ceph/src/rocksdb/util/cast_util.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  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 <type_traits>
   9
  10 #include "rocksdb/rocksdb_namespace.h"
  11
  12 namespace ROCKSDB_NAMESPACE {
  13 // The helper function to assert the move from dynamic_cast<> to
  14 // static_cast<> is correct. This function is to deal with legacy code.
  15 // It is not recommended to add new code to issue class casting. The preferred
  16 // solution is to implement the functionality without a need of casting.
  17 template <class DestClass, class SrcClass>
  18 inline DestClass* static_cast_with_check(SrcClass* x) {
  19   DestClass* ret = static_cast<DestClass*>(x);
  20 #ifdef ROCKSDB_USE_RTTI
  21   assert(ret == dynamic_cast<DestClass*>(x));
  22 #endif
  23   return ret;
  24 }
  25
  26 // A wrapper around static_cast for lossless conversion between integral
  27 // types, including enum types. For example, this can be used for converting
  28 // between signed/unsigned or enum type and underlying type without fear of
  29 // stripping away data, now or in the future.
  30 template <typename To, typename From>
  31 inline To lossless_cast(From x) {
  32   using FromValue = typename std::remove_reference<From>::type;
  33   static_assert(
  34       std::is_integral<FromValue>::value || std::is_enum<FromValue>::value,
  35       "Only works on integral types");
  36   static_assert(std::is_integral<To>::value || std::is_enum<To>::value,
  37                 "Only works on integral types");
  38   static_assert(sizeof(To) >= sizeof(FromValue), "Must be lossless");
  39   return static_cast<To>(x);
  40 }
  41
  42 }  // namespace ROCKSDB_NAMESPACE