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    <p>I am facing with interfacing with C libraries in this period (I am writing a <a href="https://github.com/ProGNOMmers/gtop" rel="nofollow">wrapper for libgtop</a>), and I choosed to use <a href="https://github.com/ffi/ffi" rel="nofollow">ffi</a>, which is <a href="https://github.com/ffi/ffi/wiki" rel="nofollow">quite well documented</a> (although the documentation sometimes is a bit outdated) and above all its mailing list is full of people who give you an helping hand when you are in trouble.</p> <p>So I propose you a solution which uses ffi:</p> <pre><code>require 'ffi' module LibX11 extend FFI::Library ffi_lib 'libX11.so.6' # Display *XkbOpenDisplay (char *display_name, int *event_rtrn, int *error_rtrn, int *major_in_out, int *minor_in_out, int *reason_rtrn) attach_function :XkbOpenDisplay, [:pointer, :pointer, :pointer, :pointer, :pointer, :pointer], :pointer end </code></pre> <p>Then you have to describe the <code>Display</code> struct layout, like written <a href="https://github.com/ffi/ffi/wiki/Structs" rel="nofollow">here</a>:</p> <pre><code>class Display &lt; FFI::Struct layout :value, :double, :other_value, :char, ... end </code></pre> <p>And then you do something like this:</p> <pre><code>p1 = FFI::MemoryPointer.new(:char) p2 = FFI::MemoryPointer.new(:int) p3 = FFI::MemoryPointer.new(:int) p4 = FFI::MemoryPointer.new(:int) p5 = FFI::MemoryPointer.new(:int) p6 = FFI::MemoryPointer.new(:int) # write to pointer if needed, otherwise it is a null pointer # p1.write_char('a') # p2.write_int(1) # ... struct_pointer = LibX11.XkbOpenDisplay(p1, p2, p3, p4, p5, p6) # read the struct struct = Display.new(display_struct_pointer) p Hash[ s.members.map { |m| [ m, s[m] ] } ] </code></pre> <p>I didn't tested the code, but it should be roughly correct. Let me now if it isn't.</p> <hr> <p>After some research about DL on ruby 2.0 I found that it is deprecated and replaced with fiddle, you would consider to use it rather than DL if you can't use FFI. Fiddle seems to be available for ruby 1.9.3 and 1.9.2 too</p>
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    1. POHow to interface more complex shared library?
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    1. POHow to interface more complex shared library?
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    1. COGreat comprehensive information. I would either try to mimic it with `ruby/dl` or try to persuade a customer to allow installation of *ffi* gem. Luckily it does not have any extra dependencies.
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    2. COafter some research about DL on ruby 2.0 I found that it is deprecated and replaced with [fiddle](http://www.ruby-doc.org/stdlib-2.0/libdoc/fiddle/rdoc/Fiddle.html), you would consider to use it rather than DL if you can't use FFI. Fiddle seems to be available for ruby 1.9.3 and 1.9.2 too (I updated the answer)
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    3. COOh, thanks for that information. Good to know, even the target platform is running the 1.9 version yet.
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