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> 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> 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> 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> 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
