1// SPDX-License-Identifier: Apache-2.0
2// ----------------------------------------------------------------------------
3// Copyright 2011-2021 Arm Limited
4//
5// Licensed under the Apache License, Version 2.0 (the "License"); you may not
6// use this file except in compliance with the License. You may obtain a copy
7// of the License at:
8//
9//     http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing, software
12// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
13// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
14// License for the specific language governing permissions and limitations
15// under the License.
16// ----------------------------------------------------------------------------
17
18#include "astcenc_mathlib.h"
19
20/**
21 * @brief 64-bit rotate left.
22 *
23 * @param val   The value to rotate.
24 * @param count The rotation, in bits.
25 */
26static inline uint64_t rotl(uint64_t val, int count)
27{
28	return (val << count) | (val >> (64 - count));
29}
30
31/* See header for documentation. */
32void astc::rand_init(uint64_t state[2])
33{
34	state[0] = 0xfaf9e171cea1ec6bULL;
35	state[1] = 0xf1b318cc06af5d71ULL;
36}
37
38/* See header for documentation. */
39uint64_t astc::rand(uint64_t state[2])
40{
41	uint64_t s0 = state[0];
42	uint64_t s1 = state[1];
43	uint64_t res = s0 + s1;
44	s1 ^= s0;
45	state[0] = rotl(s0, 24) ^ s1 ^ (s1 << 16);
46	state[1] = rotl(s1, 37);
47	return res;
48}
49