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+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+/**
+ * Constructs a ConsArray object. It is used mainly for tree traversal.
+ * In this use case we have lots of arrays that we need to iterate
+ * sequentally. The internal Array implementation is horribly slow
+ * when concatenating on large (10K items) arrays due to memory copying.
+ * That's why we avoid copying memory and insead build a linked list
+ * of arrays to iterate through.
+ *
+ * @constructor
+ */
+export function ConsArray() {
+  this.tail_ = new ConsArray.Cell(null, null);
+  this.currCell_ = this.tail_;
+  this.currCellPos_ = 0;
+};
+
+
+/**
+ * Concatenates another array for iterating. Empty arrays are ignored.
+ * This operation can be safely performed during ongoing ConsArray
+ * iteration.
+ *
+ * @param {Array} arr Array to concatenate.
+ */
+ConsArray.prototype.concat = function(arr) {
+  if (arr.length > 0) {
+    this.tail_.data = arr;
+    this.tail_ = this.tail_.next = new ConsArray.Cell(null, null);
+  }
+};
+
+
+/**
+ * Whether the end of iteration is reached.
+ */
+ConsArray.prototype.atEnd = function() {
+  return this.currCell_ === null ||
+      this.currCell_.data === null ||
+      this.currCellPos_ >= this.currCell_.data.length;
+};
+
+
+/**
+ * Returns the current item, moves to the next one.
+ */
+ConsArray.prototype.next = function() {
+  var result = this.currCell_.data[this.currCellPos_++];
+  if (this.currCellPos_ >= this.currCell_.data.length) {
+    this.currCell_ = this.currCell_.next;
+    this.currCellPos_ = 0;
+  }
+  return result;
+};
+
+
+/**
+ * A cell object used for constructing a list in ConsArray.
+ *
+ * @constructor
+ */
+ConsArray.Cell = function(data, next) {
+  this.data = data;
+  this.next = next;
+};