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diff --git a/wsrep-lib/include/wsrep/id.hpp b/wsrep-lib/include/wsrep/id.hpp
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+++ b/wsrep-lib/include/wsrep/id.hpp
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+/*
+ * Copyright (C) 2018 Codership Oy <info@codership.com>
+ *
+ * This file is part of wsrep-lib.
+ *
+ * Wsrep-lib is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Wsrep-lib 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
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with wsrep-lib.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/** @file id.hpp
+ *
+ * A generic identifier utility class.
+ */
+#ifndef WSREP_ID_HPP
+#define WSREP_ID_HPP
+
+#include "exception.hpp"
+
+#include <iosfwd>
+#include <cstring> // std::memset()
+
+namespace wsrep
+{
+    /**
+     * The idientifier class stores identifiers either in UUID
+     * format or in string format. The storage format is decided
+     * upon construction. If the given string contains a valid
+     * UUID, the storage format will be binary. Otherwise the
+     * string will be copied verbatim. If the string format is used,
+     * the maximum length of the identifier is limited to 16 bytes.
+     */
+    class id
+    {
+    public:
+        typedef struct native_type { unsigned char buf[16]; } native_type;
+        /**
+         * Default constructor. Constructs an empty identifier.
+         */
+        id() : data_() { std::memset(data_.buf, 0, sizeof(data_.buf)); }
+
+        /**
+         * Construct from string. The input string may contain either
+         * valid UUID or a string with maximum 16 bytes length.
+         */
+        id(const std::string&);
+
+        /**
+         * Construct from void pointer.
+         */
+        id (const void* data, size_t size) : data_()
+        {
+            if (size > 16)
+            {
+                throw wsrep::runtime_error("Too long identifier");
+            }
+            std::memset(data_.buf, 0, sizeof(data_.buf));
+            std::memcpy(data_.buf, data, size);
+        }
+
+        bool operator<(const id& other) const
+        {
+            return (std::memcmp(data_.buf, other.data_.buf, sizeof(data_.buf)) < 0);
+        }
+
+        bool operator==(const id& other) const
+        {
+            return (std::memcmp(data_.buf, other.data_.buf, sizeof(data_.buf)) == 0);
+        }
+        bool operator!=(const id& other) const
+        {
+            return !(*this == other);
+        }
+        const void* data() const { return data_.buf; }
+
+        size_t size() const { return sizeof(data_); }
+
+        bool is_undefined() const
+        {
+            return (*this == undefined());
+        }
+
+        static const wsrep::id& undefined()
+        {
+            return undefined_;
+        }
+    private:
+        static const wsrep::id undefined_;
+        native_type data_;
+    };
+
+    std::ostream& operator<<(std::ostream&, const wsrep::id& id);
+    std::istream& operator>>(std::istream&, wsrep::id& id);
+}
+
+#endif // WSREP_ID_HPP