curlywas/examples/microw8/random.cwa

import "env.memory" memory(4);

global mut randomState: i64 = 37i64;

fn random() -> i32 {
    (random64() >> 32i64) as i32
}

fn random64() -> i64 {
    let state: i64;
    randomState = (state := (
                          state := randomState ^ (randomState #>> 12i64)
                      ) ^ (state << 25i64)
                  ) ^ (state #>> 27i64);
    randomState * 2685821657736338717i64
}

fn randomf() -> f32 {
    f32.reinterpret_i32(1065353216 | (random() #>> 9)) - 1 as f32
}

fn seed(s: i32) {
    randomState = (s as i64 << 32i64) ^ ((63 - s) as i64);
    randomState = random64();
    randomState = random64();
}

export fn tic(time: i32) {
    let i: i32;
    loop pixels {
        seed(i + (time / 10) * 320);
        i?120 = (randomf() * 256 as f32 + time as f32 / 10 as f32) as i32 & 128;
        branch_if (i := i + 1) < 320*256: pixels
    }
}