The Tor Browser / file revision

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 this.EXPORTED_SYMBOLS = [

   "DownloadPaths",

 ];

 /**

  * This module provides the DownloadPaths object which contains methods for

  * giving names and paths to files being downloaded.

  *

  * List of methods:

  *

  * nsILocalFile

  * createNiceUniqueFile(nsILocalFile aLocalFile)

  *

  * [string base, string ext]

  * splitBaseNameAndExtension(string aLeafName)

  */

 const Cc = Components.classes;

 const Ci = Components.interfaces;

 const Cu = Components.utils;

 const Cr = Components.results;

 this.DownloadPaths = {

   /**

    * Creates a uniquely-named file starting from the name of the provided file.

    * If a file with the provided name already exists, the function attempts to

    * create nice alternatives, like "base(1).ext" (instead of "base-1.ext").

    *

    * If a unique name cannot be found, the function throws the XPCOM exception

    * NS_ERROR_FILE_TOO_BIG. Other exceptions, like NS_ERROR_FILE_ACCESS_DENIED,

    * can also be expected.

    *

    * @param aTemplateFile

    *        nsILocalFile whose leaf name is going to be used as a template. The

    *        provided object is not modified.

    * @returns A new instance of an nsILocalFile object pointing to the newly

    *          created empty file. On platforms that support permission bits, the

    *          file is created with permissions 644.

    */

   createNiceUniqueFile: function DP_createNiceUniqueFile(aTemplateFile) {

     // Work on a clone of the provided template file object.

     var curFile = aTemplateFile.clone().QueryInterface(Ci.nsILocalFile);

     var [base, ext] = DownloadPaths.splitBaseNameAndExtension(curFile.leafName);

     // Try other file names, for example "base(1).txt" or "base(1).tar.gz",

     // only if the file name initially set already exists.

     for (let i = 1; i < 10000 && curFile.exists(); i++) {

       curFile.leafName = base + "(" + i + ")" + ext;

     }

     // At this point we hand off control to createUnique, which will create the

     // file with the name we chose, if it is valid. If not, createUnique will

     // attempt to modify it again, for example it will shorten very long names

     // that can't be created on some platforms, and for which a normal call to

     // nsIFile.create would result in NS_ERROR_FILE_NOT_FOUND. This can result

     // very rarely in strange names like "base(9999).tar-1.gz" or "ba-1.gz".

     curFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0644);

     return curFile;

   },

   /**

    * Separates the base name from the extension in a file name, recognizing some

    *  double extensions like ".tar.gz".

    *

    * @param aLeafName

    *        The full leaf name to be parsed. Be careful when processing names

    *        containing leading or trailing dots or spaces.

    * @returns [base, ext]

    *          The base name of the file, which can be empty, and its extension,

    *          which always includes the leading dot unless it's an empty string.

    *          Concatenating the two items always results in the original name.

    */

   splitBaseNameAndExtension: function DP_splitBaseNameAndExtension(aLeafName) {

     // The following regular expression is built from these key parts:

     //  .*?                      Matches the base name non-greedily.

     //  \.[A-Z0-9]{1,3}          Up to three letters or numbers preceding a

     //                           double extension.

     //  \.(?:gz|bz2|Z)           The second part of common double extensions.

     //  \.[^.]*                  Matches any extension or a single trailing dot.

     var [, base, ext] = /(.*?)(\.[A-Z0-9]{1,3}\.(?:gz|bz2|Z)|\.[^.]*)?$/i

                         .exec(aLeafName);

     // Return an empty string instead of undefined if no extension is found.

     return [base, ext || ""];

   }

 };