/// Transfer data between two file descriptors.
pub unsafe fn sendfile(
out_fd: i32,
in_fd: i32,
offset: &mut off_t,
count: size_t,
) -> Result<ssize_t, Errno> {
let out_fd = out_fd as usize;
let in_fd = in_fd as usize;
let offset_ptr = offset as *mut off_t as usize;
syscall4(SYS_SENDFILE, out_fd, in_fd, offset_ptr, count).map(|ret| ret as ssize_t)
}