/* This file is part of GNUnet. Copyright (C) 2008, 2009 GNUnet e.V. GNUnet is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. GNUnet 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. See the GNU Affero General Public License for more details. */ /** * @file util/container_heap.c * @brief Implementation of a heap * @author Nathan Evans * @author Christian Grothoff */ #include "platform.h" #include "gnunet_container_lib.h" #define LOG(kind,...) GNUNET_log_from (kind, "util-container-heap", __VA_ARGS__) #define EXTRA_CHECKS 0 /** * Node in the heap. */ struct GNUNET_CONTAINER_HeapNode { /** * Heap this node belongs to. */ struct GNUNET_CONTAINER_Heap *heap; /** * Parent node. */ struct GNUNET_CONTAINER_HeapNode *parent; /** * Left child. */ struct GNUNET_CONTAINER_HeapNode *left_child; /** * Right child. */ struct GNUNET_CONTAINER_HeapNode *right_child; /** * Our element. */ void *element; /** * Cost for this element. */ GNUNET_CONTAINER_HeapCostType cost; /** * Number of elements below this node in the heap * (excluding this node itself). */ unsigned int tree_size; }; /** * Handle to a node in a heap. */ struct GNUNET_CONTAINER_Heap { /** * Root of the heap. */ struct GNUNET_CONTAINER_HeapNode *root; /** * Current position of our random walk. */ struct GNUNET_CONTAINER_HeapNode *walk_pos; /** * Number of elements in the heap. */ unsigned int size; /** * How is the heap sorted? */ enum GNUNET_CONTAINER_HeapOrder order; }; #if EXTRA_CHECKS /** * Check if internal invariants hold for the given node. * * @param node subtree to check */ static void check (const struct GNUNET_CONTAINER_HeapNode *node) { if (NULL == node) return; GNUNET_assert (node->tree_size == ((node->left_child == NULL) ? 0 : 1 + node->left_child->tree_size) + ((node->right_child == NULL) ? 0 : 1 + node->right_child->tree_size)); check (node->left_child); check (node->right_child); } #define CHECK(n) check(n) #else #define CHECK(n) do {} while (0) #endif /** * Create a new heap. * * @param order how should the heap be sorted? * @return handle to the heap */ struct GNUNET_CONTAINER_Heap * GNUNET_CONTAINER_heap_create (enum GNUNET_CONTAINER_HeapOrder order) { struct GNUNET_CONTAINER_Heap *heap; heap = GNUNET_new (struct GNUNET_CONTAINER_Heap); heap->order = order; return heap; } /** * Destroys the heap. Only call on a heap that * is already empty. * * @param heap heap to destroy */ void GNUNET_CONTAINER_heap_destroy (struct GNUNET_CONTAINER_Heap *heap) { GNUNET_break (heap->size == 0); GNUNET_free (heap); } /** * Get element stored at the root of @a heap. * * @param heap Heap to inspect. * @return Element at the root, or NULL if heap is empty. */ void * GNUNET_CONTAINER_heap_peek (const struct GNUNET_CONTAINER_Heap *heap) { if (heap->root == NULL) return NULL; return heap->root->element; } /** * Get @a element and @a cost stored at the root of @a heap. * * @param[in] heap Heap to inspect. * @param[out] element Root element is returned here. * @param[out] cost Cost of @a element is returned here. * @return #GNUNET_YES if an element is returned, * #GNUNET_NO if the heap is empty. */ int GNUNET_CONTAINER_heap_peek2 (const struct GNUNET_CONTAINER_Heap *heap, void **element, GNUNET_CONTAINER_HeapCostType *cost) { if (NULL == heap->root) return GNUNET_NO; if (NULL != element) *element = heap->root->element; if (NULL != cost) *cost = heap->root->cost; return GNUNET_YES; } /** * Get the current size of the heap * * @param heap the heap to get the size of * @return number of elements stored */ unsigned int GNUNET_CONTAINER_heap_get_size (const struct GNUNET_CONTAINER_Heap *heap) { return heap->size; } /** * Get the current cost of the node * * @param node the node to get the cost of * @return cost of the node */ GNUNET_CONTAINER_HeapCostType GNUNET_CONTAINER_heap_node_get_cost (const struct GNUNET_CONTAINER_HeapNode *node) { return node->cost; } /** * Iterate over the children of the given node. * * @param heap argument to give to iterator * @param node node to iterate over * @param iterator function to call on each node * @param iterator_cls closure for iterator * @return GNUNET_YES to continue to iterate */ static int node_iterator (const struct GNUNET_CONTAINER_Heap *heap, struct GNUNET_CONTAINER_HeapNode *node, GNUNET_CONTAINER_HeapIterator iterator, void *iterator_cls) { if (node == NULL) return GNUNET_YES; if (GNUNET_YES != node_iterator (heap, node->left_child, iterator, iterator_cls)) return GNUNET_NO; if (GNUNET_YES != node_iterator (heap, node->right_child, iterator, iterator_cls)) return GNUNET_NO; return iterator (iterator_cls, node, node->element, node->cost); } /** * Iterate over all entries in the heap. * * @param heap the heap * @param iterator function to call on each entry * @param iterator_cls closure for iterator */ void GNUNET_CONTAINER_heap_iterate (const struct GNUNET_CONTAINER_Heap *heap, GNUNET_CONTAINER_HeapIterator iterator, void *iterator_cls) { (void) node_iterator (heap, heap->root, iterator, iterator_cls); } /** * Perform a random walk of the tree. The walk is biased * towards elements closer to the root of the tree (since * each walk starts at the root and ends at a random leaf). * The heap internally tracks the current position of the * walk. * * @param heap heap to walk * @return data stored at the next random node in the walk; * NULL if the tree is empty. */ void * GNUNET_CONTAINER_heap_walk_get_next (struct GNUNET_CONTAINER_Heap *heap) { struct GNUNET_CONTAINER_HeapNode *pos; void *element; if (heap->root == NULL) return NULL; pos = heap->walk_pos; if (pos == NULL) pos = heap->root; element = pos->element; heap->walk_pos = (0 == GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 2)) ? pos->right_child : pos->left_child; return element; } /** * Insert the given node 'node' into the subtree starting * at 'pos' (while keeping the tree somewhat balanced). * * @param heap heap to modify * @param pos existing tree * @param node node to insert (which may be a subtree itself) */ static void insert_node (struct GNUNET_CONTAINER_Heap *heap, struct GNUNET_CONTAINER_HeapNode *pos, struct GNUNET_CONTAINER_HeapNode *node) { struct GNUNET_CONTAINER_HeapNode *parent; GNUNET_assert (node->parent == NULL); while ((heap->order == GNUNET_CONTAINER_HEAP_ORDER_MAX) ? (pos->cost >= node->cost) : (pos->cost <= node->cost)) { /* node is descendent of pos */ pos->tree_size += (1 + node->tree_size); if (pos->left_child == NULL) { pos->left_child = node; node->parent = pos; return; } if (pos->right_child == NULL) { pos->right_child = node; node->parent = pos; return; } /* keep it balanced by descending into smaller subtree */ if (pos->left_child->tree_size < pos->right_child->tree_size) pos = pos->left_child; else pos = pos->right_child; } /* make 'node' parent of 'pos' */ parent = pos->parent; pos->parent = NULL; node->parent = parent; if (NULL == parent) { heap->root = node; } else { if (parent->left_child == pos) parent->left_child = node; else parent->right_child = node; } /* insert 'pos' below 'node' */ insert_node (heap, node, pos); CHECK (pos); } /** * Inserts a new element into the heap. * * @param heap heap to modify * @param element element to insert * @param cost cost for the element * @return node for the new element */ struct GNUNET_CONTAINER_HeapNode * GNUNET_CONTAINER_heap_insert (struct GNUNET_CONTAINER_Heap *heap, void *element, GNUNET_CONTAINER_HeapCostType cost) { struct GNUNET_CONTAINER_HeapNode *node; node = GNUNET_new (struct GNUNET_CONTAINER_HeapNode); node->heap = heap; node->element = element; node->cost = cost; heap->size++; if (NULL == heap->root) heap->root = node; else insert_node (heap, heap->root, node); GNUNET_assert (heap->size == heap->root->tree_size + 1); CHECK (heap->root); return node; } /** * Remove root of the heap. * * @param heap heap to modify * @return element data stored at the root node, NULL if heap is empty */ void * GNUNET_CONTAINER_heap_remove_root (struct GNUNET_CONTAINER_Heap *heap) { void *ret; struct GNUNET_CONTAINER_HeapNode *root; if (NULL == (root = heap->root)) return NULL; heap->size--; ret = root->element; if (root->left_child == NULL) { heap->root = root->right_child; if (root->right_child != NULL) root->right_child->parent = NULL; } else if (root->right_child == NULL) { heap->root = root->left_child; root->left_child->parent = NULL; } else { root->left_child->parent = NULL; root->right_child->parent = NULL; heap->root = root->left_child; insert_node (heap, heap->root, root->right_child); } if (heap->walk_pos == root) heap->walk_pos = heap->root; GNUNET_free (root); #if EXTRA_CHECKS GNUNET_assert (((heap->size == 0) && (heap->root == NULL)) || (heap->size == heap->root->tree_size + 1)); CHECK (heap->root); #endif return ret; } /** * Remove the given node 'node' from the tree and update * the 'tree_size' fields accordingly. Preserves the * children of 'node' and does NOT change the overall * 'size' field of the tree. */ static void remove_node (struct GNUNET_CONTAINER_HeapNode *node) { struct GNUNET_CONTAINER_HeapNode *ancestor; struct GNUNET_CONTAINER_Heap *heap = node->heap; /* update 'size' of the ancestors */ ancestor = node; while (NULL != (ancestor = ancestor->parent)) ancestor->tree_size--; /* update 'size' of node itself */ if (node->left_child != NULL) node->tree_size -= (1 + node->left_child->tree_size); if (node->right_child != NULL) node->tree_size -= (1 + node->right_child->tree_size); /* unlink 'node' itself and insert children in its place */ if (node->parent == NULL) { if (node->left_child != NULL) { heap->root = node->left_child; node->left_child->parent = NULL; if (node->right_child != NULL) { node->right_child->parent = NULL; insert_node (heap, heap->root, node->right_child); } } else { heap->root = node->right_child; if (node->right_child != NULL) node->right_child->parent = NULL; } } else { if (node->parent->left_child == node) node->parent->left_child = NULL; else node->parent->right_child = NULL; if (node->left_child != NULL) { node->left_child->parent = NULL; node->parent->tree_size -= (1 + node->left_child->tree_size); insert_node (heap, node->parent, node->left_child); } if (node->right_child != NULL) { node->right_child->parent = NULL; node->parent->tree_size -= (1 + node->right_child->tree_size); insert_node (heap, node->parent, node->right_child); } } node->parent = NULL; node->left_child = NULL; node->right_child = NULL; GNUNET_assert (node->tree_size == 0); CHECK (heap->root); } /** * Removes a node from the heap. * * @param node node to remove * @return element data stored at the node */ void * GNUNET_CONTAINER_heap_remove_node (struct GNUNET_CONTAINER_HeapNode *node) { void *ret; struct GNUNET_CONTAINER_Heap *heap; heap = node->heap; CHECK (heap->root); if (heap->walk_pos == node) (void) GNUNET_CONTAINER_heap_walk_get_next (heap); remove_node (node); heap->size--; ret = node->element; if (heap->walk_pos == node) heap->walk_pos = NULL; GNUNET_free (node); #if EXTRA_CHECKS CHECK (heap->root); GNUNET_assert (((heap->size == 0) && (heap->root == NULL)) || (heap->size == heap->root->tree_size + 1)); #endif return ret; } /** * Updates the cost of any node in the tree * * @param node node for which the cost is to be changed * @param new_cost new cost for the node */ void GNUNET_CONTAINER_heap_update_cost (struct GNUNET_CONTAINER_HeapNode *node, GNUNET_CONTAINER_HeapCostType new_cost) { struct GNUNET_CONTAINER_Heap *heap = node->heap; remove_node (node); node->cost = new_cost; if (NULL == heap->root) heap->root = node; else insert_node (heap, heap->root, node); } /* end of heap.c */