1 files changed, 79 insertions, 0 deletions
diff --git a/dbm/sdbm/sdbm_lock.c b/dbm/sdbm/sdbm_lock.c
new file mode 100644
index 0000000..7d62ffd
--- /dev/null
+++ b/dbm/sdbm/sdbm_lock.c
@@ -0,0 +1,79 @@
+/* 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_file_info.h"
+#include "apr_file_io.h"
+#include "apr_sdbm.h"
+
+#include "sdbm_private.h"
+#include "sdbm_tune.h"
+
+/* NOTE: this function may block until it acquires the lock */
+APU_DECLARE(apr_status_t) apr_sdbm_lock(apr_sdbm_t *db, int type)
+{
+    apr_status_t status;
+    int lock_type = type & APR_FLOCK_TYPEMASK;
+
+    if (!(lock_type == APR_FLOCK_SHARED || lock_type == APR_FLOCK_EXCLUSIVE))
+        return APR_EINVAL;
+
+    if (db->flags & SDBM_EXCLUSIVE_LOCK) {
+        ++db->lckcnt;
+        return APR_SUCCESS;
+    }
+    else if (db->flags & SDBM_SHARED_LOCK) {
+        /*
+         * Cannot promote a shared lock to an exlusive lock
+         * in a cross-platform compatibile manner.
+         */
+        if (type == APR_FLOCK_EXCLUSIVE)
+            return APR_EINVAL;
+        ++db->lckcnt;
+        return APR_SUCCESS;
+    }
+    /*
+     * zero size: either a fresh database, or one with a single,
+     * unsplit data page: dirpage is all zeros.
+     */
+    if ((status = apr_file_lock(db->dirf, type)) == APR_SUCCESS) 
+    {
+        apr_finfo_t finfo;
+        if ((status = apr_file_info_get(&finfo, APR_FINFO_SIZE, db->dirf))
+                != APR_SUCCESS) {
+            (void) apr_file_unlock(db->dirf);
+            return status;
+        }
+
+        SDBM_INVALIDATE_CACHE(db, finfo);
+
+        ++db->lckcnt;
+        if (type == APR_FLOCK_SHARED)
+            db->flags |= SDBM_SHARED_LOCK;
+        else if (type == APR_FLOCK_EXCLUSIVE)
+            db->flags |= SDBM_EXCLUSIVE_LOCK;
+    }
+    return status;
+}
+
+APU_DECLARE(apr_status_t) apr_sdbm_unlock(apr_sdbm_t *db)
+{
+    if (!(db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK)))
+        return APR_EINVAL;
+    if (--db->lckcnt > 0)
+        return APR_SUCCESS;
+    db->flags &= ~(SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK);
+    return apr_file_unlock(db->dirf);
+}