Le 17/06/2017 à 20:53, Matt Wette a écrit :
The following seems to be a Guile architecture wrt how FFI-based interfaces
should be implemented.
I am working on a ffi-helper: a program that will read in a C dot-h file and
generate a Guile dot-scm file which defines a module to provide hooks into the
associated C library. I am looking for concurrence on the following:
Enums and #defines:
Here is how I plan to handle enums and #defines
1) visibility to values is provided through an access function
e.g., (get-foo-val ‘ABC)
not ABC via (define ABC 1)
2) only #defined symbols that evaluate to constants (e.g., 123, “ABC”, etc)
will be visible
3) all enum-defined symbols will be visible
4) for enum typedefs and enum def's I will provide (but not export) wrappers so
that functions that
take an enum type as argument will require the symbolic form
e.g., if signature is
typedef enum { ABC = 1 } foo_enum_t;
typedef enum { OK = 0, ERROR = 1 } foo_status_t;
foo_status_t bar(foo_enum_t flag)
then the guile un-wrapper/wrapper will convert symbols<=>ints to allow
users code to look like
(bar ‘ABC) => ‘OK
Optionally, the un-wrappers could be coded tolerate integers.
OK?
Matt
P.S. auto-generated and hand-clean-up (i.e., not fully working yet)
;; access to #define constants:
(define cairo-svg-def-val
(let ((deftab
'((CAIRO_VERSION_MAJOR . 1)
(CAIRO_VERSION_MINOR . 14)
...
(CAIRO_SVG_VERSION_1_1 . 1)
(CAIRO_SVG_VERSION_1_2 . 2))))
(lambda (k) (assq-ref deftab k))))
(export cairo-svg-def-val)
;; typedef struct _cairo_font_options cairo_font_options_t;
(define-std-pointer-wrapper cairo_font_options_t*)
;; typedef enum _cairo_status cairo_status_t;
(define wrap-cairo_status_t
(let ((vnl '((0 . CAIRO_STATUS_SUCCESS)
(1 . CAIRO_STATUS_NO_MEMORY)
...
(38 . CAIRO_STATUS_JBIG2_GLOBAL_MISSING)
(39 . CAIRO_STATUS_LAST_STATUS))))
(lambda (code) (assq-ref vnl code))))
(define unwrap-cairo_status_t
(let ((nvl '((CAIRO_STATUS_SUCCESS . 0)
(CAIRO_STATUS_NO_MEMORY . 1)
...
(CAIRO_STATUS_JBIG2_GLOBAL_MISSING . 38)
(CAIRO_STATUS_LAST_STATUS . 39))))
(lambda (name) (assq-ref nvl name))))
(define wrap-enum-_cairo_status
(let ((vnl '((0 . CAIRO_STATUS_SUCCESS)
(1 . CAIRO_STATUS_NO_MEMORY)
(2 . CAIRO_STATUS_INVALID_RESTORE)
...
(38 . CAIRO_STATUS_JBIG2_GLOBAL_MISSING)
(39 . CAIRO_STATUS_LAST_STATUS))))
(lambda (code) (assq-ref vnl code))))
(define unwrap-enum-_cairo_status
(let ((nvl '((CAIRO_STATUS_SUCCESS . 0)
(CAIRO_STATUS_NO_MEMORY . 1)
...
(CAIRO_STATUS_JBIG2_GLOBAL_MISSING . 38)
(CAIRO_STATUS_LAST_STATUS . 39))))
(lambda (name) (assq-ref nvl name))))
;; cairo_status_t cairo_font_options_status(cairo_font_options_t *options);
(define cairo_font_options_status
(let ((f (ffi:pointer->procedure
ffi:int
(lib-func "cairo_font_options_status")
(list '*))))
(lambda (options)
(let ((~options (unwrap-cairo_font_options_t* options)))
(wrap-cairo_status_t (f ~options))))))
(export cairo_font_options_status)
It makes sens to me.
