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:

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

require'fiddle'libm=Fiddle.dlopen('/lib/libm.so.6')floor=Fiddle::Function.new(libm['floor'],[Fiddle::TYPE_DOUBLE],Fiddle::TYPE_DOUBLE)putsfloor.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:

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:

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:

# order of members in memory: position, id, dimensionsRect=struct[{position: struct(['float x','float y'])},'int id',{dimensions: struct(['float w','float h'])}]# order of members in memory: id, position, dimensionsRect=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 Ruby's and/or BSD-2-Clause.