As you might already know, the Ruby interpreter you’re (probably) using (the one at ruby-lang.org) know as MRI, for Matz Ruby Interpreter, is written in C. The VM is entirely written in C and most of the standard libraries too. So it seems that the way to make code run faster is really to dive into C.
Now I hear you yell with your ears all red, eyes full of blood and a big vein pumping on your forehead: But it will be unmaintainable!
If everything seems under control, you’re not going fast enough
- Mario Andretti
The hard part is that the C API of MRI lacks documentation. You either have to search through the mailinglist, look at other people’s code or try to guess from Ruby’s code. I recently ported a bit of code from Ruby to C and here are a couple of Ruby to C mapping that might help you.
If you’ve never written or looked at a Ruby extension before, I suggestion reading Peter Cooper excellent and very simple tutorial on how to set things up.
Objects are VALUEs
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Strings
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Object to C struct
In C you’ll probably want to store your data in a struct. Ruby provide some things to wrap a struct inside a Ruby object. Also, since Ruby is not aware of the stuff created in the C world we have to be pretty explicit about everything.
module MyModule
class MyClass
def close
@closed = true
end
end
end
In C
/* This is called by Ruby GC when the object is freed
* so free all resources used here. We hook it up
* in the Data_Wrap_Struct call down there. */
void my_obj_free(my_struct_t *s)
{
free(s);
}
/* Called by Ruby then and instance of your class is created
* hooked by rb_define_alloc_func. */
VALUE my_obj_alloc(VALUE klass)
{
my_struct_t *s = ALLOC_N(my_struct_t, 1);
/* This stores the struct inside the Ruby object, so you
* can get the struct back on each method call. */
return Data_Wrap_Struct(klass, NULL, my_obj_free, s);
}
/* The actual MyClass#close method, first argument is the
* instance object. It’s hook into our class by the rb_define_method
* call in Init_ */
VALUE my_obj_close(VALUE self)
{
my_struct_t *s;
/* This is where we get the struct back from the Ruby object */
Data_Get_Struct(self, my_struct_t, s);
s->closed = 1;
}
/* Init_* is magically called by Ruby to bootstrap your extension,
* it’s like a main function if you will. */
void Init_name_of_your_extension()
{
VALUE mMyModule = rb_define_module("MyModule");
VALUE cMyClass = rb_define_class_under(mMyModule, "MyClass", rb_cObject);
rb_define_alloc_func(cMyClass, my_obj_alloc);
rb_define_method(cMyClass, "close", my_obj_close, 0);
}
Calling methods
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Blocks
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Error handling
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Garbage Collection
When creating Ruby objects in the C world, Ruby is not aware of the scope of each, it’s impossible to track when a variable is used and when it’s not, so it’s impossible for the garbage collector to know when do leave or sweep objects. If you create a long live object, that will persist for several method calls you have to tell Ruby’s garbage collector when it’s in use and when you’re finished with it. If you don’t, Ruby GC will free your variable in the worst possible time, ending up with unthinkable tragedies around the world, leaving you homeless and poor for all eternity.
VALUE var = rb_str_new2("prout");
/* Tell Ruby GC this object is in use */
rb_gc_register_address(&var);
/* when you’re finished you can unregister it and let the GC free it */
rb_gc_unregister_address(&var);
Note that you don’t need to do this if you only use the variable in one method since the control is not given back to Ruby during the method call. Also if the variable is still referenced in the Ruby world it’s already registered.
More, more, more!
This is far from a complete guide to MRI, you’ll need to dig the Ruby doxygen doc if you need more info.
Now lets port Rails to C!
With all the Ruby frameworks popping up, we’re starting to see some similarities. All of them provide something new or unique but one part of their code is always the same. The part that plugs it into a web server. Ultimately, all web servers have to support all frameworks and vice-versa. That is a lot of duplicated code! That makes me yell, running in circles, waving my arms: not DRY, not DRY, not DRY!
I don’t really check the fat quantity. Saturated fat should be low. But the important thing is Trans fat should be 0. Almost no product with trans fat ever enter my house. This type of fat is transformed in a way your body can not recognize it as fat, so it won’t end up in the right place and it’s not the type of fat you can loose by exercising. It’s there forever, like Microsoft hidden libraries when you install Office!
This one is important because it’s high on several products that are low fat or low calories. If it’s low in fat but has more then half your daily value in sodium (often the case for dried noodle soup) it’s a no-no, it would be like eating salt!
Ever wondered why drinking a glass full of fruit juice will keep you hungry and only one apple can sustain you for a couple of hours ? That’s because the juice doesn’t hold any proteins. Proteins expand in your stomach and make you feel satisfied. If a meal hold lots of proteins you won’t need to eat as much to get going!
Even if you have to eat frozen food for lunch there are some good choices out there, just check out those 3 things. Plus, fruits and vegetables are always a winner. But cutting, wrapping the thing can be pretty annoying. To bring back excitement, joy and extaze to your meal think about trying new fruits like: asian pear, dragon fruit, kaki, kiwi, mango… OK that’s enough I’m starting to dribble.
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