# Utilities for FFI Programming

# begin-ffi

(begin-ffi (id ...) body ...)

; expands to
(extern id ...)
(begin-foreign
  (namespace (<module-namespace> id ...))
  prelude-macros ...
  prelude-decls ...
  body ...
  prelude-defs ...

The following prelude macros are available within the body:

(define-c-lambda id args ret [name/code])
(define-const id)
(define-const* id)
(define-guard guard defn)
(define-with-errno id ffi-id args)
(define-c-struct struct-name members release-function)

The following declarations are included before the body:

#include <stdlib.h>
#define U8_DATA(u8vector) ...
#define U8_LEN(u8vector) ...
static ___SCMOBJ ffi_free (void *ptr);

In case you are using define-c-struct without a release function and have a string member, then a <struct-name>_ffi_free function is included, which apart from freeing the ptr also cleans up any string member.

The following definitions are included after the body:

#ifndef ___HAVE_FFI_FREE
#define ___HAVE_FFI_FREE
___SCMOBJ ffi_free (void *ptr) { ...}
#endif