109 lines
3.9 KiB
C++
109 lines
3.9 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 "base/base_export.h"
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#include "base/basictypes.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/memory/ref_counted.h"
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#include "base/message_loop/message_loop_proxy.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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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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typedef base::Callback<void(const FilePath& path, bool error)> Callback;
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// Used internally to encapsulate different members on different platforms.
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class PlatformDelegate : public base::RefCountedThreadSafe<PlatformDelegate> {
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public:
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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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// It can be called from any thread.
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virtual void Cancel() = 0;
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protected:
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friend class base::RefCountedThreadSafe<PlatformDelegate>;
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friend class FilePathWatcher;
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virtual ~PlatformDelegate();
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// Stop watching. This is only called on the thread of the appropriate
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// message loop. Since it can also be called more than once, it should
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// check |is_cancelled()| to avoid duplicate work.
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virtual void CancelOnMessageLoopThread() = 0;
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scoped_refptr<base::MessageLoopProxy> message_loop() const {
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return message_loop_;
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}
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void set_message_loop(base::MessageLoopProxy* loop) {
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message_loop_ = loop;
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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<base::MessageLoopProxy> message_loop_;
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bool cancelled_;
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};
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FilePathWatcher();
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virtual ~FilePathWatcher();
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// A callback that always cleans up the PlatformDelegate, either when executed
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// or when deleted without having been executed at all, as can happen during
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// shutdown.
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static void CancelWatch(const scoped_refptr<PlatformDelegate>& delegate);
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// Invokes |callback| whenever updates to |path| are detected. This should be
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// called at most once, and from a MessageLoop of TYPE_IO. Set |recursive| to
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// true, to watch |path| and its children. The callback will be invoked on
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// the same loop. Returns true on success.
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//
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// NOTE: 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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scoped_refptr<PlatformDelegate> impl_;
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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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