Fiddle::Function

Class

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

Read

The ABI of the Function.

ptr

Read

The address of this function

name

Read

The name of this function

Class Methods

new(ptr, args, ret_type, abi = DEFAULT)

ext/fiddle/function.c View on GitHub

          
            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);
    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;
}

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

Instance Methods

call(*args)

ext/fiddle/function.c View on GitHub

          
            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);

    if (rb_safe_level() >= 1) {
        for (i = 0; i < argc; i++) {
            VALUE src = argv[i];
            if (OBJ_TAINTED(src)) {
                rb_raise(rb_eSecurityError, "tainted parameter not allowed");
            }
        }
    }

    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);
}

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

to_i

ext/fiddle/lib/fiddle/function.rb View on GitHub

          
            # File tmp/rubies/ruby-2.6.10/ext/fiddle/lib/fiddle/function.rb, line 14
def to_i
  ptr.to_i
end

The integer memory location of this function