95 lines
2.9 KiB
C++
95 lines
2.9 KiB
C++
/**
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This file is a part of rexy's general purpose library
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Copyright (C) 2020 rexy712
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef REXY_DEFAULT_ALLOCATOR_HPP
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#define REXY_DEFAULT_ALLOCATOR_HPP
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#include <cstdlib> //size_t
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#include <type_traits> //true_type, false_type
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#include <new>
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namespace rexy{
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namespace detail{
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template<class T>
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struct default_allocator
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{
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using pointer = T*;
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using const_pointer = const T*;
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using void_pointer = void*;
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using const_void_pointer = const void*;
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using value_type = T;
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using size_type = size_t;
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using difference_type = ptrdiff_t;
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using is_always_equal = std::true_type;
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using propagate_on_container_copy_assignment = std::false_type;
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using propagate_on_container_move_assignment = std::false_type;
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using propagate_on_container_swap = std::false_type;
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template<class U>
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struct rebind{
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using other = default_allocator<U>;
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};
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private:
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constexpr bool has_overflow(size_type n)const{
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return n > max_size();
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}
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public:
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default_allocator(void) = default;
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default_allocator(const default_allocator&) = default;
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default_allocator(default_allocator&&) = default;
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template<class U>
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constexpr default_allocator(const default_allocator<U>&)noexcept{}
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~default_allocator(void) = default;
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pointer allocate(size_type n){
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size_type bytes = has_overflow(n) ? size_type{-1} : n*sizeof(T);
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if constexpr(alignof(T) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__){
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return reinterpret_cast<pointer>(::operator new(bytes));
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}else{
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return reinterpret_cast<pointer>(::operator new(bytes, static_cast<std::align_val_t>(alignof(T))));
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}
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}
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void deallocate(pointer p, size_type n){
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size_type bytes = has_overflow(n) ? size_type{-1} : n*sizeof(T);
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if constexpr(alignof(T) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__){
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::operator delete(p, bytes);
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}else{
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::operator delete(p, bytes, static_cast<std::align_val_t>(alignof(T)));
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}
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}
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constexpr size_type max_size(void)const{
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return size_type{-1}/sizeof(T);
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}
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};
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template<class T, class U>
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constexpr bool operator==(const default_allocator<T>&, const default_allocator<U>&){
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return true;
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}
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template<class T, class U>
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constexpr bool operator!=(const default_allocator<T>&, const default_allocator<U>&){
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return false;
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}
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}
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}
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#endif
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