pdns/lazy_allocator.hh

   1 /*
   2  * This file is part of PowerDNS or dnsdist.
   3  * Copyright -- PowerDNS.COM B.V. and its contributors
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of version 2 of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * In addition, for the avoidance of any doubt, permission is granted to
  10  * link this program with OpenSSL and to (re)distribute the binaries
  11  * produced as the result of such linking.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22 #ifndef LAZY_ALLOCATOR_HH
  23 #define LAZY_ALLOCATOR_HH
  24
  25 #include <cstddef>
  26 #include <utility>
  27 #include <type_traits>
  28
  29 template <typename T>
  30 struct lazy_allocator {
  31     using value_type = T;
  32     using pointer = T*;
  33     using size_type = std::size_t;
  34     static_assert (std::is_trivial<T>::value,
  35                    "lazy_allocator must only be used with trivial types");
  36
  37     pointer
  38     allocate (size_type const n) {
  39         return static_cast<pointer>(::operator new (n * sizeof(value_type)));
  40     }
  41
  42     void
  43     deallocate (pointer const ptr, size_type const n) noexcept {
  44 #if defined(__cpp_sized_deallocation) &&  (__cpp_sized_deallocation >= 201309)
  45         ::operator delete (ptr, n * sizeof(value_type));
  46 #else
  47         (void) n;
  48         ::operator delete (ptr);
  49 #endif
  50     }
  51
  52     void construct (T*) const noexcept {}
  53
  54     template <typename X, typename... Args>
  55     void
  56     construct (X* place, Args&&... args) const noexcept {
  57         new (static_cast<void*>(place)) X (std::forward<Args>(args)...);
  58     }
  59 };
  60
  61 template <typename T> inline
  62 bool operator== (lazy_allocator<T> const&, lazy_allocator<T> const&) noexcept {
  63     return true;
  64 }
  65
  66 template <typename T> inline
  67 bool operator!= (lazy_allocator<T> const&, lazy_allocator<T> const&) noexcept {
  68     return false;
  69 }
  70
  71 #endif // LAZY_ALLOCATOR_HH