src/TortoiseMerge/libsvn_diff/dso.c

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