1/*-
2 * Copyright (c) 2016 (Graeme Jenkinson)
3 * All rights reserved.
4 *
5 * This software was developed by BAE Systems, the University of Cambridge
6 * Computer Laboratory, and Memorial University under DARPA/AFRL contract
7 * FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent Computing
8 * (TC) research program.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 */
32
33#include <sys/types.h>
34
35#include "dtrace_xoroshiro128_plus.h"
36
37static __inline uint64_t
38rotl(const uint64_t x, int k)
39{
40	return (x << k) | (x >> (64 - k));
41}
42
43/*
44 * This is the jump function for the generator. It is equivalent to 2^64 calls
45 * to next(); it can be used to generate 2^64 non-overlapping subsequences for
46 * parallel computations.
47 */
48void
49dtrace_xoroshiro128_plus_jump(uint64_t * const state,
50	uint64_t * const jump_state)
51{
52	static const uint64_t JUMP[] = { 0xbeac0467eba5facb,
53		0xd86b048b86aa9922 };
54
55	uint64_t s0 = 0;
56	uint64_t s1 = 0;
57	int i = 0;
58	int b = 0;
59	for (i = 0; i < sizeof JUMP / sizeof *JUMP; i++) {
60		for (b = 0; b < 64; b++) {
61			if (JUMP[i] & 1ULL << b) {
62				s0 ^= state[0];
63				s1 ^= state[1];
64			}
65			dtrace_xoroshiro128_plus_next(state);
66		}
67	}
68	jump_state[0] = s0;
69	jump_state[1] = s1;
70}
71
72/*
73 * xoroshiro128+ - XOR/rotate/shift/rotate
74 * xorshift.di.unimi.it
75 */
76uint64_t
77dtrace_xoroshiro128_plus_next(uint64_t * const state)
78{
79	const uint64_t s0 = state[0];
80	uint64_t s1 = state[1];
81	uint64_t result;
82	result = s0 + s1;
83
84	s1 ^= s0;
85	state[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14);
86	state[1] = rotl(s1, 36);
87
88	return result;
89}
90