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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.
- // This module provides a way to monitor a file or directory for changes.
- #ifndef BASE_FILES_FILE_PATH_WATCHER_H_
- #define BASE_FILES_FILE_PATH_WATCHER_H_
- #include <memory>
- #include <utility>
- #include "base/base_export.h"
- #include "base/callback_forward.h"
- #include "base/memory/scoped_refptr.h"
- #include "base/sequence_checker.h"
- #include "base/task/sequenced_task_runner.h"
- #include "build/build_config.h"
- namespace base {
- class FilePath;
- // This class lets you register interest in changes on a FilePath.
- // The callback will get called whenever the file or directory referenced by the
- // FilePath is changed, including created or deleted. Due to limitations in the
- // underlying OS APIs, FilePathWatcher has slightly different semantics on OS X
- // than on Windows or Linux. FilePathWatcher on Linux and Windows will detect
- // modifications to files in a watched directory. FilePathWatcher on Mac will
- // detect the creation and deletion of files in a watched directory, but will
- // not detect modifications to those files. See file_path_watcher_kqueue.cc for
- // details.
- //
- // Must be destroyed on the sequence that invokes Watch().
- class BASE_EXPORT FilePathWatcher {
- public:
- enum class Type {
- // Indicates that the watcher should watch the given path and its
- // ancestors for changes. If the path does not exist, its ancestors will
- // be watched in anticipation of it appearing later. If the path names a
- // directory, changes within the directory are not watched.
- kNonRecursive,
- // Indicates that the watcher should watch the given path, its ancestors,
- // and its descendants for changes. If the path names a directory, changes
- // within the directory are watched.
- kRecursive,
- #if BUILDFLAG(IS_MAC)
- // Indicates that the watcher should watch the given path only (neither
- // ancestors nor descendants). The watch fails if the path does not exist.
- kTrivial,
- #endif // BUILDFLAG(IS_MAC)
- };
- // Callback type for Watch(). |path| points to the file that was updated,
- // and |error| is true if the platform specific code detected an error. In
- // that case, the callback won't be invoked again.
- using Callback =
- base::RepeatingCallback<void(const FilePath& path, bool error)>;
- // Used internally to encapsulate different members on different platforms.
- class PlatformDelegate {
- public:
- using Type = FilePathWatcher::Type;
- PlatformDelegate();
- PlatformDelegate(const PlatformDelegate&) = delete;
- PlatformDelegate& operator=(const PlatformDelegate&) = delete;
- virtual ~PlatformDelegate();
- // Start watching for the given |path| and notify |delegate| about changes.
- [[nodiscard]] virtual bool Watch(const FilePath& path,
- Type type,
- const Callback& callback) = 0;
- // Stop watching. This is called from FilePathWatcher's dtor in order to
- // allow to shut down properly while the object is still alive.
- virtual void Cancel() = 0;
- protected:
- friend class FilePathWatcher;
- scoped_refptr<SequencedTaskRunner> task_runner() const {
- return task_runner_;
- }
- void set_task_runner(scoped_refptr<SequencedTaskRunner> runner) {
- task_runner_ = std::move(runner);
- }
- // Must be called before the PlatformDelegate is deleted.
- void set_cancelled() {
- cancelled_ = true;
- }
- bool is_cancelled() const {
- return cancelled_;
- }
- private:
- scoped_refptr<SequencedTaskRunner> task_runner_;
- bool cancelled_ = false;
- };
- FilePathWatcher();
- FilePathWatcher(const FilePathWatcher&) = delete;
- FilePathWatcher& operator=(const FilePathWatcher&) = delete;
- ~FilePathWatcher();
- // Returns true if the platform and OS version support recursive watches.
- static bool RecursiveWatchAvailable();
- #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- // Whether there are outstanding inotify watches.
- static bool HasWatchesForTest();
- #endif // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- // Starts watching |path| (and its descendants if |type| is kRecursive) for
- // changes. |callback| will be run on the caller's sequence to report such
- // changes. Returns true if the watch was started successfully and |callback|
- // may one day be run, or false in case of failure (e.g., a recursive watch on
- // platforms that do not support such).
- //
- // On POSIX, this must be called from a thread that supports
- // FileDescriptorWatcher.
- bool Watch(const FilePath& path, Type type, const Callback& callback);
- private:
- std::unique_ptr<PlatformDelegate> impl_;
- SequenceChecker sequence_checker_;
- };
- } // namespace base
- #endif // BASE_FILES_FILE_PATH_WATCHER_H_
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