refactored

dataguard/include/dataguard/dataguard.h

@@ -0,0 +1,2 @@
+#include "dataguard/snapshot.h"
+#include "dataguard/txn_logger.h"

dataguard/include/dataguard/snapshot.h

@@ -0,0 +1,15 @@
+#ifndef SNAP_SHOT_H
+#define SNAP_SHOT_H
+#include <string>
+#include "map.hpp"
+#include "vector.hpp"
+class SnapShotManager {
+ public:
+  // For safety and simplicity, we delete all the copy/move constructor and copy/move assignment operator. Please
+  // manager it using smart pointer.
+  SnapShotManager(const SnapShotManager &) = delete;
+  SnapShotManager(SnapShotManager &&) = delete;
+  SnapShotManager &operator=(const SnapShotManager &) = delete;
+  SnapShotManager &operator=(SnapShotManager &&) = delete;
+};
+#endif  // SNAP_SHOT_H

dataguard/include/dataguard/txn_logger.h

@@ -0,0 +1,4 @@
+#ifndef TXN_LOGGER_H
+#define TXN_LOGGER_H
+
+#endif