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Diffstat (limited to 'include/apr_skiplist.h')
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diff --git a/include/apr_skiplist.h b/include/apr_skiplist.h new file mode 100644 index 0000000..eeab10b --- /dev/null +++ b/include/apr_skiplist.h @@ -0,0 +1,381 @@ +/* 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 */ |