1 files changed, 89 insertions, 0 deletions
diff --git a/toolkit/mozapps/downloads/DownloadPaths.jsm b/toolkit/mozapps/downloads/DownloadPaths.jsm
new file mode 100644
index 000000000..6ca6dfc13
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+++ b/toolkit/mozapps/downloads/DownloadPaths.jsm
@@ -0,0 +1,89 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 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, 0o644);
+    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 || ""];
+  }
+};