RedBear-OS/recipes/core/base/ipcd/examples/main.rs

use std::{
    fs::{File, OpenOptions},
    io::{self, prelude::*},
    os::unix::io::{AsRawFd, FromRawFd, RawFd},
    thread,
    time::Duration,
};

fn from_syscall_error(error: syscall::Error) -> io::Error {
    io::Error::from_raw_os_error(error.errno as i32)
}
fn nonblock(file: &File) -> io::Result<()> {
    syscall::fcntl(
        file.as_raw_fd() as usize,
        syscall::F_SETFL,
        syscall::O_NONBLOCK,
    )
    .map(|_| ())
    .map_err(from_syscall_error)
}
fn dup(file: &File, buf: &str) -> io::Result<File> {
    let stream =
        syscall::dup(file.as_raw_fd() as usize, buf.as_bytes()).map_err(from_syscall_error)?;
    Ok(unsafe { File::from_raw_fd(stream as RawFd) })
}

fn main() -> io::Result<()> {
    let mut buf = [0; 5];
    let server = File::create("chan:hello_world")?;
    {
        println!("Testing O_EXCL...");
        assert_eq!(
            OpenOptions::new()
                .write(true)
                .create_new(true)
                .open("chan:hello_world")
                .unwrap_err()
                .kind(),
            io::ErrorKind::AlreadyExists
        );

        println!("Testing connecting...");

        File::open("chan:hello_world")?; // closed connection will silently be skipped
        let mut client = File::create("chan:hello_world")?; // O_CREAT without O_EXCL does nothing
        let tmp = File::open("chan:hello_world")?; // multiple connections are handled

        let mut stream = dup(&server, "listen")?;
        assert!(dup(&server, "listen").is_ok());
        drop(tmp);

        println!("Testing basic I/O...");

        stream.write(b"abc")?;
        stream.flush()?;
        println!("-> Wrote message");

        assert_eq!(client.read(&mut buf)?, 3);
        assert_eq!(&buf[..3], b"abc");
        println!("-> Read message");

        println!("Testing close...");

        drop(client);
        assert_eq!(
            stream.write(b"a").unwrap_err().kind(),
            io::ErrorKind::BrokenPipe
        );
        assert_eq!(stream.read(&mut buf)?, 0);
    }
    println!("Testing alternative connect method...");

    let mut client = dup(&server, "connect")?;
    let mut stream = dup(&server, "listen")?;

    println!("Testing blocking I/O...");

    let mut client_clone = client.try_clone()?;

    let thread = thread::spawn(move || -> io::Result<()> {
        println!("--> Thread: Sleeping for 1 second...");
        thread::sleep(Duration::from_secs(1));
        println!("--> Thread: Writing...");
        client_clone.write(b"def")?;
        client_clone.flush()?;
        Ok(())
    });

    assert_eq!(stream.read(&mut buf)?, 3);
    assert_eq!(&buf[..3], b"def");
    println!("-> Read message");

    thread.join().unwrap().unwrap();

    println!("Testing non-blocking I/O...");

    nonblock(&client)?;
    nonblock(&server)?;

    assert_eq!(
        client.read(&mut buf).unwrap_err().kind(),
        io::ErrorKind::WouldBlock
    );
    println!("-> Read would block");

    assert_eq!(
        dup(&server, "listen").unwrap_err().kind(),
        io::ErrorKind::WouldBlock
    );
    println!("-> Accept would block");

    drop(client);
    {
        let mut client = File::open("chan:hello_world")?;
        nonblock(&client)?;

        assert_eq!(
            client.write(b"a").unwrap_err().kind(),
            io::ErrorKind::WouldBlock
        );
        println!("-> Write before accept would block");
    }

    let mut client = dup(&server, "connect")?;
    nonblock(&client)?;

    assert_eq!(
        client.write(b"a").unwrap_err().kind(),
        io::ErrorKind::WouldBlock
    );
    println!("-> Write before accept would block (alternative connection method)");

    println!("Everything tested!");
    Ok(())
}