dso.c revision 299742 
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_thread_mutex.h>
23#include <apr_hash.h>
24
25#include "svn_hash.h"
26#include "svn_dso.h"
27#include "svn_pools.h"
28#include "svn_private_config.h"
29
30#include "private/svn_mutex.h"
31#include "private/svn_atomic.h"
32#include "private/svn_subr_private.h"
33
34/* A mutex to protect our global pool and cache. */
35static svn_mutex__t *dso_mutex = NULL;
36
37/* Global pool to allocate DSOs in. */
38static apr_pool_t *dso_pool;
39
40/* Global cache for storing DSO objects. */
41static apr_hash_t *dso_cache;
42
43/* Just an arbitrary location in memory... */
44static int not_there_sentinel;
45
46static volatile svn_atomic_t atomic_init_status = 0;
47
48/* A specific value we store in the dso_cache to indicate that the
49   library wasn't found.  This keeps us from allocating extra memory
50   from dso_pool when trying to find libraries we already know aren't
51   there.  */
52#define NOT_THERE ((void *) &not_there_sentinel)
53
54static svn_error_t *
55atomic_init_func(void *baton,
56                 apr_pool_t *pool)
57{
58  dso_pool = svn_pool_create(NULL);
59
60  SVN_ERR(svn_mutex__init(&dso_mutex, TRUE, dso_pool));
61
62  dso_cache = apr_hash_make(dso_pool);
63  return SVN_NO_ERROR;
64}
65
66svn_error_t *
67svn_dso_initialize2(void)
68{
69  SVN_ERR(svn_atomic__init_once(&atomic_init_status, atomic_init_func,
70                                NULL, NULL));
71
72  return SVN_NO_ERROR;
73}
74
75#if APR_HAS_DSO
76static svn_error_t *
77svn_dso_load_internal(apr_dso_handle_t **dso, const char *fname)
78{
79  *dso = svn_hash_gets(dso_cache, fname);
80
81  /* First check to see if we've been through this before...  We do this
82     to avoid calling apr_dso_load multiple times for a given library,
83     which would result in wasting small amounts of memory each time. */
84  if (*dso == NOT_THERE)
85    {
86      *dso = NULL;
87      return SVN_NO_ERROR;
88    }
89
90  /* If we got nothing back from the cache, try and load the library. */
91  if (! *dso)
92    {
93      apr_status_t status = apr_dso_load(dso, fname, dso_pool);
94      if (status)
95        {
96#ifdef SVN_DEBUG_DSO
97          char buf[1024];
98          fprintf(stderr,
99                  "Dynamic loading of '%s' failed with the following error:\n%s\n",
100                  fname,
101                  apr_dso_error(*dso, buf, 1024));
102#endif
103          *dso = NULL;
104
105          /* It wasn't found, so set the special "we didn't find it" value. */
106          svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), NOT_THERE);
107
108          return SVN_NO_ERROR;
109        }
110
111      /* Stash the dso so we can use it next time. */
112      svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), *dso);
113    }
114
115  return SVN_NO_ERROR;
116}
117
118svn_error_t *
119svn_dso_load(apr_dso_handle_t **dso, const char *fname)
120{
121  SVN_ERR(svn_dso_initialize2());
122
123  SVN_MUTEX__WITH_LOCK(dso_mutex, svn_dso_load_internal(dso, fname));
124
125  return SVN_NO_ERROR;
126}
127
128apr_pool_t *
129svn_dso__pool(void)
130{
131  return dso_pool;
132}
133
134#endif /* APR_HAS_DSO */
135