blob: 777038fdfadbe20b6840fb8600744f39c6a6af87 [file] [log] [blame]
// Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'dart:async';
import 'dart:io';
import '../file_watcher.dart';
import '../resubscribable.dart';
import '../stat.dart';
import '../watch_event.dart';
/// Periodically polls a file for changes.
class PollingFileWatcher extends ResubscribableWatcher implements FileWatcher {
PollingFileWatcher(String path, {Duration pollingDelay})
: super(path, () {
return _PollingFileWatcher(
path, pollingDelay != null ? pollingDelay : Duration(seconds: 1));
});
}
class _PollingFileWatcher implements FileWatcher, ManuallyClosedWatcher {
final String path;
Stream<WatchEvent> get events => _eventsController.stream;
final _eventsController = StreamController<WatchEvent>.broadcast();
bool get isReady => _readyCompleter.isCompleted;
Future get ready => _readyCompleter.future;
final _readyCompleter = Completer();
/// The timer that controls polling.
Timer _timer;
/// The previous modification time of the file.
///
/// Used to tell when the file was modified. This is `null` before the file's
/// mtime has first been checked.
DateTime _lastModified;
_PollingFileWatcher(this.path, Duration pollingDelay) {
_timer = Timer.periodic(pollingDelay, (_) => _poll());
_poll();
}
/// Checks the mtime of the file and whether it's been removed.
Future _poll() async {
// We don't mark the file as removed if this is the first poll (indicated by
// [_lastModified] being null). Instead, below we forward the dart:io error
// that comes from trying to read the mtime below.
var pathExists = await File(path).exists();
if (_eventsController.isClosed) return;
if (_lastModified != null && !pathExists) {
_eventsController.add(WatchEvent(ChangeType.REMOVE, path));
close();
return;
}
DateTime modified;
try {
try {
modified = await getModificationTime(path);
} finally {
if (_eventsController.isClosed) return;
}
} on FileSystemException catch (error, stackTrace) {
_eventsController.addError(error, stackTrace);
close();
return;
}
if (_lastModified == modified) return;
if (_lastModified == null) {
// If this is the first poll, don't emit an event, just set the last mtime
// and complete the completer.
_lastModified = modified;
_readyCompleter.complete();
} else {
_lastModified = modified;
_eventsController.add(WatchEvent(ChangeType.MODIFY, path));
}
}
void close() {
_timer.cancel();
_eventsController.close();
}
}