class Fiddle::Function

Description ↑

A representation of a C function

Examples ↑

‘strcpy’ ↑

@libc = Fiddle.dlopen "/lib/libc.so.6"
   #=> #<Fiddle::Handle:0x00000001d7a8d8>
f = Fiddle::Function.new(
  @libc['strcpy'],
  [Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP],
  Fiddle::TYPE_VOIDP)
   #=> #<Fiddle::Function:0x00000001d8ee00>
buff = "000"
   #=> "000"
str = f.call(buff, "123")
   #=> #<Fiddle::Pointer:0x00000001d0c380 ptr=0x000000018a21b8 size=0 free=0x00000000000000>
str.to_s
=> "123"

ABI check ↑

@libc = Fiddle.dlopen "/lib/libc.so.6"
   #=> #<Fiddle::Handle:0x00000001d7a8d8>
f = Fiddle::Function.new(@libc['strcpy'], [TYPE_VOIDP, TYPE_VOIDP], TYPE_VOIDP)
   #=> #<Fiddle::Function:0x00000001d8ee00>
f.abi == Fiddle::Function::DEFAULT
   #=> true

Constants

DEFAULT

DEFAULT

Default ABI

STDCALL

STDCALL

FFI implementation of WIN32 stdcall convention

Attributes

abi[R]

The ABI of the Function.

name[R]

The name of this function

ptr[R]

The address of this function

Public Class Methods

new(ptr, args, ret_type, abi = DEFAULT) click to toggle source

Constructs a Function object.

  • ptr is a referenced function, of a Fiddle::Handle

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

  • ret_type is the return type of the function

  • abi is the ABI of the function

static VALUE
initialize(int argc, VALUE argv[], VALUE self)
{
    ffi_cif * cif;
    ffi_type **arg_types, *rtype;
    ffi_status result;
    VALUE ptr, args, ret_type, abi, kwds, ary;
    int i, len;
    int nabi;
    void *cfunc;

    rb_scan_args(argc, argv, "31:", &ptr, &args, &ret_type, &abi, &kwds);
    rb_iv_set(self, "@closure", ptr);

    ptr = rb_Integer(ptr);
    cfunc = NUM2PTR(ptr);
    PTR2NUM(cfunc);
    nabi = NIL_P(abi) ? FFI_DEFAULT_ABI : NUM2INT(abi);
    abi = INT2FIX(nabi);
    i = NUM2INT(ret_type);
    rtype = INT2FFI_TYPE(i);
    ret_type = INT2FIX(i);

    Check_Type(args, T_ARRAY);
    len = RARRAY_LENINT(args);
    Check_Max_Args("args", len);
    ary = rb_ary_subseq(args, 0, len);
    for (i = 0; i < RARRAY_LEN(args); i++) {
        VALUE a = RARRAY_AREF(args, i);
        int type = NUM2INT(a);
        (void)INT2FFI_TYPE(type); /* raise */
        if (INT2FIX(type) != a) rb_ary_store(ary, i, INT2FIX(type));
    }
    OBJ_FREEZE(ary);

    rb_iv_set(self, "@ptr", ptr);
    rb_iv_set(self, "@args", args);
    rb_iv_set(self, "@return_type", ret_type);
    rb_iv_set(self, "@abi", abi);

    if (!NIL_P(kwds)) rb_hash_foreach(kwds, parse_keyword_arg_i, self);

    TypedData_Get_Struct(self, ffi_cif, &function_data_type, cif);

    arg_types = xcalloc(len + 1, sizeof(ffi_type *));

    for (i = 0; i < RARRAY_LEN(args); i++) {
        int type = NUM2INT(RARRAY_AREF(args, i));
        arg_types[i] = INT2FFI_TYPE(type);
    }
    arg_types[len] = NULL;

    result = ffi_prep_cif(cif, nabi, len, rtype, arg_types);

    if (result)
        rb_raise(rb_eRuntimeError, "error creating CIF %d", result);

    return self;
}

Public Instance Methods

call(*args) click to toggle source

Calls the constructed Function, with args. Caller must ensure the underlying function is called in a thread-safe manner if running in a multi-threaded process.

For an example see Fiddle::Function

static VALUE
function_call(int argc, VALUE argv[], VALUE self)
{
    struct nogvl_ffi_call_args args = { 0 };
    fiddle_generic *generic_args;
    VALUE cfunc, types, cPointer;
    int i;
    VALUE alloc_buffer = 0;

    cfunc    = rb_iv_get(self, "@ptr");
    types    = rb_iv_get(self, "@args");
    cPointer = rb_const_get(mFiddle, rb_intern("Pointer"));

    Check_Max_Args("number of arguments", argc);
    if (argc != (i = RARRAY_LENINT(types))) {
        rb_error_arity(argc, i, i);
    }

    TypedData_Get_Struct(self, ffi_cif, &function_data_type, args.cif);

    generic_args = ALLOCV(alloc_buffer,
        (size_t)(argc + 1) * sizeof(void *) + (size_t)argc * sizeof(fiddle_generic));
    args.values = (void **)((char *)generic_args +
                            (size_t)argc * sizeof(fiddle_generic));

    for (i = 0; i < argc; i++) {
        VALUE type = RARRAY_AREF(types, i);
        VALUE src = argv[i];
        int argtype = FIX2INT(type);

        if (argtype == TYPE_VOIDP) {
            if(NIL_P(src)) {
                src = INT2FIX(0);
            } else if(cPointer != CLASS_OF(src)) {
                src = rb_funcall(cPointer, rb_intern("[]"), 1, src);
            }
            src = rb_Integer(src);
        }

        VALUE2GENERIC(argtype, src, &generic_args[i]);
        args.values[i] = (void *)&generic_args[i];
    }
    args.values[argc] = NULL;
    args.fn = (void(*)(void))NUM2PTR(cfunc);

    (void)rb_thread_call_without_gvl(nogvl_ffi_call, &args, 0, 0);

    rb_funcall(mFiddle, rb_intern("last_error="), 1, INT2NUM(errno));
#if defined(_WIN32)
    rb_funcall(mFiddle, rb_intern("win32_last_error="), 1, INT2NUM(errno));
#endif

    ALLOCV_END(alloc_buffer);

    return GENERIC2VALUE(rb_iv_get(self, "@return_type"), args.retval);
}
to_i() click to toggle source

The integer memory location of this function

# File fiddle/lib/fiddle/function.rb, line 14
def to_i
  ptr.to_i
end