Source file body.ml

(*----------------------------------------------------------------------------
    Copyright (c) 2018 Inhabited Type LLC.

    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

    3. Neither the name of the author nor the names of his contributors
       may be used to endorse or promote products derived from this software
       without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND ANY EXPRESS
    OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
    ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
    STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
  ----------------------------------------------------------------------------*)

type _ t =
  { faraday                        : Faraday.t
  ; mutable read_scheduled         : bool
  ; mutable write_final_if_chunked : bool
  ; mutable on_eof                 : unit -> unit
  ; mutable on_read                : Bigstringaf.t -> off:int -> len:int -> unit
  ; mutable when_ready_to_write    : Optional_thunk.t
  ; buffered_bytes                 : int ref
  }

let default_on_eof         = Sys.opaque_identity (fun () -> ())
let default_on_read        = Sys.opaque_identity (fun _ ~off:_ ~len:_ -> ())

let of_faraday faraday =
  { faraday
  ; read_scheduled         = false
  ; write_final_if_chunked = true
  ; on_eof                 = default_on_eof
  ; on_read                = default_on_read
  ; when_ready_to_write    = Optional_thunk.none
  ; buffered_bytes         = ref 0
  }

let create buffer =
  of_faraday (Faraday.of_bigstring buffer)

let create_empty () =
  let t = create Bigstringaf.empty in
  Faraday.close t.faraday;
  t

let empty = create_empty ()

let write_char t c =
  Faraday.write_char t.faraday c

let write_string t ?off ?len s =
  Faraday.write_string ?off ?len t.faraday s

let write_bigstring t ?off ?len b =
  Faraday.write_bigstring ?off ?len t.faraday b

let schedule_bigstring t ?off ?len (b:Bigstringaf.t) =
  Faraday.schedule_bigstring ?off ?len t.faraday b

let ready_to_write t =
  let callback = t.when_ready_to_write in
  t.when_ready_to_write <- Optional_thunk.none;
  Optional_thunk.call_if_some callback

let flush t kontinue =
  Faraday.flush t.faraday kontinue;
  ready_to_write t

let is_closed t =
  Faraday.is_closed t.faraday

let close_writer t =
  Faraday.close t.faraday;
  ready_to_write t;
;;

let unsafe_faraday t =
  t.faraday

let rec do_execute_read t on_eof on_read =
  match Faraday.operation t.faraday with
  | `Yield           -> ()
  | `Close           ->
    t.read_scheduled <- false;
    t.on_eof         <- default_on_eof;
    t.on_read        <- default_on_read;
    on_eof ()
  | `Writev []       -> assert false
  | `Writev (iovec::_) ->
    t.read_scheduled <- false;
    t.on_eof         <- default_on_eof;
    t.on_read        <- default_on_read;
    let { IOVec.buffer; off; len } = iovec in
    Faraday.shift t.faraday len;
    on_read buffer ~off ~len;
    execute_read t
and execute_read t =
  if t.read_scheduled then do_execute_read t t.on_eof t.on_read

let schedule_read t ~on_eof ~on_read =
  if t.read_scheduled
  then failwith "Body.schedule_read: reader already scheduled";
  if is_closed t
  then do_execute_read t on_eof on_read
  else begin
    t.read_scheduled <- true;
    t.on_eof         <- on_eof;
    t.on_read        <- on_read
  end

let has_pending_output t =
  (* Force another write poll to make sure that the final chunk is emitted for
     chunk-encoded bodies.

     Note that the body data type does not keep track of encodings, so it is
     necessary for [transfer_to_writer_with_encoding] to check the encoding and
     clear the [write_final_if_chunked] field when outputting a fixed or
     close-delimited body. *)
  Faraday.has_pending_output t.faraday
  || (Faraday.is_closed t.faraday && t.write_final_if_chunked)

let close_reader t =
  Faraday.close t.faraday;
  execute_read t
;;

let when_ready_to_write t callback =
  if is_closed t
  then callback ()
  else if Optional_thunk.is_some t.when_ready_to_write 
  then failwith "Body.when_ready_to_write: only one callback can be registered at a time"
  else t.when_ready_to_write <- Optional_thunk.some callback

let transfer_to_writer_with_encoding t ~encoding writer =
  let faraday = t.faraday in
  begin match Faraday.operation faraday with
  | `Yield -> ()
  | `Close ->
    let must_write_the_final_chunk = t.write_final_if_chunked in
    t.write_final_if_chunked <- false;
    if must_write_the_final_chunk
    then
      begin match encoding with
      | `Chunked                    -> Serialize.Writer.schedule_chunk writer []
      | `Fixed _ | `Close_delimited -> ()
      end;
    Serialize.Writer.unyield writer;
  | `Writev iovecs ->
    let buffered = t.buffered_bytes in
    begin match IOVec.shiftv iovecs !buffered with
    | []     -> ()
    | iovecs ->
      let lengthv  = IOVec.lengthv iovecs in
      buffered := !buffered + lengthv;
      begin match encoding with
      | `Fixed _ | `Close_delimited ->
        (* Play nicely with [has_pending_output] in the case of a fixed or
           close-delimited encoding. *)
        t.write_final_if_chunked <- false;
        Serialize.Writer.schedule_fixed writer iovecs
      | `Chunked ->
        Serialize.Writer.schedule_chunk writer iovecs
      end;
      Serialize.Writer.flush writer (fun () ->
        Faraday.shift faraday lengthv;
        buffered := !buffered - lengthv)
    end
  end