| /* |
| * Copyright 2015 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef SkTDPQueue_DEFINED |
| #define SkTDPQueue_DEFINED |
| |
| #include "include/private/SkTDArray.h" |
| #include "src/core/SkTSort.h" |
| |
| #include <utility> |
| |
| /** |
| * This class implements a priority queue. T is the type of the elements in the queue. LESS is a |
| * function that compares two Ts and returns true if the first is higher priority than the second. |
| * |
| * Optionally objects may know their index into the priority queue. The queue will update the index |
| * as the objects move through the queue. This is enabled by using a non-nullptr function for INDEX. |
| * When an INDEX function is provided random deletes from the queue are allowed using remove(). |
| * Additionally, the * priority is allowed to change as long as priorityDidChange() is called |
| * afterwards. In debug builds the index will be set to -1 before an element is removed from the |
| * queue. |
| */ |
| template <typename T, |
| bool (*LESS)(const T&, const T&), |
| int* (*INDEX)(const T&) = (int* (*)(const T&))nullptr> |
| class SkTDPQueue { |
| public: |
| SkTDPQueue() {} |
| SkTDPQueue(int reserve) { fArray.reserve(reserve); } |
| |
| SkTDPQueue(SkTDPQueue&&) = default; |
| SkTDPQueue& operator =(SkTDPQueue&&) = default; |
| |
| SkTDPQueue(const SkTDPQueue&) = delete; |
| SkTDPQueue& operator=(const SkTDPQueue&) = delete; |
| |
| /** Number of items in the queue. */ |
| int count() const { return fArray.size(); } |
| |
| /** Gets the next item in the queue without popping it. */ |
| const T& peek() const { return fArray[0]; } |
| T& peek() { return fArray[0]; } |
| |
| /** Removes the next item. */ |
| void pop() { |
| this->validate(); |
| SkDEBUGCODE(if (SkToBool(INDEX)) { *INDEX(fArray[0]) = -1; }) |
| if (1 == fArray.size()) { |
| fArray.pop_back(); |
| return; |
| } |
| |
| fArray[0] = fArray[fArray.size() - 1]; |
| this->setIndex(0); |
| fArray.pop_back(); |
| this->percolateDownIfNecessary(0); |
| |
| this->validate(); |
| } |
| |
| /** Inserts a new item in the queue based on its priority. */ |
| void insert(T entry) { |
| this->validate(); |
| int index = fArray.size(); |
| *fArray.append() = entry; |
| this->setIndex(fArray.size() - 1); |
| this->percolateUpIfNecessary(index); |
| this->validate(); |
| } |
| |
| /** Random access removal. This requires that the INDEX function is non-nullptr. */ |
| void remove(T entry) { |
| SkASSERT(nullptr != INDEX); |
| int index = *INDEX(entry); |
| SkASSERT(index >= 0 && index < fArray.size()); |
| this->validate(); |
| SkDEBUGCODE(*INDEX(fArray[index]) = -1;) |
| if (index == fArray.size() - 1) { |
| fArray.pop_back(); |
| return; |
| } |
| fArray[index] = fArray[fArray.size() - 1]; |
| fArray.pop_back(); |
| this->setIndex(index); |
| this->percolateUpOrDown(index); |
| this->validate(); |
| } |
| |
| /** Notification that the priority of an entry has changed. This must be called after an |
| item's priority is changed to maintain correct ordering. Changing the priority is only |
| allowed if an INDEX function is provided. */ |
| void priorityDidChange(T entry) { |
| SkASSERT(nullptr != INDEX); |
| int index = *INDEX(entry); |
| SkASSERT(index >= 0 && index < fArray.size()); |
| this->validate(index); |
| this->percolateUpOrDown(index); |
| this->validate(); |
| } |
| |
| /** Gets the item at index i in the priority queue (for i < this->count()). at(0) is equivalent |
| to peek(). Otherwise, there is no guarantee about ordering of elements in the queue. */ |
| T at(int i) const { return fArray[i]; } |
| |
| /** Sorts the queue into priority order. The queue is only guarenteed to remain in sorted order |
| * until any other operation, other than at(), is performed. |
| */ |
| void sort() { |
| if (fArray.size() > 1) { |
| SkTQSort<T>(fArray.begin(), fArray.end(), LESS); |
| for (int i = 0; i < fArray.size(); i++) { |
| this->setIndex(i); |
| } |
| this->validate(); |
| } |
| } |
| |
| private: |
| static int LeftOf(int x) { SkASSERT(x >= 0); return 2 * x + 1; } |
| static int ParentOf(int x) { SkASSERT(x > 0); return (x - 1) >> 1; } |
| |
| void percolateUpOrDown(int index) { |
| SkASSERT(index >= 0); |
| if (!percolateUpIfNecessary(index)) { |
| this->validate(index); |
| this->percolateDownIfNecessary(index); |
| } |
| } |
| |
| bool percolateUpIfNecessary(int index) { |
| SkASSERT(index >= 0); |
| bool percolated = false; |
| do { |
| if (0 == index) { |
| this->setIndex(index); |
| return percolated; |
| } |
| int p = ParentOf(index); |
| if (LESS(fArray[index], fArray[p])) { |
| using std::swap; |
| swap(fArray[index], fArray[p]); |
| this->setIndex(index); |
| index = p; |
| percolated = true; |
| } else { |
| this->setIndex(index); |
| return percolated; |
| } |
| this->validate(index); |
| } while (true); |
| } |
| |
| void percolateDownIfNecessary(int index) { |
| SkASSERT(index >= 0); |
| do { |
| int child = LeftOf(index); |
| |
| if (child >= fArray.size()) { |
| // We're a leaf. |
| this->setIndex(index); |
| return; |
| } |
| |
| if (child + 1 >= fArray.size()) { |
| // We only have a left child. |
| if (LESS(fArray[child], fArray[index])) { |
| using std::swap; |
| swap(fArray[child], fArray[index]); |
| this->setIndex(child); |
| this->setIndex(index); |
| return; |
| } |
| } else if (LESS(fArray[child + 1], fArray[child])) { |
| // The right child is the one we should swap with, if we swap. |
| child++; |
| } |
| |
| // Check if we need to swap. |
| if (LESS(fArray[child], fArray[index])) { |
| using std::swap; |
| swap(fArray[child], fArray[index]); |
| this->setIndex(index); |
| index = child; |
| } else { |
| // We're less than both our children. |
| this->setIndex(index); |
| return; |
| } |
| this->validate(index); |
| } while (true); |
| } |
| |
| void setIndex(int index) { |
| SkASSERT(index < fArray.size()); |
| if (SkToBool(INDEX)) { |
| *INDEX(fArray[index]) = index; |
| } |
| } |
| |
| void validate(int excludedIndex = -1) const { |
| #ifdef SK_DEBUG |
| for (int i = 1; i < fArray.size(); ++i) { |
| int p = ParentOf(i); |
| if (excludedIndex != p && excludedIndex != i) { |
| SkASSERT(!(LESS(fArray[i], fArray[p]))); |
| SkASSERT(!SkToBool(INDEX) || *INDEX(fArray[i]) == i); |
| } |
| } |
| #endif |
| } |
| |
| SkTDArray<T> fArray; |
| }; |
| |
| #endif |