112 lines
3.6 KiB
C++
112 lines
3.6 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// This module provides a way to monitor a file or directory for changes.
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#ifndef BASE_FILES_FILE_PATH_WATCHER_H_
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#define BASE_FILES_FILE_PATH_WATCHER_H_
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#include <memory>
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#include "base/base_export.h"
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#include "base/callback.h"
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#include "base/files/file_path.h"
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#include "base/macros.h"
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#include "base/memory/ref_counted.h"
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#include "base/sequence_checker.h"
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#include "base/sequenced_task_runner.h"
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namespace base {
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// This class lets you register interest in changes on a FilePath.
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// The callback will get called whenever the file or directory referenced by the
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// FilePath is changed, including created or deleted. Due to limitations in the
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// underlying OS APIs, FilePathWatcher has slightly different semantics on OS X
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// than on Windows or Linux. FilePathWatcher on Linux and Windows will detect
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// modifications to files in a watched directory. FilePathWatcher on Mac will
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// detect the creation and deletion of files in a watched directory, but will
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// not detect modifications to those files. See file_path_watcher_kqueue.cc for
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// details.
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//
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// Must be destroyed on the sequence that invokes Watch().
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class BASE_EXPORT FilePathWatcher {
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public:
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// Callback type for Watch(). |path| points to the file that was updated,
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// and |error| is true if the platform specific code detected an error. In
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// that case, the callback won't be invoked again.
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using Callback =
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base::RepeatingCallback<void(const FilePath& path, bool error)>;
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// Used internally to encapsulate different members on different platforms.
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class PlatformDelegate {
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public:
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PlatformDelegate();
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virtual ~PlatformDelegate();
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// Start watching for the given |path| and notify |delegate| about changes.
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virtual bool Watch(const FilePath& path,
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bool recursive,
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const Callback& callback) WARN_UNUSED_RESULT = 0;
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// Stop watching. This is called from FilePathWatcher's dtor in order to
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// allow to shut down properly while the object is still alive.
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virtual void Cancel() = 0;
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protected:
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friend class FilePathWatcher;
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scoped_refptr<SequencedTaskRunner> task_runner() const {
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return task_runner_;
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}
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void set_task_runner(scoped_refptr<SequencedTaskRunner> runner) {
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task_runner_ = std::move(runner);
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}
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// Must be called before the PlatformDelegate is deleted.
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void set_cancelled() {
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cancelled_ = true;
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}
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bool is_cancelled() const {
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return cancelled_;
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}
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private:
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scoped_refptr<SequencedTaskRunner> task_runner_;
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bool cancelled_;
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DISALLOW_COPY_AND_ASSIGN(PlatformDelegate);
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};
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FilePathWatcher();
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~FilePathWatcher();
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// Returns true if the platform and OS version support recursive watches.
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static bool RecursiveWatchAvailable();
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// Invokes |callback| whenever updates to |path| are detected. This should be
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// called at most once. Set |recursive| to true to watch |path| and its
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// children. The callback will be invoked on the same sequence. Returns true
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// on success.
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//
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// On POSIX, this must be called from a thread that supports
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// FileDescriptorWatcher.
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//
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// Recursive watch is not supported on all platforms and file systems.
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// Watch() will return false in the case of failure.
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bool Watch(const FilePath& path, bool recursive, const Callback& callback);
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private:
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std::unique_ptr<PlatformDelegate> impl_;
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SequenceChecker sequence_checker_;
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DISALLOW_COPY_AND_ASSIGN(FilePathWatcher);
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};
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} // namespace base
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#endif // BASE_FILES_FILE_PATH_WATCHER_H_
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