// SPDX-License-Identifier: Apache-2.0

// ----------------------------------------------------------------------------

// Copyright 2011-2021 Arm Limited

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not

// use this file except in compliance with the License. You may obtain a copy

// of the License at:

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

// License for the specific language governing permissions and limitations

// under the License.

// ----------------------------------------------------------------------------

#include "astcenc_mathlib.h"

/**

 * @brief 64-bit rotate left.

 *

 * @param val   The value to rotate.

 * @param count The rotation, in bits.

 */

static inline uint64_t rotl(uint64_t val, int count)

{

  return (val << count) | (val >> (64 - count));

}

/* See header for documentation. */

void astc::rand_init(uint64_t state[2])

{

  state[0] = 0xfaf9e171cea1ec6bULL;

  state[1] = 0xf1b318cc06af5d71ULL;

}

/* See header for documentation. */

uint64_t astc::rand(uint64_t state[2])

{

  uint64_t s0 = state[0];

  uint64_t s1 = state[1];

  uint64_t res = s0 + s1;

  s1 ^= s0;

  state[0] = rotl(s0, 24) ^ s1 ^ (s1 << 16);

  state[1] = rotl(s1, 37);

  return res;

}