1/*
2 * Copyright (C) 2010 Apple Inc. All Rights Reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 */
26
27#ifndef WTF_NonCopyingSort_h
28#define WTF_NonCopyingSort_h
29
30namespace WTF {
31
32using std::swap;
33
34template<typename RandomAccessIterator, typename Predicate>
35inline void siftDown(RandomAccessIterator array, ptrdiff_t start, ptrdiff_t end, Predicate compareLess)
36{
37    ptrdiff_t root = start;
38
39    while (root * 2 + 1 <= end) {
40        ptrdiff_t child = root * 2 + 1;
41        if (child < end && compareLess(array[child], array[child + 1]))
42            child++;
43
44        if (compareLess(array[root], array[child])) {
45            swap(array[root], array[child]);
46            root = child;
47        } else
48            return;
49    }
50}
51
52template<typename RandomAccessIterator, typename Predicate>
53inline void heapify(RandomAccessIterator array, ptrdiff_t count, Predicate compareLess)
54{
55    ptrdiff_t start = (count - 2) / 2;
56
57    while (start >= 0) {
58        siftDown(array, start, count - 1, compareLess);
59        start--;
60    }
61}
62
63template<typename RandomAccessIterator, typename Predicate>
64void heapSort(RandomAccessIterator start, RandomAccessIterator end, Predicate compareLess)
65{
66    ptrdiff_t count = end - start;
67    heapify(start, count, compareLess);
68
69    ptrdiff_t endIndex = count - 1;
70    while (endIndex > 0) {
71        swap(start[endIndex], start[0]);
72        siftDown(start, 0, endIndex - 1, compareLess);
73        endIndex--;
74    }
75}
76
77template<typename RandomAccessIterator, typename Predicate>
78inline void nonCopyingSort(RandomAccessIterator start, RandomAccessIterator end, Predicate compareLess)
79{
80    // heapsort happens to use only swaps, not copies, but the essential thing about
81    // this function is the fact that it does not copy, not the specific algorithm
82    heapSort(start, end, compareLess);
83}
84
85} // namespace WTF
86
87using WTF::nonCopyingSort;
88
89#endif // WTF_NonCopyingSort_h
90