Index: kernel/generic/src/adt/btree.c =================================================================== --- kernel/generic/src/adt/btree.c (revision aafed151536405cdb1390b88b7e4ac7c285dd53e) +++ (revision ) @@ -1,1070 +1,0 @@ -/* - * Copyright (c) 2006 Jakub Jermar - * All rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * - * - Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. - * - Redistributions in binary form must reproduce the above copyright - * notice, this list of conditions and the following disclaimer in the - * documentation and/or other materials provided with the distribution. - * - The name of the author may not be used to endorse or promote products - * derived from this software without specific prior written permission. - * - * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR - * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES - * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. - * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, - * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT - * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, - * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY - * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT - * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF - * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. - */ - -/** @addtogroup kernel_generic_adt - * @{ - */ - -/** - * @file - * @brief B+tree implementation. - * - * This file implements B+tree type and operations. - * - * The B+tree has the following properties: - * @li it is a balanced 3-4-5 tree (i.e. BTREE_M = 5) - * @li values (i.e. pointers to values) are stored only in leaves - * @li leaves are linked in a list - * - * Be careful when using these trees. They need to allocate - * and deallocate memory for their index nodes and as such - * can sleep. - */ - -#include -#include -#include -#include -#include -#include -#include - -static slab_cache_t *btree_node_cache; - -#define ROOT_NODE(n) (!(n)->parent) -#define INDEX_NODE(n) ((n)->subtree[0] != NULL) -#define LEAF_NODE(n) ((n)->subtree[0] == NULL) - -#define FILL_FACTOR ((BTREE_M - 1) / 2) - -#define MEDIAN_LOW_INDEX(n) (((n)->keys-1) / 2) -#define MEDIAN_HIGH_INDEX(n) ((n)->keys / 2) -#define MEDIAN_LOW(n) ((n)->key[MEDIAN_LOW_INDEX((n))]); -#define MEDIAN_HIGH(n) ((n)->key[MEDIAN_HIGH_INDEX((n))]); - -/** Initialize B-trees. */ -void btree_init(void) -{ - btree_node_cache = slab_cache_create("btree_node_t", - sizeof(btree_node_t), 0, NULL, NULL, SLAB_CACHE_MAGDEFERRED); -} - -/** Initialize B-tree node. - * - * @param node B-tree node. - * - */ -NO_TRACE static void node_initialize(btree_node_t *node) -{ - unsigned int i; - - node->keys = 0; - - /* Clean also space for the extra key. */ - for (i = 0; i < BTREE_MAX_KEYS + 1; i++) { - node->key[i] = 0; - node->value[i] = NULL; - node->subtree[i] = NULL; - } - - node->subtree[i] = NULL; - node->parent = NULL; - - link_initialize(&node->leaf_link); - link_initialize(&node->bfs_link); - node->depth = 0; -} - -/** Create empty B-tree. - * - * @param t B-tree. - * - */ -void btree_create(btree_t *t) -{ - list_initialize(&t->leaf_list); - t->root = (btree_node_t *) slab_alloc(btree_node_cache, 0); - node_initialize(t->root); - list_append(&t->root->leaf_link, &t->leaf_list); -} - -/** Destroy subtree rooted in a node. - * - * @param root Root of the subtree. - * - */ -NO_TRACE static void btree_destroy_subtree(btree_node_t *root) -{ - size_t i; - - if (root->keys) { - for (i = 0; i < root->keys + 1; i++) { - if (root->subtree[i]) - btree_destroy_subtree(root->subtree[i]); - } - } - - slab_free(btree_node_cache, root); -} - -/** Destroy empty B-tree. */ -void btree_destroy(btree_t *t) -{ - btree_destroy_subtree(t->root); -} - -/** Insert key-value-rsubtree triplet into B-tree node. - * - * It is actually possible to have more keys than BTREE_MAX_KEYS. - * This feature is used during splitting the node when the - * number of keys is BTREE_MAX_KEYS + 1. Insert by left rotation - * also makes use of this feature. - * - * @param node B-tree node into which the new key is to be inserted. - * @param key The key to be inserted. - * @param value Pointer to value to be inserted. - * @param rsubtree Pointer to the right subtree. - * - */ -NO_TRACE static void node_insert_key_and_rsubtree(btree_node_t *node, - btree_key_t key, void *value, btree_node_t *rsubtree) -{ - size_t i; - - for (i = 0; i < node->keys; i++) { - if (key < node->key[i]) { - size_t j; - - for (j = node->keys; j > i; j--) { - node->key[j] = node->key[j - 1]; - node->value[j] = node->value[j - 1]; - node->subtree[j + 1] = node->subtree[j]; - } - - break; - } - } - - node->key[i] = key; - node->value[i] = value; - node->subtree[i + 1] = rsubtree; - node->keys++; -} - -/** Find key by its left or right subtree. - * - * @param node B-tree node. - * @param subtree Left or right subtree of a key found in node. - * @param right If true, subtree is a right subtree. If false, - * subtree is a left subtree. - * - * @return Index of the key associated with the subtree. - * - */ -NO_TRACE static size_t find_key_by_subtree(btree_node_t *node, - btree_node_t *subtree, bool right) -{ - size_t i; - - for (i = 0; i < node->keys + 1; i++) { - if (subtree == node->subtree[i]) - return i - (int) (right != false); - } - - panic("Node %p does not contain subtree %p.", node, subtree); -} - -/** Remove key and its left subtree pointer from B-tree node. - * - * Remove the key and eliminate gaps in node->key array. - * Note that the value pointer and the left subtree pointer - * is removed from the node as well. - * - * @param node B-tree node. - * @param key Key to be removed. - * - */ -NO_TRACE static void node_remove_key_and_lsubtree(btree_node_t *node, - btree_key_t key) -{ - size_t i; - size_t j; - - for (i = 0; i < node->keys; i++) { - if (key == node->key[i]) { - for (j = i + 1; j < node->keys; j++) { - node->key[j - 1] = node->key[j]; - node->value[j - 1] = node->value[j]; - node->subtree[j - 1] = node->subtree[j]; - } - - node->subtree[j - 1] = node->subtree[j]; - node->keys--; - - return; - } - } - - panic("Node %p does not contain key %" PRIu64 ".", node, key); -} - -/** Remove key and its right subtree pointer from B-tree node. - * - * Remove the key and eliminate gaps in node->key array. - * Note that the value pointer and the right subtree pointer - * is removed from the node as well. - * - * @param node B-tree node. - * @param key Key to be removed. - * - */ -NO_TRACE static void node_remove_key_and_rsubtree(btree_node_t *node, - btree_key_t key) -{ - size_t i, j; - - for (i = 0; i < node->keys; i++) { - if (key == node->key[i]) { - for (j = i + 1; j < node->keys; j++) { - node->key[j - 1] = node->key[j]; - node->value[j - 1] = node->value[j]; - node->subtree[j] = node->subtree[j + 1]; - } - - node->keys--; - return; - } - } - - panic("Node %p does not contain key %" PRIu64 ".", node, key); -} - -/** Insert key-value-lsubtree triplet into B-tree node. - * - * It is actually possible to have more keys than BTREE_MAX_KEYS. - * This feature is used during insert by right rotation. - * - * @param node B-tree node into which the new key is to be inserted. - * @param key The key to be inserted. - * @param value Pointer to value to be inserted. - * @param lsubtree Pointer to the left subtree. - * - */ -NO_TRACE static void node_insert_key_and_lsubtree(btree_node_t *node, - btree_key_t key, void *value, btree_node_t *lsubtree) -{ - size_t i; - - for (i = 0; i < node->keys; i++) { - if (key < node->key[i]) { - size_t j; - - for (j = node->keys; j > i; j--) { - node->key[j] = node->key[j - 1]; - node->value[j] = node->value[j - 1]; - node->subtree[j + 1] = node->subtree[j]; - } - - node->subtree[j + 1] = node->subtree[j]; - break; - } - } - - node->key[i] = key; - node->value[i] = value; - node->subtree[i] = lsubtree; - - node->keys++; -} - -/** Rotate one key-value-rsubtree triplet from the left sibling to the right sibling. - * - * The biggest key and its value and right subtree is rotated - * from the left node to the right. If the node is an index node, - * than the parent node key belonging to the left node takes part - * in the rotation. - * - * @param lnode Left sibling. - * @param rnode Right sibling. - * @param idx Index of the parent node key that is taking part - * in the rotation. - * - */ -NO_TRACE static void rotate_from_left(btree_node_t *lnode, btree_node_t *rnode, - size_t idx) -{ - btree_key_t key = lnode->key[lnode->keys - 1]; - - if (LEAF_NODE(lnode)) { - void *value = lnode->value[lnode->keys - 1]; - - node_remove_key_and_rsubtree(lnode, key); - node_insert_key_and_lsubtree(rnode, key, value, NULL); - lnode->parent->key[idx] = key; - } else { - btree_node_t *rsubtree = lnode->subtree[lnode->keys]; - - node_remove_key_and_rsubtree(lnode, key); - node_insert_key_and_lsubtree(rnode, lnode->parent->key[idx], NULL, rsubtree); - lnode->parent->key[idx] = key; - - /* Fix parent link of the reconnected right subtree. */ - rsubtree->parent = rnode; - } -} - -/** Rotate one key-value-lsubtree triplet from the right sibling to the left sibling. - * - * The smallest key and its value and left subtree is rotated - * from the right node to the left. If the node is an index node, - * than the parent node key belonging to the right node takes part - * in the rotation. - * - * @param lnode Left sibling. - * @param rnode Right sibling. - * @param idx Index of the parent node key that is taking part - * in the rotation. - * - */ -NO_TRACE static void rotate_from_right(btree_node_t *lnode, btree_node_t *rnode, - size_t idx) -{ - btree_key_t key = rnode->key[0]; - - if (LEAF_NODE(rnode)) { - void *value = rnode->value[0]; - - node_remove_key_and_lsubtree(rnode, key); - node_insert_key_and_rsubtree(lnode, key, value, NULL); - rnode->parent->key[idx] = rnode->key[0]; - } else { - btree_node_t *lsubtree = rnode->subtree[0]; - - node_remove_key_and_lsubtree(rnode, key); - node_insert_key_and_rsubtree(lnode, rnode->parent->key[idx], NULL, lsubtree); - rnode->parent->key[idx] = key; - - /* Fix parent link of the reconnected left subtree. */ - lsubtree->parent = lnode; - } -} - -/** Insert key-value-rsubtree triplet and rotate the node to the left, if this operation can be done. - * - * Left sibling of the node (if it exists) is checked for free space. - * If there is free space, the key is inserted and the smallest key of - * the node is moved there. The index node which is the parent of both - * nodes is fixed. - * - * @param node B-tree node. - * @param inskey Key to be inserted. - * @param insvalue Value to be inserted. - * @param rsubtree Right subtree of inskey. - * - * @return True if the rotation was performed, false otherwise. - * - */ -NO_TRACE static bool try_insert_by_rotation_to_left(btree_node_t *node, - btree_key_t inskey, void *insvalue, btree_node_t *rsubtree) -{ - size_t idx; - btree_node_t *lnode; - - /* - * If this is root node, the rotation can not be done. - */ - if (ROOT_NODE(node)) - return false; - - idx = find_key_by_subtree(node->parent, node, true); - if ((int) idx == -1) { - /* - * If this node is the leftmost subtree of its parent, - * the rotation can not be done. - */ - return false; - } - - lnode = node->parent->subtree[idx]; - if (lnode->keys < BTREE_MAX_KEYS) { - /* - * The rotaion can be done. The left sibling has free space. - */ - node_insert_key_and_rsubtree(node, inskey, insvalue, rsubtree); - rotate_from_right(lnode, node, idx); - return true; - } - - return false; -} - -/** Insert key-value-rsubtree triplet and rotate the node to the right, if this operation can be done. - * - * Right sibling of the node (if it exists) is checked for free space. - * If there is free space, the key is inserted and the biggest key of - * the node is moved there. The index node which is the parent of both - * nodes is fixed. - * - * @param node B-tree node. - * @param inskey Key to be inserted. - * @param insvalue Value to be inserted. - * @param rsubtree Right subtree of inskey. - * - * @return True if the rotation was performed, false otherwise. - * - */ -NO_TRACE static bool try_insert_by_rotation_to_right(btree_node_t *node, - btree_key_t inskey, void *insvalue, btree_node_t *rsubtree) -{ - size_t idx; - btree_node_t *rnode; - - /* - * If this is root node, the rotation can not be done. - */ - if (ROOT_NODE(node)) - return false; - - idx = find_key_by_subtree(node->parent, node, false); - if (idx == node->parent->keys) { - /* - * If this node is the rightmost subtree of its parent, - * the rotation can not be done. - */ - return false; - } - - rnode = node->parent->subtree[idx + 1]; - if (rnode->keys < BTREE_MAX_KEYS) { - /* - * The rotation can be done. The right sibling has free space. - */ - node_insert_key_and_rsubtree(node, inskey, insvalue, rsubtree); - rotate_from_left(node, rnode, idx); - return true; - } - - return false; -} - -/** Split full B-tree node and insert new key-value-right-subtree triplet. - * - * This function will split a node and return a pointer to a newly created - * node containing keys greater than or equal to the greater of medians - * (or median) of the old keys and the newly added key. It will also write - * the median key to a memory address supplied by the caller. - * - * If the node being split is an index node, the median will not be - * included in the new node. If the node is a leaf node, - * the median will be copied there. - * - * @param node B-tree node which is going to be split. - * @param key The key to be inserted. - * @param value Pointer to the value to be inserted. - * @param rsubtree Pointer to the right subtree of the key being added. - * @param median Address in memory, where the median key will be stored. - * - * @return Newly created right sibling of node. - * - */ -NO_TRACE static btree_node_t *node_split(btree_node_t *node, btree_key_t key, - void *value, btree_node_t *rsubtree, btree_key_t *median) -{ - btree_node_t *rnode; - size_t i; - size_t j; - - assert(median); - assert(node->keys == BTREE_MAX_KEYS); - - /* - * Use the extra space to store the extra node. - */ - node_insert_key_and_rsubtree(node, key, value, rsubtree); - - /* - * Compute median of keys. - */ - *median = MEDIAN_HIGH(node); - - /* - * Allocate and initialize new right sibling. - */ - rnode = (btree_node_t *) slab_alloc(btree_node_cache, 0); - node_initialize(rnode); - rnode->parent = node->parent; - rnode->depth = node->depth; - - /* - * Copy big keys, values and subtree pointers to the new right sibling. - * If this is an index node, do not copy the median. - */ - i = (size_t) INDEX_NODE(node); - for (i += MEDIAN_HIGH_INDEX(node), j = 0; i < node->keys; i++, j++) { - rnode->key[j] = node->key[i]; - rnode->value[j] = node->value[i]; - rnode->subtree[j] = node->subtree[i]; - - /* - * Fix parent links in subtrees. - */ - if (rnode->subtree[j]) - rnode->subtree[j]->parent = rnode; - } - - rnode->subtree[j] = node->subtree[i]; - if (rnode->subtree[j]) - rnode->subtree[j]->parent = rnode; - - rnode->keys = j; /* Set number of keys of the new node. */ - node->keys /= 2; /* Shrink the old node. */ - - return rnode; -} - -/** Recursively insert into B-tree. - * - * @param t B-tree. - * @param key Key to be inserted. - * @param value Value to be inserted. - * @param rsubtree Right subtree of the inserted key. - * @param node Start inserting into this node. - * - */ -NO_TRACE static void _btree_insert(btree_t *t, btree_key_t key, void *value, - btree_node_t *rsubtree, btree_node_t *node) -{ - if (node->keys < BTREE_MAX_KEYS) { - /* - * Node contains enough space, the key can be stored immediately. - */ - node_insert_key_and_rsubtree(node, key, value, rsubtree); - } else if (try_insert_by_rotation_to_left(node, key, value, rsubtree)) { - /* - * The key-value-rsubtree triplet has been inserted because - * some keys could have been moved to the left sibling. - */ - } else if (try_insert_by_rotation_to_right(node, key, value, rsubtree)) { - /* - * The key-value-rsubtree triplet has been inserted because - * some keys could have been moved to the right sibling. - */ - } else { - btree_node_t *rnode; - btree_key_t median; - - /* - * Node is full and both siblings (if both exist) are full too. - * Split the node and insert the smallest key from the node containing - * bigger keys (i.e. the new node) into its parent. - */ - - rnode = node_split(node, key, value, rsubtree, &median); - - if (LEAF_NODE(node)) { - list_insert_after(&rnode->leaf_link, &node->leaf_link); - } - - if (ROOT_NODE(node)) { - /* - * We split the root node. Create new root. - */ - t->root = (btree_node_t *) slab_alloc(btree_node_cache, 0); - node->parent = t->root; - rnode->parent = t->root; - node_initialize(t->root); - - /* - * Left-hand side subtree will be the old root (i.e. node). - * Right-hand side subtree will be rnode. - */ - t->root->subtree[0] = node; - - t->root->depth = node->depth + 1; - } - _btree_insert(t, median, NULL, rnode, node->parent); - } -} - -/** Insert key-value pair into B-tree. - * - * @param t B-tree. - * @param key Key to be inserted. - * @param value Value to be inserted. - * @param leaf_node Leaf node where the insertion should begin. - * - */ -void btree_insert(btree_t *t, btree_key_t key, void *value, - btree_node_t *leaf_node) -{ - btree_node_t *lnode; - - assert(value); - - lnode = leaf_node; - if (!lnode) { - if (btree_search(t, key, &lnode)) - panic("B-tree %p already contains key %" PRIu64 ".", t, key); - } - - _btree_insert(t, key, value, NULL, lnode); -} - -/** Rotate in a key from the left sibling or from the index node, if this operation can be done. - * - * @param rnode Node into which to add key from its left sibling - * or from the index node. - * - * @return True if the rotation was performed, false otherwise. - * - */ -NO_TRACE static bool try_rotation_from_left(btree_node_t *rnode) -{ - size_t idx; - btree_node_t *lnode; - - /* - * If this is root node, the rotation can not be done. - */ - if (ROOT_NODE(rnode)) - return false; - - idx = find_key_by_subtree(rnode->parent, rnode, true); - if ((int) idx == -1) { - /* - * If this node is the leftmost subtree of its parent, - * the rotation can not be done. - */ - return false; - } - - lnode = rnode->parent->subtree[idx]; - if (lnode->keys > FILL_FACTOR) { - rotate_from_left(lnode, rnode, idx); - return true; - } - - return false; -} - -/** Rotate in a key from the right sibling or from the index node, if this operation can be done. - * - * @param lnode Node into which to add key from its right sibling - * or from the index node. - * - * @return True if the rotation was performed, false otherwise. - * - */ -NO_TRACE static bool try_rotation_from_right(btree_node_t *lnode) -{ - size_t idx; - btree_node_t *rnode; - - /* - * If this is root node, the rotation can not be done. - */ - if (ROOT_NODE(lnode)) - return false; - - idx = find_key_by_subtree(lnode->parent, lnode, false); - if (idx == lnode->parent->keys) { - /* - * If this node is the rightmost subtree of its parent, - * the rotation can not be done. - */ - return false; - } - - rnode = lnode->parent->subtree[idx + 1]; - if (rnode->keys > FILL_FACTOR) { - rotate_from_right(lnode, rnode, idx); - return true; - } - - return false; -} - -/** Combine node with any of its siblings. - * - * The siblings are required to be below the fill factor. - * - * @param node Node to combine with one of its siblings. - * - * @return Pointer to the rightmost of the two nodes. - * - */ -NO_TRACE static btree_node_t *node_combine(btree_node_t *node) -{ - size_t idx; - btree_node_t *rnode; - size_t i; - - assert(!ROOT_NODE(node)); - - idx = find_key_by_subtree(node->parent, node, false); - if (idx == node->parent->keys) { - /* - * Rightmost subtree of its parent, combine with the left sibling. - */ - idx--; - rnode = node; - node = node->parent->subtree[idx]; - } else - rnode = node->parent->subtree[idx + 1]; - - /* Index nodes need to insert parent node key in between left and right node. */ - if (INDEX_NODE(node)) - node->key[node->keys++] = node->parent->key[idx]; - - /* Copy the key-value-subtree triplets from the right node. */ - for (i = 0; i < rnode->keys; i++) { - node->key[node->keys + i] = rnode->key[i]; - node->value[node->keys + i] = rnode->value[i]; - - if (INDEX_NODE(node)) { - node->subtree[node->keys + i] = rnode->subtree[i]; - rnode->subtree[i]->parent = node; - } - } - - if (INDEX_NODE(node)) { - node->subtree[node->keys + i] = rnode->subtree[i]; - rnode->subtree[i]->parent = node; - } - - node->keys += rnode->keys; - return rnode; -} - -/** Recursively remove B-tree node. - * - * @param t B-tree. - * @param key Key to be removed from the B-tree along with its associated value. - * @param node Node where the key being removed resides. - * - */ -NO_TRACE static void _btree_remove(btree_t *t, btree_key_t key, - btree_node_t *node) -{ - if (ROOT_NODE(node)) { - if ((node->keys == 1) && (node->subtree[0])) { - /* - * Free the current root and set new root. - */ - t->root = node->subtree[0]; - t->root->parent = NULL; - slab_free(btree_node_cache, node); - } else { - /* - * Remove the key from the root node. - * Note that the right subtree is removed because when - * combining two nodes, the left-side sibling is preserved - * and the right-side sibling is freed. - */ - node_remove_key_and_rsubtree(node, key); - } - - return; - } - - if (node->keys <= FILL_FACTOR) { - /* - * If the node is below the fill factor, - * try to borrow keys from left or right sibling. - */ - if (!try_rotation_from_left(node)) - try_rotation_from_right(node); - } - - if (node->keys > FILL_FACTOR) { - size_t i; - - /* - * The key can be immediately removed. - * - * Note that the right subtree is removed because when - * combining two nodes, the left-side sibling is preserved - * and the right-side sibling is freed. - */ - node_remove_key_and_rsubtree(node, key); - - for (i = 0; i < node->parent->keys; i++) { - if (node->parent->key[i] == key) - node->parent->key[i] = node->key[0]; - } - } else { - size_t idx; - btree_node_t *rnode; - btree_node_t *parent; - - /* - * The node is below the fill factor as well as its left and right sibling. - * Resort to combining the node with one of its siblings. - * The node which is on the left is preserved and the node on the right is - * freed. - */ - parent = node->parent; - node_remove_key_and_rsubtree(node, key); - rnode = node_combine(node); - - if (LEAF_NODE(rnode)) - list_remove(&rnode->leaf_link); - - idx = find_key_by_subtree(parent, rnode, true); - assert((int) idx != -1); - slab_free(btree_node_cache, rnode); - _btree_remove(t, parent->key[idx], parent); - } -} - -/** Remove B-tree node. - * - * @param t B-tree. - * @param key Key to be removed from the B-tree along - * with its associated value. - * @param leaf_node If not NULL, pointer to the leaf node where - * the key is found. - * - */ -void btree_remove(btree_t *t, btree_key_t key, btree_node_t *leaf_node) -{ - btree_node_t *lnode; - - lnode = leaf_node; - if (!lnode) { - if (!btree_search(t, key, &lnode)) - panic("B-tree %p does not contain key %" PRIu64 ".", t, key); - } - - _btree_remove(t, key, lnode); -} - -/** Search key in a B-tree. - * - * @param t B-tree. - * @param key Key to be searched. - * @param leaf_node Address where to put pointer to visited leaf node. - * - * @return Pointer to value or NULL if there is no such key. - * - */ -void *btree_search(btree_t *t, btree_key_t key, btree_node_t **leaf_node) -{ - btree_node_t *cur, *next; - bool descend; - - /* - * Iteratively descend to the leaf that can contain the searched key. - */ - for (cur = t->root; cur; cur = next) { - /* - * Last iteration will set this with proper - * leaf node address. - */ - *leaf_node = cur; - - if (cur->keys == 0) - return NULL; - - /* - * The key can be in the leftmost subtree. - * Test it separately. - */ - if (key < cur->key[0]) { - next = cur->subtree[0]; - continue; - } else { - void *val; - size_t i; - - /* - * Now if the key is smaller than cur->key[i] - * it can only mean that the value is in cur->subtree[i] - * or it is not in the tree at all. - */ - descend = false; - for (i = 1; i < cur->keys; i++) { - if (key < cur->key[i]) { - next = cur->subtree[i]; - val = cur->value[i - 1]; - - if (LEAF_NODE(cur)) - return key == cur->key[i - 1] ? val : NULL; - - descend = true; - break; - } - } - - if (descend) - continue; - - /* - * Last possibility is that the key is - * in the rightmost subtree. - */ - next = cur->subtree[i]; - val = cur->value[i - 1]; - - if (LEAF_NODE(cur)) - return key == cur->key[i - 1] ? val : NULL; - } - } - - /* - * The key was not found in the *leaf_node and - * is smaller than any of its keys. - */ - return NULL; -} - -/** Return pointer to B-tree leaf node's left neighbour. - * - * @param t B-tree. - * @param node Node whose left neighbour will be returned. - * - * @return Left neighbour of the node or NULL if the node - * does not have the left neighbour. - * - */ -btree_node_t *btree_leaf_node_left_neighbour(btree_t *t, btree_node_t *node) -{ - assert(LEAF_NODE(node)); - - if (node->leaf_link.prev != &t->leaf_list.head) - return list_get_instance(node->leaf_link.prev, btree_node_t, leaf_link); - else - return NULL; -} - -/** Return pointer to B-tree leaf node's right neighbour. - * - * @param t B-tree. - * @param node Node whose right neighbour will be returned. - * - * @return Right neighbour of the node or NULL if the node - * does not have the right neighbour. - * - */ -btree_node_t *btree_leaf_node_right_neighbour(btree_t *t, btree_node_t *node) -{ - assert(LEAF_NODE(node)); - - if (node->leaf_link.next != &t->leaf_list.head) - return list_get_instance(node->leaf_link.next, btree_node_t, leaf_link); - else - return NULL; -} - -/** Print B-tree. - * - * @param t Print out B-tree. - * - */ -void btree_print(btree_t *t) -{ - size_t i; - int depth = t->root->depth; - list_t list; - - printf("Printing B-tree:\n"); - list_initialize(&list); - list_append(&t->root->bfs_link, &list); - - /* - * Use BFS search to print out the tree. - * Levels are distinguished from one another by node->depth. - */ - while (!list_empty(&list)) { - link_t *hlp; - btree_node_t *node; - - hlp = list_first(&list); - assert(hlp != NULL); - node = list_get_instance(hlp, btree_node_t, bfs_link); - list_remove(hlp); - - assert(node); - - if (node->depth != depth) { - printf("\n"); - depth = node->depth; - } - - printf("("); - - for (i = 0; i < node->keys; i++) { - printf("%" PRIu64 "%s", node->key[i], i < node->keys - 1 ? "," : ""); - if (node->depth && node->subtree[i]) { - list_append(&node->subtree[i]->bfs_link, &list); - } - } - - if (node->depth && node->subtree[i]) - list_append(&node->subtree[i]->bfs_link, &list); - - printf(")"); - } - - printf("\n"); - - printf("Printing list of leaves:\n"); - list_foreach(t->leaf_list, leaf_link, btree_node_t, node) { - assert(node); - - printf("("); - - for (i = 0; i < node->keys; i++) - printf("%" PRIu64 "%s", node->key[i], i < node->keys - 1 ? "," : ""); - - printf(")"); - } - - printf("\n"); -} - -/** Return number of B-tree elements. - * - * @param t B-tree to count. - * - * @return Return number of B-tree elements. - * - */ -unsigned long btree_count(btree_t *t) -{ - unsigned long count = 0; - - list_foreach(t->leaf_list, leaf_link, btree_node_t, node) { - count += node->keys; - } - - return count; -} - -/** @} - */