From: Charles Oliver Nutter <charles.nutter@...>
Date: 2008-11-01T08:16:39+09:00
Subject: [ANN] FFI 0.1.1 (Foreign Function Interface) for Ruby 1.8.6/7 and 1.9

The JRuby team is proud to announce the release of FFI for Ruby 1.8.6/7 
and 1.9!

FFI (gem install ffi) is a library for programmatically loading dynamic 
libraries, binding functions within them, and calling those functions 
from Ruby code. Here's a quick sample of binding and calling the getpid 
C library function:


require 'ffi'

module GetPid
   extend FFI::Library

   attach_function :getpid, [], :uint
end

puts GetPid.getpid


Here's another, calling qsort and passing a Ruby block as a C callback:


require 'ffi'

module LibC
   extend FFI::Library
   callback :qsort_cmp, [ :pointer, :pointer ], :int
   attach_function :qsort, [ :pointer, :int, :int, :qsort_cmp ], :int
end

p = MemoryPointer.new(:int, 2)
p.put_array_of_int32(0, [ 2, 1 ])
puts "Before qsort #{p.get_array_of_int32(0, 2).join(', ')}"
LibC.qsort(p, 2, 4) do |p1, p2|
   i1 = p1.get_int32(0)
   i2 = p2.get_int32(0)
   i1 < i2 ? -1 : i1 > i2 ? 1 : 0
end
puts "After qsort #{p.get_array_of_int32(0, 2).join(', ')}"


I posted a blog entry with a longer description of the library, 
additional examples, and links to some other documentation and posts. 
Docs are a little slim at this point, so feel free to experiment and 
update the JRuby wiki page:

http://wiki.jruby.org/wiki/Calling_C_from_JRuby

I'm sure docs from here will filter back into the library and out into 
the general cosmos.

Finally, there's no need to write a C extension to call C libraries, and 
the same FFI code will work in Ruby 1.8.6/7, Ruby 1.9, JRuby 1.1.4+, and 
Rubinius (though Rubinius has no callback support yet).

Don't be an extension stooge! Use FFI!

- Charlie