translate_offset

# File activesupport/lib/active_support/multibyte/chars.rb, line 430
        def translate_offset(byte_offset) #:nodoc:
          return nil if byte_offset.nil?
          return 0   if @wrapped_string == ''

          if @wrapped_string.respond_to?(:force_encoding)
            @wrapped_string = @wrapped_string.dup.force_encoding(Encoding::ASCII_8BIT)
          end

          begin
            @wrapped_string[0...byte_offset].unpack('U*').length
          rescue ArgumentError => e
            byte_offset -= 1
            retry
          end
        end