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type t = {
me : int;
players : int;
inputs : (int * int, string) Hashtbl.t;
contiguous : int array;
acked : int array;
mine : (int, int32) Hashtbl.t;
mutable latest : (int * int32) option;
theirs : (int * int, int32) Hashtbl.t;
mutable desync : (int * int) option;
mutable dropped : int;
mutable inputs_sent : int;
}
let max_inputs = 60
let create ~(me : int) ~(players : int) ~(delay : int) : t =
let inputs = Hashtbl.create 1024 in
for tick = 0 to delay - 1 do
for p = 0 to players - 1 do
Hashtbl.replace inputs (tick, p) ""
done
done;
{
me;
players;
inputs;
contiguous = Array.make players (delay - 1);
acked = Array.make players (delay - 1);
mine = Hashtbl.create 64;
latest = None;
theirs = Hashtbl.create 64;
desync = None;
dropped = 0;
inputs_sent = 0;
}
let me (t : t) : int = t.me
let players (t : t) : int = t.players
let find (t : t) ~(tick : int) (player : int) : string option = Hashtbl.find_opt t.inputs (tick, player)
let known_upto (t : t) (player : int) : int = t.contiguous.(player)
let desync (t : t) : (int * int) option = t.desync
let dropped (t : t) : int = t.dropped
let inputs_sent (t : t) : int = t.inputs_sent
let extend (t : t) (player : int) : unit =
while Hashtbl.mem t.inputs (t.contiguous.(player) + 1, player) do
t.contiguous.(player) <- t.contiguous.(player) + 1
done
let add_mine (t : t) ~(tick : int) (input : string) : unit =
Hashtbl.replace t.inputs (tick, t.me) input;
extend t t.me
let compare (t : t) (player : int) (tick : int) : unit =
match (t.desync, Hashtbl.find_opt t.mine tick, Hashtbl.find_opt t.theirs (player, tick)) with
| None, Some a, Some b when a <> b -> t.desync <- Some (tick, player)
| _ -> ()
let checksum (t : t) ~(tick : int) (sum : int32) : unit =
Hashtbl.replace t.mine tick sum;
t.latest <- Some (tick, sum);
for p = 0 to t.players - 1 do
if p <> t.me then compare t p tick
done
let others (t : t) : int list = List.filter (( <> ) t.me) (List.init t.players Fun.id)
let packet (t : t) : string =
let first = 1 + List.fold_left (fun m p -> min m t.acked.(p)) max_int (others t) in
let last = min t.contiguous.(t.me) (first + max_inputs - 1) in
let count = max 0 (last - first + 1) in
t.inputs_sent <- t.inputs_sent + count;
Wire.to_bytes (fun w ->
Wire.put_u8 w 1;
Wire.put_varint w t.me;
Wire.put_varint w (t.players - 1);
List.iter
(fun p ->
Wire.put_varint w p;
Wire.put_signed w t.contiguous.(p))
(others t);
Wire.put_varint w first;
Wire.put_varint w count;
for tick = first to first + count - 1 do
Wire.put_string w (Hashtbl.find t.inputs (tick, t.me))
done;
match t.latest with
| None -> Wire.put_u8 w 0
| Some (tick, sum) ->
Wire.put_u8 w 1;
Wire.put_varint w tick;
Wire.put_u16 w (Int32.to_int (Int32.shift_right_logical sum 16));
Wire.put_u16 w (Int32.to_int (Int32.logand sum 0xffffl)))
type message = { from : int; acks : (int * int) list; first : int; sent : string list; sum : (int * int32) option }
let read (players : int) (r : Wire.reader) : message =
if Wire.get_u8 r <> 1 then Wire.fail r "not an inputs packet";
let player r = match Wire.get_varint r with p when p < players -> p | p -> Wire.fail r (Printf.sprintf "no player %d" p) in
let from = player r in
let n = Wire.get_varint r in
if n >= players then Wire.fail r "too many acks";
let acks =
List.init n (fun _ ->
let p = player r in
(p, Wire.get_signed r))
in
let first = Wire.get_varint r in
let count = Wire.get_varint r in
if count > max_inputs then Wire.fail r "too many inputs";
let sent = List.init count (fun _ -> Wire.get_string r) in
let sum =
match Wire.get_u8 r with
| 0 -> None
| 1 ->
let tick = Wire.get_varint r in
let hi = Wire.get_u16 r in
let lo = Wire.get_u16 r in
Some (tick, Int32.logor (Int32.shift_left (Int32.of_int hi) 16) (Int32.of_int lo))
| _ -> Wire.fail r "bad checksum flag"
in
{ from; acks; first; sent; sum }
let receive (t : t) (bytes : string) : unit =
match Wire.parse (read t.players) bytes with
| Error _ -> t.dropped <- t.dropped + 1
| Ok m when m.from = t.me -> t.dropped <- t.dropped + 1
| Ok m ->
List.iteri
(fun i input -> if not (Hashtbl.mem t.inputs (m.first + i, m.from)) then Hashtbl.replace t.inputs (m.first + i, m.from) input)
m.sent;
extend t m.from;
List.iter (fun (p, ack) -> if p = t.me then t.acked.(m.from) <- max t.acked.(m.from) ack) m.acks;
Option.iter
(fun (tick, sum) ->
Hashtbl.replace t.theirs (m.from, tick) sum;
compare t m.from tick)
m.sum