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apr_skiplist.h
/* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef APR_SKIPLIST_H #define APR_SKIPLIST_H /** * @file apr_skiplist.h * @brief APR skip list implementation */ #include "apr.h" #include "apr_portable.h" #include <stdlib.h> #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ /** * @defgroup apr_skiplist Skip list implementation * Refer to http://en.wikipedia.org/wiki/Skip_list for information * about the purpose of and ideas behind skip lists. * @ingroup APR * @{ */ /** * apr_skiplist_compare is the function type that must be implemented * per object type that is used in a skip list for comparisons to maintain * order * */ typedef int (*apr_skiplist_compare) (void *, void *); /** * apr_skiplist_freefunc is the function type that must be implemented * to handle elements as they are removed from a skip list. */ typedef void (*apr_skiplist_freefunc) (void *); /** Opaque structure used to represent the skip list */ struct apr_skiplist; /** Opaque structure used to represent the skip list */ typedef struct apr_skiplist apr_skiplist; /** * Opaque structure used to represent abstract nodes in the skip list * (an abstraction above the raw elements which are collected in the * skip list). */ struct apr_skiplistnode; /** Opaque structure */ typedef struct apr_skiplistnode apr_skiplistnode; /** * Allocate memory using the same mechanism as the skip list. * @param sl The skip list * @param size The amount to allocate * @remark If a pool was provided to apr_skiplist_init(), memory will * be allocated from the pool or from a free list maintained with * the skip list. Otherwise, memory will be allocated using the * C standard library heap functions. */ APR_DECLARE(void *) apr_skiplist_alloc(apr_skiplist *sl, size_t size); /** * Free memory using the same mechanism as the skip list. * @param sl The skip list * @param mem The object to free * @remark If a pool was provided to apr_skiplist_init(), memory will * be added to a free list maintained with the skip list and be available * to operations on the skip list or to other calls to apr_skiplist_alloc(). * Otherwise, memory will be freed using the C standard library heap * functions. */ APR_DECLARE(void) apr_skiplist_free(apr_skiplist *sl, void *mem); /** * Allocate a new skip list * @param sl The pointer in which to return the newly created skip list * @param p The pool from which to allocate the skip list (optional). * @remark Unlike most APR functions, a pool is optional. If no pool * is provided, the C standard library heap functions will be used instead. */ APR_DECLARE(apr_status_t) apr_skiplist_init(apr_skiplist **sl, apr_pool_t *p); /** * Set the comparison functions to be used for searching the skip list. * @param sl The skip list * @param XXX1 FIXME * @param XXX2 FIXME * * @remark If existing comparison functions are being replaced, the index * will be replaced during this call. That is a potentially expensive * operation. */ APR_DECLARE(void) apr_skiplist_set_compare(apr_skiplist *sl, apr_skiplist_compare XXX1, apr_skiplist_compare XXX2); /** * Set the indexing functions to the specified comparison functions and * rebuild the index. * @param sl The skip list * @param XXX1 FIXME * @param XXX2 FIXME * * @remark If an index already exists, it will not be replaced and the * comparison functions will not be changed. */ APR_DECLARE(void) apr_skiplist_add_index(apr_skiplist *sl, apr_skiplist_compare XXX1, apr_skiplist_compare XXX2); /** * Return the list maintained by the skip list abstraction. * @param sl The skip list */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_getlist(apr_skiplist *sl); /** * Return the next matching element in the skip list using the specified * comparison function. * @param sl The skip list * @param data The value to search for * @param iter A pointer to the returned skip list node representing the element * found * @param func The comparison function to use */ APR_DECLARE(void *) apr_skiplist_find_compare(apr_skiplist *sl, void *data, apr_skiplistnode **iter, apr_skiplist_compare func); /** * Return the next matching element in the skip list using the current comparison * function. * @param sl The skip list * @param data The value to search for * @param iter A pointer to the returned skip list node representing the element * found */ APR_DECLARE(void *) apr_skiplist_find(apr_skiplist *sl, void *data, apr_skiplistnode **iter); /** * Return the last matching element in the skip list using the specified * comparison function. * @param sl The skip list * @param data The value to search for * @param iter A pointer to the returned skip list node representing the element * found * @param comp The comparison function to use */ APR_DECLARE(void *) apr_skiplist_last_compare(apr_skiplist *sl, void *data, apr_skiplistnode **iter, apr_skiplist_compare comp); /** * Return the last matching element in the skip list using the current comparison * function. * @param sl The skip list * @param data The value to search for * @param iter A pointer to the returned skip list node representing the element * found */ APR_DECLARE(void *) apr_skiplist_last(apr_skiplist *sl, void *data, apr_skiplistnode **iter); /** * Return the next element in the skip list. * @param sl The skip list * @param iter On entry, a pointer to the skip list node to start with; on return, * a pointer to the skip list node representing the element returned * @remark If iter points to a NULL value on entry, NULL will be returned. */ APR_DECLARE(void *) apr_skiplist_next(apr_skiplist *sl, apr_skiplistnode **iter); /** * Return the previous element in the skip list. * @param sl The skip list * @param iter On entry, a pointer to the skip list node to start with; on return, * a pointer to the skip list node representing the element returned * @remark If iter points to a NULL value on entry, NULL will be returned. */ APR_DECLARE(void *) apr_skiplist_previous(apr_skiplist *sl, apr_skiplistnode **iter); /** * Return the element of the skip list node * @param iter The skip list node */ APR_DECLARE(void *) apr_skiplist_element(apr_skiplistnode *iter); /** * Insert an element into the skip list using the specified comparison function * if it does not already exist. * @param sl The skip list * @param data The element to insert * @param comp The comparison function to use for placement into the skip list */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_insert_compare(apr_skiplist *sl, void *data, apr_skiplist_compare comp); /** * Insert an element into the skip list using the existing comparison function * if it does not already exist. * @param sl The skip list * @param data The element to insert * @remark If no comparison function has been set for the skip list, the element * will not be inserted and NULL will be returned. */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_insert(apr_skiplist* sl, void *data); /** * Add an element into the skip list using the specified comparison function * allowing for duplicates. * @param sl The skip list * @param data The element to add * @param comp The comparison function to use for placement into the skip list */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_add_compare(apr_skiplist *sl, void *data, apr_skiplist_compare comp); /** * Add an element into the skip list using the existing comparison function * allowing for duplicates. * @param sl The skip list * @param data The element to insert * @remark If no comparison function has been set for the skip list, the element * will not be inserted and NULL will be returned. */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_add(apr_skiplist* sl, void *data); /** * Add an element into the skip list using the specified comparison function * removing the existing duplicates. * @param sl The skip list * @param data The element to insert * @param comp The comparison function to use for placement into the skip list * @param myfree A function to be called for each removed duplicate * @remark If no comparison function has been set for the skip list, the element * will not be inserted, none will be replaced, and NULL will be returned. */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_replace_compare(apr_skiplist *sl, void *data, apr_skiplist_freefunc myfree, apr_skiplist_compare comp); /** * Add an element into the skip list using the existing comparison function * removing the existing duplicates. * @param sl The skip list * @param data The element to insert * @param myfree A function to be called for each removed duplicate * @remark If no comparison function has been set for the skip list, the element * will not be inserted, none will be replaced, and NULL will be returned. */ APR_DECLARE(apr_skiplistnode *) apr_skiplist_replace(apr_skiplist *sl, void *data, apr_skiplist_freefunc myfree); /** * Remove a node from the skip list. * @param sl The skip list * @param iter The skip list node to remove * @param myfree A function to be called for the removed element */ APR_DECLARE(int) apr_skiplist_remove_node(apr_skiplist *sl, apr_skiplistnode *iter, apr_skiplist_freefunc myfree); /** * Remove an element from the skip list using the specified comparison function for * locating the element. In the case of duplicates, the 1st entry will be removed. * @param sl The skip list * @param data The element to remove * @param myfree A function to be called for each removed element * @param comp The comparison function to use for placement into the skip list * @remark If the element is not found, 0 will be returned. Otherwise, the heightXXX * will be returned. */ APR_DECLARE(int) apr_skiplist_remove_compare(apr_skiplist *sl, void *data, apr_skiplist_freefunc myfree, apr_skiplist_compare comp); /** * Remove an element from the skip list using the existing comparison function for * locating the element. In the case of duplicates, the 1st entry will be removed. * @param sl The skip list * @param data The element to remove * @param myfree A function to be called for each removed element * @remark If the element is not found, 0 will be returned. Otherwise, the heightXXX * will be returned. * @remark If no comparison function has been set for the skip list, the element * will not be removed and 0 will be returned. */ APR_DECLARE(int) apr_skiplist_remove(apr_skiplist *sl, void *data, apr_skiplist_freefunc myfree); /** * Remove all elements from the skip list. * @param sl The skip list * @param myfree A function to be called for each removed element */ APR_DECLARE(void) apr_skiplist_remove_all(apr_skiplist *sl, apr_skiplist_freefunc myfree); /** * Remove each element from the skip list. * @param sl The skip list * @param myfree A function to be called for each removed element */ APR_DECLARE(void) apr_skiplist_destroy(apr_skiplist *sl, apr_skiplist_freefunc myfree); /** * Return the first element in the skip list, removing the element from the skip list. * @param sl The skip list * @param myfree A function to be called for the removed element * @remark NULL will be returned if there are no elements */ APR_DECLARE(void *) apr_skiplist_pop(apr_skiplist *sl, apr_skiplist_freefunc myfree); /** * Return the first element in the skip list, leaving the element in the skip list. * @param sl The skip list * @remark NULL will be returned if there are no elements */ APR_DECLARE(void *) apr_skiplist_peek(apr_skiplist *sl); /** * Return the size of the list (number of elements), in O(1). * @param sl The skip list */ APR_DECLARE(size_t) apr_skiplist_size(const apr_skiplist *sl); /** * Return the height of the list (number of skip paths), in O(1). * @param sl The skip list */ APR_DECLARE(int) apr_skiplist_height(const apr_skiplist *sl); /** * Return the predefined maximum height of the skip list. * @param sl The skip list */ APR_DECLARE(int) apr_skiplist_preheight(const apr_skiplist *sl); /** * Set a predefined maximum height for the skip list. * @param sl The skip list * @param to The preheight to set, or a nul/negative value to disable. * @remark When a preheight is used, the height of each inserted element is * computed randomly up to this preheight instead of the current skip list's * height plus one used by the default implementation. Using a preheight can * probably ensure more fairness with long living elements (since with an * adaptative height, former elements may have been created with a low height, * hence a longest path to reach them while the skip list grows). On the other * hand, the default behaviour (preheight <= 0) with a growing and decreasing * maximum height is more adaptative/suitable for short living values. * @note Should be called before any insertion/add. */ APR_DECLARE(void) apr_skiplist_set_preheight(apr_skiplist *sl, int to); /** * Merge two skip lists. XXX SEMANTICS * @param sl1 One of two skip lists to be merged * @param sl2 The other of two skip lists to be merged */ APR_DECLARE(apr_skiplist *) apr_skiplist_merge(apr_skiplist *sl1, apr_skiplist *sl2); /** @} */ #ifdef __cplusplus } #endif #endif /* ! APR_SKIPLIST_H */
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