Add missing files from previous commit

sdk/lib/io/io_stream_consumer.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.
+
+part of dart.io;
+
+/**
+ * Helper class to wrap a [StreamConsumer<List<int>, T>] and provide utility
+ * functions for writing to the StreamConsumer directly. The [IOSink]
+ * buffers the input given by [add] and [addString] and will delay a [consume]
+ * or [addStream] until the buffer is flushed.
+ *
+ * When the [IOSink] is bound to a stream (through either [comsume]
+ * or [addStream]) any call to the [IOSink] will throw a
+ * [StateError].
+ */
+class IOSink<T> implements StreamConsumer<List<int>, T> {
+  final StreamConsumer<List<int>, T> _target;
+
+  StreamController<List<int>> _controllerInstance;
+  Future<T> _pipeFuture;
+  StreamSubscription<List<int>> _bindSubscription;
+  bool _paused = true;
+
+  IOSink(StreamConsumer<List<int>, T> target) : _target = target;
+
+  /**
+   * Provide functionality for piping to the [IOSink].
+   */
+  Future<T> consume(Stream<List<int>> stream) {
+    if (_isBound) {
+      throw new StateError("IOSink is already bound to a stream");
+    }
+    return _fillFromStream(stream);
+  }
+
+  /**
+   * Like [consume], but will not close the target when done.
+   */
+  Future<T> addStream(Stream<List<int>> stream) {
+    if (_isBound) {
+      throw new StateError("IOSink is already bound to a stream");
+    }
+    return _fillFromStream(stream, unbind: true);
+  }
+
+  /**
+   * Write a list of bytes to the target.
+   */
+  void add(List<int> data) {
+    if (_isBound) {
+      throw new StateError("IOSink is already bound to a stream");
+    }
+    _controller.add(data);
+  }
+
+  /**
+   * Write a String to the target.
+   */
+  void addString(String string, [Encoding encoding = Encoding.UTF_8]) {
+    add(_encodeString(string, encoding));
+  }
+
+  /**
+   * Close the target.
+   */
+  void close() {
+    if (_isBound) {
+      throw new StateError("IOSink is already bound to a stream");
+    }
+    _controller.close();
+  }
+
+  /**
+   * Get future that will complete when all data has been written to
+   * the IOSink and it has been closed.
+   */
+  Future<T> get done {
+    _controller;
+    return _pipeFuture.then((_) => this);
+  }
+
+  StreamController<List<int>> get _controller {
+    if (_controllerInstance == null) {
+      _controllerInstance = new StreamController<List<int>>(
+          onPauseStateChange: _onPauseStateChange,
+          onSubscriptionStateChange: _onSubscriptionStateChange);
+      _pipeFuture = _controller.stream.pipe(_target);
+    }
+    return _controllerInstance;
+  }
+
+  bool get _isBound => _bindSubscription != null;
+
+  void _onPauseStateChange() {
+    _paused = _controller.isPaused;
+    if (_controller.isPaused) {
+      _pause();
+    } else {
+      _resume();
+    }
+  }
+
+  void _pause() {
+    if (_bindSubscription != null) {
+      try {
+        // The subscription can be canceled at this point.
+        _bindSubscription.pause();
+      } catch (e) {
+      }
+    }
+  }
+
+  void _resume() {
+    if (_bindSubscription != null) {
+      try {
+        // The subscription can be canceled at this point.
+        _bindSubscription.resume();
+      } catch (e) {
+      }
+    }
+  }
+
+  void _onSubscriptionStateChange() {
+    if (_controller.hasSubscribers) {
+      _paused = false;
+      _resume();
+    } else {
+      if (_bindSubscription != null) {
+        _bindSubscription.cancel();
+        _bindSubscription = null;
+      }
+    }
+  }
+
+  Future<T> _fillFromStream(Stream<List<int>> stream, {unbind: false}) {
+    _controller;
+    Completer<T> unbindCompleter;
+    if (unbind) {
+      unbindCompleter = new Completer<T>();
+    }
+    _bindSubscription = stream.listen(
+        _controller.add,
+        onDone: () {
+          _bindSubscription = null;
+          if (unbind) {
+            unbindCompleter.complete(null);
+          } else {
+            _controller.close();
+          }
+        },
+        onError: _controller.signalError);
+    if (_paused) _pause();
+    if (unbind) {
+      return unbindCompleter.future;
+    } else {
+      return _pipeFuture;
+    }
+  }
+}