Ruru (Rust + Ruby)

Native Ruby extensions in Rust

Documentation

Have you ever considered rewriting some parts of your ~~slow~~ Ruby application?

Just replace your Ruby application with Rust, method by method, class by class. It does not require you to change the interface of your classes or to change any other Ruby code.

As simple as Ruby, as efficient as Rust.

Examples

The famous String#blank? method

The fast String#blank? implementation by Yehuda Katz

```rust,no_run

[macro_use]

extern crate ruru;

use ruru::{Boolean, Class, Object, RString};

methods!( RString, itself,

fn stringisblank() -> Boolean { Boolean::new(itself.tostring().chars().all(|c| c.iswhitespace())) } );

[no_mangle]

pub extern fn initializestring() { Class::fromexisting("String").define(|itself| { itself.def("blank?", stringisblank); }); } ```

Simple Sidekiq-compatible server

Link to the repository

Safe conversions

Since 0.8.0 safe conversions are available for built-in Ruby types and for custom types.

Let's imagine that we are writing an HTTP server. It should handle requests which are passed from Ruby side.

Any object which responds to #body method is considered as a valid request.

```rust,no_run

[macro_use]

extern crate ruru;

use std::error::Error; use ruru::{Class, Object, RString, VerifiedObject, VM};

class!(Request);

impl VerifiedObject for Request { fn iscorrecttype(object: &T) -> bool { object.respond_to("body") }

fn error_message() -> &'static str {
    "Not a valid request"
}

}

class!(Server);

methods!( Server, itself,

fn process_request(request: Request) -> RString {
    let body = request
        .and_then(|request| request.send("body", vec![]).try_convert_to::<RString>())
        .map(|body| body.to_string());

    // Either request does not respond to `body` or `body` is not a String
    if let Err(ref error) = body {
        VM::raise(error.to_exception(), error.description());
    }

    let formatted_body = format!("[BODY] {}", body.unwrap());

    RString::new(&formatted_body)
}

);

[no_mangle]

pub extern fn initializeserver() { Class::new("Server", None).define(|itself| { itself.def("processrequest", process_request); }); } ```

True parallelism

Ruru provides a way to enable true parallelism for Ruby threads by releasing GVL (GIL).

It means that a thread with released GVL runs in parallel with other threads without being interrupted by GVL.

Current example demonstrates a "heavy" computation (2 * 2 for simplicity) run in parallel.

```rust,no_run

[macro_use] extern crate ruru;

use ruru::{Class, Fixnum, Object, VM};

class!(Calculator);

methods!( Calculator, itself,

fn heavy_computation() -> Fixnum {
    let computation = || { 2 * 2 };
    let unblocking_function = || {};

    // release GVL for current thread until `computation` is completed
    let result = VM::thread_call_without_gvl(
        computation,
        Some(unblocking_function)
    );

    Fixnum::new(result)
}

);

fn main() { Class::new("Calculator", None).define(|itself| { itself.def("heavycomputation", heavycomputation); }); } ```

Defining a new class

Let's say you have a Calculator class.

```ruby class Calculator def pow3(number) (1..number).eachwith_object({}) do |index, hash| hash[index] = index ** 3 end end end

... somewhere in the application code ...

Calculator.new.pow_3(5) #=> { 1 => 1, 2 => 8, 3 => 27, 4 => 64, 5 => 125 } ```

You have found that it's very slow to call pow_3 for big numbers and decided to replace the whole class with Rust.

```rust,no_run

[macro_use]

extern crate ruru;

use std::error::Error; use ruru::{Class, Fixnum, Hash, Object, VM};

class!(Calculator);

methods!( Calculator, itself,

fn pow_3(number: Fixnum) -> Hash {
    let mut result = Hash::new();

    // Raise an exception if `number` is not a Fixnum
    if let Err(ref error) = number {
        VM::raise(error.to_exception(), error.description());
    }

    for i in 1..number.unwrap().to_i64() + 1 {
        result.store(Fixnum::new(i), Fixnum::new(i.pow(3)));
    }

    result
}

);

[no_mangle]

pub extern fn initializecalculator() { Class::new("Calculator", None).define(|itself| { itself.def("pow3", pow_3); }); } ```

Ruby:

```ruby

No Calculator class in Ruby anymore

... somewhere in the application ...

Calculator.new.pow_3(5) #=> { 1 => 1, 2 => 8, 3 => 27, 4 => 64, 5 => 125 } ```

Nothing has changed in the API of class, thus there is no need to change any code elsewhere in the app.

Replacing only several methods instead of the whole class

If the Calculator class from the example above has more Ruby methods, but we want to replace only pow_3, use Class::from_existing()

rust,ignore Class::from_existing("Calculator").define(|itself| { itself.def("pow_3", pow_3); });

Class definition DSL

```rust,norun Class::new("Hello", None).define(|itself| { itself.attrreader("reader");

itself.def_self("greeting", greeting);
itself.def("many_greetings", many_greetings);

itself.define_nested_class("Nested", None).define(|itself| {
    itself.def_self("nested_greeting", nested_greeting);
});

}); ```

Which corresponds to the following Ruby code:

```ruby class Hello attr_reader :reader

def self.greeting # ... end

def many_greetings # ... end

class Nested def self.nested_greeting # ... end end end ```

See documentation for Class and Object for more information.

Calling Ruby code from Rust

Getting an account balance of some User whose name is John and who is 18 or 19 years old.

```ruby default_balance = 0

accountbalance = User .findby(age: [18, 19], name: 'John') .account_balance

accountbalance = defaultbalance unless accountbalance.isa?(Fixnum) ```

```rust,no_run

[macro_use]

extern crate ruru;

use ruru::{Array, Class, Fixnum, Hash, Object, RString, Symbol};

fn main() { let default_balance = 0; let mut conditions = Hash::new();

conditions.store(
    Symbol::new("age"),
    Array::new().push(Fixnum::new(18)).push(Fixnum::new(19))
);

conditions.store(
    Symbol::new("name"),
    RString::new("John")
);

// Fetch user and his balance
// and set it to 0 if balance is not a Fixnum (for example `nil`)
let account_balance =
    Class::from_existing("User")
        .send("find_by", vec![conditions.to_any_object()])
        .send("account_balance", vec![])
        .try_convert_to::<Fixnum>()
        .map(|balance| balance.to_i64())
        .unwrap_or(default_balance);

} ```

Check out Documentation for much more examples!

... and why is FFI not enough?

• No support of native Ruby types;

• No way to create a standalone application to run the Ruby VM separately;

• No way to call your Ruby code from Rust;

How do I use it?

Warning! The crate is a WIP.

It is recommended to use Thermite gem, a Rake-based helper for building and distributing Rust-based Ruby extensions.

To be able to use Ruru, make sure that your Ruby version is 2.2.0 or higher.

1. Your local MRI copy has to be built with the --enable-shared option. For example, using rbenv:

   bash CONFIGURE_OPTS=--enable-shared rbenv install 2.3.0

2. Add Ruru to Cargo.toml

   toml [dependencies] ruru = "0.8.0"

3. Compile your library as a dylib

   toml [lib] crate-type = ["dylib"]

4. Create a function which will initialize the extension

   ```rust,ignore

   [no_mangle]

   pub extern fn initializemyapp() { Class::new("SomeClass");

   /// ... etc } ```

5. Build extension

   bash $ cargo build --release

   or using Thermite

   bash $ rake thermite:build

6. On the ruby side, open the compiled dylib and call the function to initialize extension

   ```ruby require 'fiddle'

   library = Fiddle::dlopen('pathtodylib/libmy_library.dylib')

   Fiddle::Function.new(library['initializemyapp'], [], Fiddle::TYPE_VOIDP).call ```

7. Ruru is ready :heart:

Contributors are welcome!

If you have any questions, join Ruru on Gitter