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

From: Geoffrey
Subject: Re: [Chicken-users] how to declare foreign variably size structs?
Date: Fri, 21 Jun 2013 07:27:14 +1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6


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.


Specifying a buffer of size

sizeof(struct inotify_event) + NAME_MAX + 1

will be sufficient to read at least one event.


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.


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