/*

 * PCG Random Number Generation for C.

 *

 * Copyright 2014 Melissa O'Neill <oneill@pcg-random.org>

 *

 * 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.

 *

 * For additional information about the PCG random number generation scheme,

 * including its license and other licensing options, visit

 *

 *       http://www.pcg-random.org

 */

#include "pcg_basic.h"

void pcg32_srandom_r(pcg32_random_t* rng, uint64_t initial_state, uint64_t initseq) {

    rng->state = 0U;

    rng->inc = (initseq << 1u) | 1u;

    pcg32_random_r(rng);

    rng->state += initial_state;

    pcg32_random_r(rng);

}

uint32_t pcg32_random_r(pcg32_random_t* rng) {

    uint64_t oldstate = rng->state;

    rng->state = oldstate * 6364136223846793005ULL + rng->inc;

    uint32_t xorshifted = (uint32_t)(((oldstate >> 18u) ^ oldstate) >> 27u);

    uint32_t rot = (uint32_t)(oldstate >> 59u);

    return (xorshifted >> rot) | (xorshifted << ((~rot + 1u) & 31)); /* was (xorshifted >> rot) | (xorshifted << ((-rot) & 31)) */

}