ceph/src/rocksdb/include/rocksdb/data_structure.h

   1 //  Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5
   6 #pragma once
   7
   8 #include <assert.h>
   9
  10 #include <cstddef>
  11 #include <cstdint>
  12 #include <vector>
  13
  14 #include "rocksdb/rocksdb_namespace.h"
  15
  16 namespace ROCKSDB_NAMESPACE {
  17
  18 // This is a data structure specifically designed as a "Set" for a
  19 // pretty small scale of Enum structure. For now, it can support up
  20 // to 64 element, and it is expandable in the future.
  21 template <typename ENUM_TYPE, ENUM_TYPE MAX_VALUE>
  22 class SmallEnumSet {
  23  public:
  24   SmallEnumSet() : state_(0) {}
  25
  26   ~SmallEnumSet() {}
  27
  28   // Return true if the input enum is included in the "Set" (i.e., changes the
  29   // internal scalar state successfully), otherwise, it will return false.
  30   bool Add(const ENUM_TYPE value) {
  31     static_assert(MAX_VALUE <= 63, "Size currently limited to 64");
  32     assert(value >= 0 && value <= MAX_VALUE);
  33     uint64_t old_state = state_;
  34     uint64_t tmp = 1;
  35     state_ |= (tmp << value);
  36     return old_state != state_;
  37   }
  38
  39   // Return true if the input enum is contained in the "Set".
  40   bool Contains(const ENUM_TYPE value) {
  41     static_assert(MAX_VALUE <= 63, "Size currently limited to 64");
  42     assert(value >= 0 && value <= MAX_VALUE);
  43     uint64_t tmp = 1;
  44     return state_ & (tmp << value);
  45   }
  46
  47  private:
  48   uint64_t state_;
  49 };
  50
  51 }  // namespace ROCKSDB_NAMESPACE