//ww:run-exit 55
// Migrated from 778_bufio_vstream_run row stream_unread.
package main;
import bufio;
import memio;
import io;
export fn main() i32 = {
    let raw: [4]u8;
    raw[0]=88u8; raw[1]=89u8; raw[2]=90u8;
    let mst: memio.stream = memio.dynamicfrom(raw[0:3]);
    let vs: io.stream = &mst.vt;
    let rbuf: [4]u8;
    let wbuf: [4]u8;
    let b: bufio.stream = bufio.newstream(vs, rbuf[0:4], wbuf[0:4]);
    let bvs: io.stream = &b.vt;
    let out: [4]u8;
    let rd = io.read(bvs, out[0:3]);
    let n: size = 0;
    if (rd is size) { n = rd as size; };
    if (n != 3: size || out[0] != 88u8 || out[2] != 90u8) { return 81; };
    let push: [2]u8;
    push[0]=88u8; push[1]=89u8;
    bufio.unread(&b, push[0:2]);
    let out2: [2]u8;
    let rd2 = io.read(bvs, out2[0:2]);
    let n2: size = 0;
    if (rd2 is size) { n2 = rd2 as size; };
    if (n2 != 2: size || out2[0] != 88u8 || out2[1] != 89u8) { return 82; };
    return 55;
};