is_utf8?

# File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 46
    def is_utf8? #:nodoc
      case encoding
      when Encoding::UTF_8
        valid_encoding?
      when Encoding::ASCII_8BIT, Encoding::US_ASCII
        dup.force_encoding(Encoding::UTF_8).valid_encoding?
      else
        false
      end
    end