Re-work I/O

* Auto-register interest whenever we see WouldBlock
* Remove implementations of `Stream<Item=Ready>`, no longer needed
* Add explicit `poll_{read,write}` methods, if needed
* Remove all I/O streams, libstd ones suffice
* Update all I/O futures

tests/stream-buffered.rs

@@ -3,13 +3,14 @@ extern crate futures_io;
 extern crate futures_mio;
 extern crate env_logger;
 
-use std::net::TcpStream;
+use std::sync::Arc;
 use std::thread;
-use std::io::{Read, Write};
+use std::io::{self, Read, Write};
 
 use futures::Future;
 use futures::stream::Stream;
-use futures_io::{copy, TaskIo};
+use futures_io::copy;
+use futures_mio::TcpStream;
 
 macro_rules! t {
     ($e:expr) => (match $e {
@@ -28,6 +29,8 @@ fn echo_server() {
     let addr = t!(srv.local_addr());
 
     let t = thread::spawn(move || {
+        use std::net::TcpStream;
+
         let mut s1 = t!(TcpStream::connect(&addr));
         let mut s2 = t!(TcpStream::connect(&addr));
 
@@ -42,9 +45,9 @@ fn echo_server() {
     });
 
     let future = srv.incoming()
-                    .and_then(|s| TaskIo::new(s.0))
-                    .map(|i| i.split())
-                    .map(|(a,b)| copy(a,b).map(|_| ()))
+                    .map(|s| Arc::new(s.0))
+                    .map(|i| (SocketIo(i.clone()), SocketIo(i)))
+                    .map(|(a, b)| copy(a, b).map(|_| ()))
                     .buffered(10)
                     .take(2)
                     .collect();
@@ -53,3 +56,21 @@ fn echo_server() {
 
     t.join().unwrap();
 }
+
+struct SocketIo(Arc<TcpStream>);
+
+impl Read for SocketIo {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        (&*self.0).read(buf)
+    }
+}
+
+impl Write for SocketIo {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (&*self.0).write(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        (&*self.0).flush()
+    }
+}