# 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