Add Interest::PRIORITY

This adds a PRIORITY interest, that is supported on linux. This makes
priority events work on TcpStream again.

src/interest.rs

@@ -33,6 +33,8 @@ const AIO: u8 = 0b0100;
 #[cfg_attr(not(target_os = "freebsd"), allow(dead_code))]
 const LIO: u8 = 0b1000;
 
+const PRIORITY: u8 = 0b10000;
+
 impl Interest {
     /// Returns a `Interest` set representing readable interests.
     pub const READABLE: Interest = Interest(unsafe { NonZeroU8::new_unchecked(READABLE) });
@@ -53,6 +55,9 @@ impl Interest {
     #[cfg(target_os = "freebsd")]
     pub const LIO: Interest = Interest(unsafe { NonZeroU8::new_unchecked(LIO) });
 
+    /// Returns a `Interest` set representing priority interests.
+    pub const PRIORITY: Interest = Interest(unsafe { NonZeroU8::new_unchecked(PRIORITY) });
+
     /// Add together two `Interest`.
     ///
     /// This does the same thing as the `BitOr` implementation, but is a
@@ -113,6 +118,11 @@ impl Interest {
     pub const fn is_lio(self) -> bool {
         (self.0.get() & LIO) != 0
     }
+
+    /// Returns true if `Interest` contains PRIORITY readiness
+    pub const fn is_priority(self) -> bool {
+        (self.0.get() & PRIORITY) != 0
+    }
 }
 
 impl ops::BitOr for Interest {
@@ -173,6 +183,13 @@ impl fmt::Debug for Interest {
                 one = true
             }
         }
+        if self.is_priority() {
+            if one {
+                write!(fmt, " | ")?
+            }
+            write!(fmt, "PRIORITY")?;
+            one = true
+        }
         debug_assert!(one, "printing empty interests");
         Ok(())
     }

src/sys/unix/selector/epoll.rs

@@ -1,6 +1,6 @@
 use crate::{Interest, Token};
 
-use libc::{EPOLLET, EPOLLIN, EPOLLOUT, EPOLLRDHUP};
+use libc::{EPOLLET, EPOLLIN, EPOLLOUT, EPOLLPRI, EPOLLRDHUP};
 use log::error;
 use std::os::unix::io::{AsRawFd, RawFd};
 #[cfg(debug_assertions)]
@@ -177,6 +177,10 @@ fn interests_to_epoll(interests: Interest) -> u32 {
         kind |= EPOLLOUT;
     }
 
+    if interests.is_priority() {
+        kind |= EPOLLPRI;
+    }
+
     kind as u32
 }
 

tests/tcp_stream.rs

@@ -832,7 +832,11 @@ fn pollpri() {
 
     let (mut sock, _) = listener.accept().unwrap();
     poll.registry()
-        .register(&mut sock, Token(1), Interest::READABLE)
+        .register(
+            &mut sock,
+            Token(1),
+            Interest::READABLE.add(Interest::PRIORITY),
+        )
         .unwrap();
 
     // MsgFlags::MSG_OOB sends a tcp packet which is received by linux kernel with
@@ -841,6 +845,6 @@ fn pollpri() {
     expect_events(
         &mut poll,
         &mut events,
-        vec![ExpectEvent::new(Token(1), Readiness::PRIORITY)],
+        vec![ExpectEvent::new(Token(1), Interest::PRIORITY)],
     );
 }

tests/util/mod.rs

@@ -130,6 +130,9 @@ impl From<Interest> for Readiness {
         if interests.is_lio() {
             readiness.0 |= LIO;
         }
+        if interests.is_priority() {
+            readiness.0 |= PRIORITY;
+        }
         readiness
     }
 }