/**
	This file is a part of rexy's general purpose library
	Copyright (C) 2020 rexy712

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Affero General Public License for more details.

	You should have received a copy of the GNU Affero General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef REXY_DEFAULT_ALLOCATOR_HPP
#define REXY_DEFAULT_ALLOCATOR_HPP

#include <cstdlib> //size_t
#include <type_traits> //true_type, false_type
#include <new>

namespace rexy{

	namespace detail{

		template<class T>
		struct default_allocator
		{
			using pointer = T*;
			using const_pointer = const T*;
			using void_pointer = void*;
			using const_void_pointer = const void*;
			using value_type = T;
			using size_type = size_t;
			using difference_type = ptrdiff_t;
			using is_always_equal = std::true_type;
			using propagate_on_container_copy_assignment = std::false_type;
			using propagate_on_container_move_assignment = std::false_type;
			using propagate_on_container_swap = std::false_type;

			template<class U>
			struct rebind{
				using other = default_allocator<U>;
			};

		private:
			constexpr bool has_overflow(size_type n)const{
				return n > max_size();
			}

		public:
			default_allocator(void) = default;
			default_allocator(const default_allocator&) = default;
			default_allocator(default_allocator&&) = default;
			template<class U>
			constexpr default_allocator(const default_allocator<U>&)noexcept{}
			~default_allocator(void) = default;

			pointer allocate(size_type n){
				size_type bytes = has_overflow(n) ? size_type{-1} : n*sizeof(T);
				if constexpr(alignof(T) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__){
					return reinterpret_cast<pointer>(::operator new(bytes));
				}else{
					return reinterpret_cast<pointer>(::operator new(bytes, static_cast<std::align_val_t>(alignof(T))));
				}
			}
			void deallocate(pointer p, size_type n){
				size_type bytes = has_overflow(n) ? size_type{-1} : n*sizeof(T);
				if constexpr(alignof(T) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__){
					::operator delete(p, bytes);
				}else{
					::operator delete(p, bytes, static_cast<std::align_val_t>(alignof(T)));
				}
			}
			constexpr size_type max_size(void)const{
				return size_type{-1}/sizeof(T);
			}
		};
		template<class T, class U>
		constexpr bool operator==(const default_allocator<T>&, const default_allocator<U>&){
			return true;
		}
		template<class T, class U>
		constexpr bool operator!=(const default_allocator<T>&, const default_allocator<U>&){
			return false;
		}
	}
}

#endif