guarded-list: New data structure for thread-safe queue.

[sliver-openvswitch.git] / lib / guarded-list.c

diff --git a/lib/guarded-list.c b/lib/guarded-list.c
new file mode 100644 (file)
index 0000000..cbb2030
--- /dev/null
+++ b/lib/guarded-list.c
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2013 Nicira, Inc.
+ *
+ * Licensed 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 <config.h>
+
+#include "guarded-list.h"
+
+void
+guarded_list_init(struct guarded_list *list)
+{
+    ovs_mutex_init(&list->mutex);
+    list_init(&list->list);
+    list->n = 0;
+}
+
+void
+guarded_list_destroy(struct guarded_list *list)
+{
+    ovs_mutex_destroy(&list->mutex);
+}
+
+bool
+guarded_list_is_empty(const struct guarded_list *list)
+{
+    bool empty;
+
+    ovs_mutex_lock(&list->mutex);
+    empty = list->n == 0;
+    ovs_mutex_unlock(&list->mutex);
+
+    return empty;
+}
+
+/* If 'list' has fewer than 'max' elements, adds 'node' at the end of the list
+ * and returns the number of elements now on the list.
+ *
+ * If 'list' already has at least 'max' elements, returns 0 without modifying
+ * the list. */
+size_t
+guarded_list_push_back(struct guarded_list *list,
+                       struct list *node, size_t max)
+{
+    size_t retval = 0;
+
+    ovs_mutex_lock(&list->mutex);
+    if (list->n < max) {
+        list_push_back(&list->list, node);
+        retval = ++list->n;
+    }
+    ovs_mutex_unlock(&list->mutex);
+
+    return retval;
+}
+
+struct list *
+guarded_list_pop_front(struct guarded_list *list)
+{
+    struct list *node = NULL;
+
+    ovs_mutex_lock(&list->mutex);
+    if (list->n) {
+        node = list_pop_front(&list->list);
+        list->n--;
+    }
+    ovs_mutex_unlock(&list->mutex);
+
+    return node;
+}
+
+size_t
+guarded_list_pop_all(struct guarded_list *list, struct list *elements)
+{
+    size_t n;
+
+    ovs_mutex_lock(&list->mutex);
+    list_move(elements, &list->list);
+    n = list->n;
+
+    list_init(&list->list);
+    list->n = 0;
+    ovs_mutex_unlock(&list->mutex);
+
+    return n;
+}