DownElement.h

/**
 * @file
 *  This file is part of PUML
 *
 *  For conditions of distribution and use, please see the copyright
 *  notice in the file 'COPYING' at the root directory of this package
 *  and the copyright notice at https://github.com/TUM-I5/PUMGen
 *
 * @copyright 2017 Technische Universitaet Muenchen
 * @author Sebastian Rettenberger <sebastian.rettenberger@tum.de>
 */

#ifndef PUML_DOWNELEMENT_H
#define PUML_DOWNELEMENT_H

#include <algorithm>
#include <cstring>
#include <unordered_set>

namespace PUML
{

namespace internal
{

/**
 * A hashable element defined by the global ids of
 * the down elements
 *
 * @tparam N The number of down elements
 */
template<unsigned int N>
struct DownElement
{
	/** The global ids of the downward elements */
	unsigned long down[N];

	DownElement(const unsigned long down[N])
	{
		memcpy(this->down, down, N*sizeof(unsigned long));
		std::sort(this->down, this->down+N);
	}

	bool operator==(const DownElement &other) const
	{
		return memcmp(down, other.down, N*sizeof(unsigned long)) == 0;
	}
};

template<unsigned int N>
struct DownElementHash
{
	std::size_t operator()(const DownElement<N> &element) const
	{
		std::size_t h = std::hash<unsigned long>{}(element.down[0]);
		for (unsigned int i = 1; i < N; i++)
			hash_combine(h, element.down[i]);

		return h;
	}

	/**
	 * Taken from: https://stackoverflow.com/questions/2590677/how-do-i-combine-hash-values-in-c0x
	 */
	template<typename T>
	static void hash_combine(std::size_t& seed, const T& v)
	{
		std::hash<T> hasher;
		seed ^= hasher(v) + 0x9e3779b9 + (seed<<6) + (seed>>2);
	}
};

}

}

#endif // PUML_DOWNELEMENT_H