/*
 * memalignment.h
 *
 *  Created on: Dec 13, 2013
 *      Author: gregor
 */

#ifndef GLTB_MEMALIGNMENT_H_
#define GLTB_MEMALIGNMENT_H_

#include <memory>
#include <utility>
#include <cstdlib>

namespace gltb {
	template<typename T, std::size_t alignment>
	class AlignedAllocator {
		typedef T value_type;
		typedef T* pointer;
		typedef T& reference;
		typedef const T* const_pointer;
		typedef const T& const_reference;
		typedef std::size_t size_type;
		typedef std::ptrdiff_t difference_type;

		template <class Type>
		struct rebind {
			typedef AlignedAllocator<Type, alignment> other;
		};

		pointer address(reference x) const noexcept
		{
			return std::addressof(x);
		}

		const_pointer address(const_reference x) const noexcept
		{
			return std::addressof(x);
		}

		pointer allocate(size_type n, AlignedAllocator<void>::const_pointer hint = 0)
		{
			// compute required size of allocation
			std::size_t allocationSize = n + alignment + std::max(alignment, sizeof(void *));

			char *realBase = reinterpret_cast<char *>(std::malloc(allocationSize));

			char *alignedBase;
			// align base address
			alignedBase = (realBase + alignment) % alignment;
			// make sure there is room for the base address at the start of the aligned block
			if(alignedBase - realBase < sizeof(void *)) {
				alignedBase += alignment;
			}

			// store original base address before aligned block starts
			reinterpret_cast<void *>(alignedBase)[-1] = realBase;

			return reinterpret_cast<pointer>(alignedBase);
		}

		void deallocate (pointer p, size_type n)
		{
			// the real base address of the block is a pointer stored before the aligned start address
			void *realPointer = reinterpret_cast<void *>(p) - 1;

			std::free(realPointer);
		}

		size_type max_size() const throw()
		{
			// analogous to GCC STL:
			return std::size_t(-1) / sizeof(T);
		}

		template<class U, class... Args>
		void construct(U* p, Args&&... args)
		{
			::new( (void *) p)(std::forward<Args>(args)...);
		}

		template <class U>
		void destroy(U* p)
		{
			p->~_Tp();
		}
	};
}

#endif /* GLTB_MEMALIGNMENT_H_ */