From: Ken Bloom <kbloom@...>
Date: 2008-11-04T23:38:43+09:00
Subject: Re: [ANN] FFI 0.1.1 (Foreign Function Interface) for Ruby 1.8.6/7 and	1.9

On Fri, 31 Oct 2008 18:16:39 -0500, Charles Oliver Nutter wrote:

> 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

Based on all of the examples I've seen, there's something that's still 
not clear to me. How does ruby-ffi know which library to load to find the 
specified function?

--Ken

-- 
Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/