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-rw-r--r--dbm/sdbm/sdbm_lock.c79
1 files changed, 79 insertions, 0 deletions
diff --git a/dbm/sdbm/sdbm_lock.c b/dbm/sdbm/sdbm_lock.c
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index 0000000..7d62ffd
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+++ 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);
+}