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/// Receive a message from a socket.
///
/// # Examples
///
/// ```
/// use std::thread;
///
/// const READ_SIDE: usize = 0;
/// const WRITE_SIDE: usize = 1;
///
/// fn main() {
/// let mut fds = [-1_i32; 2];
///
/// let ret = unsafe { nc::socketpair(nc::AF_UNIX, nc::SOCK_STREAM, 0, &mut fds) };
/// assert!(ret.is_ok());
/// println!("socket pairs: {}, {}", fds[0], fds[1]);
///
/// // Start worker thread
/// thread::spawn(move || {
/// println!("worker thread started");
/// let msg = "Hello, Rust";
/// println!("[worker] Will send msg: {msg}");
/// let ret = unsafe { nc::sendto(fds[WRITE_SIDE], msg.as_bytes(), 0, None, 0) };
/// assert!(ret.is_ok());
/// assert_eq!(ret, Ok(msg.len() as nc::ssize_t));
/// });
///
/// let mut buf = [0_u8; 1024];
/// let ret = unsafe { nc::recvfrom(fds[READ_SIDE], &mut buf, 0, None, None) };
/// assert!(ret.is_ok());
/// let nread = ret.unwrap();
/// let msg = std::str::from_utf8(&buf[..nread as usize]).unwrap();
/// println!("[main] recv msg: {msg}");
///
/// unsafe {
/// let _ = nc::close(fds[0]);
/// let _ = nc::close(fds[1]);
/// }
/// }
/// ```
pub unsafe fn recvfrom(
sockfd: i32,
buf: &mut [u8],
flags: i32,
src_addr: Option<*mut sockaddr_t>,
addrlen: Option<&mut socklen_t>,
) -> Result<ssize_t, Errno> {
let sockfd = sockfd as usize;
let buf_ptr = buf.as_mut_ptr() as usize;
let buflen = buf.len();
let flags = flags as usize;
let src_addr_ptr = src_addr.map_or(core::ptr::null_mut::<sockaddr_t>() as usize, |src_addr| {
src_addr as usize
});
let addrlen_ptr = addrlen.map_or(core::ptr::null_mut::<socklen_t>() as usize, |addrlen| {
addrlen as *mut socklen_t as usize
});
syscall6(
SYS_RECVFROM,
sockfd,
buf_ptr,
buflen,
flags,
src_addr_ptr,
addrlen_ptr,
)
.map(|ret| ret as ssize_t)
}