Cleanups in collection.

sdk/lib/collection/queue.dart

 // Copyright (c) 2011, 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.collection;
 
 /**
  * A [Queue] is a collection that can be manipulated at both ends. One
  * can iterate over the elements of a queue through [forEach] or with
  * an [Iterator].
@@ skipping 144 matching lines @@
 
 /**
  * A [Queue] implementation based on a double-linked list.
  *
  * Allows constant time add, remove-at-ends and peek operations.
  *
  * Can do [removeAll] and [retainAll] in linear time.
  */
 class DoubleLinkedQueue<E> extends Collection<E> implements Queue<E> {
   _DoubleLinkedQueueEntrySentinel<E> _sentinel;
+  int _elementCount = 0;
 
   DoubleLinkedQueue() {
     _sentinel = new _DoubleLinkedQueueEntrySentinel<E>();
   }
 
   factory DoubleLinkedQueue.from(Iterable<E> other) {
     Queue<E> list = new DoubleLinkedQueue();
     for (final e in other) {
       list.addLast(e);
     }
     return list;
   }
 
+  int get length => _elementCount;
+
   void addLast(E value) {
     _sentinel.prepend(value);
+    _elementCount++;
   }
 
   void addFirst(E value) {
     _sentinel.append(value);
+    _elementCount++;
   }
 
   void add(E value) {
-    addLast(value);
+    _sentinel.prepend(value);
+    _elementCount++;
   }
 
   void addAll(Iterable<E> iterable) {
-    for (final e in iterable) {
-      add(e);
+    for (final E value in iterable) {
+      _sentinel.prepend(value);
+      _elementCount++;
     }
   }
 
   E removeLast() {
-    return _sentinel._previous.remove();
+    E result = _sentinel._previous.remove();
+    _elementCount--;
+    return result;
   }
 
   E removeFirst() {
-    return _sentinel._next.remove();
+    E result = _sentinel._next.remove();
+    _elementCount--;
+    return result;
   }
 
   void remove(Object o) {
     DoubleLinkedQueueEntry<E> entry = firstEntry();
     while (!identical(entry, _sentinel)) {
       if (entry.element == o) {
         entry.remove();
+        _elementCount--;
         return;
       }
       entry = entry._next;
     }
   }
 
   void removeAll(Iterable elements) {
     // Use this method when remove is slow and removeMatching more efficient.
     IterableMixinWorkaround.removeAllList(this, elements);
   }
 
   void removeMatching(bool test(E element)) {
     DoubleLinkedQueueEntry<E> entry = firstEntry();
     while (!identical(entry, _sentinel)) {
       DoubleLinkedQueueEntry<E> next = entry._next;
       if (test(entry.element)) {
         entry.remove();
+        _elementCount--;
       }
       entry = next;
     }
   }
 
   void retainMatching(bool test(E element)) {
     DoubleLinkedQueueEntry<E> entry = firstEntry();
     while (!identical(entry, _sentinel)) {
       DoubleLinkedQueueEntry<E> next = entry._next;
       if (!test(entry.element)) {
         entry.remove();
+        _elementCount--;
       }
       entry = next;
     }
   }
 
   E get first {
     return _sentinel._next.element;
   }
 
   E get last {
@@ skipping 16 matching lines @@
     return _sentinel.nextEntry();
   }
 
   bool get isEmpty {
     return (identical(_sentinel._next, _sentinel));
   }
 
   void clear() {
     _sentinel._next = _sentinel;
     _sentinel._previous = _sentinel;
+    _elementCount = 0;
   }
 
   void forEachEntry(void f(DoubleLinkedQueueEntry<E> element)) {
     DoubleLinkedQueueEntry<E> entry = _sentinel._next;
     while (!identical(entry, _sentinel)) {
       DoubleLinkedQueueEntry<E> nextEntry = entry._next;
       f(entry);
       entry = nextEntry;
     }
   }
@@ skipping 409 matching lines @@
     _queue._checkModification(_modificationCount);
     if (_position == _end) {
       _current = null;
       return false;
     }
     _current = _queue._table[_position];
     _position = (_position + 1) & (_queue._table.length - 1);
     return true;
   }
 }