Touch up comments on echo, add connect example

examples/connect.rs

@@ -0,0 +1,119 @@
+//! A simple example of hooking up stdin/stdout to a TCP stream.
+//!
+//! This example will connect to a server specified in the argument list and
+//! then forward all data read on stdin to the server, printing out all data
+//! received on stdout.
+//!
+//! Note that this is not currently optimized for performance, especially around
+//! buffer management. Rather it's intended to show an example of working with a
+//! client.
+
+extern crate futures;
+extern crate tokio_core;
+
+use std::env;
+use std::io::{self, Read, Write};
+use std::net::SocketAddr;
+use std::thread;
+
+use futures::{Sink, Future, Stream};
+use futures::sync::mpsc;
+use tokio_core::reactor::Core;
+use tokio_core::io::{Io, EasyBuf, Codec};
+use tokio_core::net::TcpStream;
+
+fn main() {
+    // Parse what address we're going to connect to
+    let addr = env::args().nth(1).unwrap_or_else(|| {
+        panic!("this program requires at least one argument")
+    });
+    let addr = addr.parse::<SocketAddr>().unwrap();
+
+    // Create the event loop and initiate the connection to the remote server
+    let mut core = Core::new().unwrap();
+    let handle = core.handle();
+    let tcp = TcpStream::connect(&addr, &handle);
+
+    // Right now Tokio doesn't support a handle to stdin running on the event
+    // loop, so we farm out that work to a separate thread. This thread will
+    // read data from stdin and then send it to the event loop over a standard
+    // futures channel.
+    let (stdin_tx, stdin_rx) = mpsc::channel(0);
+    thread::spawn(|| read_stdin(stdin_tx));
+    let stdin_rx = stdin_rx.map_err(|_| panic!()); // errors not possible on rx
+
+    // After the TCP connection has been established, we set up our client to
+    // start forwarding data.
+    //
+    // First we use the `Io::framed` method with a simple implementation of a
+    // `Codec` (listed below) that just ships bytes around. We then split that
+    // in two to work with the stream and sink separately.
+    //
+    // Half of the work we're going to do is to take all data we receive on
+    // stdin (`stdin_rx`) and send that along the TCP stream (`sink`). The
+    // second half is to take all the data we receive (`stream`) and then write
+    // that to stdout. Currently we just write to stdout in a synchronous
+    // fashion.
+    //
+    // Finally we set the client to terminate once either half of this work
+    // finishes. If we don't have any more data to read or we won't receive any
+    // more work from the remote then we can exit.
+    let mut stdout = io::stdout();
+    let client = tcp.and_then(|(sink, stream)| {
+        let (sink, stream) = stream.framed(Bytes).split();
+        let send_stdin = stdin_rx.forward(sink);
+        let write_stdout = stream.for_each(move |buf| {
+            stdout.write_all(buf.as_slice())
+        });
+
+        send_stdin.map(|_| ())
+                  .select(write_stdout.map(|_| ()))
+                  .then(|_| Ok(()))
+    });
+
+    // And now that we've got our client, we execute it in the event loop!
+    core.run(client).unwrap();
+}
+
+/// A simple `Codec` implementation that just ships bytes around.
+///
+/// This type is used for "framing" a TCP stream of bytes but it's really just a
+/// convenient method for us to work with streams/sinks for now. This'll just
+/// take any data read and interpret it as a "frame" and conversely just shove
+/// data into the output location without looking at it.
+struct Bytes;
+
+impl Codec for Bytes {
+    type In = EasyBuf;
+    type Out = Vec<u8>;
+
+    fn decode(&mut self, buf: &mut EasyBuf) -> io::Result<Option<EasyBuf>> {
+        if buf.len() > 0 {
+            let len = buf.len();
+            Ok(Some(buf.drain_to(len)))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn encode(&mut self, data: Vec<u8>, buf: &mut Vec<u8>) -> io::Result<()> {
+        buf.extend(data);
+        Ok(())
+    }
+}
+
+// Our helper method which will read data from stdin and send it along the
+// sender provided.
+fn read_stdin(mut rx: mpsc::Sender<Vec<u8>>) {
+    let mut stdin = io::stdin();
+    loop {
+        let mut buf = vec![0; 1024];
+        let n = match stdin.read(&mut buf) {
+            Err(_) |
+            Ok(0) => break,
+            Ok(n) => n,
+        };
+        buf.truncate(n);
+        rx = rx.send(buf).wait().unwrap();
+    }
+}