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// 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 "base/file_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 FileWatcherImpl : public FileWatcher::PlatformDelegate,
public base::ObjectWatcher::Delegate {
public:
FileWatcherImpl() : delegate_(NULL), handle_(INVALID_HANDLE_VALUE) {}
virtual bool Watch(const FilePath& path, FileWatcher::Delegate* delegate,
MessageLoop* backend_loop);
// Callback from MessageLoopForIO.
virtual void OnObjectSignaled(HANDLE object);
private:
virtual ~FileWatcherImpl();
// Delegate to notify upon changes.
FileWatcher::Delegate* delegate_;
// Path we're watching (passed to delegate).
FilePath path_;
// 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_;
DISALLOW_COPY_AND_ASSIGN(FileWatcherImpl);
};
FileWatcherImpl::~FileWatcherImpl() {
if (handle_ != INVALID_HANDLE_VALUE) {
watcher_.StopWatching();
FindCloseChangeNotification(handle_);
}
}
bool FileWatcherImpl::Watch(const FilePath& path,
FileWatcher::Delegate* delegate,
MessageLoop* backend_loop) {
DCHECK(path_.value().empty()); // Can only watch one path.
file_util::FileInfo file_info;
if (file_util::GetFileInfo(path, &file_info))
last_modified_ = file_info.last_modified;
// FindFirstChangeNotification watches directories, so use the parent path.
handle_ = FindFirstChangeNotification(
path.DirName().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);
if (handle_ == INVALID_HANDLE_VALUE)
return false;
delegate_ = delegate;
path_ = path;
watcher_.StartWatching(handle_, this);
return true;
}
void FileWatcherImpl::OnObjectSignaled(HANDLE object) {
DCHECK(object == handle_);
// Make sure we stay alive through the body of this function.
scoped_refptr<FileWatcherImpl> keep_alive(this);
file_util::FileInfo file_info;
bool file_exists = file_util::GetFileInfo(path_, &file_info);
if (file_exists && (last_modified_.is_null() ||
last_modified_ != file_info.last_modified)) {
last_modified_ = file_info.last_modified;
delegate_->OnFileChanged(path_);
} else if (file_exists && (base::Time::Now() - last_modified_ <
base::TimeDelta::FromSeconds(2))) {
// Since we only have a resolution of 1s, if we get a callback within
// 2s of the file having changed, go ahead and notify our observer. This
// might be from a different file change, but it's better to notify too
// much rather than miss a notification.
delegate_->OnFileChanged(path_);
} else if (!file_exists && !last_modified_.is_null()) {
last_modified_ = base::Time();
delegate_->OnFileChanged(path_);
}
// Register for more notifications on file change.
BOOL ok = FindNextChangeNotification(object);
DCHECK(ok);
watcher_.StartWatching(object, this);
}
} // namespace
FileWatcher::FileWatcher() {
impl_ = new FileWatcherImpl();
}
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