std: Add close_{read,write}() methods to I/O

Two new methods were added to TcpStream and UnixStream:

    fn close_read(&mut self) -> IoResult<()>;
    fn close_write(&mut self) -> IoResult<()>;

These two methods map to shutdown()'s behavior (the system call on unix),
closing the reading or writing half of a duplex stream. These methods are
primarily added to allow waking up a pending read in another task. By closing
the reading half of a connection, all pending readers will be woken up and will
return with EndOfFile. The close_write() method was added for symmetry with
close_read(), and I imagine that it will be quite useful at some point.

Implementation-wise, librustuv got the short end of the stick this time. The
native versions just delegate to the shutdown() syscall (easy). The uv versions
can leverage uv_shutdown() for tcp/unix streams, but only for closing the
writing half. Closing the reading half is done through some careful dancing to
wake up a pending reader.

As usual, windows likes to be different from unix. The windows implementation
uses shutdown() for sockets, but shutdown() is not available for named pipes.
Instead, CancelIoEx was used with same fancy synchronization to make sure
everyone knows what's up.

cc #11165

src/libstd/io/net/tcp.rs

@@ -32,7 +32,7 @@ use rt::rtio::{RtioTcpAcceptor, RtioTcpStream};
 ///
 /// # Example
 ///
-/// ```rust
+/// ```no_run
 /// # #![allow(unused_must_use)]
 /// use std::io::net::tcp::TcpStream;
 /// use std::io::net::ip::{Ipv4Addr, SocketAddr};
@@ -109,6 +109,48 @@ impl TcpStream {
             None => self.obj.letdie(),
         }
     }
+
+    /// Closes the reading half of this connection.
+    ///
+    /// This method will close the reading portion of this connection, causing
+    /// all pending and future reads to immediately return with an error.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// # #![allow(unused_must_use)]
+    /// use std::io::timer;
+    /// use std::io::net::tcp::TcpStream;
+    /// use std::io::net::ip::{Ipv4Addr, SocketAddr};
+    ///
+    /// let addr = SocketAddr { ip: Ipv4Addr(127, 0, 0, 1), port: 34254 };
+    /// let mut stream = TcpStream::connect(addr).unwrap();
+    /// let stream2 = stream.clone();
+    ///
+    /// spawn(proc() {
+    ///     // close this stream after one second
+    ///     timer::sleep(1000);
+    ///     let mut stream = stream2;
+    ///     stream.close_read();
+    /// });
+    ///
+    /// // wait for some data, will get canceled after one second
+    /// let mut buf = [0];
+    /// stream.read(buf);
+    /// ```
+    ///
+    /// Note that this method affects all cloned handles associated with this
+    /// stream, not just this one handle.
+    pub fn close_read(&mut self) -> IoResult<()> { self.obj.close_read() }
+
+    /// Closes the writing half of this connection.
+    ///
+    /// This method will close the writing portion of this connection, causing
+    /// all future writes to immediately return with an error.
+    ///
+    /// Note that this method affects all cloned handles associated with this
+    /// stream, not just this one handle.
+    pub fn close_write(&mut self) -> IoResult<()> { self.obj.close_write() }
 }
 
 impl Clone for TcpStream {
@@ -839,7 +881,11 @@ mod test {
 
         // Also make sure that even though the timeout is expired that we will
         // continue to receive any pending connections.
-        let l = TcpStream::connect(addr).unwrap();
+        let (tx, rx) = channel();
+        spawn(proc() {
+            tx.send(TcpStream::connect(addr).unwrap());
+        });
+        let l = rx.recv();
         for i in range(0, 1001) {
             match a.accept() {
                 Ok(..) => break,
@@ -853,8 +899,69 @@ mod test {
         // Unset the timeout and make sure that this always blocks.
         a.set_timeout(None);
         spawn(proc() {
-            drop(TcpStream::connect(addr));
+            drop(TcpStream::connect(addr).unwrap());
         });
         a.accept().unwrap();
     })
+
+    iotest!(fn close_readwrite_smoke() {
+        let addr = next_test_ip4();
+        let a = TcpListener::bind(addr).listen().unwrap();
+        let (_tx, rx) = channel::<()>();
+        spawn(proc() {
+            let mut a = a;
+            let _s = a.accept().unwrap();
+            let _ = rx.recv_opt();
+        });
+
+        let mut b = [0];
+        let mut s = TcpStream::connect(addr).unwrap();
+        let mut s2 = s.clone();
+
+        // closing should prevent reads/writes
+        s.close_write().unwrap();
+        assert!(s.write([0]).is_err());
+        s.close_read().unwrap();
+        assert!(s.read(b).is_err());
+
+        // closing should affect previous handles
+        assert!(s2.write([0]).is_err());
+        assert!(s2.read(b).is_err());
+
+        // closing should affect new handles
+        let mut s3 = s.clone();
+        assert!(s3.write([0]).is_err());
+        assert!(s3.read(b).is_err());
+
+        // make sure these don't die
+        let _ = s2.close_read();
+        let _ = s2.close_write();
+        let _ = s3.close_read();
+        let _ = s3.close_write();
+    })
+
+    iotest!(fn close_read_wakes_up() {
+        let addr = next_test_ip4();
+        let a = TcpListener::bind(addr).listen().unwrap();
+        let (_tx, rx) = channel::<()>();
+        spawn(proc() {
+            let mut a = a;
+            let _s = a.accept().unwrap();
+            let _ = rx.recv_opt();
+        });
+
+        let mut s = TcpStream::connect(addr).unwrap();
+        let s2 = s.clone();
+        let (tx, rx) = channel();
+        spawn(proc() {
+            let mut s2 = s2;
+            assert!(s2.read([0]).is_err());
+            tx.send(());
+        });
+        // this should wake up the child task
+        s.close_read().unwrap();
+
+        // this test will never finish if the child doesn't wake up
+        rx.recv();
+    })
 }