class Fiddle::Closure


An FFI closure wrapper, for handling callbacks.


closure = {
  def call
}.new(Fiddle::TYPE_INT, [])
   #=> #<#<Class:0x0000000150d308>:0x0000000150d240>
func =, [], Fiddle::TYPE_INT)
   #=> #<Fiddle::Function:0x00000001516e58>
   #=> 10



arguments of the FFI closure


the C type of the return of the FFI closure

Public Class Methods

new(ret, args, abi = Fiddle::DEFAULT) click to toggle source

Construct a new Closure object.

  • ret is the C type to be returned

  • args is an Array of arguments, passed to the callback function

  • abi is the abi of the closure

If there is an error in preparing the ffi_cif or ffi_prep_closure, then a RuntimeError will be raised.

static VALUE
initialize(int rbargc, VALUE argv[], VALUE self)
    VALUE ret;
    VALUE args;
    VALUE abi;
    fiddle_closure * cl;
    ffi_cif * cif;
    ffi_closure *pcl;
    ffi_status result;
    int i, argc;

    if (2 == rb_scan_args(rbargc, argv, "21", &ret, &args, &abi))
        abi = INT2NUM(FFI_DEFAULT_ABI);

    Check_Type(args, T_ARRAY);

    argc = RARRAY_LENINT(args);

    TypedData_Get_Struct(self, fiddle_closure, &closure_data_type, cl);

    cl->argv = (ffi_type **)xcalloc(argc + 1, sizeof(ffi_type *));

    for (i = 0; i < argc; i++) {
        int type = NUM2INT(RARRAY_AREF(args, i));
        cl->argv[i] = INT2FFI_TYPE(type);
    cl->argv[argc] = NULL;

    rb_iv_set(self, "@ctype", ret);
    rb_iv_set(self, "@args", args);

    cif = &cl->cif;
    pcl = cl->pcl;

    result = ffi_prep_cif(cif, NUM2INT(abi), argc,

    if (FFI_OK != result)
        rb_raise(rb_eRuntimeError, "error prepping CIF %d", result);

    result = ffi_prep_closure_loc(pcl, cif, callback,
                (void *)self, cl->code);
    result = ffi_prep_closure(pcl, cif, callback, (void *)self);
    cl->code = (void *)pcl;
    i = mprotect(pcl, sizeof(*pcl), PROT_READ | PROT_EXEC);
    if (i) {

    if (FFI_OK != result)
        rb_raise(rb_eRuntimeError, "error prepping closure %d", result);

    return self;

Public Instance Methods

to_i() click to toggle source

Returns the memory address for this closure

static VALUE
to_i(VALUE self)
    fiddle_closure * cl;
    void *code;

    TypedData_Get_Struct(self, fiddle_closure, &closure_data_type, cl);

    code = cl->code;

    return PTR2NUM(code);