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
30 namespace WTF {
31
32 using std::swap;
33
34 template<typename RandomAccessIterator, typename Predicate>
siftDown(RandomAccessIterator array,ptrdiff_t start,ptrdiff_t end,Predicate compareLess)35 inline 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
52 template<typename RandomAccessIterator, typename Predicate>
heapify(RandomAccessIterator array,ptrdiff_t count,Predicate compareLess)53 inline 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
63 template<typename RandomAccessIterator, typename Predicate>
heapSort(RandomAccessIterator start,RandomAccessIterator end,Predicate compareLess)64 void 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
77 template<typename RandomAccessIterator, typename Predicate>
nonCopyingSort(RandomAccessIterator start,RandomAccessIterator end,Predicate compareLess)78 inline 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
87 using WTF::nonCopyingSort;
88
89 #endif // WTF_NonCopyingSort_h
90