Function preadv

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

Available on crate feature dep_nc only.

Read from a file descriptor without changing file offset.

Examples

use core::ffi::c_void;

let path = "/etc/passwd";
let ret = unsafe { nc::openat(nc::AT_FDCWD, 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 *const c_void,
    });
}
let iov_len = iov.len();
let ret = unsafe { nc::preadv(fd as usize, &mut iov, 0, iov_len - 1) };
assert!(ret.is_ok());
assert_eq!(ret, Ok(capacity as nc::ssize_t));
let ret = unsafe { nc::close(fd) };
assert!(ret.is_ok());