cache_cache.c

/* 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.
 */

#include "apr_general.h"

#include "mod_cache.h"
#include "cache_hash.h"
#include "cache_pqueue.h"
#include "cache_cache.h"

#if APR_HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if APR_HAVE_STRING_H
#include <string.h>
#endif

struct cache_cache_t  {
    int             max_entries;
    apr_size_t      max_size;
    apr_size_t      current_size;
    int             total_purges;
    long            queue_clock;
    cache_hash_t   *ht;
    cache_pqueue_t *pq;
    cache_pqueue_set_priority set_pri;
    cache_pqueue_get_priority get_pri;
    cache_cache_inc_frequency *inc_entry;
    cache_cache_get_size *size_entry;
    cache_cache_get_key *key_entry;
    cache_cache_free *free_entry;
};

cache_cache_t* cache_init(int max_entries,
                                         apr_size_t max_size,
                                         cache_pqueue_get_priority get_pri,
                                         cache_pqueue_set_priority set_pri,
                                         cache_pqueue_getpos get_pos,
                                         cache_pqueue_setpos set_pos,
                                         cache_cache_inc_frequency *inc_entry,
                                         cache_cache_get_size *size_entry,
                                         cache_cache_get_key* key_entry,
                                         cache_cache_free *free_entry)
{
    cache_cache_t *tmp;
    tmp = malloc(sizeof(cache_cache_t));
    tmp->max_entries = max_entries;
    tmp->max_size = max_size;
    tmp->current_size = 0;
    tmp->total_purges = 0;
    tmp->queue_clock = 0;
    tmp->get_pri = get_pri;
    tmp->set_pri = set_pri;
    tmp->inc_entry = inc_entry;
    tmp->size_entry = size_entry;
    tmp->key_entry = key_entry;
    tmp->free_entry = free_entry;

    tmp->ht = cache_hash_make(max_entries);
    tmp->pq = cache_pq_init(max_entries, get_pri, get_pos, set_pos);

    return tmp;
}

void cache_free(cache_cache_t *c)
{
    cache_pq_free(c->pq);
    cache_hash_free(c->ht);
    free(c);
}


void* cache_find(cache_cache_t* c, const char *key)
{
    return cache_hash_get(c->ht, key, CACHE_HASH_KEY_STRING);
}

void cache_update(cache_cache_t* c, void *entry)
{
    long old_priority;
    long new_priority;

    old_priority = c->set_pri(c->queue_clock, entry);
    c->inc_entry(entry);
    new_priority = c->set_pri(c->queue_clock, entry);
    cache_pq_change_priority(c->pq, old_priority, new_priority, entry);
}

void cache_insert(cache_cache_t* c, void *entry)
{
    void *ejected = NULL;
    long priority;

    c->set_pri(c->queue_clock, entry);
    /* FIX: check if priority of bottom item is greater than inserted one */
    while ((cache_pq_size(c->pq) >= c->max_entries) ||
            ((c->current_size + c->size_entry(entry)) > c->max_size)) {

        ejected = cache_pq_pop(c->pq);
        /* FIX: If ejected is NULL, we'll segfault here */
        priority = c->get_pri(ejected);

        if (c->queue_clock > priority)
            c->queue_clock = priority;

        cache_hash_set(c->ht,
                       c->key_entry(ejected),
                       CACHE_HASH_KEY_STRING,
                       NULL);

        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, NULL, "Cache Purge of %s",c->key_entry(ejected));
        c->current_size -= c->size_entry(ejected);
        c->free_entry(ejected);
        c->total_purges++;
    }
    c->current_size += c->size_entry(entry);

    cache_pq_insert(c->pq, entry);
    cache_hash_set(c->ht, c->key_entry(entry), CACHE_HASH_KEY_STRING, entry);
}

void* cache_pop(cache_cache_t *c)
{
    void *entry;

    if (!c)
        return NULL;

    entry = cache_pq_pop(c->pq);

    if (!entry)
        return NULL;

    c->current_size -= c->size_entry(entry);
    cache_hash_set(c->ht, c->key_entry(entry), CACHE_HASH_KEY_STRING, NULL);

    return entry;
}

apr_status_t cache_remove(cache_cache_t *c, void *entry)
{
    apr_size_t entry_size = c->size_entry(entry);
    apr_status_t rc;
    rc = cache_pq_remove(c->pq, entry);
    if (rc != APR_SUCCESS)
        return rc;

    cache_hash_set(c->ht, c->key_entry(entry), CACHE_HASH_KEY_STRING, NULL);
    c->current_size -= entry_size;

    return APR_SUCCESS;
}

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