eio(client): Client.read_fixed take_all

RFC https://www.rfc-editor.org/rfc/rfc7230#section-3.3.3 point 7 states
that responses with missing Content-Length/Transfer-Encoding headers
should read the message body until the end of file.

This commit implements the above spec. Since now that read_fixed is
different in client and server, we also remove it from the Body module.

Author: bikallem

cohttp-eio/examples/client1.ml

@@ -13,4 +13,4 @@ let () =
   Eio_main.run @@ fun env ->
   Switch.run @@ fun sw ->
   let res = Client.get (conn env sw) "/" in
-  match Client.read_fixed res with Some b -> print_string b | None -> ()
+  print_string @@ Client.read_fixed res

cohttp-eio/examples/docker_client.ml

@@ -20,8 +20,6 @@ let () =
   Printf.printf "Response code: %d\n" code;
   Printf.printf "Headers: %s\n"
     (fst res |> Response.headers |> Http.Header.to_string);
-  match Client.read_fixed res with
-  | Some body ->
-      Printf.printf "Body of length: %d\n" (String.length body);
-      print_endline ("Received body\n" ^ body)
-  | None -> ()
+  let body = Client.read_fixed res in
+  Printf.printf "Body of length: %d\n" (String.length body);
+  print_endline ("Received body\n" ^ body)

cohttp-eio/src/body.ml

@@ -45,13 +45,6 @@ let pp_chunk fmt = function
         fmt chunk
   | Last_chunk extensions -> pp_chunk_extension fmt extensions
 
-let read_fixed t headers =
-  let ( let* ) o f = Option.bind o f in
-  let ( let+ ) o f = Option.map f o in
-  let* v = Http.Header.get headers "Content-Length" in
-  let+ content_length = int_of_string_opt v in
-  Buf_read.take content_length t
-
 (* Chunked encoding parser *)
 
 let hex_digit = function

cohttp-eio/src/client.ml

@@ -63,7 +63,7 @@ let response buf_read =
 
 let call ?(meth = `GET) ?(version = `HTTP_1_1) ?(headers = Http.Header.init ())
     ?(body = Body.Empty) conn_fn uri =
-  let (resource_path, (host_name, host_port), flow) = conn_fn uri in
+  let resource_path, (host_name, host_port), flow = conn_fn uri in
   let host =
     match host_port with
     | Some port -> host_name ^ ":" ^ string_of_int port
@@ -103,7 +103,13 @@ let patch ?version ?headers ?body stream uri =
 (* Response Body *)
 
 let read_fixed ((response, reader) : Http.Response.t * Buf_read.t) =
-  Body.read_fixed reader response.headers
+  match
+    Option.bind
+      (Http.Header.get response.headers "Content-Length")
+      int_of_string_opt
+  with
+  | Some content_length -> Buf_read.take content_length reader
+  | None -> Buf_read.take_all reader
 
 let read_chunked : response -> (Body.chunk -> unit) -> Http.Header.t option =
  fun (response, reader) f -> Body.read_chunked reader response.headers f

cohttp-eio/src/cohttp_eio.mli

@@ -160,10 +160,11 @@ module Client : sig
 
   (** {1 Response Body} *)
 
-  val read_fixed : response -> string option
-  (** [read_fixed (response,reader)] is [Some bytes], where [bytes] is of length
-      [n] if "Content-Length" header is a valid integer value [n] in [response].
-      [reader] is updated to reflect that [n] bytes was read. *)
+  val read_fixed : response -> string
+  (** [read_fixed (response,reader)] is [body_content], where [body_content] is
+      of length [n] if "Content-Length" header exists and is a valid integer
+      value [n] in [response]. Otherwise [body_content] holds all bytes until
+      eof. *)
 
   val read_chunked : response -> (Body.chunk -> unit) -> Http.Header.t option
   (** [read_chunked response chunk_handler] is [Some updated_headers] if

cohttp-eio/src/server.ml

@@ -16,7 +16,12 @@ let domain_count =
 
 let read_fixed request reader =
   match Http.Request.meth request with
-  | `POST | `PUT | `PATCH -> Body.read_fixed reader request.headers
+  | `POST | `PUT | `PATCH ->
+      let ( let* ) o f = Option.bind o f in
+      let ( let+ ) o f = Option.map f o in
+      let* v = Http.Header.get request.headers "Content-Length" in
+      let+ content_length = int_of_string_opt v in
+      Buf_read.take content_length reader
   | _ -> None
 
 let read_chunked request reader f =

cohttp-eio/tests/test_client.ml

@@ -15,7 +15,7 @@ let get env sw port =
       ~headers:(Http.Header.of_list [ ("Accept", "application/json") ])
       (conn env sw port) "/get"
   in
-  match Client.read_fixed res with Some s -> print_string s | None -> ()
+  print_string @@ Client.read_fixed res
 
 let post env sw port =
   let content = "hello world!" in
@@ -29,7 +29,7 @@ let post env sw port =
            ])
       ~body:(Body.Fixed content) (conn env sw port) "/post"
   in
-  match Client.read_fixed res with Some s -> print_string s | None -> ()
+  print_string @@ Client.read_fixed res
 
 (** Write chunk test.
 
@@ -82,9 +82,7 @@ let post_chunk env sw port =
           (Body.Chunked { body_writer = body_writer chan 0; trailer_writer })
         (conn env sw port) "/handle_chunk")
   |> Client.read_fixed
-  |> function
-  | Some r -> print_string r
-  | None -> ()
+  |> print_string
 
 (* Read chunk and dump to a "client_chunks2.txt" *)
 let get_chunk env sw port =