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Diffstat (limited to 'src/util/container_heap.c')
| -rw-r--r-- | src/util/container_heap.c | 550 |
1 files changed, 550 insertions, 0 deletions
diff --git a/src/util/container_heap.c b/src/util/container_heap.c new file mode 100644 index 0000000..c34e220 --- /dev/null +++ b/src/util/container_heap.c @@ -0,0 +1,550 @@ +/* + This file is part of GNUnet. + (C) 2008, 2009 Christian Grothoff (and other contributing authors) + + GNUnet 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; either version 2, 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 + General Public License for more details. + + You should have received a copy of the GNU General Public License + along with GNUnet; see the file COPYING. If not, write to the + Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. +*/ + +/** + * @file util/container_heap.c + * @brief Implementation of a heap + * @author Nathan Evans + * @author Christian Grothoff + */ + +#include "platform.h" +#include "gnunet_util_lib.h" + +#define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__) + +#define DEBUG 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 DEBUG +/** + * 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_malloc (sizeof (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 root of heap. + * + * @param heap heap to inspect + * @return 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 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_malloc (sizeof (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); + } + GNUNET_free (root); +#if DEBUG + 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 DEBUG + 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 heap heap to modify + * @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_Heap *heap, + struct GNUNET_CONTAINER_HeapNode *node, + GNUNET_CONTAINER_HeapCostType new_cost) +{ +#if DEBUG + GNUNET_assert (((heap->size == 0) && (heap->root == NULL)) || + (heap->size == heap->root->tree_size + 1)); + CHECK (heap->root); +#endif + remove_node (node); +#if DEBUG + CHECK (heap->root); + GNUNET_assert (((heap->size == 1) && (heap->root == NULL)) || + (heap->size == heap->root->tree_size + 2)); +#endif + node->cost = new_cost; + if (heap->root == NULL) + heap->root = node; + else + insert_node (heap, heap->root, node); +#if DEBUG + CHECK (heap->root); + GNUNET_assert (((heap->size == 0) && (heap->root == NULL)) || + (heap->size == heap->root->tree_size + 1)); +#endif +} + + +/* end of heap.c */ |