Fiddle

A libffi wrapper for Ruby.

Fiddle is an extension to translate a foreign function interface (FFI) with ruby.

It wraps libffi, a popular C library which provides a portable interface that allows code written in one language to call code written in another language.

Installation

Add this line to your application’s Gemfile:

ruby gem 'fiddle'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fiddle

Usage

Here we will use Fiddle::Function to wrap floor(3) from libm

```ruby require ‘fiddle’

libm = Fiddle.dlopen(‘/lib/libm.so.6’)

floor = Fiddle::Function.new( libm[‘floor’], [Fiddle::TYPE_DOUBLE], Fiddle::TYPE_DOUBLE )

puts floor.call(3.14159) #=> 3.0 ```

Nested Structs

You can use hashes to create nested structs, where the hash keys are member names and the values are the nested structs:

```ruby StudentCollegeDetail = struct [ ‘int college_id’, ‘char college_name[50]’ ]

StudentDetail = struct [ ‘int id’, ‘char name[20]’, { clg_data: StudentCollegeDetail } ] ```

You can also specify an anonymous nested struct, like so:

ruby StudentDetail = struct [ 'int id', 'char name[20]', { clg_data: struct([ 'int college_id', 'char college_name[50]' ]) } ]

The position of a hash (and the order of the keys in the hash, in the case of a hash with multiple entries), dictate the offsets of the nested struct in memory. The following examples are both syntactically valid but will lay out the structs differently in memory:

```ruby # order of members in memory: position, id, dimensions Rect = struct [ { position: struct([‘float x’, ‘float y’]) }, ‘int id’, { dimensions: struct([‘float w’, ‘float h’]) } ]

order of members in memory: id, position, dimensions

Rect = struct [ ‘int id’, { position: struct([‘float x’, ‘float y’]), dimensions: struct([‘float w’, ‘float h’]) } ] ```

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/fiddle.

License

The gem is available as open source under the terms of the BSD-2-Clause.