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-rw-r--r--src/mongo/util/auto_clear_ptr.h58
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+/**
+ * Copyright (C) 2020-present MongoDB, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the Server Side Public License, version 1,
+ * as published by MongoDB, Inc.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * Server Side Public License for more details.
+ *
+ * You should have received a copy of the Server Side Public License
+ * along with this program. If not, see
+ * <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ * As a special exception, the copyright holders give permission to link the
+ * code of portions of this program with the OpenSSL library under certain
+ * conditions as described in each individual source file and distribute
+ * linked combinations including the program with the OpenSSL library. You
+ * must comply with the Server Side Public License in all respects for
+ * all of the code used other than as permitted herein. If you modify file(s)
+ * with this exception, you may extend this exception to your version of the
+ * file(s), but you are not obligated to do so. If you do not wish to do so,
+ * delete this exception statement from your version. If you delete this
+ * exception statement from all source files in the program, then also delete
+ * it in the license file.
+ */
+
+#pragma once
+
+#include <memory>
+
+namespace mongo {
+
+template <class Container>
+class ClearDeleter {
+public:
+ void operator()(Container* container) {
+ container->clear();
+ }
+};
+
+/**
+ * A RAII style move-only pointer that calls clear() when going out of scope
+ */
+template <class Container>
+using AutoClearPtr = std::unique_ptr<Container, ClearDeleter<Container>>;
+
+template <class Container>
+auto makeAutoClearPtr(Container* container) {
+ // It should always be cleared when it is accessed
+ dassert(container);
+ dassert(container->empty());
+ return AutoClearPtr<Container>{container, ClearDeleter<Container>{}};
+}
+
+} // namespace mongo