feat(http2): add HTTP/2 support for Client and Server

src/common/exec.rs

@@ -0,0 +1,38 @@
+use std::fmt;
+use std::sync::Arc;
+
+use futures::future::{Executor, Future};
+use tokio_executor::spawn;
+
+/// Either the user provides an executor for background tasks, or we use
+/// `tokio::spawn`.
+#[derive(Clone)]
+pub(crate) enum Exec {
+    Default,
+    Executor(Arc<Executor<Box<Future<Item=(), Error=()> + Send>> + Send + Sync>),
+}
+
+
+impl Exec {
+    pub(crate) fn execute<F>(&self, fut: F)
+    where
+        F: Future<Item=(), Error=()> + Send + 'static,
+    {
+        match *self {
+            Exec::Default => spawn(fut),
+            Exec::Executor(ref e) => {
+                let _ = e.execute(Box::new(fut))
+                    .map_err(|err| {
+                        panic!("executor error: {:?}", err.kind());
+                    });
+            },
+        }
+    }
+}
+
+impl fmt::Debug for Exec {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Exec")
+            .finish()
+    }
+}