1 files changed, 117 insertions, 0 deletions
diff --git a/subversion/libsvn_subr/dso.c b/subversion/libsvn_subr/dso.c
new file mode 100644
index 0000000..3fa2517
--- /dev/null
+++ b/subversion/libsvn_subr/dso.c
@@ -0,0 +1,117 @@
+/*
+ * ====================================================================
+ *    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_thread_mutex.h>
+#include <apr_hash.h>
+
+#include "svn_hash.h"
+#include "svn_dso.h"
+#include "svn_pools.h"
+#include "svn_private_config.h"
+
+#include "private/svn_mutex.h"
+
+/* A mutex to protect our global pool and cache. */
+static svn_mutex__t *dso_mutex = NULL;
+
+/* Global pool to allocate DSOs in. */
+static apr_pool_t *dso_pool;
+
+/* Global cache for storing DSO objects. */
+static apr_hash_t *dso_cache;
+
+/* Just an arbitrary location in memory... */
+static int not_there_sentinel;
+
+/* A specific value we store in the dso_cache to indicate that the
+   library wasn't found.  This keeps us from allocating extra memory
+   from dso_pool when trying to find libraries we already know aren't
+   there.  */
+#define NOT_THERE ((void *) &not_there_sentinel)
+
+svn_error_t *
+svn_dso_initialize2(void)
+{
+  if (dso_pool)
+    return SVN_NO_ERROR;
+
+  dso_pool = svn_pool_create(NULL);
+
+  SVN_ERR(svn_mutex__init(&dso_mutex, TRUE, dso_pool));
+
+  dso_cache = apr_hash_make(dso_pool);
+  return SVN_NO_ERROR;
+}
+
+#if APR_HAS_DSO
+static svn_error_t *
+svn_dso_load_internal(apr_dso_handle_t **dso, const char *fname)
+{
+  *dso = svn_hash_gets(dso_cache, fname);
+
+  /* First check to see if we've been through this before...  We do this
+     to avoid calling apr_dso_load multiple times for a given library,
+     which would result in wasting small amounts of memory each time. */
+  if (*dso == NOT_THERE)
+    {
+      *dso = NULL;
+      return SVN_NO_ERROR;
+    }
+
+  /* If we got nothing back from the cache, try and load the library. */
+  if (! *dso)
+    {
+      apr_status_t status = apr_dso_load(dso, fname, dso_pool);
+      if (status)
+        {
+#ifdef SVN_DEBUG_DSO
+          char buf[1024];
+          fprintf(stderr,
+                  "Dynamic loading of '%s' failed with the following error:\n%s\n",
+                  fname,
+                  apr_dso_error(*dso, buf, 1024));
+#endif
+          *dso = NULL;
+
+          /* It wasn't found, so set the special "we didn't find it" value. */
+          svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), NOT_THERE);
+
+          return SVN_NO_ERROR;
+        }
+
+      /* Stash the dso so we can use it next time. */
+      svn_hash_sets(dso_cache, apr_pstrdup(dso_pool, fname), *dso);
+    }
+
+  return SVN_NO_ERROR;
+}
+
+svn_error_t *
+svn_dso_load(apr_dso_handle_t **dso, const char *fname)
+{
+  if (! dso_pool)
+    SVN_ERR(svn_dso_initialize2());
+
+  SVN_MUTEX__WITH_LOCK(dso_mutex, svn_dso_load_internal(dso, fname));
+
+  return SVN_NO_ERROR;
+}
+#endif /* APR_HAS_DSO */