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+/*
+ * Copyright (C) 2010 Apple Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``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 APPLE COMPUTER, INC. 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. 
+ *
+ */
+
+#ifndef WTF_NonCopyingSort_h
+#define WTF_NonCopyingSort_h
+
+namespace WTF {
+
+using std::swap;
+
+template<typename RandomAccessIterator, typename Predicate>
+inline void siftDown(RandomAccessIterator array, ptrdiff_t start, ptrdiff_t end, Predicate compareLess) 
+{
+    ptrdiff_t root = start;
+
+    while (root * 2 + 1 <= end) {
+        ptrdiff_t child = root * 2 + 1;
+        if (child < end && compareLess(array[child], array[child + 1]))
+            child++;
+        
+        if (compareLess(array[root], array[child])) {
+            swap(array[root], array[child]);
+            root = child;
+        } else
+            return;
+    }
+}
+
+template<typename RandomAccessIterator, typename Predicate>
+inline void heapify(RandomAccessIterator array, ptrdiff_t count, Predicate compareLess) 
+{
+    ptrdiff_t start = (count - 2) / 2;
+     
+    while (start >= 0) {
+        siftDown(array, start, count - 1, compareLess);
+        start--;
+    }
+}
+
+template<typename RandomAccessIterator, typename Predicate>
+void heapSort(RandomAccessIterator start, RandomAccessIterator end, Predicate compareLess)
+{
+    ptrdiff_t count = end - start;
+    heapify(start, count, compareLess);
+
+    ptrdiff_t endIndex = count - 1;
+    while (endIndex > 0) {
+        swap(start[endIndex], start[0]);
+        siftDown(start, 0, endIndex - 1, compareLess);
+        endIndex--;
+    }
+}
+
+template<typename RandomAccessIterator, typename Predicate>
+inline void nonCopyingSort(RandomAccessIterator start, RandomAccessIterator end, Predicate compareLess)
+{
+    // heapsort happens to use only swaps, not copies, but the essential thing about
+    // this function is the fact that it does not copy, not the specific algorithm
+    heapSort(start, end, compareLess);
+}
+
+} // namespace WTF
+
+using WTF::nonCopyingSort;
+
+#endif // WTF_NonCopyingSort_h