class PDF::Reader::PageLayout

def local_string_insert(haystack, needle, index)

See my bug report at https://github.com/rubinius/rubinius/issues/1985

method as it's buggy on rubinius 2.0rc1 (in 1.9 mode)
This is a simple alternative to String#[]=. We can't use the string 
def local_string_insert(haystack, needle, index)
  if @current_platform_is_rbx_19
    char_count = needle.length
    haystack.replace(
      (haystack[0,index] || "") +
      needle +
      (haystack[index+char_count,500] || "")
    )
  else
    haystack[Range.new(index, index + needle.length - 1)] = String.new(needle)
  end
end