Runtime builder (#234)

* Split runtime module into files
* Add runtime::Builder to set up thread pool.

src/runtime/task_executor.rs

@@ -0,0 +1,98 @@
+
+use tokio_threadpool::Sender;
+
+use futures::future::{self, Future};
+#[cfg(feature = "unstable-futures")]
+use futures2;
+
+/// Executes futures on the runtime
+///
+/// All futures spawned using this executor will be submitted to the associated
+/// Runtime's executor. This executor is usually a thread pool.
+///
+/// For more details, see the [module level](index.html) documentation.
+#[derive(Debug, Clone)]
+pub struct TaskExecutor {
+    pub(super) inner: Sender,
+}
+
+impl TaskExecutor {
+    /// Spawn a future onto the Tokio runtime.
+    ///
+    /// This spawns the given future onto the runtime's executor, usually a
+    /// thread pool. The thread pool is then responsible for polling the future
+    /// until it completes.
+    ///
+    /// See [module level][mod] documentation for more details.
+    ///
+    /// [mod]: index.html
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # extern crate tokio;
+    /// # extern crate futures;
+    /// # use futures::{future, Future, Stream};
+    /// use tokio::runtime::Runtime;
+    ///
+    /// # fn dox() {
+    /// // Create the runtime
+    /// let mut rt = Runtime::new().unwrap();
+    /// let executor = rt.executor();
+    ///
+    /// // Spawn a future onto the runtime
+    /// executor.spawn(future::lazy(|| {
+    ///     println!("now running on a worker thread");
+    ///     Ok(())
+    /// }));
+    /// # }
+    /// # pub fn main() {}
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if the spawn fails. Failure occurs if the executor
+    /// is currently at capacity and is unable to spawn a new future.
+    pub fn spawn<F>(&self, future: F)
+    where F: Future<Item = (), Error = ()> + Send + 'static,
+    {
+        self.inner.spawn(future).unwrap();
+    }
+}
+
+impl<T> future::Executor<T> for TaskExecutor
+where T: Future<Item = (), Error = ()> + Send + 'static,
+{
+    fn execute(&self, future: T) -> Result<(), future::ExecuteError<T>> {
+        self.inner.execute(future)
+    }
+}
+
+impl ::executor::Executor for TaskExecutor {
+    fn spawn(&mut self, future: Box<Future<Item = (), Error = ()> + Send>)
+        -> Result<(), ::executor::SpawnError>
+    {
+        self.inner.spawn(future)
+    }
+
+    #[cfg(feature = "unstable-futures")]
+    fn spawn2(&mut self, future: Box<futures2::Future<Item = (), Error = futures2::Never> + Send>)
+        -> Result<(), futures2::executor::SpawnError>
+    {
+        self.inner.spawn2(future)
+    }
+}
+
+#[cfg(feature = "unstable-futures")]
+type Task2 = Box<futures2::Future<Item = (), Error = futures2::Never> + Send>;
+
+#[cfg(feature = "unstable-futures")]
+impl futures2::executor::Executor for TaskExecutor {
+    fn spawn(&mut self, f: Task2) -> Result<(), futures2::executor::SpawnError> {
+        futures2::executor::Executor::spawn(&mut self.inner, f)
+    }
+
+    fn status(&self) -> Result<(), futures2::executor::SpawnError> {
+        futures2::executor::Executor::status(&self.inner)
+    }
+}