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/*
* ngtcp2
*
* Copyright (c) 2025 ngtcp2 contributors
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include "ngtcp2_pcg.h"
#include <assert.h>
/*
* PCG implementation from
* https://github.com/imneme/pcg-c/blob/83252d9c23df9c82ecb42210afed61a7b42402d7/include/pcg_variants.h
*
* PCG Random Number Generation for C.
*
* Copyright 2014-2019 Melissa O'Neill <oneill@pcg-random.org>,
* and the PCG Project contributors.
*
* SPDX-License-Identifier: (Apache-2.0 OR MIT)
*
* Licensed under the Apache License, Version 2.0 (provided in
* LICENSE-APACHE.txt and at http://www.apache.org/licenses/LICENSE-2.0)
* or under the MIT license (provided in LICENSE-MIT.txt and at
* http://opensource.org/licenses/MIT), at your option. This file may not
* be copied, modified, or distributed except according to those terms.
*
* Distributed on an "AS IS" BASIS, WITHOUT WARRANTY OF ANY KIND, either
* express or implied. See your chosen license for details.
*
* For additional information about the PCG random number generation scheme,
* visit http://www.pcg-random.org/.
*/
#define NGTCP2_PCG_DEFAULT_MULTIPLIER_64 6364136223846793005ULL
#define NGTCP2_PCG_DEFAULT_INCREMENT_64 1442695040888963407ULL
static void pcg_oneseq_64_step_r(ngtcp2_pcg32 *pcg) {
pcg->state = pcg->state * NGTCP2_PCG_DEFAULT_MULTIPLIER_64 +
NGTCP2_PCG_DEFAULT_INCREMENT_64;
}
void ngtcp2_pcg32_init(ngtcp2_pcg32 *pcg, uint64_t seed) {
pcg->state = 0;
pcg_oneseq_64_step_r(pcg);
pcg->state += seed;
pcg_oneseq_64_step_r(pcg);
}
static uint32_t pcg_rotr_32(uint32_t value, unsigned int rot) {
return (value >> rot) | (value << ((-rot) & 31));
}
static uint32_t pcg_output_xsh_rr_64_32(uint64_t state) {
return pcg_rotr_32((uint32_t)(((state >> 18u) ^ state) >> 27u),
(unsigned int)(state >> 59u));
}
uint32_t ngtcp2_pcg32_rand(ngtcp2_pcg32 *pcg) {
uint64_t oldstate = pcg->state;
pcg_oneseq_64_step_r(pcg);
return pcg_output_xsh_rr_64_32(oldstate);
}
uint32_t ngtcp2_pcg32_rand_n(ngtcp2_pcg32 *pcg, uint32_t n) {
assert(n);
return (uint32_t)(((uint64_t)ngtcp2_pcg32_rand(pcg) * n) >> 32);
}
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