2.6 Closure Example

A trivial example that creates a new puts by binding fputs with stdin.

     #include <stdio.h>
     #include <ffi.h>
     
     /* Acts like puts with the file given at time of enclosure. */
     void puts_binding(ffi_cif *cif, unsigned int *ret, void* args[],
                       FILE *stream)
     {
       *ret = fputs(*(char **)args[0], stream);
     }
     
     int main()
     {
       ffi_cif cif;
       ffi_type *args[1];
       ffi_closure *closure;
     
       int (*bound_puts)(char *);
       int rc;
     
       /* Allocate closure and bound_puts */
       closure = ffi_closure_alloc(sizeof(ffi_closure), &bound_puts);
     
       if (closure)
         {
           /* Initialize the argument info vectors */
           args[0] = &ffi_type_pointer;
     
           /* Initialize the cif */
           if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1,
                            &ffi_type_uint, args) == FFI_OK)
             {
               /* Initialize the closure, setting stream to stdout */
               if (ffi_prep_closure_loc(closure, &cif, puts_binding,
                                        stdout, bound_puts) == FFI_OK)
                 {
                   rc = bound_puts("Hello World!");
                   /* rc now holds the result of the call to fputs */
                 }
             }
         }
     
       /* Deallocate both closure, and bound_puts */
       ffi_closure_free(closure);
     
       return 0;
     }