Re: [Chicken-users] how to declare foreign variably size structs?

[Geoffrey]

Dan,

You are imagining i am cleverer than I am.

Currently i do:
  (define-foreign-record-type (inotify_event "struct inotify_event")
    (constructor: make-inotify_event)
    (destructor: free-inotify_event)
    (unsigned-int32 mask mask)
    (unsigned-int32 cookie cookie)
    (unsigned-int32 len len)
    (unsigned-int32 name name)
    )
Obviously name is wrong (except for file names of 2 chars length)

I syntactically don't know how to make the allocated size bigger.


On 21/06/13 06:32, Dan Leslie wrote:

Probably the simplest solution would be to treat it as fixed size and use the maximum possible size for the object.

From http://linux.die.net/man/7/inotify

Specifying a buffer of size

sizeof(struct inotify_event) + NAME_MAX + 1

will be sufficient to read at least one event.

-Dan

On 6/20/2013 12:58 PM, Geoffrey wrote:

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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