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chrome/browser/file_path_watcher_win.cc

Index: chrome/browser/file_path_watcher_win.cc
===================================================================
--- chrome/browser/file_path_watcher_win.cc	(revision 68044)
+++ chrome/browser/file_path_watcher_win.cc	(working copy)
@@ -1,244 +0,0 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "chrome/browser/file_path_watcher.h"
-
-#include "base/file_path.h"
-#include "base/file_util.h"
-#include "base/logging.h"
-#include "base/object_watcher.h"
-#include "base/ref_counted.h"
-#include "base/time.h"
-
-namespace {
-
-class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
-                            public base::ObjectWatcher::Delegate {
- public:
-  FilePathWatcherImpl() : delegate_(NULL), handle_(INVALID_HANDLE_VALUE) {}
-
-  virtual bool Watch(const FilePath& path, FilePathWatcher::Delegate* delegate);
-  virtual void Cancel();
-
-  // Callback from MessageLoopForIO.
-  virtual void OnObjectSignaled(HANDLE object);
-
- private:
-  virtual ~FilePathWatcherImpl();
-
-  // Setup a watch handle for directory |dir|. Returns true if no fatal error
-  // occurs. |handle| will receive the handle value if |dir| is watchable,
-  // otherwise INVALID_HANDLE_VALUE.
-  static bool SetupWatchHandle(const FilePath& dir, HANDLE* handle)
-      WARN_UNUSED_RESULT;
-
-  // (Re-)Initialize the watch handle.
-  bool UpdateWatch() WARN_UNUSED_RESULT;
-
-  // Destroy the watch handle.
-  void DestroyWatch();
-
-  // Delegate to notify upon changes.
-  scoped_refptr<FilePathWatcher::Delegate> delegate_;
-
-  // Path we're supposed to watch (passed to delegate).
-  FilePath target_;
-
-  // Handle for FindFirstChangeNotification.
-  HANDLE handle_;
-
-  // ObjectWatcher to watch handle_ for events.
-  base::ObjectWatcher watcher_;
-
-  // Keep track of the last modified time of the file.  We use nulltime
-  // to represent the file not existing.
-  base::Time last_modified_;
-
-  // The time at which we processed the first notification with the
-  // |last_modified_| time stamp.
-  base::Time first_notification_;
-
-  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
-};
-
-bool FilePathWatcherImpl::Watch(const FilePath& path,
-                                FilePathWatcher::Delegate* delegate) {
-  DCHECK(target_.value().empty());  // Can only watch one path.
-  delegate_ = delegate;
-  target_ = path;
-
-  if (!UpdateWatch())
-    return false;
-
-  watcher_.StartWatching(handle_, this);
-
-  return true;
-}
-
-void FilePathWatcherImpl::Cancel() {
-  // Switch to the file thread if necessary so we can stop |watcher_|.
-  if (!BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
-    BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
-        NewRunnableMethod(this, &FilePathWatcherImpl::Cancel));
-    return;
-  }
-
-  if (handle_ != INVALID_HANDLE_VALUE)
-    DestroyWatch();
-}
-
-void FilePathWatcherImpl::OnObjectSignaled(HANDLE object) {
-  DCHECK(object == handle_);
-  // Make sure we stay alive through the body of this function.
-  scoped_refptr<FilePathWatcherImpl> keep_alive(this);
-
-  if (!UpdateWatch()) {
-    delegate_->OnError();
-    return;
-  }
-
-  // Check whether the event applies to |target_| and notify the delegate.
-  base::PlatformFileInfo file_info;
-  bool file_exists = file_util::GetFileInfo(target_, &file_info);
-  if (file_exists && (last_modified_.is_null() ||
-      last_modified_ != file_info.last_modified)) {
-    last_modified_ = file_info.last_modified;
-    first_notification_ = base::Time::Now();
-    delegate_->OnFilePathChanged(target_);
-  } else if (file_exists && !first_notification_.is_null()) {
-    // The target's last modification time is equal to what's on record. This
-    // means that either an unrelated event occurred, or the target changed
-    // again (file modification times only have a resolution of 1s). Comparing
-    // file modification times against the wall clock is not reliable to find
-    // out whether the change is recent, since this code might just run too
-    // late. Moreover, there's no guarantee that file modification time and wall
-    // clock times come from the same source.
-    //
-    // Instead, the time at which the first notification carrying the current
-    // |last_notified_| time stamp is recorded. Later notifications that find
-    // the same file modification time only need to be forwarded until wall
-    // clock has advanced one second from the initial notification. After that
-    // interval, client code is guaranteed to having seen the current revision
-    // of the file.
-    if (base::Time::Now() - first_notification_ >
-        base::TimeDelta::FromSeconds(1)) {
-      // Stop further notifications for this |last_modification_| time stamp.
-      first_notification_ = base::Time();
-    }
-    delegate_->OnFilePathChanged(target_);
-  } else if (!file_exists && !last_modified_.is_null()) {
-    last_modified_ = base::Time();
-    delegate_->OnFilePathChanged(target_);
-  }
-
-  // The watch may have been cancelled by the callback.
-  if (handle_ != INVALID_HANDLE_VALUE)
-    watcher_.StartWatching(handle_, this);
-}
-
-FilePathWatcherImpl::~FilePathWatcherImpl() {
-  if (handle_ != INVALID_HANDLE_VALUE)
-    DestroyWatch();
-}
-
-// static
-bool FilePathWatcherImpl::SetupWatchHandle(const FilePath& dir,
-                                           HANDLE* handle) {
-  *handle = FindFirstChangeNotification(
-      dir.value().c_str(),
-      false,  // Don't watch subtrees
-      FILE_NOTIFY_CHANGE_FILE_NAME | FILE_NOTIFY_CHANGE_SIZE |
-      FILE_NOTIFY_CHANGE_LAST_WRITE | FILE_NOTIFY_CHANGE_DIR_NAME |
-      FILE_NOTIFY_CHANGE_ATTRIBUTES | FILE_NOTIFY_CHANGE_SECURITY);
-  if (*handle != INVALID_HANDLE_VALUE) {
-    // Make sure the handle we got points to an existing directory. It seems
-    // that windows sometimes hands out watches to direectories that are
-    // about to go away, but doesn't sent notifications if that happens.
-    if (!file_util::DirectoryExists(dir)) {
-      FindCloseChangeNotification(*handle);
-      *handle = INVALID_HANDLE_VALUE;
-    }
-    return true;
-  }
-
-  // If FindFirstChangeNotification failed because the target directory
-  // doesn't exist, access is denied (happens if the file is already gone but
-  // there are still handles open), or the target is not a directory, try the
-  // immediate parent directory instead.
-  DWORD error_code = GetLastError();
-  if (error_code != ERROR_FILE_NOT_FOUND &&
-      error_code != ERROR_PATH_NOT_FOUND &&
-      error_code != ERROR_ACCESS_DENIED &&
-      error_code != ERROR_SHARING_VIOLATION &&
-      error_code != ERROR_DIRECTORY) {
-    PLOG(ERROR) << "FindFirstChangeNotification failed for "
-                << dir.value();
-    return false;
-  }
-
-  return true;
-}
-
-bool FilePathWatcherImpl::UpdateWatch() {
-  if (handle_ != INVALID_HANDLE_VALUE)
-    DestroyWatch();
-
-  base::PlatformFileInfo file_info;
-  if (file_util::GetFileInfo(target_, &file_info)) {
-    last_modified_ = file_info.last_modified;
-    first_notification_ = base::Time::Now();
-  }
-
-  // Start at the target and walk up the directory chain until we succesfully
-  // create a watch handle in |handle_|. |child_dirs| keeps a stack of child
-  // directories stripped from target, in reverse order.
-  std::vector<FilePath> child_dirs;
-  FilePath watched_path(target_);
-  while (true) {
-    if (!SetupWatchHandle(watched_path, &handle_))
-      return false;
-
-    // Break if a valid handle is returned. Try the parent directory otherwise.
-    if (handle_ != INVALID_HANDLE_VALUE)
-      break;
-
-    // Abort if we hit the root directory.
-    child_dirs.push_back(watched_path.BaseName());
-    FilePath parent(watched_path.DirName());
-    if (parent == watched_path) {
-      LOG(ERROR) << "Reached the root directory";
-      return false;
-    }
-    watched_path = parent;
-  }
-
-  // At this point, handle_ is valid. However, the bottom-up search that the
-  // above code performs races against directory creation. So try to walk back
-  // down and see whether any children appeared in the mean time.
-  while (!child_dirs.empty()) {
-    watched_path = watched_path.Append(child_dirs.back());
-    child_dirs.pop_back();
-    HANDLE temp_handle = INVALID_HANDLE_VALUE;
-    if (!SetupWatchHandle(watched_path, &temp_handle))
-      return false;
-    if (temp_handle == INVALID_HANDLE_VALUE)
-      break;
-    FindCloseChangeNotification(handle_);
-    handle_ = temp_handle;
-  }
-
-  return true;
-}
-
-void FilePathWatcherImpl::DestroyWatch() {
-  watcher_.StopWatching();
-  FindCloseChangeNotification(handle_);
-  handle_ = INVALID_HANDLE_VALUE;
-}
-
-}  // namespace
-
-FilePathWatcher::FilePathWatcher() {
-  impl_ = new FilePathWatcherImpl();
-}