random.c

#include "random.h"

#include <inttypes.h>

// pro tip: never code your own random number generator.
//          always copy someone else

uint64_t keys[2];

inline uint64_t rotate(uint64_t v, uint8_t s) {
  return (v >> s) | (v << (64 - s));
}

inline uint64_t RandomUInt64() {
  uint64_t tmp = keys[0];
  keys[0] += rotate(keys[1] ^ 0xc5462216u ^ ((uint64_t) 0xcf14f4ebu << 32), 1);
  return keys[1] += rotate(tmp ^ 0x75ecfc58u ^ ((uint64_t) 0x9576080cu << 32), 9);
}

void SeedRandom(uint64_t seed) {
  keys[0] = seed;
  keys[1] = seed;

  for (int i = 0; i < 64; i++) {
    RandomUInt64();
  }
}

uint64_t RandomMagic() {
  return RandomUInt64() & RandomUInt64() & RandomUInt64();
}