1 files changed, 51 insertions, 0 deletions
diff --git a/src/rocksdb/include/rocksdb/data_structure.h b/src/rocksdb/include/rocksdb/data_structure.h
new file mode 100644
index 000000000..f868a6be5
--- /dev/null
+++ b/src/rocksdb/include/rocksdb/data_structure.h
@@ -0,0 +1,51 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <assert.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// This is a data structure specifically designed as a "Set" for a
+// pretty small scale of Enum structure. For now, it can support up
+// to 64 element, and it is expandable in the future.
+template <typename ENUM_TYPE, ENUM_TYPE MAX_VALUE>
+class SmallEnumSet {
+ public:
+  SmallEnumSet() : state_(0) {}
+
+  ~SmallEnumSet() {}
+
+  // Return true if the input enum is included in the "Set" (i.e., changes the
+  // internal scalar state successfully), otherwise, it will return false.
+  bool Add(const ENUM_TYPE value) {
+    static_assert(MAX_VALUE <= 63, "Size currently limited to 64");
+    assert(value >= 0 && value <= MAX_VALUE);
+    uint64_t old_state = state_;
+    uint64_t tmp = 1;
+    state_ |= (tmp << value);
+    return old_state != state_;
+  }
+
+  // Return true if the input enum is contained in the "Set".
+  bool Contains(const ENUM_TYPE value) {
+    static_assert(MAX_VALUE <= 63, "Size currently limited to 64");
+    assert(value >= 0 && value <= MAX_VALUE);
+    uint64_t tmp = 1;
+    return state_ & (tmp << value);
+  }
+
+ private:
+  uint64_t state_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE