Dynamically Typed Languages

Languages such as Jython or JRuby may find it more convenient to access the NativeLibrary and Function classes directly rather than establishing a dedicated interface. Here's a brief example of using JNA from JRuby:

require 'java'

module Libc
  @@lib = com.sun.jna.NativeLibrary.getInstance("c")
  @@ptr_funcs = [ 'fopen', 'malloc', 'calloc' ]
  def self.method_missing(meth, *args)
    if @@ptr_funcs.include?(meth.to_s)
      @@lib.getFunction(meth.to_s).invokePointer(args.to_java)
    else
      @@lib.getFunction(meth.to_s).invokeInt(args.to_java)
    end
  end
  O_RDONLY = 0
  O_WRONLY = 1
  O_RDWR = 2
end

Libc.puts("puts from libc")
Libc.printf("Hello %s, from printf\n", "World")

file = Libc.open("/dev/stdout", 1, Libc::O_WRONLY)
n = Libc.write(file, "Test\n", 5)
puts "Wrote #{n} bytes via Libc"

path = "/dev/stdout"
fp = Libc.fopen(path, "w+")
Libc.fprintf(fp, "fprintf to %s via stdio\n", path)
Libc.fflush(fp)
Libc.fclose(fp)