Add Timeline to dart:developer

sdk/lib/developer/timeline.dart

+// Copyright (c) 2015, 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.developer;
+
+typedef dynamic TimelineSyncFunction();
+
+/// Add to the timeline.
+class Timeline {
+  /// Open a synchronous block of time for |category| with |name|.
+  /// A |SyncBlock| should not be kept open across isolate messages.
+  static SyncBlock openSync(String category, String name) {
+    if (category is! String) {
+      throw new ArgumentError.value(category,
+                                    'category',
+                                    'Must be a String');
+    }
+    if (name is! String) {
+      throw new ArgumentError.value(name,
+                                    'name',
+                                    'Must be a String');
+    }
+    return new SyncBlock._(category, name, _getTraceClock());
+  }
+
+  /// A utility method to time a synchronous |function|. Opens a block
+  /// for |category| with |name|.
+  static dynamic timeSync(String category,
+                          String name,
+                          TimelineSyncFunction function,
+                          {Map arguments}) {
+    final block = openSync(category, name);
+    final returnValue = function();

[rmacnak, 2015/09/29 22:36:41]

try {
  return function();
} finally {
  if (arguments is Map) {
    block.arguments.addAll(arguments);
  }
  block.close();
}

[Cutch, 2015/09/30 14:42:29]

Done.

+    if (arguments is Map) {
+      block.arguments.addAll(arguments);
+    }
+    block.close();
+    return returnValue;
+  }
+}
+
+/// A synchronous block of time on the timeline. This block should not be
+/// kept open across isolate messages.
+class SyncBlock {
+  /// The category this block belongs to.
+  final String category;
+  /// The name of this block.
+  final String name;
+  /// An (optional) set of arguments which will be serialized to JSON and
+  /// associated with this block.
+  final Map arguments = {};
+  // The start time stamp.
+  final int _start;
+  // Has this block been closed?
+  bool _closed = false;
+
+  SyncBlock._(this.category,
+              this.name,
+              this._start);
+
+  /// Close this block of time. At this point, this block can no longer be
+  /// used.
+  void close() {
+    if (_closed) {
+      throw new StateError(
+          'It is illegal to call close twice on the same SyncBlock');
+    }
+    _closed = true;
+    var end = _getTraceClock();
+
+    // Encode arguments map as JSON before reporting.
+    var argumentsAsJson = JSON.encode(arguments);
+
+    // Report event to runtime.
+    _reportCompleteEvent(_start,
+                         end,
+                         category,
+                         name,
+                         argumentsAsJson);
+  }
+}
+
+/// Returns the current value from the trace clock.
+external int _getTraceClock();
+
+/// Reports a complete synchronous event.
+external void _reportCompleteEvent(int start,
+                                   int end,
+                                   String category,
+                                   String name,
+                                   String argumentsAsJson);