Support interactive stdin/stdout streams (#136)

* Support interactive stdin/stdout streams

This adds support for streaming stdin, stderr, and stdout independently
to a running container.

The underlying API is futures-based, meaning the code is implemented
asynchronously. A synchronous API is also exposed, which is implemented
by simply waiting on the asynchronous API futures.

This also modifies the existing Tty logic so that the storage type of
the data is a Vec<u8> rather than a String. This is also how the Rust
standard library persists data from the standard streams. In my
particular application, I'm using stdin/stdout as the communication
method between a container a host application. In it, a byte-based protocol is
used.

Streaming works by performing a TCP upgrade; upgrading a higher-level
HTTP connection to a lower-level TCP byte stream upon agreement with the
server. Docker will automatically upgrade HTTP container log requests to
TCP byte streams of a custom std{in,out,err} multiplexing protocol if
the client requests it with the 'Connection: Upgrade' header.

* Return an error rather than panic when Docker refuses to upgrade to TCP

* Add interpret-as-string accessors to tty::Chunk

Also updates the examples to use them.

2 files changed, 10 insertions, 8 deletions

diff --git a/examples/containerexec.rs b/examples/containerexec.rs
index 0b3575b..0bfd640 100644
--- a/examples/containerexec.rs
+++ b/examples/containerexec.rs
@@ -25,10 +25,11 @@ fn main() {
         .containers()
         .get(&id)
         .exec(&options)
-        .for_each(|line| {
-            match line.stream_type {
-                StreamType::StdOut => println!("Stdout: {}", line.data),
-                StreamType::StdErr => eprintln!("Stderr: {}", line.data),
+        .for_each(|chunk| {
+            match chunk.stream_type {
+                StreamType::StdOut => println!("Stdout: {}", chunk.as_string_lossy()),
+                StreamType::StdErr => eprintln!("Stderr: {}", chunk.as_string_lossy()),
+                StreamType::StdIn => unreachable!(),
             }
             Ok(())
         })
diff --git a/examples/logs.rs b/examples/logs.rs
index b35b0a3..6fad7d6 100644
--- a/examples/logs.rs
+++ b/examples/logs.rs
@@ -14,10 +14,11 @@ fn main() {
         .containers()
         .get(&id)
         .logs(&LogsOptions::builder().stdout(true).stderr(true).build())
-        .for_each(|line| {
-            match line.stream_type {
-                StreamType::StdOut => println!("Stdout: {}", line.data),
-                StreamType::StdErr => eprintln!("Stderr: {}", line.data),
+        .for_each(|chunk| {
+            match chunk.stream_type {
+                StreamType::StdOut => println!("Stdout: {}", chunk.as_string_lossy()),
+                StreamType::StdErr => eprintln!("Stderr: {}", chunk.as_string_lossy()),
+                StreamType::StdIn => unreachable!(),
             }
             Ok(())
         })