ffi-compiler is a ruby library for automating compilation of native libraries for use with ffi

To use, define your own ruby->native API using ffi, implement it in C, then use ffi-compiler to compile it.

Example

Directory layout

lib
  |- example
      |- example.rb
      
ext
  |- example.c
  |- Rakefile
  
example.gemspec

lib/example/example.rb

require 'ffi'
require 'ffi-compiler/loader'

module Example
  extend FFI::Library
  ffi_lib FFI::Compiler::Loader.find('example')
  
  # example function which takes no parameters and returns long
  attach_function :example, [], :long
end

ext/example.c

long
example(void)
{
    return 0xdeadbeef;
}

ext/Rakefile

require 'ffi-compiler/compile_task'

FFI::Compiler::CompileTask.new('example') do |c|
  c.have_header?('stdio.h', '/usr/local/include')
  c.have_func?('puts')
  c.have_library?('z')
end

example.gemspec

Gem::Specification.new do |s|
  s.extensions << 'ext/Rakefile'
  s.name = 'example'
  s.version = '0.0.1'
  s.email = 'ffi-example'
  s.files = %w(example.gemspec) + Dir.glob("{lib,spec,ext}/**/*")
  s.add_dependency 'rake'
  s.add_dependency 'ffi-compiler'
end

Build gem and install it

gem build example.gemspec && gem install example-0.0.1.gem
Successfully built RubyGem
  Name: example
  Version: 0.0.1
  File: example-0.0.1.gem
Building native extensions.  This could take a while...
Successfully installed example-0.0.1

Test it

$ irb
2.0.0dev :001 > require 'example/example'
 => true 
2.0.0dev :002 > puts "Example.example=#{Example.example.to_s(16)}"
Example.example=deadbeef
 => nil