2 * This file is part of PowerDNS or dnsdist.
3 * Copyright -- PowerDNS.COM B.V. and its contributors
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.
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.
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.
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.
22 #ifndef LAZY_ALLOCATOR_HH
23 #define LAZY_ALLOCATOR_HH
27 #include <type_traits>
31 // On OpenBSD mem used as stack should be marked MAP_STACK
32 #if !defined(MAP_STACK)
37 struct lazy_allocator {
40 using size_type = std::size_t;
41 static_assert (std::is_trivial<T>::value,
42 "lazy_allocator must only be used with trivial types");
45 allocate (size_type const n) {
47 void *p = mmap(nullptr, n * sizeof(value_type),
48 PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON | MAP_STACK, -1, 0);
50 throw std::bad_alloc();
51 return static_cast<pointer>(p);
53 return static_cast<pointer>(::operator new (n * sizeof(value_type)));
58 deallocate (pointer const ptr, size_type const n) noexcept {
60 munmap(ptr, n * sizeof(value_type));
62 #if defined(__cpp_sized_deallocation) && (__cpp_sized_deallocation >= 201309)
63 ::operator delete (ptr, n * sizeof(value_type));
66 ::operator delete (ptr);
71 void construct (T*) const noexcept {}
73 template <typename X, typename... Args>
75 construct (X* place, Args&&... args) const noexcept {
76 new (static_cast<void*>(place)) X (std::forward<Args>(args)...);
80 template <typename T> inline
81 bool operator== (lazy_allocator<T> const&, lazy_allocator<T> const&) noexcept {
85 template <typename T> inline
86 bool operator!= (lazy_allocator<T> const&, lazy_allocator<T> const&) noexcept {
90 #endif // LAZY_ALLOCATOR_HH