inline unpacking

As a performance enhancement, try adding this:

# for ExternalIndex
if RUBY_PLATFORM.index('mswin').nil?
  require 'inline'
  inline do |builder|
    #builder.include "<rubyio.h>"
    # Array.new(str.length/frame_size) do |i|
    #     str[i*frame_size, frame_size].unpack(format)
    #   end
    builder.c %Q{
      static VALUE unpack(VALUE str)
      {
        char *p = RSTRING(str)->ptr;
        int str_len = RSTRING(str)->len;
        int frame_size = NUM2INT(rb_iv_get(self, "@frame_size"));
        int frame = NUM2INT(rb_iv_get(self, "@frame"));
        int i, j, times = str_len/frame_size;
        VALUE fmt = rb_iv_get(self, "@format");
        VALUE results, arr;

        if(times <= 1)
          return rb_funcall(str, rb_intern("unpack"), 1, fmt);

        results = rb_ary_new();
        i = 0;
        while(i < times)
        {
          j = 0;
          arr = rb_ary_new();
          while(j < frame)
          {
            // no need to copy the data at *p,
                // apparently the conversion can
                // happen directly from the pointer
                rb_ary_push(arr, UINT2NUM(*p));
                p += 4;


            ++j;
          }

          rb_ary_push(results, arr);
          ++i;
        }
        return results;
      }

    }#File.read(File.dirname(__FILE__) + "/../../src/inline.c")
  end
else
  # on windows when it's not likely that the user has
  # a compiler, include the precompiled binaries
  # require ...
end