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by ryan davis


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RubyToRubyC - ruby's first real obfuscator?

Published 2005-05-05 @ 17:08

Tagged ruby, metaruby, ruby2c, toys, zenobfuscate

Eric did something very very cool the other day. He wrote a new tail to the ruby2c pipeline that outputs Ruby C instead of generic C. As a result, he is able to automatically translate the following:

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$ cat demo/factorial.rb
class F
  def factorial(n)
    f = 1
    n.downto(2) { |x| f *= x }
    return f
  end

  def main # horrid but funny hack
    return factorial(5)
  end
end

into:

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// BEGIN METARUBY PREAMBLE
#include <ruby.h>
#define case_equal_long(x, y) (rb_funcall((x), rb_intern("==="), 1, (y)))
// END METARUBY PREAMBLE
// class F < Object

static VALUE
rrc_cF_factorial(VALUE __self, VALUE n) {
VALUE f;
VALUE x;
f = LONG2FIX(1);
x = n;
while (RTEST(rb_funcall(x, rb_intern(">="), 1, LONG2FIX(2)))) {
f = rb_funcall(f, rb_intern("*"), 1, x);
x = rb_funcall(x, rb_intern("-"), 1, LONG2FIX(1));
};
return f;
}

void
Init_F() {
VALUE rrc_cF = rb_define_class("F", rb_path2class("Object"));
rb_define_method(rrc_cF, "factorial", rrc_cF_factorial, 1);
}

As a result, pretty much any ruby code can be automatically translated to C with no real effort on our part. We can even bypass the type inference engine (for now at least). I think this is the first real step towards a ruby obfuscator.

“More matter, with less art” — Gertrude, Hamlet.