/*  Written in 2019 by David Blackman and Sebastiano Vigna (vigna@acm.org)

To the extent possible under law, the author has dedicated all copyright
and related and neighboring rights to this software to the public domain
worldwide.

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <stdint.h>
#include <string.h>

/* This is xoshiro512++ 1.0, one of our all-purpose, rock-solid
   generators. It has excellent (about 1ns) speed, a state (512 bits) that
   is large enough for any parallel application, and it passes all tests
   we are aware of.

   For generating just floating-point numbers, xoshiro512+ is even faster.

   The state must be seeded so that it is not everywhere zero. If you have
   a 64-bit seed, we suggest to seed a splitmix64 generator and use its
   output to fill s. */

static inline uint64_t rotl(const uint64_t x, int k) {
	return (x << k) | (x >> (64 - k));
}


static uint64_t s[8];

uint64_t next(void) {
	const uint64_t result = rotl(s[0] + s[2], 17) + s[2];

	const uint64_t t = s[1] << 11;

	s[2] ^= s[0];
	s[5] ^= s[1];
	s[1] ^= s[2];
	s[7] ^= s[3];
	s[3] ^= s[4];
	s[4] ^= s[5];
	s[0] ^= s[6];
	s[6] ^= s[7];

	s[6] ^= t;

	s[7] = rotl(s[7], 21);

	return result;
}


/* This is the jump function for the generator. It is equivalent
   to 2^256 calls to next(); it can be used to generate 2^256
   non-overlapping subsequences for parallel computations. */

void jump(void) {
	static const uint64_t JUMP[] = { 0x33ed89b6e7a353f9, 0x760083d7955323be, 0x2837f2fbb5f22fae, 0x4b8c5674d309511c, 0xb11ac47a7ba28c25, 0xf1be7667092bcc1c, 0x53851efdb6df0aaf, 0x1ebbc8b23eaf25db };

	uint64_t t[sizeof s / sizeof *s];
	memset(t, 0, sizeof t);
	for(int i = 0; i < sizeof JUMP / sizeof *JUMP; i++)
		for(int b = 0; b < 64; b++) {
			if (JUMP[i] & UINT64_C(1) << b)
				for(int w = 0; w < sizeof s / sizeof *s; w++)
					t[w] ^= s[w];
			next();
		}
	
	memcpy(s, t, sizeof s);	
}


/* This is the long-jump function for the generator. It is equivalent to
   2^384 calls to next(); it can be used to generate 2^128 starting points,
   from each of which jump() will generate 2^128 non-overlapping
   subsequences for parallel distributed computations. */

void long_jump(void) {
	static const uint64_t LONG_JUMP[] = { 0x11467fef8f921d28, 0xa2a819f2e79c8ea8, 0xa8299fc284b3959a, 0xb4d347340ca63ee1, 0x1cb0940bedbff6ce, 0xd956c5c4fa1f8e17, 0x915e38fd4eda93bc, 0x5b3ccdfa5d7daca5 };

	uint64_t t[sizeof s / sizeof *s];
	memset(t, 0, sizeof t);
	for(int i = 0; i < sizeof LONG_JUMP / sizeof *LONG_JUMP; i++)
		for(int b = 0; b < 64; b++) {
			if (LONG_JUMP[i] & UINT64_C(1) << b)
				for(int w = 0; w < sizeof s / sizeof *s; w++)
					t[w] ^= s[w];
			next();
		}
	
	memcpy(s, t, sizeof s);	
}