add h2c example

actix-http/examples/h2c-detect.rs

@@ -0,0 +1,54 @@
+//! An example that supports automatic selection of plaintext h1/h2c connections.
+//!
+//! Notably, both the following commands will work.
+//! ```console
+//! $ curl --http1.1 'http://localhost:8080/'
+//! $ curl --http2-prior-knowledge 'http://localhost:8080/'
+//! ```
+
+use std::{convert::Infallible, io};
+
+use actix_http::{HttpService, Protocol, Request, Response, StatusCode};
+use actix_rt::net::TcpStream;
+use actix_server::Server;
+use actix_service::{fn_service, ServiceFactoryExt};
+
+const H2_PREFACE: &[u8] = b"PRI * HTTP/2";
+
+#[actix_rt::main]
+async fn main() -> io::Result<()> {
+    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));
+
+    Server::build()
+        .bind("h2c-detect", ("127.0.0.1", 8080), || {
+            fn_service(move |io: TcpStream| async move {
+                let mut buf = [0; 12];
+
+                io.peek(&mut buf).await?;
+
+                let proto = if buf == H2_PREFACE {
+                    tracing::info!("selecting h2c");
+                    Protocol::Http2
+                } else {
+                    tracing::info!("selecting h1");
+                    Protocol::Http1
+                };
+
+                let peer_addr = io.peer_addr().ok();
+                Ok::<_, io::Error>((io, proto, peer_addr))
+            })
+            .and_then(
+                HttpService::build()
+                    .finish(|_req: Request| async move {
+                        Ok::<_, Infallible>(Response::build(StatusCode::OK).body("Hello!"))
+                    })
+                    .map_err(|err| {
+                        tracing::error!("{}", err);
+                        io::Error::new(io::ErrorKind::Other, "http service dispatch error")
+                    }),
+            )
+        })?
+        .workers(2)
+        .run()
+        .await
+}