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493 lines
13 KiB
C++
493 lines
13 KiB
C++
/*
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* This file is part of OpenTTD.
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* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
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* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @file queue.cpp Implementation of the #BinaryHeap/#Hash. */
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#include "../../stdafx.h"
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#include "../../core/alloc_func.hpp"
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#include "queue.h"
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#include "../../safeguards.h"
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/*
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* Binary Heap
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* For information, see: http://www.policyalmanac.org/games/binaryHeaps.htm
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*/
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const int BinaryHeap::BINARY_HEAP_BLOCKSIZE_BITS = 10; ///< The number of elements that will be malloc'd at a time.
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const int BinaryHeap::BINARY_HEAP_BLOCKSIZE = 1 << BinaryHeap::BINARY_HEAP_BLOCKSIZE_BITS;
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const int BinaryHeap::BINARY_HEAP_BLOCKSIZE_MASK = BinaryHeap::BINARY_HEAP_BLOCKSIZE - 1;
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/**
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* Clears the queue, by removing all values from it. Its state is
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* effectively reset. If free_items is true, each of the items cleared
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* in this way are free()'d.
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*/
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void BinaryHeap::Clear(bool free_values)
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{
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/* Free all items if needed and free all but the first blocks of memory */
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uint i;
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uint j;
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for (i = 0; i < this->blocks; i++) {
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if (this->elements[i] == nullptr) {
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/* No more allocated blocks */
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break;
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}
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/* For every allocated block */
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if (free_values) {
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for (j = 0; j < (1 << BINARY_HEAP_BLOCKSIZE_BITS); j++) {
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/* For every element in the block */
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if ((this->size >> BINARY_HEAP_BLOCKSIZE_BITS) == i &&
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(this->size & BINARY_HEAP_BLOCKSIZE_MASK) == j) {
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break; // We're past the last element
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}
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free(this->elements[i][j].item);
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}
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}
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if (i != 0) {
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/* Leave the first block of memory alone */
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free(this->elements[i]);
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this->elements[i] = nullptr;
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}
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}
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this->size = 0;
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this->blocks = 1;
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}
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/**
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* Frees the queue, by reclaiming all memory allocated by it. After
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* this it is no longer usable. If free_items is true, any remaining
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* items are free()'d too.
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*/
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void BinaryHeap::Free(bool free_values)
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{
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uint i;
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this->Clear(free_values);
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for (i = 0; i < this->blocks; i++) {
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if (this->elements[i] == nullptr) break;
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free(this->elements[i]);
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}
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free(this->elements);
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}
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/**
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* Pushes an element into the queue, at the appropriate place for the queue.
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* Requires the queue pointer to be of an appropriate type, of course.
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*/
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bool BinaryHeap::Push(void *item, int priority)
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{
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if (this->size == this->max_size) return false;
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assert(this->size < this->max_size);
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if (this->elements[this->size >> BINARY_HEAP_BLOCKSIZE_BITS] == nullptr) {
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/* The currently allocated blocks are full, allocate a new one */
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assert((this->size & BINARY_HEAP_BLOCKSIZE_MASK) == 0);
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this->elements[this->size >> BINARY_HEAP_BLOCKSIZE_BITS] = MallocT<BinaryHeapNode>(BINARY_HEAP_BLOCKSIZE);
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this->blocks++;
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}
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/* Add the item at the end of the array */
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this->GetElement(this->size + 1).priority = priority;
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this->GetElement(this->size + 1).item = item;
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this->size++;
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/* Now we are going to check where it belongs. As long as the parent is
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* bigger, we switch with the parent */
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{
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BinaryHeapNode temp;
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int i;
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int j;
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i = this->size;
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while (i > 1) {
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/* Get the parent of this object (divide by 2) */
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j = i / 2;
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/* Is the parent bigger than the current, switch them */
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if (this->GetElement(i).priority <= this->GetElement(j).priority) {
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temp = this->GetElement(j);
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this->GetElement(j) = this->GetElement(i);
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this->GetElement(i) = temp;
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i = j;
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} else {
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/* It is not, we're done! */
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break;
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}
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}
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}
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return true;
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}
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/**
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* Deletes the item from the queue. priority should be specified if
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* known, which speeds up the deleting for some queue's. Should be -1
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* if not known.
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*/
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bool BinaryHeap::Delete(void *item, int priority)
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{
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uint i = 0;
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/* First, we try to find the item.. */
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do {
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if (this->GetElement(i + 1).item == item) break;
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i++;
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} while (i < this->size);
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/* We did not find the item, so we return false */
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if (i == this->size) return false;
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/* Now we put the last item over the current item while decreasing the size of the elements */
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this->size--;
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this->GetElement(i + 1) = this->GetElement(this->size + 1);
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/* Now the only thing we have to do, is resort it..
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* On place i there is the item to be sorted.. let's start there */
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{
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uint j;
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BinaryHeapNode temp;
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/* Because of the fact that Binary Heap uses array from 1 to n, we need to
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* increase i by 1
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*/
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i++;
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for (;;) {
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j = i;
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/* Check if we have 2 children */
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if (2 * j + 1 <= this->size) {
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/* Is this child smaller than the parent? */
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if (this->GetElement(j).priority >= this->GetElement(2 * j).priority) i = 2 * j;
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/* Yes, we _need_ to use i here, not j, because we want to have the smallest child
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* This way we get that straight away! */
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if (this->GetElement(i).priority >= this->GetElement(2 * j + 1).priority) i = 2 * j + 1;
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/* Do we have one child? */
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} else if (2 * j <= this->size) {
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if (this->GetElement(j).priority >= this->GetElement(2 * j).priority) i = 2 * j;
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}
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/* One of our children is smaller than we are, switch */
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if (i != j) {
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temp = this->GetElement(j);
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this->GetElement(j) = this->GetElement(i);
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this->GetElement(i) = temp;
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} else {
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/* None of our children is smaller, so we stay here.. stop :) */
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break;
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}
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}
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}
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return true;
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}
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/**
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* Pops the first element from the queue. What exactly is the first element,
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* is defined by the exact type of queue.
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*/
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void *BinaryHeap::Pop()
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{
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void *result;
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if (this->size == 0) return nullptr;
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/* The best item is always on top, so give that as result */
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result = this->GetElement(1).item;
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/* And now we should get rid of this item... */
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this->Delete(this->GetElement(1).item, this->GetElement(1).priority);
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return result;
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}
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/**
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* Initializes a binary heap and allocates internal memory for maximum of
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* max_size elements
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*/
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void BinaryHeap::Init(uint max_size)
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{
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this->max_size = max_size;
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this->size = 0;
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/* We malloc memory in block of BINARY_HEAP_BLOCKSIZE
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* It autosizes when it runs out of memory */
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this->elements = CallocT<BinaryHeapNode*>((max_size - 1) / BINARY_HEAP_BLOCKSIZE + 1);
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this->elements[0] = MallocT<BinaryHeapNode>(BINARY_HEAP_BLOCKSIZE);
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this->blocks = 1;
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}
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/* Because we don't want anyone else to bother with our defines */
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#undef BIN_HEAP_ARR
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/*
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* Hash
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*/
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/**
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* Builds a new hash in an existing struct. Make sure that hash() always
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* returns a hash less than num_buckets! Call delete_hash after use
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*/
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void Hash::Init(Hash_HashProc *hash, uint num_buckets)
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{
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/* Allocate space for the Hash, the buckets and the bucket flags */
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uint i;
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/* Ensure the size won't overflow. */
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CheckAllocationConstraints(sizeof(*this->buckets) + sizeof(*this->buckets_in_use), num_buckets);
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this->hash = hash;
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this->size = 0;
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this->num_buckets = num_buckets;
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this->buckets = (HashNode*)MallocT<byte>(num_buckets * (sizeof(*this->buckets) + sizeof(*this->buckets_in_use)));
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this->buckets_in_use = (bool*)(this->buckets + num_buckets);
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for (i = 0; i < num_buckets; i++) this->buckets_in_use[i] = false;
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}
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/**
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* Deletes the hash and cleans up. Only cleans up memory allocated by new_Hash
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* & friends. If free is true, it will call free() on all the values that
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* are left in the hash.
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*/
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void Hash::Delete(bool free_values)
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{
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uint i;
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/* Iterate all buckets */
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for (i = 0; i < this->num_buckets; i++) {
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if (this->buckets_in_use[i]) {
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HashNode *node;
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/* Free the first value */
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if (free_values) free(this->buckets[i].value);
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node = this->buckets[i].next;
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while (node != nullptr) {
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HashNode *prev = node;
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node = node->next;
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/* Free the value */
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if (free_values) free(prev->value);
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/* Free the node */
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free(prev);
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}
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}
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}
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free(this->buckets);
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/* No need to free buckets_in_use, it is always allocated in one
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* malloc with buckets */
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}
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#ifdef HASH_STATS
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void Hash::PrintStatistics() const
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{
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uint used_buckets = 0;
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uint max_collision = 0;
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uint max_usage = 0;
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uint usage[200];
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uint i;
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for (i = 0; i < lengthof(usage); i++) usage[i] = 0;
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for (i = 0; i < this->num_buckets; i++) {
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uint collision = 0;
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if (this->buckets_in_use[i]) {
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const HashNode *node;
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used_buckets++;
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for (node = &this->buckets[i]; node != nullptr; node = node->next) collision++;
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if (collision > max_collision) max_collision = collision;
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}
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if (collision >= lengthof(usage)) collision = lengthof(usage) - 1;
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usage[collision]++;
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if (collision > 0 && usage[collision] >= max_usage) {
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max_usage = usage[collision];
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}
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}
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printf(
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"---\n"
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"Hash size: %u\n"
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"Nodes used: %u\n"
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"Non empty buckets: %u\n"
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"Max collision: %u\n",
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this->num_buckets, this->size, used_buckets, max_collision
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);
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printf("{ ");
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for (i = 0; i <= max_collision; i++) {
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if (usage[i] > 0) {
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printf("%u:%u ", i, usage[i]);
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#if 0
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if (i > 0) {
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uint j;
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for (j = 0; j < usage[i] * 160 / 800; j++) putchar('#');
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}
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printf("\n");
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#endif
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}
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}
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printf ("}\n");
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}
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#endif
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/**
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* Cleans the hash, but keeps the memory allocated
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*/
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void Hash::Clear(bool free_values)
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{
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uint i;
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#ifdef HASH_STATS
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if (this->size > 2000) this->PrintStatistics();
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#endif
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/* Iterate all buckets */
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for (i = 0; i < this->num_buckets; i++) {
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if (this->buckets_in_use[i]) {
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HashNode *node;
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this->buckets_in_use[i] = false;
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/* Free the first value */
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if (free_values) free(this->buckets[i].value);
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node = this->buckets[i].next;
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while (node != nullptr) {
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HashNode *prev = node;
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node = node->next;
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if (free_values) free(prev->value);
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free(prev);
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}
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}
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}
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this->size = 0;
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}
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/**
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* Finds the node that that saves this key pair. If it is not
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* found, returns nullptr. If it is found, *prev is set to the
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* node before the one found, or if the node found was the first in the bucket
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* to nullptr. If it is not found, *prev is set to the last HashNode in the
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* bucket, or nullptr if it is empty. prev can also be nullptr, in which case it is
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* not used for output.
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*/
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HashNode *Hash::FindNode(uint key1, uint key2, HashNode** prev_out) const
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{
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uint hash = this->hash(key1, key2);
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HashNode *result = nullptr;
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/* Check if the bucket is empty */
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if (!this->buckets_in_use[hash]) {
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if (prev_out != nullptr) *prev_out = nullptr;
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result = nullptr;
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/* Check the first node specially */
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} else if (this->buckets[hash].key1 == key1 && this->buckets[hash].key2 == key2) {
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/* Save the value */
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result = this->buckets + hash;
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if (prev_out != nullptr) *prev_out = nullptr;
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/* Check all other nodes */
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} else {
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HashNode *prev = this->buckets + hash;
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HashNode *node;
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for (node = prev->next; node != nullptr; node = node->next) {
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if (node->key1 == key1 && node->key2 == key2) {
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/* Found it */
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result = node;
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break;
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}
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prev = node;
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}
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if (prev_out != nullptr) *prev_out = prev;
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}
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return result;
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}
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/**
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* Deletes the value with the specified key pair from the hash and returns
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* that value. Returns nullptr when the value was not present. The value returned
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* is _not_ free()'d!
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*/
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void *Hash::DeleteValue(uint key1, uint key2)
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{
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void *result;
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HashNode *prev; // Used as output var for below function call
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HashNode *node = this->FindNode(key1, key2, &prev);
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if (node == nullptr) {
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/* not found */
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result = nullptr;
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} else if (prev == nullptr) {
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/* It is in the first node, we can't free that one, so we free
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* the next one instead (if there is any)*/
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/* Save the value */
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result = node->value;
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if (node->next != nullptr) {
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HashNode *next = node->next;
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/* Copy the second to the first */
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*node = *next;
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/* Free the second */
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free(next);
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} else {
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/* This was the last in this bucket
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* Mark it as empty */
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uint hash = this->hash(key1, key2);
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this->buckets_in_use[hash] = false;
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}
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} else {
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/* It is in another node
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* Save the value */
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result = node->value;
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/* Link previous and next nodes */
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prev->next = node->next;
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/* Free the node */
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free(node);
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}
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if (result != nullptr) this->size--;
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return result;
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}
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/**
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* Sets the value associated with the given key pair to the given value.
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* Returns the old value if the value was replaced, nullptr when it was not yet present.
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*/
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void *Hash::Set(uint key1, uint key2, void *value)
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{
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HashNode *prev;
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HashNode *node = this->FindNode(key1, key2, &prev);
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if (node != nullptr) {
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/* Found it */
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void *result = node->value;
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node->value = value;
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return result;
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}
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/* It is not yet present, let's add it */
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if (prev == nullptr) {
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/* The bucket is still empty */
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uint hash = this->hash(key1, key2);
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this->buckets_in_use[hash] = true;
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node = this->buckets + hash;
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} else {
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/* Add it after prev */
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node = MallocT<HashNode>(1);
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prev->next = node;
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}
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node->next = nullptr;
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node->key1 = key1;
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node->key2 = key2;
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node->value = value;
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this->size++;
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return nullptr;
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}
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/**
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* Gets the value associated with the given key pair, or nullptr when it is not
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* present.
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*/
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void *Hash::Get(uint key1, uint key2) const
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{
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HashNode *node = this->FindNode(key1, key2, nullptr);
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return (node != nullptr) ? node->value : nullptr;
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}
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