lio_listio(2) support (tokio-rs#780)

On FreeBSD and DragonflyBSD, kevent(2) has a distinct filter type for
use with lio_listio(2).  This commit adds 2 new public methods:
UnixReady::lio and UnixReady::is_lio.

This patch also deprecates AIO fns on platforms that do not
support AIO.

src/sys/unix/kqueue.rs

@@ -299,6 +299,12 @@ impl Events {
                     event::kind_mut(&mut self.events[idx]).insert(UnixReady::aio());
                 }
             }
+#[cfg(any(target_os = "dragonfly", target_os = "freebsd"))]
+            {
+                if e.filter == libc::EVFILT_LIO {
+                    event::kind_mut(&mut self.events[idx]).insert(UnixReady::lio());
+                }
+            }
 
             if e.flags & libc::EV_EOF != 0 {
                 event::kind_mut(&mut self.events[idx]).insert(UnixReady::hup());

src/sys/unix/ready.rs

@@ -92,9 +92,13 @@ use std::fmt;
 #[derive(Copy, PartialEq, Eq, Clone, PartialOrd, Ord)]
 pub struct UnixReady(Ready);
 
-const ERROR: usize = 0b00100;
-const HUP: usize   = 0b01000;
-const AIO: usize   = 0b10000;
+const ERROR: usize = 0b000100;
+const HUP: usize   = 0b001000;
+#[cfg(any(target_os = "dragonfly",
+    target_os = "freebsd", target_os = "ios", target_os = "macos"))]
+const AIO: usize   = 0b010000;
+#[cfg(any(target_os = "dragonfly", target_os = "freebsd"))]
+const LIO: usize   = 0b100000;
 
 impl UnixReady {
     /// Returns a `Ready` representing AIO completion readiness
@@ -113,10 +117,20 @@ impl UnixReady {
     ///
     /// [`Poll`]: ../struct.Poll.html
     #[inline]
+    #[cfg(any(target_os = "dragonfly",
+        target_os = "freebsd", target_os = "ios", target_os = "macos"))]
     pub fn aio() -> UnixReady {
         UnixReady(ready_from_usize(AIO))
     }
 
+    #[cfg(not(any(target_os = "dragonfly",
+        target_os = "freebsd", target_os = "ios", target_os = "macos")))]
+    #[deprecated(since = "0.6.12", note = "this function is now platform specific")]
+    #[doc(hidden)]
+    pub fn aio() -> UnixReady {
+        UnixReady(Ready::empty())
+    }
+
     /// Returns a `Ready` representing error readiness.
     ///
     /// **Note that only readable and writable readiness is guaranteed to be
@@ -172,6 +186,27 @@ impl UnixReady {
         UnixReady(ready_from_usize(HUP))
     }
 
+    /// Returns a `Ready` representing LIO completion readiness
+    ///
+    /// See [`Poll`] for more documentation on polling.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use mio::unix::UnixReady;
+    ///
+    /// let ready = UnixReady::lio();
+    ///
+    /// assert!(ready.is_lio());
+    /// ```
+    ///
+    /// [`Poll`]: struct.Poll.html
+    #[inline]
+    #[cfg(any(target_os = "dragonfly", target_os = "freebsd"))]
+    pub fn lio() -> UnixReady {
+        UnixReady(ready_from_usize(LIO))
+    }
+
     /// Returns true if `Ready` contains AIO readiness
     ///
     /// See [`Poll`] for more documentation on polling.
@@ -188,10 +223,21 @@ impl UnixReady {
     ///
     /// [`Poll`]: ../struct.Poll.html
     #[inline]
+    #[cfg(any(target_os = "dragonfly",
+        target_os = "freebsd", target_os = "ios", target_os = "macos"))]
     pub fn is_aio(&self) -> bool {
         self.contains(ready_from_usize(AIO))
     }
 
+    #[deprecated(since = "0.6.12", note = "this function is now platform specific")]
+    #[cfg(feature = "with-deprecated")]
+    #[cfg(not(any(target_os = "dragonfly",
+        target_os = "freebsd", target_os = "ios", target_os = "macos")))]
+    #[doc(hidden)]
+    pub fn is_aio(&self) -> bool {
+        false
+    }
+
     /// Returns true if the value includes error readiness
     ///
     /// **Note that only readable and writable readiness is guaranteed to be
@@ -246,6 +292,25 @@ impl UnixReady {
     pub fn is_hup(&self) -> bool {
         self.contains(ready_from_usize(HUP))
     }
+
+    /// Returns true if `Ready` contains LIO readiness
+    ///
+    /// See [`Poll`] for more documentation on polling.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use mio::unix::UnixReady;
+    ///
+    /// let ready = UnixReady::lio();
+    ///
+    /// assert!(ready.is_lio());
+    /// ```
+    #[inline]
+    #[cfg(any(target_os = "dragonfly", target_os = "freebsd"))]
+    pub fn is_lio(&self) -> bool {
+        self.contains(ready_from_usize(LIO))
+    }
 }
 
 impl From<Ready> for UnixReady {
@@ -330,6 +395,7 @@ impl fmt::Debug for UnixReady {
             (UnixReady(Ready::writable()), "Writable"),
             (UnixReady::error(), "Error"),
             (UnixReady::hup(), "Hup"),
+            #[allow(deprecated)]
             (UnixReady::aio(), "Aio")];
 
         for &(flag, msg) in &flags {