chrome/browser/download/download_path_reservation_tracker.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PATH_RESERVATION_TRACKER_H_
   6 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PATH_RESERVATION_TRACKER_H_
   7
   8 #include "base/callback_forward.h"
   9
  10 namespace base {
  11 class FilePath;
  12 }
  13
  14 namespace content {
  15 class DownloadItem;
  16 }
  17
  18 // Chrome attempts to uniquify filenames that are assigned to downloads in order
  19 // to avoid overwriting files that already exist on the file system. Downloads
  20 // that are considered potentially dangerous use random intermediate filenames.
  21 // Therefore only considering files that exist on the filesystem is
  22 // insufficient. This class tracks files that are assigned to active downloads
  23 // so that uniquification can take those into account as well.
  24 class DownloadPathReservationTracker {
  25  public:
  26   // Callback used with |GetReservedPath|. |target_path| specifies the target
  27   // path for the download. |target_path_verified| is true if all of the
  28   // following is true:
  29   // - |requested_target_path| (passed into GetReservedPath()) was writeable.
  30   // - |target_path| was verified as being unique if uniqueness was
  31   //   required.
  32   //
  33   // If |requested_target_path| was not writeable, then the parent directory of
  34   // |target_path| may be different from that of |requested_target_path|.
  35   typedef base::Callback<void(const base::FilePath& target_path,
  36                               bool target_path_verified)> ReservedPathCallback;
  37
  38   // The largest index for the uniquification suffix that we will try while
  39   // attempting to come up with a unique path.
  40   static const int kMaxUniqueFiles = 100;
  41
  42   enum FilenameConflictAction {
  43     UNIQUIFY,
  44     OVERWRITE,
  45     PROMPT,
  46   };
  47
  48   // When a path needs to be assigned to a download, this method is called on
  49   // the UI thread along with a reference to the download item that will
  50   // eventually receive the reserved path. This method creates a path
  51   // reservation that will live until |download_item| is interrupted, cancelled,
  52   // completes or is removed. This method will not modify |download_item|.
  53   //
  54   // The process of issuing a reservation happens on the FILE thread, and
  55   // involves:
  56   //
  57   // - Creating |requested_target_path.DirName()| if it doesn't already exist
  58   //   and either |create_directory| or |requested_target_path.DirName() ==
  59   //   default_download_path|.
  60   //
  61   // - Verifying that |requested_target_path| is writeable. If not, the user's
  62   //   documents folder is used instead.
  63   //
  64   // - Uniquifying |requested_target_path| by suffixing the filename with a
  65   //   uniquifier (e.g. "foo.txt" -> "foo (1).txt") in order to avoid conflicts
  66   //   with files that already exist on the file system or other download path
  67   //   reservations. Uniquifying is only done if |conflict_action| is UNIQUIFY.
  68   //
  69   // - Posting a task back to the UI thread to invoke |completion_callback| with
  70   //   the reserved path and a bool indicating whether the returned path was
  71   //   verified as being writeable and unique.
  72   //
  73   // In addition, if the target path of |download_item| is changed to a path
  74   // other than the reserved path, then the reservation will be updated to
  75   // match. Such changes can happen if a "Save As" dialog was displayed and the
  76   // user chose a different path. The new target path is not checked against
  77   // active paths to enforce uniqueness. It is only used for uniquifying new
  78   // reservations.
  79   //
  80   // Once |completion_callback| is invoked, it is the caller's responsibility to
  81   // handle cases where the target path could not be verified and set the target
  82   // path of the |download_item| appropriately.
  83   //
  84   // The current implementation doesn't look at symlinks/mount points. E.g.: It
  85   // considers 'foo/bar/x.pdf' and 'foo/baz/x.pdf' to be two different paths,
  86   // even though 'bar' might be a symlink to 'baz'.
  87   static void GetReservedPath(
  88       content::DownloadItem* download_item,
  89       const base::FilePath& requested_target_path,
  90       const base::FilePath& default_download_path,
  91       bool create_directory,
  92       FilenameConflictAction conflict_action,
  93       const ReservedPathCallback& callback);
  94
  95   // Returns true if |path| is in use by an existing path reservation. Should
  96   // only be called on the FILE thread. Currently only used by tests.
  97   static bool IsPathInUseForTesting(const base::FilePath& path);
  98 };
  99
 100 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PATH_RESERVATION_TRACKER_H_