1 // Copyright (c) 2011 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 // This module provides a way to monitor a file or directory for changes. 6 7 #ifndef BASE_FILES_FILE_PATH_WATCHER_H_ 8 #define BASE_FILES_FILE_PATH_WATCHER_H_ 9 #pragma once 10 11 #include "base/basictypes.h" 12 #include "base/file_path.h" 13 #include "base/memory/ref_counted.h" 14 #include "base/message_loop_proxy.h" 15 16 namespace base { 17 namespace files { 18 19 // This class lets you register interest in changes on a FilePath. 20 // The delegate will get called whenever the file or directory referenced by the 21 // FilePath is changed, including created or deleted. Due to limitations in the 22 // underlying OS APIs, FilePathWatcher has slightly different semantics on OS X 23 // than on Windows or Linux. FilePathWatcher on Linux and Windows will detect 24 // modifications to files in a watched directory. FilePathWatcher on Mac will 25 // detect the creation and deletion of files in a watched directory, but will 26 // not detect modifications to those files. See file_path_watcher_mac.cc for 27 // details. 28 class FilePathWatcher { 29 public: 30 // Declares the callback client code implements to receive notifications. Note 31 // that implementations of this interface should not keep a reference to the 32 // corresponding FileWatcher object to prevent a reference cycle. 33 class Delegate : public base::RefCountedThreadSafe<Delegate> { 34 public: ~Delegate()35 virtual ~Delegate() {} 36 virtual void OnFilePathChanged(const FilePath& path) = 0; 37 // Called when platform specific code detected an error. The watcher will 38 // not call OnFilePathChanged for future changes. OnFilePathError(const FilePath & path)39 virtual void OnFilePathError(const FilePath& path) {} 40 }; 41 42 FilePathWatcher(); 43 ~FilePathWatcher(); 44 45 // Register interest in any changes on |path|. OnPathChanged will be called 46 // back for each change. Returns true on success. 47 // OnFilePathChanged() will be called on the same thread as Watch() is called, 48 // which should have a MessageLoop of TYPE_IO. 49 bool Watch(const FilePath& path, Delegate* delegate) WARN_UNUSED_RESULT; 50 51 class PlatformDelegate; 52 53 // A custom Task that always cleans up the PlatformDelegate, either when 54 // executed or when deleted without having been executed at all, as can 55 // happen during shutdown. 56 class CancelTask : public Task { 57 public: CancelTask(PlatformDelegate * delegate)58 CancelTask(PlatformDelegate* delegate): delegate_(delegate) {} ~CancelTask()59 virtual ~CancelTask() { 60 delegate_->CancelOnMessageLoopThread(); 61 } 62 Run()63 virtual void Run() { 64 delegate_->CancelOnMessageLoopThread(); 65 } 66 private: 67 scoped_refptr<PlatformDelegate> delegate_; 68 69 DISALLOW_COPY_AND_ASSIGN(CancelTask); 70 }; 71 72 // Used internally to encapsulate different members on different platforms. 73 class PlatformDelegate : public base::RefCountedThreadSafe<PlatformDelegate> { 74 public: 75 PlatformDelegate(); 76 77 // Start watching for the given |path| and notify |delegate| about changes. 78 virtual bool Watch(const FilePath& path, 79 Delegate* delegate) WARN_UNUSED_RESULT = 0; 80 81 // Stop watching. This is called from FilePathWatcher's dtor in order to 82 // allow to shut down properly while the object is still alive. 83 // It can be called from any thread. 84 virtual void Cancel() = 0; 85 86 protected: 87 virtual ~PlatformDelegate(); 88 89 // Stop watching. This is only called on the thread of the appropriate 90 // message loop. Since it can also be called more than once, it should 91 // check |is_cancelled()| to avoid duplicate work. 92 virtual void CancelOnMessageLoopThread() = 0; 93 message_loop()94 scoped_refptr<base::MessageLoopProxy> message_loop() const { 95 return message_loop_; 96 } 97 set_message_loop(base::MessageLoopProxy * loop)98 void set_message_loop(base::MessageLoopProxy* loop) { 99 message_loop_ = loop; 100 } 101 102 // Must be called before the PlatformDelegate is deleted. set_cancelled()103 void set_cancelled() { 104 cancelled_ = true; 105 } 106 is_cancelled()107 bool is_cancelled() const { 108 return cancelled_; 109 } 110 111 private: 112 friend class base::RefCountedThreadSafe<PlatformDelegate>; 113 friend class CancelTask; 114 115 scoped_refptr<base::MessageLoopProxy> message_loop_; 116 bool cancelled_; 117 }; 118 119 private: 120 scoped_refptr<PlatformDelegate> impl_; 121 122 DISALLOW_COPY_AND_ASSIGN(FilePathWatcher); 123 }; 124 125 } // namespace files 126 } // namespace base 127 128 #endif // BASE_FILES_FILE_PATH_WATCHER_H_ 129