* toc
{:toc}

     def sort_input(input, property, order)
          if !input #################加入这三行
            return	#################加入这三行
          end		#################加入这三行
          input.map { |item| [item_property(item, property), item] }
            .sort! do |apple_info, orange_info|
              apple_property = apple_info.first
              orange_property = orange_info.first
              
              if !apple_property.nil? && orange_property.nil?
                - order
              elsif apple_property.nil? && !orange_property.nil?
                + order
              else
                apple_property <=> orange_property
              end
            end
            .map!(&:last)
     end

def prevent_directory_traversal(req, res)
        # Preventing directory traversal on Windows platforms;
        # Backslashes (0x5c) in path_info are not interpreted as special
        # character in URI notation. So the value of path_info should be
        # normalize before accessing to the filesystem.

        # dirty hack for filesystem encoding; in nature, File.expand_path
        # should not be used for path normalization.  [Bug #3345]
        path = req.path_info.dup.force_encoding(Encoding.find("filesystem"))
		path.force_encoding("UTF-8") #################强制使用UTF-8编码
        if trailing_pathsep?(req.path_info)
          # File.expand_path removes the trailing path separator.
          # Adding a character is a workaround to save it.
          #  File.expand_path("/aaa/")        #=> "/aaa"
          #  File.expand_path("/aaa/" + "x")  #=> "/aaa/x"
          expanded = File.expand_path(path + "x")
          expanded.chop!  # remove trailing "x"
        else
          expanded = File.expand_path(path)
        end
        expanded.force_encoding(req.path_info.encoding)
        req.path_info = expanded
      end



      def set_filename(req, res)
        res.filename = @root.dup
        path_info = req.path_info.scan(%r|/[^/]*|)

        path_info.unshift("")  # dummy for checking @root dir
        while base = path_info.first
          break if base == "/"
		  base.force_encoding("UTF-8")#################强制使用UTF-8编码
          break unless File.directory?(File.expand_path(res.filename + base))
          shift_path_info(req, res, path_info)
          call_callback(:DirectoryCallback, req, res)
        end

        if base = path_info.first
          if base == "/"
            if file = search_index_file(req, res)
              shift_path_info(req, res, path_info, file)
              call_callback(:FileCallback, req, res)
              return true
            end
            shift_path_info(req, res, path_info)
          elsif file = search_file(req, res, base)
            shift_path_info(req, res, path_info, file)
            call_callback(:FileCallback, req, res)
            return true
          else
            raise HTTPStatus::NotFound, "`#{req.path}' not found."
          end
        end

        return false
      end

<script>
        MathJax = {
		tex: {
			inlineMath: [['$', '$']],
			displayMath: [['$$', '$$']],
			processEnvironments: true,
			processRefs: true
		},
		options: {
			skipHtmlTags: ['noscript', 'style', 'textarea', 'pre', 'code'],
			ignoreHtmlClass: 'tex2jax_ignore',
			renderActions: {
				find_script_mathtex: [10, function (doc) {
					for (const node of document.querySelectorAll('script[type^="math/tex"]')) {
						const display = !!node.type.match(/; *mode=display/);
						const math = new doc.options.MathItem(node.textContent, doc.inputJax[0], display);
						const text = document.createTextNode('');
						node.parentNode.replaceChild(text, node);
						math.start = { node: text, delim: '', n: 0 };
						math.end = { node: text, delim: '', n: 0 };
						doc.math.push(math);
					}
				}, '']
			}
		},
		svg: {
			fontCache: 'global'
		}
	};
</script>
<script id="MathJax-script" async src="https://cdn.staticfile.org/mathjax/3.0.1/es5/tex-svg.js"></script>

MathJax = {
  tex: {
    packages: ['base'],        // extensions to use
    inlineMath: [              // start/end delimiter pairs for in-line math
      ['\\(', '\\)']
    ],
    displayMath: [             // start/end delimiter pairs for display math
      ['$$', '$$'],
      ['\\[', '\\]']
    ],
    processEscapes: true,      // use \$ to produce a literal dollar sign
    processEnvironments: true, // process \begin{xxx}...\end{xxx} outside math mode
    processRefs: true,         // process \ref{...} outside of math mode
    digits: /^(?:[0-9]+(?:\{,\}[0-9]{3})*(?:\.[0-9]*)?|\.[0-9]+)/,
                               // pattern for recognizing numbers
    tags: 'none',              // or 'ams' or 'all'
    tagSide: 'right',          // side for \tag macros
    tagIndent: '0.8em',        // amount to indent tags
    useLabelIds: true,         // use label name rather than tag for ids
    multlineWidth: '85%',      // width of multline environment
    maxMacros: 1000,           // maximum number of macro substitutions per expression
    maxBuffer: 5 * 1024,       // maximum size for the internal TeX string (5K)
    baseURL:                   // URL for use with links to tags (when there is a <base> tag in effect)
       (document.getElementsByTagName('base').length === 0) ?
        '' : String(document.location).replace(/#.*$/, ''))
  }
};