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| 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 #include "content/common/file_path_watcher/file_path_watcher.h" | |
| 6 | |
| 7 #include "base/file_path.h" | |
| 8 #include "base/file_util.h" | |
| 9 #include "base/logging.h" | |
| 10 #include "base/memory/ref_counted.h" | |
| 11 #include "base/message_loop_proxy.h" | |
| 12 #include "base/time.h" | |
| 13 #include "base/win/object_watcher.h" | |
| 14 | |
| 15 namespace { | |
| 16 | |
| 17 class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate, | |
| 18 public base::win::ObjectWatcher::Delegate, | |
| 19 public MessageLoop::DestructionObserver { | |
| 20 public: | |
| 21 FilePathWatcherImpl() : delegate_(NULL), handle_(INVALID_HANDLE_VALUE) {} | |
| 22 | |
| 23 // FilePathWatcher::PlatformDelegate overrides. | |
| 24 virtual bool Watch(const FilePath& path, | |
| 25 FilePathWatcher::Delegate* delegate) OVERRIDE; | |
| 26 virtual void Cancel() OVERRIDE; | |
| 27 | |
| 28 // Deletion of the FilePathWatcher will call Cancel() to dispose of this | |
| 29 // object in the right thread. This also observes destruction of the required | |
| 30 // cleanup thread, in case it quits before Cancel() is called. | |
| 31 virtual void WillDestroyCurrentMessageLoop() OVERRIDE; | |
| 32 | |
| 33 // Callback from MessageLoopForIO. | |
| 34 virtual void OnObjectSignaled(HANDLE object); | |
| 35 | |
| 36 private: | |
| 37 virtual ~FilePathWatcherImpl() {} | |
| 38 | |
| 39 // Setup a watch handle for directory |dir|. Returns true if no fatal error | |
| 40 // occurs. |handle| will receive the handle value if |dir| is watchable, | |
| 41 // otherwise INVALID_HANDLE_VALUE. | |
| 42 static bool SetupWatchHandle(const FilePath& dir, HANDLE* handle) | |
| 43 WARN_UNUSED_RESULT; | |
| 44 | |
| 45 // (Re-)Initialize the watch handle. | |
| 46 bool UpdateWatch() WARN_UNUSED_RESULT; | |
| 47 | |
| 48 // Destroy the watch handle. | |
| 49 void DestroyWatch(); | |
| 50 | |
| 51 // Cleans up and stops observing the |message_loop_| thread. | |
| 52 void CancelOnMessageLoopThread() OVERRIDE; | |
| 53 | |
| 54 // Delegate to notify upon changes. | |
| 55 scoped_refptr<FilePathWatcher::Delegate> delegate_; | |
| 56 | |
| 57 // Path we're supposed to watch (passed to delegate). | |
| 58 FilePath target_; | |
| 59 | |
| 60 // Handle for FindFirstChangeNotification. | |
| 61 HANDLE handle_; | |
| 62 | |
| 63 // ObjectWatcher to watch handle_ for events. | |
| 64 base::win::ObjectWatcher watcher_; | |
| 65 | |
| 66 // Keep track of the last modified time of the file. We use nulltime | |
| 67 // to represent the file not existing. | |
| 68 base::Time last_modified_; | |
| 69 | |
| 70 // The time at which we processed the first notification with the | |
| 71 // |last_modified_| time stamp. | |
| 72 base::Time first_notification_; | |
| 73 | |
| 74 DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl); | |
| 75 }; | |
| 76 | |
| 77 bool FilePathWatcherImpl::Watch(const FilePath& path, | |
| 78 FilePathWatcher::Delegate* delegate) { | |
| 79 DCHECK(target_.value().empty()); // Can only watch one path. | |
| 80 | |
| 81 set_message_loop(base::MessageLoopProxy::CreateForCurrentThread()); | |
| 82 delegate_ = delegate; | |
| 83 target_ = path; | |
| 84 MessageLoop::current()->AddDestructionObserver(this); | |
| 85 | |
| 86 if (!UpdateWatch()) | |
| 87 return false; | |
| 88 | |
| 89 watcher_.StartWatching(handle_, this); | |
| 90 | |
| 91 return true; | |
| 92 } | |
| 93 | |
| 94 void FilePathWatcherImpl::Cancel() { | |
| 95 if (!delegate_) { | |
| 96 // Watch was never called, or the |message_loop_| has already quit. | |
| 97 set_cancelled(); | |
| 98 return; | |
| 99 } | |
| 100 | |
| 101 // Switch to the file thread if necessary so we can stop |watcher_|. | |
| 102 if (!message_loop()->BelongsToCurrentThread()) { | |
| 103 message_loop()->PostTask(FROM_HERE, | |
| 104 new FilePathWatcher::CancelTask(this)); | |
| 105 } else { | |
| 106 CancelOnMessageLoopThread(); | |
| 107 } | |
| 108 } | |
| 109 | |
| 110 void FilePathWatcherImpl::CancelOnMessageLoopThread() { | |
| 111 set_cancelled(); | |
| 112 | |
| 113 if (handle_ != INVALID_HANDLE_VALUE) | |
| 114 DestroyWatch(); | |
| 115 | |
| 116 if (delegate_) { | |
| 117 MessageLoop::current()->RemoveDestructionObserver(this); | |
| 118 delegate_ = NULL; | |
| 119 } | |
| 120 } | |
| 121 | |
| 122 void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() { | |
| 123 CancelOnMessageLoopThread(); | |
| 124 } | |
| 125 | |
| 126 void FilePathWatcherImpl::OnObjectSignaled(HANDLE object) { | |
| 127 DCHECK(object == handle_); | |
| 128 // Make sure we stay alive through the body of this function. | |
| 129 scoped_refptr<FilePathWatcherImpl> keep_alive(this); | |
| 130 | |
| 131 if (!UpdateWatch()) { | |
| 132 delegate_->OnFilePathError(target_); | |
| 133 return; | |
| 134 } | |
| 135 | |
| 136 // Check whether the event applies to |target_| and notify the delegate. | |
| 137 base::PlatformFileInfo file_info; | |
| 138 bool file_exists = file_util::GetFileInfo(target_, &file_info); | |
| 139 if (file_exists && (last_modified_.is_null() || | |
| 140 last_modified_ != file_info.last_modified)) { | |
| 141 last_modified_ = file_info.last_modified; | |
| 142 first_notification_ = base::Time::Now(); | |
| 143 delegate_->OnFilePathChanged(target_); | |
| 144 } else if (file_exists && !first_notification_.is_null()) { | |
| 145 // The target's last modification time is equal to what's on record. This | |
| 146 // means that either an unrelated event occurred, or the target changed | |
| 147 // again (file modification times only have a resolution of 1s). Comparing | |
| 148 // file modification times against the wall clock is not reliable to find | |
| 149 // out whether the change is recent, since this code might just run too | |
| 150 // late. Moreover, there's no guarantee that file modification time and wall | |
| 151 // clock times come from the same source. | |
| 152 // | |
| 153 // Instead, the time at which the first notification carrying the current | |
| 154 // |last_notified_| time stamp is recorded. Later notifications that find | |
| 155 // the same file modification time only need to be forwarded until wall | |
| 156 // clock has advanced one second from the initial notification. After that | |
| 157 // interval, client code is guaranteed to having seen the current revision | |
| 158 // of the file. | |
| 159 if (base::Time::Now() - first_notification_ > | |
| 160 base::TimeDelta::FromSeconds(1)) { | |
| 161 // Stop further notifications for this |last_modification_| time stamp. | |
| 162 first_notification_ = base::Time(); | |
| 163 } | |
| 164 delegate_->OnFilePathChanged(target_); | |
| 165 } else if (!file_exists && !last_modified_.is_null()) { | |
| 166 last_modified_ = base::Time(); | |
| 167 delegate_->OnFilePathChanged(target_); | |
| 168 } | |
| 169 | |
| 170 // The watch may have been cancelled by the callback. | |
| 171 if (handle_ != INVALID_HANDLE_VALUE) | |
| 172 watcher_.StartWatching(handle_, this); | |
| 173 } | |
| 174 | |
| 175 // static | |
| 176 bool FilePathWatcherImpl::SetupWatchHandle(const FilePath& dir, | |
| 177 HANDLE* handle) { | |
| 178 *handle = FindFirstChangeNotification( | |
| 179 dir.value().c_str(), | |
| 180 false, // Don't watch subtrees | |
| 181 FILE_NOTIFY_CHANGE_FILE_NAME | FILE_NOTIFY_CHANGE_SIZE | | |
| 182 FILE_NOTIFY_CHANGE_LAST_WRITE | FILE_NOTIFY_CHANGE_DIR_NAME | | |
| 183 FILE_NOTIFY_CHANGE_ATTRIBUTES | FILE_NOTIFY_CHANGE_SECURITY); | |
| 184 if (*handle != INVALID_HANDLE_VALUE) { | |
| 185 // Make sure the handle we got points to an existing directory. It seems | |
| 186 // that windows sometimes hands out watches to direectories that are | |
| 187 // about to go away, but doesn't sent notifications if that happens. | |
| 188 if (!file_util::DirectoryExists(dir)) { | |
| 189 FindCloseChangeNotification(*handle); | |
| 190 *handle = INVALID_HANDLE_VALUE; | |
| 191 } | |
| 192 return true; | |
| 193 } | |
| 194 | |
| 195 // If FindFirstChangeNotification failed because the target directory | |
| 196 // doesn't exist, access is denied (happens if the file is already gone but | |
| 197 // there are still handles open), or the target is not a directory, try the | |
| 198 // immediate parent directory instead. | |
| 199 DWORD error_code = GetLastError(); | |
| 200 if (error_code != ERROR_FILE_NOT_FOUND && | |
| 201 error_code != ERROR_PATH_NOT_FOUND && | |
| 202 error_code != ERROR_ACCESS_DENIED && | |
| 203 error_code != ERROR_SHARING_VIOLATION && | |
| 204 error_code != ERROR_DIRECTORY) { | |
| 205 PLOG(ERROR) << "FindFirstChangeNotification failed for " | |
| 206 << dir.value(); | |
| 207 return false; | |
| 208 } | |
| 209 | |
| 210 return true; | |
| 211 } | |
| 212 | |
| 213 bool FilePathWatcherImpl::UpdateWatch() { | |
| 214 if (handle_ != INVALID_HANDLE_VALUE) | |
| 215 DestroyWatch(); | |
| 216 | |
| 217 base::PlatformFileInfo file_info; | |
| 218 if (file_util::GetFileInfo(target_, &file_info)) { | |
| 219 last_modified_ = file_info.last_modified; | |
| 220 first_notification_ = base::Time::Now(); | |
| 221 } | |
| 222 | |
| 223 // Start at the target and walk up the directory chain until we succesfully | |
| 224 // create a watch handle in |handle_|. |child_dirs| keeps a stack of child | |
| 225 // directories stripped from target, in reverse order. | |
| 226 std::vector<FilePath> child_dirs; | |
| 227 FilePath watched_path(target_); | |
| 228 while (true) { | |
| 229 if (!SetupWatchHandle(watched_path, &handle_)) | |
| 230 return false; | |
| 231 | |
| 232 // Break if a valid handle is returned. Try the parent directory otherwise. | |
| 233 if (handle_ != INVALID_HANDLE_VALUE) | |
| 234 break; | |
| 235 | |
| 236 // Abort if we hit the root directory. | |
| 237 child_dirs.push_back(watched_path.BaseName()); | |
| 238 FilePath parent(watched_path.DirName()); | |
| 239 if (parent == watched_path) { | |
| 240 LOG(ERROR) << "Reached the root directory"; | |
| 241 return false; | |
| 242 } | |
| 243 watched_path = parent; | |
| 244 } | |
| 245 | |
| 246 // At this point, handle_ is valid. However, the bottom-up search that the | |
| 247 // above code performs races against directory creation. So try to walk back | |
| 248 // down and see whether any children appeared in the mean time. | |
| 249 while (!child_dirs.empty()) { | |
| 250 watched_path = watched_path.Append(child_dirs.back()); | |
| 251 child_dirs.pop_back(); | |
| 252 HANDLE temp_handle = INVALID_HANDLE_VALUE; | |
| 253 if (!SetupWatchHandle(watched_path, &temp_handle)) | |
| 254 return false; | |
| 255 if (temp_handle == INVALID_HANDLE_VALUE) | |
| 256 break; | |
| 257 FindCloseChangeNotification(handle_); | |
| 258 handle_ = temp_handle; | |
| 259 } | |
| 260 | |
| 261 return true; | |
| 262 } | |
| 263 | |
| 264 void FilePathWatcherImpl::DestroyWatch() { | |
| 265 watcher_.StopWatching(); | |
| 266 FindCloseChangeNotification(handle_); | |
| 267 handle_ = INVALID_HANDLE_VALUE; | |
| 268 } | |
| 269 | |
| 270 } // namespace | |
| 271 | |
| 272 FilePathWatcher::FilePathWatcher() { | |
| 273 impl_ = new FilePathWatcherImpl(); | |
| 274 } | |
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Chromium Code Reviews
Issue 6793020:
Move FilePathWatcher to base/files. (Closed)
Base URL: svn://svn.chromium.org/chrome/trunk/src