Speeding up Node.nodes.addAll

tools/dom/templates/html/impl/impl_Node.darttemplate

 // 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.
 
 part of $LIBRARYNAME;
 
 /**
  * Lazy implementation of the child nodes of an element that does not request
  * the actual child nodes of an element until strictly necessary greatly
  * improving performance for the typical cases where it is not required.
@@ skipping 51 matching lines @@
   void add(Node value) {
     _this.$dom_appendChild(value);
   }
 
   void addLast(Node value) {
     _this.$dom_appendChild(value);
   }
 
 
   void addAll(Iterable<Node> iterable) {
     if (iterable is _ChildNodeListLazy) {

[Siggi Cherem (dart-lang), 2013/02/28 19:43:32]

is it worth doing this also for other types like List<Node>?

[blois, 2013/02/28 20:45:58]

The optimized loop requires that it be a browser node list as it relies on the
behavior of the items getting automatically removed from the other list.

The general for..in loop could potentially be optimized to avoid the generation
of an iterator for lists, but I'd prefer to delay a change like that until we
have prescriptive guidance around List iterating.

[Siggi Cherem (dart-lang), 2013/03/01 00:05:28]

I see, thanks! - somehow the [0] below didn't sink in =).

-      iterable = new List.from(iterable);
+      if (iterable._this != _this) {

[sra1, 2013/03/01 01:17:59]

if (!identical(iterable._this, _this))

+        // Optimized route for copying between nodes.
+        for (var i = 0, len = iterable.length; i < len; ++i) {
+          _this.$dom_appendChild(iterable[0]);

[sra1, 2013/03/01 01:17:59]

iterable.first should be slightly faster.

[sra1, 2013/03/01 01:28:46]

or, better, iterable._this.$dom_firstChild

+        }
+      }
+      return;
     }
     for (Node node in iterable) {
       _this.$dom_appendChild(node);
     }
   }
 
   Node removeLast() {
     final result = last;
     if (result != null) {
       _this.$dom_removeChild(result);
@@ skipping 196 matching lines @@
       final Node parent = this.parentNode;
       parent.$dom_replaceChild(otherNode, this);
     } catch (e) {
 
     };
     return this;
   }
 
 $!MEMBERS
 }