go-gem-wrapper

go-gem-wrapper is a wrapper for creating Ruby native extension in Go

Requirements

• Go
• Ruby

Getting started

At first, patch to make a gem into a Go gem right after bundle gem

See _tools/patch_for_go_gem/

Please also add the following depending on the CI you are using.

GitHub Actions

e.g.

- uses: actions/setup-go@v5
  with:
    go-version-file: ext/GEM_NAME/go.mod

Implementing Ruby methods in Go

For example, consider the following Ruby method implemented in Go

module Example
  def self.sum(a, b)
    a + b
  end
end

1. Implementing function in Go

// ext/GEM_NAME/GEM_NAME.go

//export rb_example_sum
func rb_example_sum(_ C.VALUE, a C.VALUE, b C.VALUE) C.VALUE {
	aLong := ruby.NUM2LONG(ruby.VALUE(a))
	bLong := ruby.NUM2LONG(ruby.VALUE(b))

	sum := aLong + bLong

	return C.VALUE(ruby.LONG2NUM(sum))
}

2. Write C function definitions for Go functions

// ext/GEM_NAME/GEM_NAME.go

/*
#include "example.h"

// TODO: Append this
VALUE rb_example_sum(VALUE self, VALUE a, VALUE b);
*/
import "C"

3. Call exported C functions with the Init function

// ext/GEM_NAME/GEM_NAME.go

//export Init_example
func Init_example() {
	rb_mExample := ruby.RbDefineModule("Example")

	// TODO: Append this
	ruby.RbDefineSingletonMethod(rb_mExample, "sum", C.rb_example_sum, 2)
}

More examples

See also

• ruby/testdata/example/ext/example/example.go
• ruby/testdata/example/ext/example/tests.go

Developing

Build

Run rake ruby:build_example. (bundle exec is not required)

See rake -T for more tasks.

See godoc in local

go install golang.org/x/tools/cmd/godoc@latest
godoc

open http://localhost:6060/pkg/github.com/ruby-go-gem/go-gem-wrapper/

Coverage

We provide auto-generated bindings for (almost) all CRuby functions available when including ruby.h 💪

See below for details.

• ruby/enum_generated.go
• ruby/function_generated.go
• ruby/type_generated.go
• _tools/ruby_h_to_go/

Reference

• Go: https://pkg.go.dev/github.com/ruby-go-gem/go-gem-wrapper
• Ruby: https://ruby-go-gem.github.io/go-gem-wrapper/

Original idea

Ruby meets Go - RubyKaigi 2015