Re: [Chicken-users] How to FFI?

[Robin Lee Powell]

Well, what I've got is working, I was just wondering if ___out could
make it simpler.  Since out doesn't work with strings, I guess not.

Anyways, here's the function:

http://doxygen.xmms2.xmms.se/clientlib/stable/xmmsclient/group__ResultValueRetrieval.html#gcabbd913954d7ad92b6d2179f1fb6a5d

-Robin

On Thu, Jul 05, 2007 at 12:25:12PM -0500, Zbigniew wrote:
> Hello,
> 
> Could you post the actual function name, signature and description.
> It may be better to write a small wrapper here but we can't know that
> from just the signature.  For example does this function malloc a
> string and return the pointer, expect you to malloc enough space for a
> string and pass -it- the pointer, return a static string pointer, do
> you have to free the returned pointer ... etc.  Also, char** seems
> more appropriate so I'm confused.
> 
> As an example, let's say your function is returning a pointer to a
> static string (into its argument) along with the return code.  You
> might be able to write a little wrapper which returns the string
> directly, or #f if the return code was bad (or the pointer was null).
> This is self-contained code:
> 
> #>!
> char *wrap_bar(void) {
>  char *ptr;
>  if (bar(&ptr) != 0)
>    return NULL;
>  else
>    return ptr;
> }
> <#
> 
> #>
> int bar(char **ptr) {
>  static char baz[] = "hello";
>  *ptr = (char *)baz;
>  return 0;            // failure code
> }
> <#
> 
> Add ___discard to wrap_bar() if bar() expects you to free the string;
> also it's just as easy to use foreign-lambda* for the wrapper.
> 
> On 7/5/07, Robin Lee Powell <address@hidden> wrote:
> >#>?
> >int bar(char *x);
> ><#
> >
> >Which I'm handling like so:
> >
> >(define-external vstring c-string "N/A")
> >
> >(bar (location vstring))
> >
> >Could I drop the (location ...) call by using ___out?
> >
> >I guess it would just be:
> >
> >(define vstring (bar))
> 
> 
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