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/* 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 CACHE_PQUEUE_H
#define CACHE_PQUEUE_H
#include <apr.h>
#include <apr_errno.h>
#if APR_HAVE_STDIO_H
#include <stdio.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif
/** the cache priority queue handle */
typedef struct cache_pqueue_t cache_pqueue_t;
/**
* callback function to assign a priority for a element
* @param a the element
* @return the score (the lower the score the longer it is kept int the queue)
*/
typedef long (*cache_pqueue_set_priority)(long queue_clock, void *a);
typedef long (*cache_pqueue_get_priority)(void *a);
/** callback function to get a position of a element */
typedef apr_ssize_t (*cache_pqueue_getpos)(void *a);
/**
* callback function to set a position of a element
* @param a the element
* @param pos the position to set it to
*/
typedef void (*cache_pqueue_setpos)(void *a, apr_ssize_t pos);
/** debug callback function to print a entry */
typedef void (*cache_pqueue_print_entry)(FILE *out, void *a);
/**
* initialize the queue
*
* @param n the initial estimate of the number of queue items for which memory
* should be preallocated
* @param pri the callback function to run to assign a score to a element
* @param get the callback function to get the current element's position
* @param set the callback function to set the current element's position
*
* @Return the handle or NULL for insufficent memory
*/
cache_pqueue_t *cache_pq_init(apr_ssize_t n,
cache_pqueue_get_priority pri,
cache_pqueue_getpos get,
cache_pqueue_setpos set);
/**
* free all memory used by the queue
* @param q the queue
*/
void cache_pq_free(cache_pqueue_t *q);
/**
* return the size of the queue.
* @param q the queue
*/
apr_ssize_t cache_pq_size(cache_pqueue_t *q);
/**
* insert an item into the queue.
* @param q the queue
* @param d the item
* @return APR_SUCCESS on success
*/
apr_status_t cache_pq_insert(cache_pqueue_t *q, void *d);
/*
* move a existing entry to a different priority
* @param q the queue
* @param old the old priority
* @param d the entry
*/
void cache_pq_change_priority(cache_pqueue_t *q,
long old_priority,
long new_priority,
void *d);
/**
* pop the highest-ranking item from the queue.
* @param p the queue
* @param d where to copy the entry to
* @return NULL on error, otherwise the entry
*/
void *cache_pq_pop(cache_pqueue_t *q);
/**
* remove an item from the queue.
* @param p the queue
* @param d the entry
* @return APR_SUCCESS on success
*/
apr_status_t cache_pq_remove(cache_pqueue_t *q, void *d);
/**
* access highest-ranking item without removing it.
* @param q the queue
* @param d the entry
* @return NULL on error, otherwise the entry
*/
void *cache_pq_peek(cache_pqueue_t *q);
/**
* print the queue
* @internal
* DEBUG function only
* @param q the queue
* @param out the output handle
* @param the callback function to print the entry
*/
void cache_pq_print(cache_pqueue_t *q,
FILE *out,
cache_pqueue_print_entry print);
/**
* dump the queue and it's internal structure
* @internal
* debug function only
* @param q the queue
* @param out the output handle
* @param the callback function to print the entry
*/
void cache_pq_dump(cache_pqueue_t *q,
FILE *out,
cache_pqueue_print_entry print);
/**
* checks that the pq is in the right order, etc
* @internal
* debug function only
* @param q the queue
*/
int cache_pq_is_valid(cache_pqueue_t *q);
#ifdef __cplusplus
}
#endif
#endif /* !CACHE_PQUEUE_H */
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