Fasta infrastructure.

pkg/fasta/lib/src/ticker.dart

+// Copyright (c) 2016, 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 fasta.ticker;
+
+class Ticker {
+  final Stopwatch sw = new Stopwatch()..start();
+
+  bool isVerbose;
+
+  Duration previousTick;
+
+  Ticker({this.isVerbose: true}) {
+    previousTick = sw.elapsed;
+  }
+
+  void logMs(Object message) {
+    log((Duration elapsed, Duration sinceStart) {
+      print("$sinceStart: $message in ${elapsed.inMilliseconds}ms.");
+    });
+  }
+
+  void log(void f(Duration elapsed, Duration sinceStart)) {
+    Duration elapsed = sw.elapsed;
+    try {
+      if (isVerbose) f(elapsed - previousTick, elapsed);
+    } finally {
+      previousTick = sw.elapsed;
+    }
+  }
+}