Add async capabilities to the crate.

Cargo.toml

@@ -14,3 +14,6 @@ exclude = [".gitignore", ".github/**"]
 
 [dependencies]
 http = "1.0.0"
+
+[features]
+async = []

src/lib.rs

@@ -50,6 +50,8 @@
 //!
 //! Several shortcut functions are provided (such as [`html_response`](fn.html_response.html)/[`binary_response`](fn.binary_response.html))
 
+#![feature(async_trait_bounds)]
+
 use std::collections::HashMap;
 use std::convert::TryFrom;
 use std::fmt::Debug;
@@ -63,6 +65,34 @@ pub type Request = http::Request<Vec<u8>>;
 /// A `Vec<u8>` Response from http
 pub type Response = http::Response<Vec<u8>>;
 
+#[cfg(feature = "async")]
+async fn handle_with_io_async<F, R, W>(func: F, mut stdin: R, mut stdout: W)
+where
+    F: async FnOnce(Request) -> Response,
+    R: Read,
+    W: Write,
+{
+    let env_vars: HashMap<String, String> = std::env::vars().collect();
+
+    // How many bytes do we have to read for request body
+    // A general stdin().read_to_end() can block if the webserver doesn't close things
+    let content_length: usize = env_vars
+        .get("CONTENT_LENGTH")
+        .and_then(|cl| cl.parse::<usize>().ok())
+        .unwrap_or(0);
+
+    let mut stdin_contents = vec![0; content_length];
+    stdin.read_exact(&mut stdin_contents).unwrap();
+
+    let request = parse_request(env_vars, stdin_contents);
+
+    let response = func(request).await;
+
+    let output = serialize_response(response);
+
+    stdout.write_all(&output).unwrap();
+}
+
 fn handle_with_io<F, R, W>(func: F, mut stdin: R, mut stdout: W)
 where
     F: FnOnce(Request) -> Response,
@@ -111,6 +141,21 @@ where
     )
 }
 
+/// Asynchronously call a function as a CGI programme.
+///
+/// This should be called from a `main` function.
+/// Parse & extract the CGI environmental variables, and HTTP request body,
+/// to create `Request`, and convert your `Response` into the correct format and
+/// print to stdout.
+#[cfg(feature = "async")]
+pub async fn handle_async<F>(func: F)
+where
+    F: async FnOnce(Request) -> Response,
+{
+    handle_with_io_async(func, std::io::stdin(), std::io::stdout()).await
+}
+
+
 /// Call a function as a CGI programme.
 ///
 /// This should be called from a `main` function.