Migrate async tests to strong

tests/lib_strong/async/slow_consumer_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_consumer_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 {
+  var current = new Future.value(0);
+  final int bytesPerSecond;
+  int finalCount;
+
+  SlowConsumer(int this.bytesPerSecond);
+
+  Future consume(Stream stream) {
+    return addStream(stream).then((_) => close());
+  }
+
+  Future addStream(Stream stream) {
+    bool done = false;
+    Completer completer = new Completer();
+    var subscription;
+    subscription = stream.listen(
+      (List<int> data) {
+        current = current
+          .then((count) {
+            // Simulated amount of time it takes to handle the data.
+            int ms = data.length * 1000 ~/ bytesPerSecond;
+            Duration duration = new Duration(milliseconds: ms);
+            if (!done) subscription.pause();
+            return new Future.delayed(duration, () {
+              if (!done) subscription.resume();
+              // Make sure we use data here to keep tracking it.
+              return count + data.length;
+            });
+          });
+        },
+      onDone: () {
+        done = true;
+        current.then((count) {
+          finalCount = count;
+          completer.complete(count);
+        });
+      });
+    return completer.future;
+  }
+
+  Future close() {
+    return new Future.value(finalCount);
+  }
+}
+
+class DataProvider {
+  final int chunkSize;
+  final int bytesPerSecond;
+  int sentCount = 0;
+  int targetCount;
+  StreamController controller;
+  Timer pendingSend;
+
+  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 (pendingSend != null) {
+      pendingSend.cancel();
+      pendingSend = null;
+    }
+    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) {
+      pendingSend = 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.
+  //
+  // This test is limited to 64MB 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))
+    .then((count) {
+      Expect.equals(100 * MB, count);
+      asyncEnd();
+    });
+}