/**
	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 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 General Public License for more details.

	You should have received a copy of the GNU 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>
#include <limits> //numeric_limits

namespace rexy{

	template<class T>
	struct 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 = allocator<U>;
		};

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

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

		pointer allocate(size_type n){
			size_type bytes = has_overflow(n) ? std::numeric_limits<size_type>::max() : 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){
#if defined(__clang__) && !defined(__cpp_sized_deallocation)
			//clang does not enable ::operator delete(void* ptr, std::size_t sz) by default for some reason
			if constexpr(alignof(T) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__){
				::operator delete(p);
			}else{
				::operator delete(p, static_cast<std::align_val_t>(alignof(T)));
			}
#else
			size_type bytes = has_overflow(n) ? std::numeric_limits<size_type>::max() : 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)));
			}
#endif
		}
		constexpr size_type max_size(void)const{
			return std::numeric_limits<size_type>::max()/sizeof(T);
		}
	};
	template<class T, class U>
	constexpr bool operator==(const allocator<T>&, const allocator<U>&){
		return true;
	}
	template<class T, class U>
	constexpr bool operator!=(const allocator<T>&, const allocator<U>&){
		return false;
	}
}

#endif