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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_DOWNLOAD_PUBLIC_COMMON_DOWNLOAD_PATH_RESERVATION_TRACKER_H_
#define COMPONENTS_DOWNLOAD_PUBLIC_COMMON_DOWNLOAD_PATH_RESERVATION_TRACKER_H_
#include "base/callback_forward.h"
#include "base/memory/ref_counted.h"
#include "components/download/public/common/download_export.h"
namespace base {
class FilePath;
class SequencedTaskRunner;
} // namespace base
namespace download {
class DownloadItem;
// Used in UMA, do not remove, change or reuse existing entries.
// Update histograms.xml and enums.xml when adding entries.
enum class PathValidationResult {
SUCCESS = 0,
PATH_NOT_WRITABLE,
NAME_TOO_LONG,
CONFLICT,
SAME_AS_SOURCE,
COUNT,
};
// Chrome attempts to uniquify filenames that are assigned to downloads in order
// to avoid overwriting files that already exist on the file system. Downloads
// that are considered potentially dangerous use random intermediate filenames.
// Therefore only considering files that exist on the filesystem is
// insufficient. This class tracks files that are assigned to active downloads
// so that uniquification can take those into account as well.
class COMPONENTS_DOWNLOAD_EXPORT DownloadPathReservationTracker {
public:
// Callback used with |GetReservedPath|. |target_path| specifies the target
// path for the download. If |result| is SUCCESS then:
// - |requested_target_path| (passed into GetReservedPath()) was writeable.
// - |target_path| was verified as being unique if uniqueness was
// required.
//
// If |requested_target_path| was not writeable, then the parent directory of
// |target_path| may be different from that of |requested_target_path|.
using ReservedPathCallback =
base::Callback<void(PathValidationResult result,
const base::FilePath& target_path)>;
// The largest index for the uniquification suffix that we will try while
// attempting to come up with a unique path.
static const int kMaxUniqueFiles = 100;
enum FilenameConflictAction {
UNIQUIFY,
OVERWRITE,
PROMPT,
};
// When a path needs to be assigned to a download, this method is called on
// the UI thread along with a reference to the download item that will
// eventually receive the reserved path. This method creates a path
// reservation that will live until |download_item| is interrupted, cancelled,
// completes or is removed. This method will not modify |download_item|.
//
// The process of issuing a reservation happens on the task runner returned by
// DownloadPathReservationTracker::GetTaskRunner(), and involves:
//
// - Creating |requested_target_path.DirName()| if it doesn't already exist
// and either |create_directory| or |requested_target_path.DirName() ==
// default_download_path|.
//
// - Verifying that |requested_target_path| is writeable. If not,
// |fallback_directory| is used instead.
//
// - Uniquifying |requested_target_path| by suffixing the filename with a
// uniquifier (e.g. "foo.txt" -> "foo (1).txt") in order to avoid conflicts
// with files that already exist on the file system or other download path
// reservations. Uniquifying is only done if |conflict_action| is UNIQUIFY.
//
// - Posting a task back to the UI thread to invoke |completion_callback| with
// the reserved path and a bool indicating whether the returned path was
// verified as being writeable and unique.
//
// In addition, if the target path of |download_item| is changed to a path
// other than the reserved path, then the reservation will be updated to
// match. Such changes can happen if a "Save As" dialog was displayed and the
// user chose a different path. The new target path is not checked against
// active paths to enforce uniqueness. It is only used for uniquifying new
// reservations.
//
// Once |completion_callback| is invoked, it is the caller's responsibility to
// handle cases where the target path could not be verified and set the target
// path of the |download_item| appropriately.
//
// The current implementation doesn't look at symlinks/mount points. E.g.: It
// considers 'foo/bar/x.pdf' and 'foo/baz/x.pdf' to be two different paths,
// even though 'bar' might be a symlink to 'baz'.
static void GetReservedPath(DownloadItem* download_item,
const base::FilePath& requested_target_path,
const base::FilePath& default_download_path,
const base::FilePath& fallback_directory,
bool create_directory,
FilenameConflictAction conflict_action,
const ReservedPathCallback& callback);
// Returns true if |path| is in use by an existing path reservation. Should
// only be called on the task runner returned by
// DownloadPathReservationTracker::GetTaskRunner(). Currently only used by
// tests.
static bool IsPathInUseForTesting(const base::FilePath& path);
static scoped_refptr<base::SequencedTaskRunner> GetTaskRunner();
};
} // namespace download
#endif // COMPONENTS_DOWNLOAD_PUBLIC_COMMON_DOWNLOAD_PATH_RESERVATION_TRACKER_H_