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,

name: nil,

need_gvl: false)

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
name is the name of the function
need_gvl is whether GVL is needed to call the function

static VALUE
initialize(int argc, VALUE argv[], VALUE self)
{
    ffi_cif * cif;
    VALUE ptr, arg_types, ret_type, abi, kwargs;
    VALUE name = Qnil;
    VALUE need_gvl = Qfalse;
    int c_ret_type;
    bool is_variadic = false;
    ffi_abi c_ffi_abi;
    void *cfunc;

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

    if (!NIL_P(kwargs)) {
        enum {
            kw_name,
            kw_need_gvl,
            kw_max_,
        };
        static ID kw[kw_max_];
        VALUE args[kw_max_];
        if (!kw[0]) {
            kw[kw_name] = rb_intern_const("name");
            kw[kw_need_gvl] = rb_intern_const("need_gvl");
        }
        rb_get_kwargs(kwargs, kw, 0, kw_max_, args);
        if (args[kw_name] != Qundef) {
            name = args[kw_name];
        }
        if (args[kw_need_gvl] != Qundef) {
            need_gvl = args[kw_need_gvl];
        }
    }
    rb_iv_set(self, "@name", name);
    rb_iv_set(self, "@need_gvl", need_gvl);

    ptr = rb_Integer(ptr);
    cfunc = NUM2PTR(ptr);
    PTR2NUM(cfunc);
    c_ffi_abi = NIL_P(abi) ? FFI_DEFAULT_ABI : NUM2INT(abi);
    abi = INT2FIX(c_ffi_abi);
    ret_type = rb_fiddle_type_ensure(ret_type);
    c_ret_type = NUM2INT(ret_type);
    (void)INT2FFI_TYPE(c_ret_type); /* raise */
    ret_type = INT2FIX(c_ret_type);

    arg_types = normalize_argument_types("argument types",
                                         arg_types,
                                         &is_variadic);
#ifndef HAVE_FFI_PREP_CIF_VAR
    if (is_variadic) {
        rb_raise(rb_eNotImpError,
                 "ffi_prep_cif_var() is required in libffi "
                 "for variadic arguments");
    }
#endif

    rb_iv_set(self, "@ptr", ptr);
    rb_iv_set(self, "@argument_types", arg_types);
    rb_iv_set(self, "@return_type", ret_type);
    rb_iv_set(self, "@abi", abi);
    rb_iv_set(self, "@is_variadic", is_variadic ? Qtrue : Qfalse);

    TypedData_Get_Struct(self, ffi_cif, &function_data_type, cif);
    cif->arg_types = NULL;

    return self;
}

Public Instance Methods

call (*args)

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.

Note that it is not thread-safe to use this method to directly or indirectly call many Ruby C-extension APIs unless you don’t pass +need_gvl: true+ to Fiddle::Function#new.

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;
    VALUE abi;
    VALUE arg_types;
    VALUE cPointer;
    VALUE is_variadic;
    VALUE need_gvl;
    int n_arg_types;
    int n_fixed_args = 0;
    int n_call_args = 0;
    int i;
    int i_call;
    VALUE converted_args = Qnil;
    VALUE alloc_buffer = 0;

    cfunc    = rb_iv_get(self, "@ptr");
    abi      = rb_iv_get(self, "@abi");
    arg_types = rb_iv_get(self, "@argument_types");
    cPointer = rb_const_get(mFiddle, rb_intern("Pointer"));
    is_variadic = rb_iv_get(self, "@is_variadic");
    need_gvl = rb_iv_get(self, "@need_gvl");

    n_arg_types = RARRAY_LENINT(arg_types);
    n_fixed_args = n_arg_types;
    if (RTEST(is_variadic)) {
        if (argc < n_arg_types) {
            rb_error_arity(argc, n_arg_types, UNLIMITED_ARGUMENTS);
        }
        if (((argc - n_arg_types) % 2) != 0) {
            rb_raise(rb_eArgError,
                     "variadic arguments must be type and value pairs: "
                     "%"PRIsVALUE,
                     rb_ary_new_from_values(argc, argv));
        }
        n_call_args = n_arg_types + ((argc - n_arg_types) / 2);
    }
    else {
        if (argc != n_arg_types) {
            rb_error_arity(argc, n_arg_types, n_arg_types);
        }
        n_call_args = n_arg_types;
    }
    Check_Max_Args("the number of arguments", n_call_args);

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

    if (is_variadic && args.cif->arg_types) {
        xfree(args.cif->arg_types);
        args.cif->arg_types = NULL;
    }

    if (!args.cif->arg_types) {
        VALUE fixed_arg_types = arg_types;
        VALUE return_type;
        int c_return_type;
        ffi_type *ffi_return_type;
        ffi_type **ffi_arg_types;
        ffi_status result;

        arg_types = rb_ary_dup(fixed_arg_types);
        for (i = n_fixed_args; i < argc; i += 2) {
          VALUE arg_type = argv[i];
          int c_arg_type;
          arg_type = rb_fiddle_type_ensure(arg_type);
          c_arg_type = NUM2INT(arg_type);
          (void)INT2FFI_TYPE(c_arg_type); /* raise */
          rb_ary_push(arg_types, INT2FIX(c_arg_type));
        }

        return_type = rb_iv_get(self, "@return_type");
        c_return_type = FIX2INT(return_type);
        ffi_return_type = INT2FFI_TYPE(c_return_type);

        ffi_arg_types = xcalloc(n_call_args + 1, sizeof(ffi_type *));
        for (i_call = 0; i_call < n_call_args; i_call++) {
            VALUE arg_type;
            int c_arg_type;
            arg_type = RARRAY_AREF(arg_types, i_call);
            c_arg_type = FIX2INT(arg_type);
            ffi_arg_types[i_call] = INT2FFI_TYPE(c_arg_type);
        }
        ffi_arg_types[i_call] = NULL;

        if (is_variadic) {
#ifdef HAVE_FFI_PREP_CIF_VAR
            result = ffi_prep_cif_var(args.cif,
                                      FIX2INT(abi),
                                      n_fixed_args,
                                      n_call_args,
                                      ffi_return_type,
                                      ffi_arg_types);
#else
            /* This code is never used because ffi_prep_cif_var()
             * availability check is done in #initialize. */
            result = FFI_BAD_TYPEDEF;
#endif
        }
        else {
            result = ffi_prep_cif(args.cif,
                                  FIX2INT(abi),
                                  n_call_args,
                                  ffi_return_type,
                                  ffi_arg_types);
        }
        if (result != FFI_OK) {
            xfree(ffi_arg_types);
            args.cif->arg_types = NULL;
            rb_raise(rb_eRuntimeError, "error creating CIF %d", result);
        }
    }

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

    for (i = 0, i_call = 0;
         i < argc && i_call < n_call_args;
         i++, i_call++) {
        VALUE arg_type;
        int c_arg_type;
        VALUE original_src;
        VALUE src;
        arg_type = RARRAY_AREF(arg_types, i_call);
        c_arg_type = FIX2INT(arg_type);
        if (i >= n_fixed_args) {
            i++;
        }
        src = argv[i];

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

        original_src = src;
        VALUE2GENERIC(c_arg_type, src, &generic_args[i_call]);
        if (src != original_src) {
            if (NIL_P(converted_args)) {
                converted_args = rb_ary_new();
            }
            rb_ary_push(converted_args, src);
        }
        args.values[i_call] = (void *)&generic_args[i_call];
    }
    args.values[i_call] = NULL;
    args.fn = (void(*)(void))NUM2PTR(cfunc);

    if (RTEST(need_gvl)) {
        ffi_call(args.cif, args.fn, &(args.retval), args.values);
    }
    else {
        (void)rb_thread_call_without_gvl(nogvl_ffi_call, &args, 0, 0);
    }

    {
        int errno_keep = errno;
#if defined(_WIN32)
        DWORD error = WSAGetLastError();
        int socket_error = WSAGetLastError();
        rb_funcall(mFiddle, rb_intern("win32_last_error="), 1,
                   ULONG2NUM(error));
        rb_funcall(mFiddle, rb_intern("win32_last_socket_error="), 1,
                   INT2NUM(socket_error));
#endif
        rb_funcall(mFiddle, rb_intern("last_error="), 1, INT2NUM(errno_keep));
    }

    ALLOCV_END(alloc_buffer);

    return GENERIC2VALUE(rb_iv_get(self, "@return_type"), args.retval);
}

need_gvl? ()

Whether GVL is needed to call this function

# File ext/fiddle/lib/fiddle/function.rb, line 14
def need_gvl?
  @need_gvl
end

to_i ()

The integer memory location of this function

# File ext/fiddle/lib/fiddle/function.rb, line 19
def to_i
  ptr.to_i
end

to_proc ()

Turn this function in to a proc

# File ext/fiddle/lib/fiddle/function.rb, line 24
def to_proc
  this = self
  lambda { |*args| this.call(*args) }
end