Function nc::io_setup

pub unsafe fn io_setup(
    nr_events: u32,
    ctx_id: &mut aio_context_t,
) -> Result<(), Errno>

Create an asynchronous I/O context.

Create an aio_context capable of receiving at least nr_events. ctx_id must not point to an aio_context that already exists, and must be initialized to 0 prior to the call.

On successful creation of the aio_context, ctx_id is filled in with the resulting handle.

Errors

• May fail with -EINVAL if *ctx_id is not initialized, if the specified nr_events exceeds internal limits.
• May fail with -EAGAIN if the specified nr_events exceeds the user’s limit of available events.
• May fail with -ENOMEM if insufficient kernel resources are available.
• May fail with -EFAULT if an invalid pointer is passed for ctx_id.
• Will fail with -ENOSYS if not implemented.

Examples

use std::alloc::{alloc, Layout};
use std::ptr;

let mut ctx: nc::aio_context_t = 0;
let nr_events = 10;

let ret = unsafe { nc::io_setup(nr_events, &mut ctx) };
assert!(ret.is_ok());

let out_filename = "/tmp/nc-io-setup";
let fd = unsafe {
    nc::openat(
        nc::AT_FDCWD,
        out_filename,
        nc::O_CREAT | nc::O_DIRECT | nc::O_WRONLY,
        nc::S_IRUSR | nc::S_IWUSR,
    )
};
assert!(fd.is_ok());
let fd = fd.unwrap();

let layout =
    Layout::from_size_align(nc::PAGE_SIZE, nc::PAGE_SIZE).expect("Failed to create mem layout");
let ptr = unsafe { alloc(layout) };
if ptr.is_null() {
    eprintln!("Failed to alloc aligned memory");
    return;
}
let mut buf: Box<[u8]> = unsafe {
    let slice = ptr::slice_from_raw_parts_mut(ptr, nc::PAGE_SIZE);
    Box::from_raw(slice)
};

let msg = "hello Rust\n";
unsafe {
    ptr::copy_nonoverlapping(msg.as_ptr(), buf.as_mut_ptr(), msg.len());
}

let mut iocb = Vec::with_capacity(1);
iocb.push(nc::iocb_t {
    aio_data: buf.as_ptr() as u64,
    aio_lio_opcode: nc::IOCB_CMD_PWRITE,
    aio_fildes: fd as u32,
    aio_buf: buf.as_ptr() as u64,
    aio_nbytes: nc::PAGE_SIZE as u64,
    ..Default::default()
});

let ret = unsafe { nc::io_submit(ctx, &iocb) };
if let Err(errno) = ret {
    eprintln!("io_submit() failed, err: {}", nc::strerror(errno));
    return;
}

let mut events = vec![nc::io_event_t::default(); 10];
let timeout = nc::timespec_t {
    tv_sec: 1,
    tv_nsec: 100,
};

let ret = unsafe { nc::io_getevents(ctx, 1, &mut events, Some(&timeout)) };
assert!(ret.is_ok());
let nread = ret.unwrap();
assert_eq!(nread, 1);

unsafe {
    let _ret = nc::close(fd);
    let _ret = nc::io_destroy(ctx);
}