//ww:run-exit 44
// Migrated from 776_memio_vstream_run row dynamicfrom_alt_rw.
package main;
import memio;
import io;
export fn main() i32 = {
    let seed: [4]u8;
    seed[0] = 1u8; seed[1] = 2u8; seed[2] = 3u8; seed[3] = 4u8;
    let st: memio.stream = memio.dynamicfrom(seed[0:4]);
    let s: io.stream = &st.vt;
    let out: [4]u8;
    let rd = io.read(s, out[0:4]);
    let rn: size = 0;
    if (rd is size) { rn = rd as size; };
    let extra: [2]u8;
    extra[0] = 99u8; extra[1] = 100u8;
    let wr = io.write(s, extra[0:2]);
    let wn: size = 0;
    if (wr is size) { wn = wr as size; };
    if (rn == 4: size && wn == 2: size && out[0] == 1u8 && out[3] == 4u8) { return 44; };
    return 99;
};