From 0a3dc0bb75203107ab44991b8548094cca70ec31 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Fri, 4 Nov 2016 09:12:00 -0700
Subject: [PATCH] Add a method to manually deregister an I/O object

Typically this happens automatically as the `E` in `PollEvented<E>` is an owned
reference (e.g. a `TcpStream`) where dropping that will close the resource,
automatically unregistering it from the event loop. In some situations, however,
this isn't always the case, so the deregistering needs to happen manually.
---
 src/reactor/mod.rs          |  4 ++++
 src/reactor/poll_evented.rs | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/reactor/mod.rs b/src/reactor/mod.rs
index eab8cfe2f..6add6141b 100644
--- a/src/reactor/mod.rs
+++ b/src/reactor/mod.rs
@@ -435,6 +435,10 @@ impl Inner {
         Ok((sched.readiness.clone(), entry.insert(sched).index()))
     }
 
+    fn deregister_source(&mut self, source: &mio::Evented) -> io::Result<()> {
+        self.io.deregister(source)
+    }
+
     fn drop_source(&mut self, token: usize) {
         debug!("dropping I/O source: {}", token);
         self.io_dispatch.remove(token).unwrap();
diff --git a/src/reactor/poll_evented.rs b/src/reactor/poll_evented.rs
index 5dd897136..e3d6ee149 100644
--- a/src/reactor/poll_evented.rs
+++ b/src/reactor/poll_evented.rs
@@ -53,6 +53,27 @@ impl<E: mio::Evented> PollEvented<E> {
             io: io,
         })
     }
+
+    /// Deregisters this source of events from the reactor core specified.
+    ///
+    /// This method can optionally be called to unregister the underlying I/O
+    /// object with the event loop that the `handle` provided points to.
+    /// Typically this method is not required as this automatically happens when
+    /// `E` is dropped, but for some use cases the `E` object doesn't represent
+    /// an owned reference, so dropping it won't automatically unreigster with
+    /// the event loop.
+    ///
+    /// This consumes `self` as it will no longer provide events after the
+    /// method is called, and will likely return an error if this `PollEvented`
+    /// was created on a separate event loop from the `handle` specified.
+    pub fn deregister(self, handle: &Handle) -> io::Result<()> {
+        let inner = match handle.inner.upgrade() {
+            Some(inner) => inner,
+            None => return Ok(()),
+        };
+        let ret = inner.borrow_mut().deregister_source(&self.io);
+        return ret
+    }
 }
 
 impl<E> PollEvented<E> {