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
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
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.
15 */
16
17#include "apr_file_info.h"
18#include "apr_file_io.h"
19#include "apr_sdbm.h"
20
21#include "sdbm_private.h"
22#include "sdbm_tune.h"
23
24/* NOTE: this function may block until it acquires the lock */
25APU_DECLARE(apr_status_t) apr_sdbm_lock(apr_sdbm_t *db, int type)
26{
27    apr_status_t status;
28    int lock_type = type & APR_FLOCK_TYPEMASK;
29
30    if (!(lock_type == APR_FLOCK_SHARED || lock_type == APR_FLOCK_EXCLUSIVE))
31        return APR_EINVAL;
32
33    if (db->flags & SDBM_EXCLUSIVE_LOCK) {
34        ++db->lckcnt;
35        return APR_SUCCESS;
36    }
37    else if (db->flags & SDBM_SHARED_LOCK) {
38        /*
39         * Cannot promote a shared lock to an exlusive lock
40         * in a cross-platform compatibile manner.
41         */
42        if (type == APR_FLOCK_EXCLUSIVE)
43            return APR_EINVAL;
44        ++db->lckcnt;
45        return APR_SUCCESS;
46    }
47    /*
48     * zero size: either a fresh database, or one with a single,
49     * unsplit data page: dirpage is all zeros.
50     */
51    if ((status = apr_file_lock(db->dirf, type)) == APR_SUCCESS)
52    {
53        apr_finfo_t finfo;
54        if ((status = apr_file_info_get(&finfo, APR_FINFO_SIZE, db->dirf))
55                != APR_SUCCESS) {
56            (void) apr_file_unlock(db->dirf);
57            return status;
58        }
59
60        SDBM_INVALIDATE_CACHE(db, finfo);
61
62        ++db->lckcnt;
63        if (type == APR_FLOCK_SHARED)
64            db->flags |= SDBM_SHARED_LOCK;
65        else if (type == APR_FLOCK_EXCLUSIVE)
66            db->flags |= SDBM_EXCLUSIVE_LOCK;
67    }
68    return status;
69}
70
71APU_DECLARE(apr_status_t) apr_sdbm_unlock(apr_sdbm_t *db)
72{
73    if (!(db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK)))
74        return APR_EINVAL;
75    if (--db->lckcnt > 0)
76        return APR_SUCCESS;
77    db->flags &= ~(SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK);
78    return apr_file_unlock(db->dirf);
79}
80