new (PDF::Reader::Encoding)

    # File lib/pdf/reader/encoding.rb, line 35
        def initialize(enc)
          if enc.kind_of?(Hash)
            self.differences=enc[:Differences] if enc[:Differences]
            enc = enc[:Encoding] || enc[:BaseEncoding]
          elsif enc != nil
            enc = enc.to_sym
          end

          case enc
            when nil                   then
              load_mapping File.dirname(__FILE__) + "/encodings/standard.txt"
              @unpack = "C*"
            when "Identity-H".to_sym   then
              @unpack = "n*"
              @to_unicode_required = true
            when :MacRomanEncoding     then
              load_mapping File.dirname(__FILE__) + "/encodings/mac_roman.txt"
              @unpack = "C*"
            when :MacExpertEncoding    then
              load_mapping File.dirname(__FILE__) + "/encodings/mac_expert.txt"
              @unpack = "C*"
            when :PDFDocEncoding       then
              load_mapping File.dirname(__FILE__) + "/encodings/pdf_doc.txt"
              @unpack = "C*"
            when :StandardEncoding     then
              load_mapping File.dirname(__FILE__) + "/encodings/standard.txt"
              @unpack = "C*"
            when :SymbolEncoding       then
              load_mapping File.dirname(__FILE__) + "/encodings/symbol.txt"
              @unpack = "C*"
            when :UTF16Encoding        then
              @unpack = "n*"
            when :WinAnsiEncoding      then
              load_mapping File.dirname(__FILE__) + "/encodings/win_ansi.txt"
              @unpack = "C*"
            when :ZapfDingbatsEncoding then
              load_mapping File.dirname(__FILE__) + "/encodings/zapf_dingbats.txt"
              @unpack = "C*"
            else raise UnsupportedFeatureError, "#{enc} is not currently a supported encoding"
          end
        end