bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2015 Google Inc. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license that can be |
| 5 | * found in the LICENSE file. |
| 6 | */ |
| 7 | |
| 8 | #ifndef SkTDPQueue_DEFINED |
| 9 | #define SkTDPQueue_DEFINED |
| 10 | |
| 11 | #include "SkTDArray.h" |
Derek Sollenberger | 5480a18 | 2017-05-25 16:43:59 -0400 | [diff] [blame] | 12 | #include "SkTSort.h" |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 13 | |
| 14 | /** |
| 15 | * This class implements a priority queue. T is the type of the elements in the queue. LESS is a |
| 16 | * function that compares two Ts and returns true if the first is higher priority than the second. |
| 17 | * |
| 18 | * Optionally objects may know their index into the priority queue. The queue will update the index |
halcanary | 96fcdcc | 2015-08-27 07:41:13 -0700 | [diff] [blame] | 19 | * as the objects move through the queue. This is enabled by using a non-nullptr function for INDEX. |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 20 | * When an INDEX function is provided random deletes from the queue are allowed using remove(). |
| 21 | * Additionally, the * priority is allowed to change as long as priorityDidChange() is called |
| 22 | * afterwards. In debug builds the index will be set to -1 before an element is removed from the |
| 23 | * queue. |
| 24 | */ |
| 25 | template <typename T, |
| 26 | bool (*LESS)(const T&, const T&), |
halcanary | 96fcdcc | 2015-08-27 07:41:13 -0700 | [diff] [blame] | 27 | int* (*INDEX)(const T&) = (int* (*)(const T&))nullptr> |
Mike Klein | bc4c96b | 2017-05-03 15:55:10 -0400 | [diff] [blame] | 28 | class SkTDPQueue { |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 29 | public: |
| 30 | SkTDPQueue() {} |
| 31 | |
Mike Klein | bc4c96b | 2017-05-03 15:55:10 -0400 | [diff] [blame] | 32 | SkTDPQueue(SkTDPQueue&&) = default; |
| 33 | SkTDPQueue& operator =(SkTDPQueue&&) = default; |
| 34 | |
| 35 | SkTDPQueue(const SkTDPQueue&) = delete; |
| 36 | SkTDPQueue& operator=(const SkTDPQueue&) = delete; |
| 37 | |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 38 | /** Number of items in the queue. */ |
| 39 | int count() const { return fArray.count(); } |
| 40 | |
| 41 | /** Gets the next item in the queue without popping it. */ |
| 42 | const T& peek() const { return fArray[0]; } |
| 43 | T& peek() { return fArray[0]; } |
halcanary | 9d524f2 | 2016-03-29 09:03:52 -0700 | [diff] [blame] | 44 | |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 45 | /** Removes the next item. */ |
| 46 | void pop() { |
| 47 | this->validate(); |
| 48 | SkDEBUGCODE(if (SkToBool(INDEX)) { *INDEX(fArray[0]) = -1; }) |
| 49 | if (1 == fArray.count()) { |
| 50 | fArray.pop(); |
| 51 | return; |
| 52 | } |
| 53 | |
| 54 | fArray[0] = fArray[fArray.count() - 1]; |
| 55 | this->setIndex(0); |
| 56 | fArray.pop(); |
| 57 | this->percolateDownIfNecessary(0); |
| 58 | |
| 59 | this->validate(); |
| 60 | } |
| 61 | |
| 62 | /** Inserts a new item in the queue based on its priority. */ |
| 63 | void insert(T entry) { |
| 64 | this->validate(); |
| 65 | int index = fArray.count(); |
| 66 | *fArray.append() = entry; |
| 67 | this->setIndex(fArray.count() - 1); |
| 68 | this->percolateUpIfNecessary(index); |
| 69 | this->validate(); |
| 70 | } |
| 71 | |
halcanary | 96fcdcc | 2015-08-27 07:41:13 -0700 | [diff] [blame] | 72 | /** Random access removal. This requires that the INDEX function is non-nullptr. */ |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 73 | void remove(T entry) { |
halcanary | 96fcdcc | 2015-08-27 07:41:13 -0700 | [diff] [blame] | 74 | SkASSERT(nullptr != INDEX); |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 75 | int index = *INDEX(entry); |
| 76 | SkASSERT(index >= 0 && index < fArray.count()); |
| 77 | this->validate(); |
| 78 | SkDEBUGCODE(*INDEX(fArray[index]) = -1;) |
| 79 | if (index == fArray.count() - 1) { |
| 80 | fArray.pop(); |
| 81 | return; |
| 82 | } |
| 83 | fArray[index] = fArray[fArray.count() - 1]; |
| 84 | fArray.pop(); |
| 85 | this->setIndex(index); |
| 86 | this->percolateUpOrDown(index); |
| 87 | this->validate(); |
| 88 | } |
| 89 | |
| 90 | /** Notification that the priority of an entry has changed. This must be called after an |
| 91 | item's priority is changed to maintain correct ordering. Changing the priority is only |
| 92 | allowed if an INDEX function is provided. */ |
| 93 | void priorityDidChange(T entry) { |
halcanary | 96fcdcc | 2015-08-27 07:41:13 -0700 | [diff] [blame] | 94 | SkASSERT(nullptr != INDEX); |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 95 | int index = *INDEX(entry); |
| 96 | SkASSERT(index >= 0 && index < fArray.count()); |
| 97 | this->validate(index); |
| 98 | this->percolateUpOrDown(index); |
| 99 | this->validate(); |
| 100 | } |
| 101 | |
bsalomon | 1a9600f | 2015-02-23 10:59:50 -0800 | [diff] [blame] | 102 | /** Gets the item at index i in the priority queue (for i < this->count()). at(0) is equivalent |
| 103 | to peek(). Otherwise, there is no guarantee about ordering of elements in the queue. */ |
bsalomon | 9f2d157 | 2015-02-17 11:47:40 -0800 | [diff] [blame] | 104 | T at(int i) const { return fArray[i]; } |
bsalomon | 9f2d157 | 2015-02-17 11:47:40 -0800 | [diff] [blame] | 105 | |
Derek Sollenberger | 5480a18 | 2017-05-25 16:43:59 -0400 | [diff] [blame] | 106 | /** Sorts the queue into priority order. The queue is only guarenteed to remain in sorted order |
| 107 | * until any other operation, other than at(), is performed. |
| 108 | */ |
| 109 | void sort() { |
| 110 | if (fArray.count() > 1) { |
| 111 | SkTQSort<T>(fArray.begin(), fArray.end() - 1, LESS); |
| 112 | for (int i = 0; i < fArray.count(); i++) { |
| 113 | this->setIndex(i); |
| 114 | } |
| 115 | this->validate(); |
| 116 | } |
| 117 | } |
| 118 | |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 119 | private: |
| 120 | static int LeftOf(int x) { SkASSERT(x >= 0); return 2 * x + 1; } |
| 121 | static int ParentOf(int x) { SkASSERT(x > 0); return (x - 1) >> 1; } |
| 122 | |
| 123 | void percolateUpOrDown(int index) { |
| 124 | SkASSERT(index >= 0); |
| 125 | if (!percolateUpIfNecessary(index)) { |
| 126 | this->validate(index); |
| 127 | this->percolateDownIfNecessary(index); |
| 128 | } |
| 129 | } |
| 130 | |
| 131 | bool percolateUpIfNecessary(int index) { |
| 132 | SkASSERT(index >= 0); |
| 133 | bool percolated = false; |
| 134 | do { |
| 135 | if (0 == index) { |
| 136 | this->setIndex(index); |
| 137 | return percolated; |
| 138 | } |
| 139 | int p = ParentOf(index); |
| 140 | if (LESS(fArray[index], fArray[p])) { |
| 141 | SkTSwap(fArray[index], fArray[p]); |
| 142 | this->setIndex(index); |
| 143 | index = p; |
| 144 | percolated = true; |
| 145 | } else { |
| 146 | this->setIndex(index); |
| 147 | return percolated; |
| 148 | } |
| 149 | this->validate(index); |
| 150 | } while (true); |
| 151 | } |
| 152 | |
| 153 | void percolateDownIfNecessary(int index) { |
| 154 | SkASSERT(index >= 0); |
| 155 | do { |
| 156 | int child = LeftOf(index); |
halcanary | 9d524f2 | 2016-03-29 09:03:52 -0700 | [diff] [blame] | 157 | |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 158 | if (child >= fArray.count()) { |
| 159 | // We're a leaf. |
| 160 | this->setIndex(index); |
| 161 | return; |
| 162 | } |
| 163 | |
| 164 | if (child + 1 >= fArray.count()) { |
| 165 | // We only have a left child. |
| 166 | if (LESS(fArray[child], fArray[index])) { |
| 167 | SkTSwap(fArray[child], fArray[index]); |
| 168 | this->setIndex(child); |
| 169 | this->setIndex(index); |
| 170 | return; |
| 171 | } |
| 172 | } else if (LESS(fArray[child + 1], fArray[child])) { |
| 173 | // The right child is the one we should swap with, if we swap. |
| 174 | child++; |
| 175 | } |
| 176 | |
| 177 | // Check if we need to swap. |
| 178 | if (LESS(fArray[child], fArray[index])) { |
| 179 | SkTSwap(fArray[child], fArray[index]); |
| 180 | this->setIndex(index); |
| 181 | index = child; |
| 182 | } else { |
| 183 | // We're less than both our children. |
| 184 | this->setIndex(index); |
| 185 | return; |
| 186 | } |
| 187 | this->validate(index); |
| 188 | } while (true); |
| 189 | } |
| 190 | |
| 191 | void setIndex(int index) { |
| 192 | SkASSERT(index < fArray.count()); |
| 193 | if (SkToBool(INDEX)) { |
| 194 | *INDEX(fArray[index]) = index; |
| 195 | } |
| 196 | } |
| 197 | |
| 198 | void validate(int excludedIndex = -1) const { |
| 199 | #ifdef SK_DEBUG |
| 200 | for (int i = 1; i < fArray.count(); ++i) { |
| 201 | int p = ParentOf(i); |
| 202 | if (excludedIndex != p && excludedIndex != i) { |
| 203 | SkASSERT(!(LESS(fArray[i], fArray[p]))); |
| 204 | SkASSERT(!SkToBool(INDEX) || *INDEX(fArray[i]) == i); |
| 205 | } |
| 206 | } |
| 207 | #endif |
| 208 | } |
| 209 | |
| 210 | SkTDArray<T> fArray; |
bsalomon | 3555bd8 | 2015-02-13 11:08:21 -0800 | [diff] [blame] | 211 | }; |
| 212 | |
| 213 | #endif |