virtualx-engine/thirdparty/misc/pcg.cpp
Rémi Verschelde b5d9099626 Revert "Properly setup seed in RNG"
This reverts commit 1dd72dca45.
As pointed out in #27171, it would break compatibility with 3.1.0.
2019-04-09 09:36:31 +02:00

15 lines
577 B
C++

// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
#include "pcg.h"
uint32_t pcg32_random_r(pcg32_random_t* rng)
{
uint64_t oldstate = rng->state;
// Advance internal state
rng->state = oldstate * 6364136223846793005ULL + (rng->inc|1);
// Calculate output function (XSH RR), uses old state for max ILP
uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
uint32_t rot = oldstate >> 59u;
return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
}