seed

pub fn seed(self: *Xoshiro256, init_s: u64) void {
    // Xoshiro requires 256-bits of seed.
    var gen = std.Random.SplitMix64.init(init_s);

    self.s[0] = gen.next();
    self.s[1] = gen.next();
    self.s[2] = gen.next();
    self.s[3] = gen.next();
}