Wait for any key to be pressed

any-key.rs

use rustix::{event, fd, io, stdio, termios};

pub fn pause() -> Result<(), io::Errno> {
    let attrs = termios::tcgetattr(FD)?;

    // clear any stray input from STDIN
    let _ = termios::tcflush(FD, termios::QueueSelector::IFlush);

    // set STDIN to trap ctrl+c, etc., disable line mode, don't echo input
    let mut new_attrs = attrs.clone();
    new_attrs.special_codes[termios::SpecialCodeIndex::VINTR] = 0;
    new_attrs.special_codes[termios::SpecialCodeIndex::VQUIT] = 0;
    new_attrs.special_codes[termios::SpecialCodeIndex::VKILL] = 0;
    new_attrs.special_codes[termios::SpecialCodeIndex::VEOF] = 0;
    new_attrs.local_modes -= termios::LocalModes::ECHO | termios::LocalModes::ICANON;
    new_attrs.local_modes |= termios::LocalModes::ISIG | termios::LocalModes::NOFLSH;
    termios::tcsetattr(FD, termios::OptionalActions::Now, &new_attrs)?;

    let reset_terminal = ResetTerminal(&attrs);

    // await input
    let events = event::PollFlags::IN
        | event::PollFlags::PRI
        | event::PollFlags::RDBAND
        | event::PollFlags::RDNORM
        | event::PollFlags::RDHUP
        | event::PollFlags::ERR
        | event::PollFlags::HUP
        | event::PollFlags::NVAL;
    match event::poll(&mut [event::PollFd::new(&FD, events)], -1) {
        Ok(_) | Err(io::Errno::WOULDBLOCK) | Err(io::Errno::INTR) => (),
        Err(err) => return Err(err),
    }

    // reset changes to terminal
    drop(reset_terminal);

    // clear any input on STDIN
    let _ = termios::tcflush(FD, termios::QueueSelector::IFlush);

    Ok(())
}

const FD: fd::BorrowedFd<'static> = stdio::stdin();

struct ResetTerminal<'a>(&'a termios::Termios);

impl Drop for ResetTerminal<'_> {
    #[inline]
    fn drop(&mut self) {
        let _ = termios::tcsetattr(FD, termios::OptionalActions::Now, self.0);
    }
}