Hi, All,
I found the format of my original email is not correct (sent with web mail), and I got no response for some while, so I resend it in Emacs, hopes it works better this time.
I am working on cl-gobject-introspection (https://github.com/andy128k/cl-gobject-introspection), a common lisp gobject introspection binding. I was trying to use extended foreign type system of CFFI to implement some foreign memory operations. I have some questions about that.
I need to manipulate foreign array. I tried to define an extended foreign array type because there are some features that are lacking in foreign-array-type of cffi. I can access/assign element of foreign array with cffi:mem-ref and (setf cffi:mem-ref). But I don't know how to free element of foreign array (the element type can be aggregated).
Then I checked foreign-array-type implementation of CFFI, and found there appears no way to free translated element of array with that type too. For example:
(defvar *string-array* (cffi:convert-to-foreign #("a" "b" "c") '(:array :string 3)))
(cffi:free-foreign-object *string-array* '(:array :string 3) t)
The translated foreign objects corresponding to string "a", "b" and "c" are not freed if my understanding were correct.
I think if there is a cffi:mem-free (I know, the name is bad) like cffi:mem-ref, may be this can be resolved.
(defun mem-free (ptr type param &optional (offset 0)) (let* ((parsed-type (parse-type type)) (ctype (canonicalize parsed-type))) (if (aggregatep parsed-type) (free-translated-object (inc-pointer ptr offset) parsed-type param) (free-translated-object (%mem-ref ptr ctype offset) parsed-type param))))
I think you guys may have better idea about how to resolve the question.
Best Regards, Huang, Ying
Hello Ying,
On Sat, Apr 11, 2015 at 1:50 AM, Huang, Ying huang_ying_caritas@163.com wrote:
I need to manipulate foreign array. I tried to define an extended foreign array type because there are some features that are lacking in foreign-array-type of cffi. I can access/assign element of foreign array with cffi:mem-ref and (setf cffi:mem-ref). But I don't know how to free element of foreign array (the element type can be aggregated).
Indeed, in src/types.lisp:455 there's a FIXME mentioning just that!
I think if there is a cffi:mem-free (I know, the name is bad) like cffi:mem-ref, may be this can be resolved.
(defun mem-free (ptr type param &optional (offset 0)) (let* ((parsed-type (parse-type type)) (ctype (canonicalize parsed-type))) (if (aggregatep parsed-type) (free-translated-object (inc-pointer ptr offset) parsed-type param) (free-translated-object (%mem-ref ptr ctype offset) parsed-type param))))
My first intuition would be to fix foreign-array-free to get a type argument. That way it would know how to free each element, essentially doing a mem-free (as you call it) for each element in the array.
I've prototyped such a smarter foreign-array-free here: https://github.com/luismbo/cffi/commit/0a7d42720eacc32abb4338df32b4e5fceecde...
Your example then becomes:
CFFI> (defparameter *string-array* (foreign-array-alloc #("a" "b" "c") '(:array :string 3))) *STRING-ARRAY* CFFI> (trace foreign-string-free) (FOREIGN-STRING-FREE) CFFI> (foreign-array-free *STRING-ARRAY* '(:array :string 3)) 0: (FOREIGN-STRING-FREE #.(SB-SYS:INT-SAP #X002054A0)) 0: FOREIGN-STRING-FREE returned NIL 0: (FOREIGN-STRING-FREE #.(SB-SYS:INT-SAP #X002054B0)) 0: FOREIGN-STRING-FREE returned NIL 0: (FOREIGN-STRING-FREE #.(SB-SYS:INT-SAP #X002054C0)) 0: FOREIGN-STRING-FREE returned NIL NIL
Let me know what you think. :)
Cheers,
Hi, Luís,
Luís Oliveira luismbo@gmail.com writes:
Hello Ying,
On Sat, Apr 11, 2015 at 1:50 AM, Huang, Ying huang_ying_caritas@163.com wrote:
I need to manipulate foreign array. I tried to define an extended foreign array type because there are some features that are lacking in foreign-array-type of cffi. I can access/assign element of foreign array with cffi:mem-ref and (setf cffi:mem-ref). But I don't know how to free element of foreign array (the element type can be aggregated).
Indeed, in src/types.lisp:455 there's a FIXME mentioning just that!
I think if there is a cffi:mem-free (I know, the name is bad) like cffi:mem-ref, may be this can be resolved.
(defun mem-free (ptr type param &optional (offset 0)) (let* ((parsed-type (parse-type type)) (ctype (canonicalize parsed-type))) (if (aggregatep parsed-type) (free-translated-object (inc-pointer ptr offset) parsed-type param) (free-translated-object (%mem-ref ptr ctype offset) parsed-type param))))
My first intuition would be to fix foreign-array-free to get a type argument. That way it would know how to free each element, essentially doing a mem-free (as you call it) for each element in the array.
I've prototyped such a smarter foreign-array-free here: https://github.com/luismbo/cffi/commit/0a7d42720eacc32abb4338df32b4e5fceecde...
Your example then becomes:
CFFI> (defparameter *string-array* (foreign-array-alloc #("a" "b" "c") '(:array :string 3))) *STRING-ARRAY* CFFI> (trace foreign-string-free) (FOREIGN-STRING-FREE) CFFI> (foreign-array-free *STRING-ARRAY* '(:array :string 3)) 0: (FOREIGN-STRING-FREE #.(SB-SYS:INT-SAP #X002054A0)) 0: FOREIGN-STRING-FREE returned NIL 0: (FOREIGN-STRING-FREE #.(SB-SYS:INT-SAP #X002054B0)) 0: FOREIGN-STRING-FREE returned NIL 0: (FOREIGN-STRING-FREE #.(SB-SYS:INT-SAP #X002054C0)) 0: FOREIGN-STRING-FREE returned NIL NIL
Let me know what you think. :)
Yes. That works for :string. But how about aggregated array element type such as :struct.
CL-USER> (defcstruct str-struct (str :string)) (:STRUCT STR-STRUCT) CL-USER> (defparameter *str-struct-array* '(:array (:struct str-struct) 2)) *STR-STRUCT-ARRAY* CL-USER> (convert-to-foreign #((str "a") (str "b")) *str-struct-array*) #.(SB-SYS:INT-SAP #X7FFFEC000960) CL-USER> (convert-from-foreign * *str-struct-array*) #((STR "a") (STR "b")) CL-USER> (free-converted-object ** *str-struct-array* t) NIL
I know the :string slot in struct is not freed now. But I think that can be fixed too.
One possible solution is to make free-translated-object doesn't free the aggregated foreign object itself, just its elements. Make something like foreign-free (should use another name) to take the type of foreign object to be freed as paramter and call the free-translated-object for the foreign object, the free the foreign object itself. Or we can define another method called something like free-translated-object-in-memory for aggregated foreign type, which corresponds to translate-into-memory, just like free-translated-object corresponds to translate-to-foreign.
Best Regards, Huang, Ying
-
Huang, Ying -
Luís Oliveira