Function nc::preadv

pub fn preadv(
    fd: i32, 
    vec: &mut [iovec_t], 
    pos_l: usize, 
    pos_h: usize
) -> Result<ssize_t, Errno>

Read from a file descriptor without changing file offset.

let path = "/etc/passwd";
let ret = nc::open(path, nc::O_RDONLY, 0);
assert!(ret.is_ok());
let fd = ret.unwrap();
let mut buf = [[0_u8; 64]; 4];
let capacity = 4 * 64;
let mut iov = Vec::with_capacity(buf.len());
for ref mut item in (&mut buf).iter() {
    iov.push(nc::iovec_t {
        iov_len: item.len(),
        iov_base: item.as_ptr() as usize,
    });
}
let iov_len = iov.len();
let ret = nc::preadv(fd, &mut iov, 0, iov_len - 1);
assert!(ret.is_ok());
assert_eq!(ret, Ok(capacity as nc::ssize_t));
assert!(nc::close(fd).is_ok());