Thanks db05.
So far i think the best technique is to use the SDL egg (which i think
Mario pointed me at) as a reference. I believe it basically creates a
blob and casts to the struct so the fields can be accessed.
Honestly at the moment, simply writing it in C looks more intelligible.
Geoff.
On 22/06/13 07:05, db05 wrote:
One possible solution read a whole object into predefined record
(define-record inotify wd mask cookie len name)
; this function make record and pass it into hepler function
(define (read-event fd)
(c-read-event (make-inotify) fd))
; map inotify fields to record fields using lowlevel function C_block_item
(define c-read-event
(foreign-safe-lambda* void ((scheme-object res) (int fd))
"struct inotify_event* e;
char buffer[sizeof(*e) + MAX_PATH];
if (read(fd,buffer,sizeof(buffer)) < 0)
C_return(C_SCHEME_FALSE);
C_word* ptr = C_alloc(C_SIZEOF_STRING(e->len));
C_block_item(res,1) = C_fix(e->wd);
C_block_item(res,2) = C_fix(e->mask);
C_block_item(res,3) = C_fix(e->cookie);
C_block_item(res,4) = C_fix(e->len);
C_block_item(res,5) = C_string(&ptr,&e->name,numbytes);
C_return(res);"))
this should work but i worry that uint32 didnt't fit into the fixnum
(C_fix stuff)
;; or something like this
(match (file-read fd 1000)
((data size)
(make-inotify wd: (read-uint32 data)
mask: (read-uint32 data)
cookie: (read-uint32 data)
len: (read-uint32 data)
name: (read-string data))))
o_O
06/20/13 23:58:52, Geoffrey <[email protected]
<mailto:[email protected]>>:
Hi I am trying to declare of variably sized c struct as a foreign
declaration.
The one i am after is:
struct inotify_event
{
int wd;/* Watch descriptor.
*/
uint32_t mask;/* Watch mask. */
uint32_t cookie;/* Cookie to synchronize
two events. */
uint32_t len;/* Length (including
NULs) of name. */
char name __flexarr;/* Name. */
};
Note that name field is variably sized. I believe in C you would allocate a
larger block of memory and then cast it to
(inotify_event*).
By the skills of copy and paste i can do fixed size,and i can do a blob.
But not a variable struct.
Some help would be appreciated.
Thanks
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