You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: process_stdin.rs
    path of file: ./repos/wasmtime/crates/wasi/tests
    
    the code of the file until where you have to start completion: use std::io::{BufRead, Write};
use std::process::Command;
use wasmtime_wasi::{HostInputStream, Subscribe};

const VAR_NAME: &str = "__CHILD_PROCESS";

fn main() {
    if cfg!(miri) {
        return;
    }
    // Skip this tests if it looks like we're in a cross-compiled situation and
    // we're emulating this test for a different platform. In that scenario
    // emulators (like QEMU) tend to not report signals the same way and such.
    if std::env::vars()
        .filter(|(k, _v)| k.starts_with("CARGO_TARGET") && k.ends_with("RUNNER"))
        .count()
        > 0
    {
        return;
    }

    match std::env::var(VAR_NAME) {
        Ok(_) => child_process(),
        Err(_) => parent_process(),
    }

    fn child_process() {
        let mut result_write = std::io::stderr();
        let mut child_running = true;
        while child_running {
            tokio::runtime::Builder::new_multi_thread(
    
fn main() {
    if cfg!(miri) {
        return;
    }
    // Skip this tests if it looks like we're in a cross-compiled situation and
    // we're emulating this test for a different platform. In that scenario
    // emulators (like QEMU) tend to not report signals the same way and such.
    if std::env::vars()
        .filter(|(k, _v)| k.starts_with("CARGO_TARGET") && k.ends_with("RUNNER"))
        .count()
        > 0
    {
        return;
    }

    match std::env::var(VAR_NAME) {
        Ok(_) => child_process(),
        Err(_) => parent_process(),
    }

    fn child_process() {
        let mut result_write = std::io::stderr();
        let mut child_running = true;
        while child_running {
            tokio::runtime::Builder::new_multi_thread()
                .enable_all()
                .build()
                .unwrap()
                .block_on(async {
                    'task: loop {
                        println!("child: creating stdin");
                        let mut stdin = wasmtime_wasi::stdin();

                        println!("child: checking that stdin is not ready");
                        assert!(
                            tokio::time::timeout(
                                std::time::Duration::from_millis(100),
                                stdin.ready()
                            )
                            .await
                            .is_err(),
                            "stdin available too soon"
                        );

                        writeln!(&mut result_write, "start").unwrap();

                        println!("child: started");

                        let mut buffer = String::new();
                        loop {
                            println!("child: waiting for stdin to be ready");
                            stdin.ready().await;

                            println!("child: reading input");
                            // We can't effectively test for the case where stdin was closed, so panic if it is...
                            let bytes = stdin.read(1024).unwrap();

                            println!("child got: {:?}", bytes);

                            buffer.push_str(std::str::from_utf8(bytes.as_ref()).unwrap());
                            if let Some((line, rest)) = buffer.split_once('\n') {
                                if line == "all done" {
                                    writeln!(&mut result_write, "done").unwrap();
                                    println!("child: exiting...");
                                    child_running = false;
                                    break 'task;
                                } else if line == "restart_runtime" {
                                    writeln!(&mut result_write, "restarting").unwrap();
                                    println!("child: restarting runtime...");
                                    break 'task;
                                } else if line == "restart_task" {
                                    writeln!(&mut result_write, "restarting").unwrap();
                                    println!("child: restarting task...");
                                    continue 'task;
                                } else {
                                    writeln!(&mut result_write, "{}", line).unwrap();
                                }

                                buffer = rest.to_owned();
                            }
                        }
                    }
                });
            println!("child: runtime exited");
        }
        println!("child: exiting");
    }
}