tokio/io-ring hello world

main.rs

use std::io;
use std::os::unix::io::AsRawFd;

use io_uring::IoUring;
use io_uring::opcode::{Write, types::Fd};

use thiserror::Error;

#[derive(Error, Debug)]
enum MyError {
    #[error("创建 io_uring 失败")] RingCreation(#[from] io::Error),
    #[error("提交 sqe 失败")] Submit,
}

fn main() -> Result<(), MyError> {
    let mut ring = IoUring::new(10)?;

    let s = String::from("hello, world!\n");
    let stdout = io::stdout();
    let stdout = stdout.lock();
    let out_fd = Fd(stdout.as_raw_fd());
    let sqe = Write::new(out_fd, s.as_ptr(), s.len() as u32).build();

    {
        let sq = ring.submission();
        let mut avail_sq = sq.available();

        unsafe {
            // SAFETY: write syscall arguments lives long enough until program
            // terminates.
            // 怎么保证参数里的 s: String 所有权转移给了内核？
            avail_sq.push(sqe).map_err(|_| MyError::Submit)?;
        };
    }

    let completed = ring.submit_and_wait(1)?;

    eprintln!("{} tasks completed", completed);

    Ok(())
}