Reorganize barback's source files.

pkg/barback/lib/src/stream_replayer.dart

-// Copyright (c) 2013, 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.
-
-library barback.stream_replayer;
-
-import 'dart:async';
-import 'dart:collection';
-
-import 'utils.dart';
-
-/// Records the values and errors that are sent through a stream and allows them
-/// to be replayed arbitrarily many times.
-///
-/// This only listens to the wrapped stream when a replayed stream gets a
-/// listener.
-class StreamReplayer<T> {
-  /// The wrapped stream.
-  final Stream<T> _stream;
-
-  /// Whether or not [this] has started listening to [_stream].
-  bool _isSubscribed = false;
-
-  /// Whether or not [_stream] has been closed.
-  bool _isClosed = false;
-
-  /// The buffer of events or errors that have already been emitted by
-  /// [_stream].
-  ///
-  /// Each element is a [Fallible] that's either a value or an error sent
-  /// through the stream.
-  final _buffer = new Queue<Fallible<T>>();
-
-  /// The controllers that are listening for future events from [_stream].
-  final _controllers = new Set<StreamController<T>>();
-
-  StreamReplayer(this._stream);
-
-  /// Returns a stream that replays the values and errors of the input stream.
-  ///
-  /// This stream is a buffered stream.
-  Stream<T> getReplay() {
-    var controller = new StreamController<T>(onListen: _subscribe);
-
-    for (var eventOrError in _buffer) {
-      if (eventOrError.hasValue) {
-        controller.add(eventOrError.value);
-      } else {
-        controller.addError(eventOrError.error, eventOrError.stackTrace);
-      }
-    }
-    if (_isClosed) {
-      controller.close();
-    } else {
-      _controllers.add(controller);
-    }
-    return controller.stream;
-  }
-
-  /// Subscribe to [_stream] if we haven't yet done so.
-  void _subscribe() {
-    if (_isSubscribed || _isClosed) return;
-    _isSubscribed = true;
-
-    _stream.listen((data) {
-      _buffer.add(new Fallible<T>.withValue(data));
-      for (var controller in _controllers) {
-        controller.add(data);
-      }
-    }, onError: (error, [stackTrace]) {
-      _buffer.add(new Fallible<T>.withError(error, stackTrace));
-      for (var controller in _controllers) {
-        controller.addError(error, stackTrace);
-      }
-    }, onDone: () {
-      _isClosed = true;
-      for (var controller in _controllers) {
-        controller.close();
-      }
-      _controllers.clear();
-    });
-  }
-}