Adds support to the server ID generation

The server ID is a sha-1 identifier generated from the mac address of the first
ethernet device plus the server name. The process is the same used by
ModSecurity 2.9

src/unique_id.h

@@ -0,0 +1,67 @@
+/*
+ * ModSecurity, http://www.modsecurity.org/
+ * Copyright (c) 2015 Trustwave Holdings, Inc. (http://www.trustwave.com/)
+ *
+ * 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
+ *
+ * If any of the files related to licensing are missing or if you have any
+ * other questions related to licensing please contact Trustwave Holdings, Inc.
+ * directly using the email address security@modsecurity.org.
+ *
+ */
+
+#ifdef __cplusplus
+#include <string>
+#endif
+
+#ifndef SRC_UNIQUE_ID_H_
+#define SRC_UNIQUE_ID_H_
+
+
+#ifdef __cplusplus
+
+namespace ModSecurity {
+
+#define MAC_ADDRESS_SIZE 19
+#define MAX_MACHINE_NAME_SIZE 256
+
+/** @ingroup ModSecurity_CPP_API */
+class UniqueId {
+ public:
+    static UniqueId& getInstance() {
+        static UniqueId instance;
+        return instance;
+    }
+
+    static std::string uniqueId() {
+        if (UniqueId::getInstance().uniqueId_str.empty()) {
+            UniqueId::getInstance().fillUniqueId();
+        }
+
+        return UniqueId::getInstance().uniqueId_str;
+    }
+
+    void fillUniqueId();
+    std::string machineName();
+    std::string ethernetMacAddress();
+
+    std::string uniqueId_str;
+
+ private:
+    UniqueId() {}
+    // C++ 03
+    UniqueId(UniqueId const&);
+    // void operator=(UniqueId const&);
+
+    // C++ 11
+    // UniqueId(UniqueId const&) = delete;
+    // void operator=(UniqueId const&) = delete;
+};
+
+}  // namespace ModSecurity
+#endif
+
+#endif  // SRC_UNIQUE_ID_H_