Calling C code from within Ruby — How to use the returned pointer?

Question

Problem:

I\'d like to use in my Ruby program an algorithm that is coded in C and exposed through a DLL.

I would like to treat the algorithm

Answer 1

While I don't know why the Win32API approach did not work, I've found an easier solution using FFI to the problem of calling C functions from within Ruby or interfacing with DLLs.

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Solution using FFI

Use FFI in Ruby for interfacing with DLLs, as follows:

• (1) Install ffi (works with ruby 1.9.3, ymmv with previous versions)

  gem install ffi

• (2) Create your own Ruby module to wrap the C function

require 'ffi'

module CodeGen                   # Ruby wrapper  (your choice)
  extend FFI::Library
  ffi_lib 'codegen'              # DLL name  (given)
  attach_function 
        :create_code,            # method name  (your choice)
        :CreateCodeShort3,       # DLL function name (given)
          [ :int, :string, :string, :uint, :ushort, :ushort], :string  
                          # specify C param / return value types 
end

ret_str = CodeGen.create_code(3, "foo", "bar", 0,0,0)

puts ret_str

• (3) Run. Result gives a string as desired.

Done!