Add Socket::nonblocking

Returns the status of the to nonblocking mode of the socket.

Author: Thomasdezeeuw

src/socket.rs

@@ -357,7 +357,21 @@ impl Socket {
         sys::try_clone(self.as_raw()).map(Socket::from_raw)
     }
 
-    /// Moves this TCP stream into or out of nonblocking mode.
+    /// Returns true if this socket is set to nonblocking mode, false otherwise.
+    ///
+    /// # Notes
+    ///
+    /// On Unix this corresponds to calling `fcntl` returning the value of
+    /// `O_NONBLOCK`.
+    ///
+    /// On Windows it is not possible retrieve the nonblocking mode status.
+    #[cfg(all(feature = "all", unix))]
+    #[cfg_attr(docsrs, doc(all(feature = "all", unix)))]
+    pub fn nonblocking(&self) -> io::Result<bool> {
+        sys::nonblocking(self.as_raw())
+    }
+
+    /// Moves this socket into or out of nonblocking mode.
     ///
     /// # Notes
     ///

src/sys/unix.rs

@@ -661,6 +661,12 @@ pub(crate) fn try_clone(fd: Socket) -> io::Result<Socket> {
     syscall!(fcntl(fd, libc::F_DUPFD_CLOEXEC, 0))
 }
 
+#[cfg(all(feature = "all", unix))]
+pub(crate) fn nonblocking(fd: Socket) -> io::Result<bool> {
+    let file_status_flags = fcntl_get(fd, libc::F_GETFL)?;
+    Ok((file_status_flags & libc::O_NONBLOCK) != 0)
+}
+
 pub(crate) fn set_nonblocking(fd: Socket, nonblocking: bool) -> io::Result<()> {
     if nonblocking {
         fcntl_add(fd, libc::F_GETFL, libc::F_SETFL, libc::O_NONBLOCK)
@@ -907,9 +913,14 @@ fn into_secs(duration: Duration) -> c_int {
     min(duration.as_secs(), c_int::MAX as u64) as c_int
 }
 
+/// Get the flags using `cmd`.
+fn fcntl_get(fd: Socket, cmd: c_int) -> io::Result<c_int> {
+    syscall!(fcntl(fd, cmd))
+}
+
 /// Add `flag` to the current set flags of `F_GETFD`.
 fn fcntl_add(fd: Socket, get_cmd: c_int, set_cmd: c_int, flag: c_int) -> io::Result<()> {
-    let previous = syscall!(fcntl(fd, get_cmd))?;
+    let previous = fcntl_get(fd, get_cmd)?;
     let new = previous | flag;
     if new != previous {
         syscall!(fcntl(fd, set_cmd, new)).map(|_| ())
@@ -921,7 +932,7 @@ fn fcntl_add(fd: Socket, get_cmd: c_int, set_cmd: c_int, flag: c_int) -> io::Res
 
 /// Remove `flag` to the current set flags of `F_GETFD`.
 fn fcntl_remove(fd: Socket, get_cmd: c_int, set_cmd: c_int, flag: c_int) -> io::Result<()> {
-    let previous = syscall!(fcntl(fd, get_cmd))?;
+    let previous = fcntl_get(fd, get_cmd)?;
     let new = previous & !flag;
     if new != previous {
         syscall!(fcntl(fd, set_cmd, new)).map(|_| ())

tests/socket.rs

@@ -227,17 +227,19 @@ fn type_nonblocking() {
 /// Assert that `NONBLOCK` is set on `socket`.
 #[cfg(unix)]
 #[track_caller]
-pub fn assert_nonblocking<S>(socket: &S, want: bool)
-where
-    S: AsRawFd,
-{
-    let flags = unsafe { libc::fcntl(socket.as_raw_fd(), libc::F_GETFL) };
-    assert_eq!(flags & libc::O_NONBLOCK != 0, want, "non-blocking option");
+pub fn assert_nonblocking(socket: &Socket, want: bool) {
+    #[cfg(all(feature = "all", unix))]
+    assert_eq!(socket.nonblocking().unwrap(), want, "non-blocking option");
+    #[cfg(not(all(feature = "all", unix)))]
+    {
+        let flags = unsafe { libc::fcntl(socket.as_raw_fd(), libc::F_GETFL) };
+        assert_eq!(flags & libc::O_NONBLOCK != 0, want, "non-blocking option");
+    }
 }
 
 #[cfg(windows)]
 #[track_caller]
-pub fn assert_nonblocking<S>(_: &S, _: bool) {
+pub fn assert_nonblocking(_: &Socket, _: bool) {
     // No way to get this information...
 }