Migrated test block 171 to Dart 2.0.

tests/lib/async/slow_consumer2_test.dart

-// Copyright (c) 2012, 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.
-
-// VMOptions=--old_gen_heap_size=64
-
-library slow_consumer2_test;
-
-import 'package:async_helper/async_helper.dart';
-import "package:expect/expect.dart";
-import 'dart:async';
-
-const int KB = 1024;
-const int MB = KB * KB;
-const int GB = KB * KB * KB;
-
-class SlowConsumer extends StreamConsumer {
-  int receivedCount = 0;
-  final int bytesPerSecond;
-  final int bufferSize;
-  final List bufferedData = [];
-  int usedBufferSize = 0;
-  int finalCount;
-
-  SlowConsumer(int this.bytesPerSecond, int this.bufferSize);
-
-  Future consume(Stream stream) {
-    return addStream(stream).then((_) => close());
-  }
-
-  Future addStream(Stream stream) {
-    Completer result = new Completer();
-    var subscription;
-    subscription = stream.listen((List<int> data) {
-      receivedCount += data.length;
-      usedBufferSize += data.length;
-      bufferedData.add(data);
-      int currentBufferedDataLength = bufferedData.length;
-      if (usedBufferSize > bufferSize) {
-        subscription.pause();
-        usedBufferSize = 0;
-        int ms = data.length * 1000 ~/ bytesPerSecond;
-        Duration duration = new Duration(milliseconds: ms);
-        new Timer(duration, () {
-          for (int i = 0; i < currentBufferedDataLength; i++) {
-            bufferedData[i] = null;
-          }
-          subscription.resume();
-        });
-      }
-    }, onDone: () {
-      finalCount = receivedCount;
-      result.complete(receivedCount);
-    });
-    return result.future;
-  }
-
-  Future close() {
-    return new Future.value(finalCount);
-  }
-}
-
-class DataProvider {
-  final int chunkSize;
-  final int bytesPerSecond;
-  int sentCount = 0;
-  int targetCount;
-  StreamController controller;
-
-  DataProvider(int this.bytesPerSecond, int this.targetCount, this.chunkSize) {
-    controller = new StreamController(
-        sync: true, onPause: onPauseStateChange, onResume: onPauseStateChange);
-    Timer.run(send);
-  }
-
-  Stream get stream => controller.stream;
-
-  send() {
-    if (controller.isPaused) return;
-    if (sentCount == targetCount) {
-      controller.close();
-      return;
-    }
-    int listSize = chunkSize;
-    sentCount += listSize;
-    if (sentCount > targetCount) {
-      listSize -= sentCount - targetCount;
-      sentCount = targetCount;
-    }
-    controller.add(new List(listSize));
-    int ms = listSize * 1000 ~/ bytesPerSecond;
-    Duration duration = new Duration(milliseconds: ms);
-    if (!controller.isPaused) new Timer(duration, send);
-  }
-
-  onPauseStateChange() {
-    // We don't care if we just unpaused or paused. In either case we just
-    // call send which will test it for us.
-    send();
-  }
-}
-
-main() {
-  asyncStart();
-  // The data provider can deliver 800MB/s of data. It sends 100MB of data to
-  // the slower consumer who can only read 200MB/s. The data is sent in 1MB
-  // chunks. The consumer has a buffer of 5MB. That is, it can accept a few
-  // packages without pausing its input.
-  //
-  // This test is limited to 32MB of heap-space (see VMOptions on top of the
-  // file). If the consumer doesn't pause the data-provider it will run out of
-  // heap-space.
-
-  new DataProvider(800 * MB, 100 * MB, 1 * MB)
-      .stream
-      .pipe(new SlowConsumer(200 * MB, 5 * MB))
-      .then((count) {
-    Expect.equals(100 * MB, count);
-    asyncEnd();
-  });
-}