# Merges a set of options with the default options.
  #
  # direction::
  #  'in':  If options should be handled for xml_in.
  #  'out': If options should be handled for xml_out.
  # options::
  #   Options to be merged with the default options.
  def handle_options(direction, options)
    @options = options || Hash.new

    raise ArgumentError, "Options must be a Hash!" unless @options.instance_of?(Hash)

    unless KNOWN_OPTIONS.has_key?(direction)
      raise ArgumentError, "Unknown direction: <#{direction}>."
    end

    known_options = KNOWN_OPTIONS[direction]
    @options = normalize_option_names(@options, known_options)

    unless @default_options.nil?
      known_options.each { |option|
        unless @options.has_key?(option)
          if @default_options.has_key?(option)
            @options[option] = @default_options[option]
          end
        end
      }
    end

    unless @options.has_key?('noattr')
        @options['noattr'] = false
    end

    if @options.has_key?('rootname')
      @options['rootname'] = '' if @options['rootname'].nil?
    else
      @options['rootname'] = DEF_ROOT_NAME
    end

    if @options.has_key?('xmldeclaration') && @options['xmldeclaration'] == true
      @options['xmldeclaration'] = DEF_XML_DECLARATION
    end

    @options['keytosymbol'] = DEF_KEY_TO_SYMBOL unless @options.has_key?('keytosymbol')

    if @options.has_key?('contentkey')
      if @options['contentkey'] =~ /^-(.*)$/
        @options['contentkey']    = $1
        @options['collapseagain'] = true
      end
    else
      @options['contentkey'] = DEF_CONTENT_KEY
    end

    unless @options.has_key?('normalisespace')
      @options['normalisespace'] = @options['normalizespace']
    end
    @options['normalisespace'] = 0 if @options['normalisespace'].nil?

    if @options.has_key?('searchpath')
      unless @options['searchpath'].instance_of?(Array)
        @options['searchpath'] = [ @options['searchpath'] ]
      end
    else
      @options['searchpath'] = []
    end

    if @options.has_key?('cache') && scalar(@options['cache'])
      @options['cache'] = [ @options['cache'] ]
    end

    @options['anonymoustag'] = DEF_ANONYMOUS_TAG unless @options.has_key?('anonymoustag')

    if !@options.has_key?('indent') || @options['indent'].nil?
      @options['indent'] = DEF_INDENTATION
    end

    @options['indent'] = '' if @options.has_key?('noindent')

    # Special cleanup for 'keyattr' which could be an array or
    # a hash or left to default to array.
    if @options.has_key?('keyattr')
      if !scalar(@options['keyattr'])
        # Convert keyattr => { elem => '+attr' }
        #      to keyattr => { elem => ['attr', '+'] }
        if @options['keyattr'].instance_of?(Hash)
          @options['keyattr'].each { |key, value|
            if value =~ /^([-+])?(.*)$/
              @options['keyattr'][key] = [$2, $1 ? $1 : '']
            end
          }
        elsif !@options['keyattr'].instance_of?(Array)
          raise ArgumentError, "'keyattr' must be String, Hash, or Array!"
        end
      else
        @options['keyattr'] = [ @options['keyattr'] ]
      end
    else
      @options['keyattr'] = DEF_KEY_ATTRIBUTES
    end

    if @options.has_key?('forcearray')
      if @options['forcearray'].instance_of?(Regexp)
        @options['forcearray'] = [ @options['forcearray'] ]
      end

      if @options['forcearray'].instance_of?(Array)
        force_list = @options['forcearray']
        unless force_list.empty?
          @options['forcearray'] = {}
          force_list.each { |tag|
            if tag.instance_of?(Regexp)
              unless @options['forcearray']['_regex'].instance_of?(Array)
                @options['forcearray']['_regex'] = []
              end
              @options['forcearray']['_regex'] << tag
            else
              @options['forcearray'][tag] = true
            end
          }
        else
          @options['forcearray'] = false
        end
      else
        @options['forcearray'] = @options['forcearray'] ? true : false
      end
    else
      @options['forcearray'] = DEF_FORCE_ARRAY
    end

    if @options.has_key?('grouptags') && !@options['grouptags'].instance_of?(Hash)
      raise ArgumentError, "Illegal value for 'GroupTags' option - expected a Hash."
    end

    if @options.has_key?('variables') && !@options['variables'].instance_of?(Hash)
      raise ArgumentError, "Illegal value for 'Variables' option - expected a Hash."
    end

    if @options.has_key?('variables')
      @_var_values = @options['variables']
    elsif @options.has_key?('varattr')
      @_var_values = {}
    end
  end