Add a hello server example using cohttp

Author: polytypic

example/dune

@@ -0,0 +1,15 @@
+(executable
+ (name hello_cohttp)
+ (modules hello_cohttp)
+ (enabled_if
+  (>= %{ocaml_version} 5.0.0))
+ (libraries
+  cohttp
+  picos_io
+  picos_io_cohttp
+  picos_mux.fifo
+  picos_mux.multififo
+  picos_mux.random
+  picos_mux.thread
+  picos_std.finally
+  picos_std.structured))

example/hello_cohttp.ml

@@ -0,0 +1,98 @@
+open Picos_io
+open Picos_io_cohttp
+open Picos_std_finally
+open Picos_std_structured
+
+module String_ext = struct
+  let drop_prefix_opt ~prefix s =
+    if String.starts_with ~prefix s then
+      let i = String.length prefix in
+      Some (String.sub s i (String.length s - i))
+    else None
+end
+
+module Option_ext = struct
+  let ( >>= ) = Option.bind
+  let ( >>- ) xO xy = Option.map xy xO
+
+  let ( <|> ) xyO1 xyO2 x =
+    match xyO1 x with Some _ as some -> some | None -> xyO2 x
+
+  let filter p x = if p x then Some x else None
+end
+
+module Scheduler = struct
+  open Option_ext
+
+  let parse =
+    let parse_0 name con s =
+      String_ext.drop_prefix_opt ~prefix:name s
+      >>- String.trim
+      >>= filter (( = ) "")
+      >>- fun _ -> con
+    and parse_1 name con s =
+      String_ext.drop_prefix_opt ~prefix:name s
+      >>- String.trim >>= int_of_string_opt
+      >>= filter (fun n -> 1 <= n && n <= Domain.recommended_domain_count ())
+      >>- con
+    in
+    fun s ->
+      match
+        String.trim s
+        |> (parse_0 "fifo" `Fifo <|> parse_0 "thread" `Thread
+           <|> parse_1 "multififo" (fun n -> `Multififo n)
+           <|> parse_1 "random" (fun n -> `Random n))
+      with
+      | None -> failwith "Unknown or unacceptable scheduler"
+      | Some s -> s
+end
+
+let main ~port ~n_connections ~n_servers () =
+  let@ server_socket =
+    finally Unix.close @@ fun () ->
+    Unix.socket ~cloexec:true PF_INET SOCK_STREAM 0
+  in
+  Unix.set_nonblock server_socket;
+  Unix.bind server_socket Unix.(ADDR_INET (inet_addr_loopback, port));
+  Unix.listen server_socket n_connections;
+  let callback _conn _req _req_body =
+    let res_body = "Hello world!\n" in
+    Server.respond_string ~status:`OK ~body:res_body ()
+  in
+  Flock.join_after @@ fun () ->
+  for _ = 1 to n_servers do
+    Flock.fork @@ fun () -> Server.run (Server.make ~callback ()) server_socket
+  done
+
+let () =
+  let port = ref 8082
+  and n_connections = ref 300
+  and scheduler = ref `Fifo
+  and n_servers = ref 1 in
+  let specs =
+    [
+      ("-port", Arg.Set_int port, "\t  Port");
+      ("-conns", Arg.Set_int n_connections, "\t  Connections");
+      ("-servers", Arg.Set_int n_servers, "\t  Server fibers");
+      ( "-scheduler",
+        Arg.String (fun s -> scheduler := Scheduler.parse s),
+        "\t  Scheduler ('fifo' | 'thread' | 'multififo n' | 'random n')" );
+    ]
+  in
+  Arg.parse specs ignore "";
+  let main =
+    main ~port:!port ~n_connections:!n_connections ~n_servers:!n_servers
+  in
+  match !scheduler with
+  | `Fifo ->
+      Printf.printf "Fifo\n%!";
+      Picos_mux_fifo.run main
+  | `Thread ->
+      Printf.printf "Thread\n%!";
+      Picos_mux_thread.run main
+  | `Multififo n_domains ->
+      Printf.printf "Multififo %d\n%!" n_domains;
+      Picos_mux_multififo.run_on ~n_domains main
+  | `Random n_domains ->
+      Printf.printf "Random %d\n%!" n_domains;
+      Picos_mux_random.run_on ~n_domains main