1/*
2 * ====================================================================
3 *    Licensed to the Apache Software Foundation (ASF) under one
4 *    or more contributor license agreements.  See the NOTICE file
5 *    distributed with this work for additional information
6 *    regarding copyright ownership.  The ASF licenses this file
7 *    to you under the Apache License, Version 2.0 (the
8 *    "License"); you may not use this file except in compliance
9 *    with the License.  You may obtain a copy of the License at
10 *
11 *      http://www.apache.org/licenses/LICENSE-2.0
12 *
13 *    Unless required by applicable law or agreed to in writing,
14 *    software distributed under the License is distributed on an
15 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 *    KIND, either express or implied.  See the License for the
17 *    specific language governing permissions and limitations
18 *    under the License.
19 * ====================================================================
20 */
21
22#include <apr_hash.h>
23
24#include "svn_hash.h"
25#include "svn_dso.h"
26#include "svn_pools.h"
27#include "svn_private_config.h"
28
29#include "private/svn_mutex.h"
30#include "private/svn_atomic.h"
31#include "private/svn_subr_private.h"
32
33/* A mutex to protect our global pool and cache. */
34static svn_mutex__t *dso_mutex = NULL;
35
36/* Global pool to allocate DSOs in. */
37static apr_pool_t *dso_pool;
38
39/* Global cache for storing DSO objects. */
40static apr_hash_t *dso_cache;
41
42/* Just an arbitrary location in memory... */
43static int not_there_sentinel;
44
45static volatile svn_atomic_t atomic_init_status = 0;
46
47/* A specific value we store in the dso_cache to indicate that the
48   library wasn't found.  This keeps us from allocating extra memory
49   from dso_pool when trying to find libraries we already know aren't
50   there.  */
51#define NOT_THERE ((void *) &not_there_sentinel)
52
53static svn_error_t *
54atomic_init_func(void *baton,
55                 apr_pool_t *pool)
56{
57  dso_pool = svn_pool_create(NULL);
58
59  SVN_ERR(svn_mutex__init(&dso_mutex, TRUE, dso_pool));
60
61  dso_cache = apr_hash_make(dso_pool);
62  return SVN_NO_ERROR;
63}
64
65svn_error_t *
66svn_dso_initialize2(void)
67{
68  SVN_ERR(svn_atomic__init_once(&atomic_init_status, atomic_init_func,
69                                NULL, NULL));
70
71  return SVN_NO_ERROR;
72}
73
74#if APR_HAS_DSO
75static svn_error_t *
76svn_dso_load_internal(apr_dso_handle_t **dso, const char *fname)
77{
78  *dso = svn_hash_gets(dso_cache, fname);
79
80  /* First check to see if we've been through this before...  We do this
81     to avoid calling apr_dso_load multiple times for a given library,
82     which would result in wasting small amounts of memory each time. */
83  if (*dso == NOT_THERE)
84    {
85      *dso = NULL;
86      return SVN_NO_ERROR;
87    }
88
89  /* If we got nothing back from the cache, try and load the library. */
90  if (! *dso)
91    {
92      apr_status_t status = apr_dso_load(dso, fname, dso_pool);
93      if (status)
94        {
95#ifdef SVN_DEBUG_DSO
96          char buf[1024];
97          fprintf(stderr,
98                  "Dynamic loading of '%s' failed with the following error:\n%s\n",
99                  fname,
100                  apr_dso_error(*dso, buf, 1024));
101#endif
102          *dso = NULL;
103
104          /* It wasn't found, so set the special "we didn't find it" value. */
105          svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), NOT_THERE);
106
107          return SVN_NO_ERROR;
108        }
109
110      /* Stash the dso so we can use it next time. */
111      svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), *dso);
112    }
113
114  return SVN_NO_ERROR;
115}
116
117svn_error_t *
118svn_dso_load(apr_dso_handle_t **dso, const char *fname)
119{
120  SVN_ERR(svn_dso_initialize2());
121
122  SVN_MUTEX__WITH_LOCK(dso_mutex, svn_dso_load_internal(dso, fname));
123
124  return SVN_NO_ERROR;
125}
126
127apr_pool_t *
128svn_dso__pool(void)
129{
130  return dso_pool;
131}
132
133#endif /* APR_HAS_DSO */
134