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Re: ffi-helper: looking for C libraries to try

From: Amirouche Boubekki
Subject: Re: ffi-helper: looking for C libraries to try
Date: Sat, 15 Jul 2017 02:44:05 +0200
User-agent: Roundcube Webmail/1.1.2

On 2017-07-15 01:17, Matt Wette wrote:
Hi All,

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.  My
goal is to have something to release ~Oct 2017.

I am looking for suggestions for libraries (w/ includes of course) to
use as test cases to flush-out and debug my code.  I have worked on
cairo and now working on gdbm.  I tried git2 but those headers are too

What do you mean by "too broken"? Maybe it will be easier in the long run to maintain our own version of the headers than manually bind everything. Even if it requires to create a shim layer in scheme to have a proper set of bindings that schemer will enjoy. Also, git is a good candidate since there are some tests already in guile-git [1].

If you have suggestions for test cases, please post.  They should be
commonly used.
(I use MacPorts and would want them to be installable in that context.)

There is wiredtiger for which I am the maintainer. I will work on it. Since there is a test suite it will be easy to make it work. Sadly there is not support for it in macports.

By the way, nyacc is missing installation instruction.


I have now been able to compile-ffi the following on my Mac. I’m sure
bugs remain.

(define-ffi-module (cairo cairo)
 #:pkg-config "cairo"
 #:include '(“cairo.h" "cairo-pdf.h" "cairo-svg.h")

 ;; the following are bent pipe to scm-module
 #:export (make-cairo-unit-matrix)

(define (make-cairo-unit-matrix)
 (make-cairo_matrix_t #(1.0 0.0 0.0 1.0 0.0 0.0)))

I convert the above “cairo.ffi” file to “cairo.scm” using the following command

        mwette$ guild compile-ffi cairo/cairo.ffi

The above generates 397 FFI declarations in cairo.scm, a file which is
about 6000 lines long, compared to the original “cairo.ffi” which is
less than 10 lines long.

Some generated code:

;; typedef struct _cairo_device cairo_device_t;
(define-fh-pointer-type cairo_device_t*)

;; union _cairo_path_data_t {
;;   struct {
;;     cairo_path_data_type_t type;
;;     int length;
;;   } header;
;;   struct {
;;     double x, y;
;;   } point;
;; };
(define cairo_path_data_t-desc
   (list `(header
               (list `(type ,cairo_path_data_type_t-desc)
                     `(length ,int))))
         `(point ,(bs:struct (list `(y ,double) `(x ,double)))))))
(export cairo_path_data_t-desc)
(define-fh-bytestructure-type/p cairo_path_data_t cairo_path_data_t-desc)
(define union-_cairo_path_data_t cairo_path_data_t)

;; typedef enum _cairo_path_data_type {
;; } cairo_path_data_type_t;
(define-fh-enum-type cairo_path_data_type_t

;; typedef void (*cairo_destroy_func_t)(void *data);
(define (wrap-cairo_destroy_func_t proc) ;; => pointer
(ffi:procedure->pointer ffi:void proc (list '*))
(export wrap-cairo_destroy_func_t)

;; cairo_status_t cairo_device_set_user_data(cairo_device_t *device, const ;; cairo_user_data_key_t *key, void *user_data, cairo_destroy_func_t
;;     destroy);
(define cairo_device_set_user_data
 (let ((~f (ffi:pointer->procedure
             (lib-func "cairo_device_set_user_data")
             (list '* '* '* '*))))
   (lambda (device key user_data destroy)
     (let ((~device (unwrap-cairo_device_t* device))
           (~key (unwrap-cairo_user_data_key_t* key))
           (~user_data (unwrap~pointer user_data))
           (~destroy (unwrap-cairo_destroy_func_t destroy)))
         (~f ~device ~key ~user_data ~destroy))))))
(export cairo_device_set_user_data)

Amirouche ~ amz3 ~

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