Runtime builder (#234)

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

src/runtime/builder.rs

@@ -0,0 +1,107 @@
+use runtime::{Inner, Runtime};
+
+use reactor::Reactor;
+
+use std::io;
+
+use tokio_threadpool::Builder as ThreadPoolBuilder;
+
+
+
+/// Builds Tokio Runtime with custom configuration values.
+///
+/// Methods can be chanined in order to set the configuration values. The
+/// Runtime is constructed by calling [`build`].
+///
+/// New instances of `Builder` are obtained via [`Builder::new`].
+///
+/// See function level documentation for details on the various configuration
+/// settings.
+///
+/// [`build`]: #method.build
+/// [`Builder::new`]: #method.new
+///
+/// # Examples
+///
+/// ```
+/// # extern crate tokio;
+/// # extern crate tokio_threadpool;
+/// # use tokio::runtime::Builder;
+///
+/// # pub fn main() {
+/// // create and configure ThreadPool
+/// let mut threadpool_builder = tokio_threadpool::Builder::new();
+/// threadpool_builder
+///     .name_prefix("my-runtime-worker-")
+///     .pool_size(4);
+///
+/// // build Runtime
+/// let runtime = Builder::new()
+///     .threadpool_builder(threadpool_builder)
+///     .build();
+/// // ... call runtime.run(...)
+/// # let _ = runtime;
+/// # }
+/// ```
+#[derive(Debug)]
+pub struct Builder {
+    /// Thread pool specific builder
+    threadpool_builder: ThreadPoolBuilder,
+}
+
+impl Builder {
+    /// Returns a new runtime builder initialized with default configuration
+    /// values.
+    ///
+    /// Configuration methods can be chained on the return value.
+    pub fn new() -> Builder {
+        let mut threadpool_builder = ThreadPoolBuilder::new();
+        threadpool_builder.name_prefix("tokio-runtime-worker-");
+
+        Builder { threadpool_builder }
+    }
+
+    /// Set builder to set up the thread pool instance.
+    pub fn threadpool_builder(&mut self, val: ThreadPoolBuilder) -> &mut Self {
+        self.threadpool_builder = val;
+        self
+    }
+
+    /// Create the configured `Runtime`.
+    ///
+    /// The returned `ThreadPool` instance is ready to spawn tasks.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # extern crate tokio;
+    /// # use tokio::runtime::Builder;
+    /// # pub fn main() {
+    /// let runtime = Builder::new().build();
+    /// // ... call runtime.run(...)
+    /// # let _ = runtime;
+    /// # }
+    /// ```
+    pub fn build(&mut self) -> io::Result<Runtime> {
+        // Spawn a reactor on a background thread.
+        let reactor = Reactor::new()?.background()?;
+
+        // Get a handle to the reactor.
+        let handle = reactor.handle().clone();
+
+        let pool = self.threadpool_builder
+            .around_worker(move |w, enter| {
+                ::tokio_reactor::with_default(&handle, enter, |_| {
+                    w.run();
+                });
+            })
+            .build();
+
+        Ok(Runtime {
+            inner: Some(Inner {
+                reactor,
+                pool,
+            }),
+        })
+    }
+}