[plt-scheme] how to use import struct in FFI?

Specifically, look therein for 3.7 ("C Struct types").  Then study the 
collects/ffi/sndfile example.

Noel Welsh wrote:
> Look at the foreign library in the PLT documentation.  A search for
> "foreign" will find it.
>
> N.
>
> On Sun, Oct 19, 2008 at 8:57 AM, zen1986 at gmail.com <zen1986 at gmail.com> wrote:
>   
>> Hi,
>> If this seems trivial, please bear with me...
>> How can I use struct defined in C in my scheme code?
>> I spent hours googled it and looked at manual but still no result.
>> I know in Lisp there is a :EXTERNAL and :TYPEDEF option to import
>> struct in header file and local file what is the equivalents in
>> scheme?
>> Thanks.
>>