mirror of
https://github.com/TerryCavanagh/VVVVVV.git
synced 2024-11-05 02:39:41 +01:00
e6a3df6ca6
In its previous location, it would only print the value of `s` after it had been mutated by `splitmix32` four times, and it doesn't get used after that, so the print isn't very useful. Mixing code and declarations here is fine because starting from a few months ago, we compile with C99 and if we ever need to compile with C90 then it's trivial to add braces surrounding the declarations.
68 lines
1.2 KiB
C
68 lines
1.2 KiB
C
#include <stdint.h>
|
|
|
|
#include "Vlogging.h"
|
|
|
|
/* Implements the xoshiro128+ PRNG. */
|
|
|
|
static uint32_t rotl(const uint32_t x, const int k)
|
|
{
|
|
return (x << k) | (x >> (32 - k));
|
|
}
|
|
|
|
static uint32_t s[4];
|
|
|
|
static uint32_t splitmix32(uint32_t* x)
|
|
{
|
|
uint32_t z = (*x += 0x9e3779b9UL);
|
|
z = (z ^ (z >> 15)) * 0xbf58476dUL;
|
|
z = (z ^ (z >> 13)) * 0x94d049bbUL;
|
|
return z ^ (z >> 16);
|
|
}
|
|
|
|
static void seed(
|
|
const uint32_t s0,
|
|
const uint32_t s1,
|
|
const uint32_t s2,
|
|
const uint32_t s3
|
|
) {
|
|
s[0] = s0;
|
|
s[1] = s1;
|
|
s[2] = s2;
|
|
s[3] = s3;
|
|
}
|
|
|
|
uint32_t xoshiro_next(void)
|
|
{
|
|
const uint32_t result = s[0] + s[3];
|
|
|
|
const uint32_t t = s[1] << 9;
|
|
|
|
s[2] ^= s[0];
|
|
s[3] ^= s[1];
|
|
s[1] ^= s[2];
|
|
s[0] ^= s[3];
|
|
|
|
s[2] ^= t;
|
|
|
|
s[3] = rotl(s[3], 11);
|
|
|
|
vlog_debug("Next xoshiro is %u.", result);
|
|
|
|
return result;
|
|
}
|
|
|
|
void xoshiro_seed(uint32_t s)
|
|
{
|
|
vlog_debug("Xoshiro seeded with %u.", s);
|
|
|
|
const uint32_t s0 = splitmix32(&s);
|
|
const uint32_t s1 = splitmix32(&s);
|
|
const uint32_t s2 = splitmix32(&s);
|
|
const uint32_t s3 = splitmix32(&s);
|
|
seed(s0, s1, s2, s3);
|
|
}
|
|
|
|
float xoshiro_rand(void)
|
|
{
|
|
return ((float) xoshiro_next()) / ((float) UINT32_MAX);
|
|
}
|