// From: http://scv.bu.edu/examples/random_numbers/xoroshiro128_plus/CPP/
// COMPILE WITH AT LEAST C++11
// e.g. gcc version 4.9.2:  g++ -std=c++0x
//      gcc version 5.3.0:  g++ -std=c++11 or -std=c++14
//      intel version 2015 or 2016:  icc -std=c++11

#ifndef XOROSHIRO128_PLUS_H
#define XOROSHIRO128_PLUS_H


#include <stdint.h>
#include <array>
#include <cstdint>
#include <exception>

namespace xoroshiro128_plus {


class Xoroshiro128_plus {
	public:
		// The seed.
		uint64_t seed_0,seed_1 ;

		// Constructor for STL iterators.
		// call with Xoroshiro128_plus(my_vec.begin(), my_vec.end())
		// Since this is templated it needs to be implemented here.
		template<typename ForwardIterator>
		Xoroshiro128_plus(ForwardIterator begin, ForwardIterator end) {
			if (end-begin < 2)
				throw "Need 2 elements to initialize the RNG." ;
			int i = 0 ;
			seed_0 = *begin;
			++begin;
			seed_1 = *begin;
		}


		// Constructor for a seed in an array.
		Xoroshiro128_plus(uint64_t seed_[]) ;

		// Return the total number of bytes in the seed
		int get_seed_bytes() ;
		// Return the number of elements in the seed.
		int get_seed_length() ;

		// Get the next uint64 random number.
		uint64_t next_uint64() ;
		// get the next double.
		double next_double() ;
		// get the next float.
		float next_float() ;

		// jump ahead by 2^64 and return a new
		// generator.
		Xoroshiro128_plus jump() ;

		// copy the RNG object.
		Xoroshiro128_plus(const Xoroshiro128_plus &obj) ;


		// Static method to get some random bytes from hardware
		static void get_random_seed(uint64_t dest[]) ;

	private:
		// rotate left.
		static inline uint64_t rotl(const uint64_t x, int k);
		// The number of elements in the seed
		static const int seed_length ;
           	inline uint64_t next() ;

};



}
#endif /* XOROSHIRO128_PLUS_H */