1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #ifndef CACHE_PQUEUE_H
18 #define CACHE_PQUEUE_H
21 #include <apr_errno.h>
31 /** the cache priority queue handle */
32 typedef struct cache_pqueue_t cache_pqueue_t;
35 * callback function to assign a priority for a element
36 * @param a the element
37 * @return the score (the lower the score the longer it is kept int the queue)
39 typedef long (*cache_pqueue_set_priority)(long queue_clock, void *a);
40 typedef long (*cache_pqueue_get_priority)(void *a);
42 /** callback function to get a position of a element */
43 typedef apr_ssize_t (*cache_pqueue_getpos)(void *a);
46 * callback function to set a position of a element
47 * @param a the element
48 * @param pos the position to set it to
50 typedef void (*cache_pqueue_setpos)(void *a, apr_ssize_t pos);
52 /** debug callback function to print a entry */
53 typedef void (*cache_pqueue_print_entry)(FILE *out, void *a);
56 * initialize the queue
58 * @param n the initial estimate of the number of queue items for which memory
59 * should be preallocated
60 * @param pri the callback function to run to assign a score to a element
61 * @param get the callback function to get the current element's position
62 * @param set the callback function to set the current element's position
64 * @Return the handle or NULL for insufficent memory
66 cache_pqueue_t *cache_pq_init(apr_ssize_t n,
67 cache_pqueue_get_priority pri,
68 cache_pqueue_getpos get,
69 cache_pqueue_setpos set);
71 * free all memory used by the queue
74 void cache_pq_free(cache_pqueue_t *q);
76 * return the size of the queue.
79 apr_ssize_t cache_pq_size(cache_pqueue_t *q);
82 * insert an item into the queue.
85 * @return APR_SUCCESS on success
87 apr_status_t cache_pq_insert(cache_pqueue_t *q, void *d);
90 * move a existing entry to a different priority
92 * @param old the old priority
95 void cache_pq_change_priority(cache_pqueue_t *q,
101 * pop the highest-ranking item from the queue.
103 * @param d where to copy the entry to
104 * @return NULL on error, otherwise the entry
106 void *cache_pq_pop(cache_pqueue_t *q);
109 * remove an item from the queue.
112 * @return APR_SUCCESS on success
114 apr_status_t cache_pq_remove(cache_pqueue_t *q, void *d);
117 * access highest-ranking item without removing it.
120 * @return NULL on error, otherwise the entry
122 void *cache_pq_peek(cache_pqueue_t *q);
127 * DEBUG function only
129 * @param out the output handle
130 * @param the callback function to print the entry
132 void cache_pq_print(cache_pqueue_t *q,
134 cache_pqueue_print_entry print);
137 * dump the queue and it's internal structure
139 * debug function only
141 * @param out the output handle
142 * @param the callback function to print the entry
144 void cache_pq_dump(cache_pqueue_t *q,
146 cache_pqueue_print_entry print);
149 * checks that the pq is in the right order, etc
151 * debug function only
154 int cache_pq_is_valid(cache_pqueue_t *q);
160 #endif /* !CACHE_PQUEUE_H */