location object)))
+		 (let ((location (foreign-location object)))
 		   (funcall destroy location offset) ; destroy old value
 		   (funcall writer value location offset))))))))
 
     (call-next-method))
   
-
   ;; TODO: call some C code to detect this a compile time
   (defconstant +struct-alignmen+ 4)
 
+  (defun align-offset (size)
+    (if (zerop (mod size +struct-alignmen+))
+	size
+      (+ size (- +struct-alignmen+ (mod size +struct-alignmen+)))))
+
   (defmethod compute-slots ((class proxy-class))
-    (loop 
-     with offset = (let ((size-of-super-classes
-			  (proxy-instance-size 
-			   (most-specific-proxy-superclass class))))
-		     (+ size-of-super-classes 
-			(mod size-of-super-classes +struct-alignmen+)))
-     with size = offset
-     for slotd in (class-direct-slots class)
-     when (eq (slot-definition-allocation slotd) :alien)
-     do (if (not (slot-boundp slotd 'offset))
-	    (setf (slot-value slotd 'offset) offset)
-	  (setq offset (slot-value slotd 'offset)))
-
-        (incf offset (size-of (slot-definition-type slotd)))
-	(incf offset (mod offset +struct-alignmen+))
-	(setq size (max size offset))
-
-     finally (unless (slot-boundp class 'size)
-	       (setf (slot-value class 'size) size)))
+    (let ((alien-slots 
+	   (remove-if-not
+	    #'(lambda (slotd)
+		(eq (slot-definition-allocation slotd) :alien))
+	    (class-direct-slots class))))      
+      (when alien-slots
+	(loop 
+	 as offset = (align-offset (foreign-size 
+				    (most-specific-proxy-superclass class)))
+	             then (align-offset 
+			   (+ 
+			    (slot-definition-offset slotd)
+			    (size-of (slot-definition-type slotd))))
+       for slotd in alien-slots
+       unless (slot-boundp slotd 'offset)
+       do (setf (slot-value slotd 'offset) offset))))
     (call-next-method))
 
-  
   (defmethod validate-superclass ((class proxy-class) (super standard-class))
     (subtypep (class-name super) 'proxy))
   
-  (defmethod proxy-instance-size (class)
-    (declare (ignore class))
-    0)
+  (defmethod foreign-size ((class-name symbol))
+    (foreign-size (find-class class-name))))
 
-  (defmethod proxy-instance-size ((class-name symbol))
-    (proxy-instance-size (find-class class-name)))
-)
+(defmethod foreign-size ((object proxy))
+  (foreign-size (class-of object)))
   
-(defmethod alien-type ((class proxy-class) &rest args)
-  (declare (ignore class args))
+
+(define-type-method alien-type ((class proxy))
+  (declare (ignore class))
   (alien-type 'pointer))
 
-(defmethod size-of ((class proxy-class) &rest args)
-  (declare (ignore class args))
+(define-type-method size-of ((class proxy))
+  (declare (ignore class))
   (size-of 'pointer))
 
-(defmethod from-alien-form (location (class proxy-class) &rest args)
-  (declare (ignore args))
-  `(ensure-proxy-instance ',(class-name class) ,location))
-
-(defmethod from-alien-function ((class proxy-class) &rest args)
-  (declare (ignore args))  
-  #'(lambda (location)
-      (ensure-proxy-instance class location)))
-
-(defmethod to-alien-form (instance (class proxy-class) &rest args)
-  (declare (ignore class args))
-  `(proxy-location ,instance))
-
-(defmethod to-alien-function ((class proxy-class) &rest args)
-  (declare (ignore class args))
-  #'proxy-location)
-
-(defmethod copy-from-alien-form (location (class proxy-class) &rest args)
-  (declare (ignore args))
-  (let ((class-name (class-name class)))
-    `(ensure-proxy-instance ',class-name
-      (reference-foreign ',class-name ,location))))
-
-(defmethod copy-from-alien-function ((class proxy-class) &rest args)
-  (declare (ignore args))  
-  #'(lambda (location)
-      (ensure-proxy-instance class (reference-foreign class location))))
-
-(defmethod copy-to-alien-form (instance (class proxy-class) &rest args)
-  (declare (ignore args))
-  `(reference-foreign ',(class-name class) (proxy-location ,instance)))
-
-(defmethod copy-to-alien-function ((class proxy-class) &rest args)
-  (declare (ignore args))
-  #'(lambda (instance)
-      (reference-foreign class (proxy-location instance))))
-
-(defmethod writer-function ((class proxy-class) &rest args)
-  (declare (ignore args))
-  #'(lambda (instance location &optional (offset 0))
-      (assert (null-pointer-p (sap-ref-sap location offset)))
-      (setf 
-       (sap-ref-sap location offset)
-       (reference-foreign class (proxy-location instance)))))
+(define-type-method from-alien-form ((type proxy) location)
+  (let ((class (type-expand type)))
+    `(ensure-proxy-instance ',class ,location)))
 
-(defmethod reader-function ((class proxy-class) &rest args)
-  (declare (ignore args))
-  #'(lambda (location &optional (offset 0))
-      (let ((instance (sap-ref-sap location offset)))
-	(unless (null-pointer-p instance)
-	  (ensure-proxy-instance class (reference-foreign class instance))))))
+(define-type-method from-alien-function ((type proxy))
+  (let ((class (type-expand type)))
+    #'(lambda (location)
+	(ensure-proxy-instance class location))))
 
-(defmethod destroy-function ((class proxy-class) &rest args)
-  (declare (ignore args))
-  #'(lambda (location &optional (offset 0))
-      (unreference-foreign class (sap-ref-sap location offset))))
+(define-type-method to-alien-form ((type proxy) instance)
+  (declare (ignore type))
+  `(foreign-location ,instance))
 
-(defmethod unbound-value ((class proxy-class) &rest args)
-  (declare (ignore args))
-  (values t nil))
+(define-type-method to-alien-function ((type proxy))
+  (declare (ignore type))
+  #'foreign-location)
+
+(define-type-method copy-from-alien-form ((type proxy) location)
+  (let ((class (type-expand type)))
+    `(ensure-proxy-instance ',class (reference-foreign ',class ,location))))
+
+(define-type-method copy-from-alien-function ((type proxy))
+  (let ((class (type-expand type)))
+    #'(lambda (location)
+	(ensure-proxy-instance class (reference-foreign class location)))))
+
+(define-type-method copy-to-alien-form ((type proxy) instance)
+  (let ((class (type-expand type)))
+    `(reference-foreign ',class (foreign-location ,instance))))
+
+(define-type-method copy-to-alien-function ((type proxy))
+  (let ((class (type-expand type)))
+    #'(lambda (instance)
+	(reference-foreign class (foreign-location instance)))))
+
+(define-type-method writer-function ((type proxy))
+  (let ((class (type-expand type)))
+    #'(lambda (instance location &optional (offset 0))
+	(assert (null-pointer-p (sap-ref-sap location offset)))
+	(setf 
+	 (sap-ref-sap location offset)
+	 (reference-foreign class (foreign-location instance))))))
+
+(define-type-method reader-function ((type proxy))
+  (let ((class (type-expand type)))
+    #'(lambda (location &optional (offset 0) weak-p)
+	(declare (ignore weak-p))
+	(let ((instance (sap-ref-sap location offset)))
+	  (unless (null-pointer-p instance)
+	    (ensure-proxy-instance class (reference-foreign class instance)))))))
+
+(define-type-method destroy-function ((type proxy))
+  (let ((class (type-expand type)))
+    #'(lambda (location &optional (offset 0))
+	(unreference-foreign class (sap-ref-sap location offset)))))
 
-(defgeneric ensure-proxy-instance (class location)
-  (:documentation "Returns a proxy object representing the foreign object at the give location."))
+(define-type-method unbound-value ((type proxy))
+  (declare (ignore type))
+  nil)
 
-(defmethod ensure-proxy-instance :around (class location)
+(defun ensure-proxy-instance (class location &rest initargs)
+  "Returns a proxy object representing the foreign object at the give
+location. If an existing object is not found in the cache
+MAKE-PROXY-INSTANCE is called to create one."
   (unless (null-pointer-p location)
     (or 
-     (find-cached-instance location)
-     (call-next-method))))
-  
-(defmethod ensure-proxy-instance ((class symbol) location)
-  (ensure-proxy-instance (find-class class) location))
-
-(defmethod ensure-proxy-instance ((class proxy-class) location)
-  (make-instance class :location location))
+     #-debug-ref-counting(find-cached-instance location)
+     #+debug-ref-counting
+     (let ((instance (find-cached-instance location)))
+       (when instance
+	 (format t "Object found in cache: ~A~%" instance)
+	 instance))
+     (let ((instance (apply #'make-proxy-instance class location initargs)))
+       (cache-instance instance)
+       instance))))
+
+(defgeneric make-proxy-instance (class location &key weak)
+  (:documentation "Creates a new proxy object representing the foreign
+object at the give location. If WEAK is non NIL the foreign memory
+will not be released when the proxy is garbage collected."))
+
+(defmethod make-proxy-instance ((class symbol) location &rest initargs)
+  (apply #'make-proxy-instance (find-class class) location initargs))
+
+(defmethod make-proxy-instance ((class proxy-class) location &key weak)
+  (let ((instance
+	 (or
+	  (find-invalidated-instance class)
+	  (allocate-instance class))))
+    (setf (foreign-location instance) location)
+    (unless weak
+      (finalize instance (instance-finalizer instance)))
+    instance))
 
 
 ;;;; Superclasses for wrapping of C structures
 
 (defclass struct (proxy)
   ()
-  (:metaclass proxy-class))
+  (:metaclass proxy-class)
+  (:size 0))
 
-(defmethod initialize-instance ((struct struct) &rest initargs)
+(defmethod allocate-foreign ((struct struct) &rest initargs)
   (declare (ignore initargs))
-  (unless (slot-boundp struct 'location)
-    (let ((size (proxy-instance-size (class-of struct))))
-      (if (zerop size)
-	  (error "~A has zero size" (class-of struct))
-	(setf (slot-value struct 'location) (allocate-memory size)))))
-  (call-next-method))
+  (let ((size (foreign-size (class-of struct))))
+    (if (zerop size)
+	(error "~A has zero size" (class-of struct))
+      (allocate-memory size))))
 
 
 ;;;; Metaclasses used for subclasses of struct
 
-(defclass struct-class (proxy-class)
-  ())
+(eval-when (:compile-toplevel :load-toplevel :execute)
+  (defclass struct-class (proxy-class)
+    ()))
 
 (defmethod direct-slot-definition-class ((class struct-class) &rest initargs)
   (if (not (getf initargs :allocation))
@@ -542,11 +617,42 @@ (defmethod direct-slot-definition-class ((class struct-class) &rest initargs)
     (call-next-method)))
 
 (defmethod reference-foreign ((class struct-class) location)
-  (copy-memory location (proxy-instance-size class)))
+  (copy-memory location (foreign-size class)))
 
 (defmethod unreference-foreign ((class struct-class) location)
   (deallocate-memory location))
 
+(defmethod compute-slots :around ((class struct-class))
+    (let ((slots (call-next-method)))
+      (when (and 
+	     #-sbcl>=0.9.8(class-finalized-p class)
+	     (not (slot-boundp class 'size)))
+        (let ((size (loop
+		     for slotd in slots
+		     when (eq (slot-definition-allocation slotd) :alien)
+		     maximize (+ 
+			       (slot-definition-offset slotd)
+			       (size-of (slot-definition-type slotd))))))
+	  (setf (slot-value class 'size) (+ size (mod size +struct-alignmen+)))))
+      slots))
+
+(define-type-method callback-from-alien-form ((type struct) form)
+  (let ((class (type-expand type)))
+    `(ensure-proxy-instance ',class ,form :weak t)))
+
+(define-type-method callback-cleanup-form ((type struct) form)
+  (declare (ignore type))
+  `(invalidate-instance ,form))
+
+(define-type-method reader-function ((type struct))
+  (let ((class (type-expand type)))
+    #'(lambda (location &optional (offset 0) weak-p)
+	(let ((instance (sap-ref-sap location offset)))
+	  (unless (null-pointer-p instance)
+	    (if weak-p
+		(ensure-proxy-instance class instance :weak t)
+	      (ensure-proxy-instance class (reference-foreign class instance))))))))
+
 
 (defclass static-struct-class (struct-class)
   ())
@@ -559,23 +665,24 @@ (defmethod unreference-foreign ((class static-struct-class) location)
   (declare (ignore class location))
   nil)
 
-
 ;;; Pseudo type for structs which are inlined in other objects
 
-(defmethod size-of ((type (eql 'inlined)) &rest args)
-  (declare (ignore type))
-  (proxy-instance-size (first args)))
+(deftype inlined (type) type)
 
-(defmethod reader-function ((type (eql 'inlined)) &rest args)
-  (declare (ignore type))
-  (destructuring-bind (class) args
-    #'(lambda (location &optional (offset 0))
+(define-type-method size-of ((type inlined))
+  (let ((class (type-expand (second type))))
+    (foreign-size class)))
+
+(define-type-method reader-function ((type inlined))
+  (let ((class (type-expand (second type))))
+    #'(lambda (location &optional (offset 0) weak-p)
+	(declare (ignore weak-p))
 	(ensure-proxy-instance class 
 	 (reference-foreign class (sap+ location offset))))))
 
-(defmethod destroy-function ((type (eql 'inlined)) &rest args)
-  (declare (ignore args))
-  #'(lambda (location &optional (offset 0))
-      (declare (ignore location offset))))
+(define-type-method writer-function ((type inlined))
+  (let ((class (type-expand (second type))))
+    #'(lambda (instance location &optional (offset 0))
+	(copy-memory (foreign-location instance) (foreign-size class) (sap+ location offset)))))
 
 (export 'inlined)