use std::{fs::File, io, mem, os::unix::io::AsRawFd, thread, time::Duration};

fn from_syscall_error(error: syscall::Error) -> io::Error {
    io::Error::from_raw_os_error(error.errno as i32)
}
fn main() -> Result<(), io::Error> {
    let file = File::open("shm:counter")?;
    println!("Reading from map... ");
    let counter = unsafe {
        &mut *(syscall::fmap(
            file.as_raw_fd() as usize,
            &syscall::Map {
                offset: 0,
                address: 0,
                size: mem::size_of::<usize>(),
                flags: syscall::PROT_READ | syscall::PROT_WRITE | syscall::MAP_SHARED,
            },
        )
        .map_err(from_syscall_error)? as *mut usize)
    };
    println!("Read value {}", counter);
    *counter += 1;
    println!("Increased value to {}", counter);

    thread::sleep(Duration::from_secs(1));
    Ok(())
}