in src/kissrandom.h [38:53]
uint32_t kiss() {
// Linear congruence generator
x = 69069 * x + 12345;
// Xor shift
y ^= y << 13;
y ^= y >> 17;
y ^= y << 5;
// Multiply-with-carry
uint64_t t = 698769069ULL * z + c;
c = t >> 32;
z = (uint32_t) t;
return x + y + z;
}