Signal driven I/O

main.rs

use nix::libc::{F_SETOWN, STDIN_FILENO};
use nix::sys::signal::{SigSet, Signal, SigHandler, SigAction, SaFlags, sigaction};
use nix::unistd::{getpid, read};
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread;
use std::time::Duration;
use nix::fcntl::fcntl;

static SIGNAL_RECEIVED: AtomicBool = AtomicBool::new(false);

extern "C" fn sigio_handler(sig: i32) {
    println!("received signal {sig}");
    SIGNAL_RECEIVED.store(true, Ordering::SeqCst);
}

fn main() {
    // Establish handler for "I/O possible" signal


    fcntl(STDIN_FILENO, nix::fcntl::FcntlArg::F_SETFL(nix::fcntl::OFlag::O_ASYNC)).unwrap();

    // Create a SigSet containing SIGIO
    let sigset = SigSet::empty();
    // Register the signal handler for SIGIO
    let sigio_action = SigAction::new(
        SigHandler::Handler(sigio_handler),
        SaFlags::SA_RESTART,
        sigset,
    );
    unsafe {
        sigaction(Signal::SIGIO, &sigio_action).unwrap();
    }

    unsafe {
        let _ =  nix::libc::fcntl(STDIN_FILENO, F_SETOWN, getpid());
    }



    // https://man7.org/tlpi/code/online/dist/tty/tty_functions.c.html
    // Chapter 62: Terminals
    let mut t = termios::Termios::from_fd(STDIN_FILENO).unwrap();

    t.c_lflag &= !(termios::ICANON | termios::ECHO);
    t.c_lflag |= termios::ISIG;
    t.c_iflag &= !termios::ICRNL;

    t.c_cc[termios::VMIN] = 1;
    t.c_cc[termios::VTIME] = 0;
    termios::tcsetattr(STDIN_FILENO, termios::TCSAFLUSH, &t).unwrap();



    let mut cnt = 0;
    'outer: loop {
        if SIGNAL_RECEIVED.load(Ordering::SeqCst){
            let mut buf = vec![0u8; 1024];
            SIGNAL_RECEIVED.store(false, Ordering::SeqCst);
            while read(STDIN_FILENO, &mut buf[..]).unwrap() > 1 {
                let content = String::from_utf8_lossy(&buf);
                println!("cnt={cnt}; read={content}");

                if content.contains("#") {
                    break 'outer;
                }
                cnt += 1;
            }
        }
        thread::sleep(Duration::from_secs(1));
    }
}