Move rb_tr_readable and rb_tr_writable entirely to C.

Author: aardvark179

lib/truffle/truffle/cext.rb

@@ -1697,14 +1697,6 @@ def rb_class_inherited_p(ruby_module, object)
     end
   end
 
-  def rb_tr_readable(mode)
-    mode & File::Constants::FMODE_READABLE != 0
-  end
-
-  def rb_tr_writable(mode)
-    mode & File::Constants::FMODE_WRITABLE != 0
-  end
-
   def rb_backref_get
     Primitive.regexp_last_match_get(Truffle::ThreadOperations.ruby_caller_special_variables([Truffle::CExt, Truffle::Interop.singleton_class]))
   end

src/main/c/cext/io.c

@@ -153,11 +153,11 @@ VALUE rb_get_path(VALUE object) {
 }
 
 int rb_tr_readable(int mode) {
-  return polyglot_as_boolean(polyglot_invoke(RUBY_CEXT, "rb_tr_readable", mode));
+  return mode & FMODE_READABLE;
 }
 
 int rb_tr_writable(int mode) {
-  return polyglot_as_boolean(polyglot_invoke(RUBY_CEXT, "rb_tr_writable", mode));
+  return mode & FMODE_WRITABLE;
 }
 
 int rb_io_extract_encoding_option(VALUE opt, rb_encoding **enc_p, rb_encoding **enc2_p, int *fmode_p) {