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