gdbsupport/hash_enum.h

   1 /* A hasher for enums.
   2
   3    Copyright (C) 2017-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef COMMON_HASH_ENUM_H
  21 #define COMMON_HASH_ENUM_H
  22
  23 /* A hasher for enums, which was missing in C++11:
  24     http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2148
  25 */
  26
  27 namespace gdb {
  28
  29 /* Helper struct for hashing enum types.  */
  30 template<typename T>
  31 struct hash_enum
  32 {
  33   typedef size_t result_type;
  34   typedef T argument_type;
  35
  36   size_t operator() (T val) const noexcept
  37   {
  38     using underlying = typename std::underlying_type<T>::type;
  39     return std::hash<underlying> () (static_cast<underlying> (val));
  40   }
  41 };
  42
  43 } /* namespace gdb */
  44
  45 #endif /* COMMON_HASH_ENUM_H */