1 // Copyright (c) 2012 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 10 #include <memory> 11 12 #include "base/base_export.h" 13 #include "base/callback.h" 14 #include "base/files/file_path.h" 15 #include "base/macros.h" 16 #include "base/memory/ref_counted.h" 17 #include "base/sequence_checker.h" 18 #include "base/sequenced_task_runner.h" 19 20 namespace base { 21 22 // This class lets you register interest in changes on a FilePath. 23 // The callback will get called whenever the file or directory referenced by the 24 // FilePath is changed, including created or deleted. Due to limitations in the 25 // underlying OS APIs, FilePathWatcher has slightly different semantics on OS X 26 // than on Windows or Linux. FilePathWatcher on Linux and Windows will detect 27 // modifications to files in a watched directory. FilePathWatcher on Mac will 28 // detect the creation and deletion of files in a watched directory, but will 29 // not detect modifications to those files. See file_path_watcher_kqueue.cc for 30 // details. 31 // 32 // Must be destroyed on the sequence that invokes Watch(). 33 class BASE_EXPORT FilePathWatcher { 34 public: 35 // Callback type for Watch(). |path| points to the file that was updated, 36 // and |error| is true if the platform specific code detected an error. In 37 // that case, the callback won't be invoked again. 38 typedef base::Callback<void(const FilePath& path, bool error)> Callback; 39 40 // Used internally to encapsulate different members on different platforms. 41 class PlatformDelegate { 42 public: 43 PlatformDelegate(); 44 virtual ~PlatformDelegate(); 45 46 // Start watching for the given |path| and notify |delegate| about changes. 47 virtual bool Watch(const FilePath& path, 48 bool recursive, 49 const Callback& callback) WARN_UNUSED_RESULT = 0; 50 51 // Stop watching. This is called from FilePathWatcher's dtor in order to 52 // allow to shut down properly while the object is still alive. 53 virtual void Cancel() = 0; 54 55 protected: 56 friend class FilePathWatcher; 57 58 scoped_refptr<SequencedTaskRunner> task_runner() const { 59 return task_runner_; 60 } 61 62 void set_task_runner(scoped_refptr<SequencedTaskRunner> runner) { 63 task_runner_ = std::move(runner); 64 } 65 66 // Must be called before the PlatformDelegate is deleted. 67 void set_cancelled() { 68 cancelled_ = true; 69 } 70 71 bool is_cancelled() const { 72 return cancelled_; 73 } 74 75 private: 76 scoped_refptr<SequencedTaskRunner> task_runner_; 77 bool cancelled_; 78 79 DISALLOW_COPY_AND_ASSIGN(PlatformDelegate); 80 }; 81 82 FilePathWatcher(); 83 ~FilePathWatcher(); 84 85 // Returns true if the platform and OS version support recursive watches. 86 static bool RecursiveWatchAvailable(); 87 88 // Invokes |callback| whenever updates to |path| are detected. This should be 89 // called at most once. Set |recursive| to true to watch |path| and its 90 // children. The callback will be invoked on the same sequence. Returns true 91 // on success. 92 // 93 // On POSIX, this must be called from a thread that supports 94 // FileDescriptorWatcher. 95 // 96 // Recursive watch is not supported on all platforms and file systems. 97 // Watch() will return false in the case of failure. 98 bool Watch(const FilePath& path, bool recursive, const Callback& callback); 99 100 private: 101 std::unique_ptr<PlatformDelegate> impl_; 102 103 SequenceChecker sequence_checker_; 104 105 DISALLOW_COPY_AND_ASSIGN(FilePathWatcher); 106 }; 107 108 } // namespace base 109 110 #endif // BASE_FILES_FILE_PATH_WATCHER_H_ 111
