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%% Copyright (c) 2011-2012, Loïc Hoguin <essen@ninenines.eu>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

%% @doc WebSocket protocol implementation.
-module(cowboy_websocket).

%% API.
-export([upgrade/4]).

%% Internal.
-export([handler_loop/4]).

-type opcode() :: 0 | 1 | 2 | 8 | 9 | 10.
-type mask_key() :: 0..16#ffffffff.

%% The websocket_data/4 function may be called multiple times for a message.
%% The websocket_dispatch/4 function is only called once for each message.
-type frag_state() ::
undefined | %% no fragmentation has been seen.
{nofin, opcode()} | %% first fragment has been seen.
{nofin, opcode(), binary()} | %% first fragment has been unmasked.
{fin, opcode(), binary()}. %% last fragment has been seen.

-record(state, {
socket = undefined :: inet:socket(),
transport = undefined :: module(),
version :: 0 | 7 | 8 | 13,
handler :: module(),
opts :: any(),
challenge = undefined :: undefined | binary() | {binary(), binary()},
timeout = infinity :: timeout(),
timeout_ref = undefined :: undefined | reference(),
messages = undefined :: undefined | {atom(), atom(), atom()},
hibernate = false :: boolean(),
eop :: undefined | tuple(), %% hixie-76 specific.
origin = undefined :: undefined | binary(), %% hixie-76 specific.
frag_state = undefined :: frag_state()
}).

%% @doc Upgrade a HTTP request to the WebSocket protocol.
%%
%% You do not need to call this function manually. To upgrade to the WebSocket
%% protocol, you simply need to return <em>{upgrade, protocol, {@module}}</em>
%% in your <em>cowboy_http_handler:init/3</em> handler function.
-spec upgrade(pid(), module(), any(), cowboy_req:req()) -> closed.
upgrade(ListenerPid, Handler, Opts, Req) ->
ranch_listener:remove_connection(ListenerPid),
{ok, Transport, Socket} = cowboy_req:transport(Req),
State = #state{socket=Socket, transport=Transport,
handler=Handler, opts=Opts},
case catch websocket_upgrade(State, Req) of
{ok, State2, Req2} -> handler_init(State2, Req2);
{'EXIT', _Reason} -> upgrade_error(Req)
end.

-spec websocket_upgrade(#state{}, Req)
-> {ok, #state{}, Req} when Req::cowboy_req:req().
websocket_upgrade(State, Req) ->
{ok, ConnTokens, Req2}
= cowboy_req:parse_header(<<"connection">>, Req),
true = lists:member(<<"upgrade">>, ConnTokens),
%% @todo Should probably send a 426 if the Upgrade header is missing.
{ok, [<<"websocket">>], Req3}
= cowboy_req:parse_header(<<"upgrade">>, Req2),
{Version, Req4} = cowboy_req:header(<<"sec-websocket-version">>, Req3),
websocket_upgrade(Version, State, Req4).

%% @todo Handle the Sec-Websocket-Protocol header.
%% @todo Reply a proper error, don't die, if a required header is undefined.
-spec websocket_upgrade(undefined | <<_:8>>, #state{}, Req)
-> {ok, #state{}, Req} when Req::cowboy_req:req().
%% No version given. Assuming hixie-76 draft.
%%
%% We need to wait to send a reply back before trying to read the
%% third part of the challenge key, because proxies will wait for
%% a reply before sending it. Therefore we calculate the challenge
%% key only in websocket_handshake/3.
websocket_upgrade(undefined, State, Req) ->
{Origin, Req2} = cowboy_req:header(<<"origin">>, Req),
{Key1, Req3} = cowboy_req:header(<<"sec-websocket-key1">>, Req2),
{Key2, Req4} = cowboy_req:header(<<"sec-websocket-key2">>, Req3),
false = lists:member(undefined, [Origin, Key1, Key2]),
EOP = binary:compile_pattern(<< 255 >>),
{ok, State#state{version=0, origin=Origin, challenge={Key1, Key2},
eop=EOP}, cowboy_req:set_meta(websocket_version, 0, Req4)};
%% Versions 7 and 8. Implementation follows the hybi 7 through 17 drafts.
websocket_upgrade(Version, State, Req)
when Version =:= <<"7">>; Version =:= <<"8">>;
Version =:= <<"13">> ->
{Key, Req2} = cowboy_req:header(<<"sec-websocket-key">>, Req),
false = Key =:= undefined,
Challenge = hybi_challenge(Key),
IntVersion = list_to_integer(binary_to_list(Version)),
{ok, State#state{version=IntVersion, challenge=Challenge},
cowboy_req:set_meta(websocket_version, IntVersion, Req2)}.

-spec handler_init(#state{}, cowboy_req:req()) -> closed.
handler_init(State=#state{transport=Transport, handler=Handler, opts=Opts},
Req) ->
try Handler:websocket_init(Transport:name(), Req, Opts) of
{ok, Req2, HandlerState} ->
websocket_handshake(State, Req2, HandlerState);
{ok, Req2, HandlerState, hibernate} ->
websocket_handshake(State#state{hibernate=true},
Req2, HandlerState);
{ok, Req2, HandlerState, Timeout} ->
websocket_handshake(State#state{timeout=Timeout},
Req2, HandlerState);
{ok, Req2, HandlerState, Timeout, hibernate} ->
websocket_handshake(State#state{timeout=Timeout,
hibernate=true}, Req2, HandlerState);
{shutdown, Req2} ->
cowboy_req:ensure_response(Req2, 400),
closed
catch Class:Reason ->
upgrade_error(Req),
PLReq = cowboy_req:to_list(Req),
error_logger:error_msg(
"** Handler ~p terminating in websocket_init/3~n"
" for the reason ~p:~p~n** Options were ~p~n"
"** Request was ~p~n** Stacktrace: ~p~n~n",
[Handler, Class, Reason, Opts, PLReq, erlang:get_stacktrace()])
end.

-spec upgrade_error(cowboy_req:req()) -> closed.
upgrade_error(Req) ->
receive
{cowboy_req, resp_sent} -> closed
after 0 ->
_ = cowboy_req:reply(400, [], [], Req),
closed
end.

-spec websocket_handshake(#state{}, cowboy_req:req(), any()) -> closed.
websocket_handshake(State=#state{socket=Socket, transport=Transport,
version=0, origin=Origin, challenge={Key1, Key2}},
Req, HandlerState) ->
{<< "http", Location/binary >>, Req1} = cowboy_req:url(Req),
{ok, Req2} = cowboy_req:upgrade_reply(
<<"101 WebSocket Protocol Handshake">>,
[{<<"Upgrade">>, <<"WebSocket">>},
{<<"Sec-Websocket-Location">>, << "ws", Location/binary >>},
{<<"Sec-Websocket-Origin">>, Origin}],
Req1),
%% Flush the resp_sent message before moving on.
receive {cowboy_req, resp_sent} -> ok after 0 -> ok end,
%% We replied with a proper response. Proxies should be happy enough,
%% we can now read the 8 last bytes of the challenge keys and send
%% the challenge response directly to the socket.
%%
%% We use a trick here to read exactly 8 bytes of the body regardless
%% of what's in the buffer.
{ok, Req3} = cowboy_req:init_stream(
fun cowboy_http:te_identity/2, {0, 8},
fun cowboy_http:ce_identity/1, Req2),
case cowboy_req:body(Req3) of
{ok, Key3, Req4} ->
Challenge = hixie76_challenge(Key1, Key2, Key3),
Transport:send(Socket, Challenge),
handler_before_loop(State#state{messages=Transport:messages()},
Req4, HandlerState, <<>>);
_Any ->
closed %% If an error happened reading the body, stop there.
end;
websocket_handshake(State=#state{transport=Transport, challenge=Challenge},
Req, HandlerState) ->
{ok, Req2} = cowboy_req:upgrade_reply(
101,
[{<<"Upgrade">>, <<"websocket">>},
{<<"Sec-Websocket-Accept">>, Challenge}],
Req),
%% Flush the resp_sent message before moving on.
receive {cowboy_req, resp_sent} -> ok after 0 -> ok end,
handler_before_loop(State#state{messages=Transport:messages()},
Req2, HandlerState, <<>>).

-spec handler_before_loop(#state{}, cowboy_req:req(), any(), binary()) -> closed.
handler_before_loop(State=#state{
socket=Socket, transport=Transport, hibernate=true},
Req, HandlerState, SoFar) ->
Transport:setopts(Socket, [{active, once}]),
State2 = handler_loop_timeout(State),
catch erlang:hibernate(?MODULE, handler_loop,
[State2#state{hibernate=false}, Req, HandlerState, SoFar]),
closed;
handler_before_loop(State=#state{socket=Socket, transport=Transport},
Req, HandlerState, SoFar) ->
Transport:setopts(Socket, [{active, once}]),
State2 = handler_loop_timeout(State),
handler_loop(State2, Req, HandlerState, SoFar).

-spec handler_loop_timeout(#state{}) -> #state{}.
handler_loop_timeout(State=#state{timeout=infinity}) ->
State#state{timeout_ref=undefined};
handler_loop_timeout(State=#state{timeout=Timeout, timeout_ref=PrevRef}) ->
_ = case PrevRef of undefined -> ignore; PrevRef ->
erlang:cancel_timer(PrevRef) end,
TRef = erlang:start_timer(Timeout, self(), ?MODULE),
State#state{timeout_ref=TRef}.

%% @private
-spec handler_loop(#state{}, cowboy_req:req(), any(), binary()) -> closed.
handler_loop(State=#state{
socket=Socket, messages={OK, Closed, Error}, timeout_ref=TRef},
Req, HandlerState, SoFar) ->
receive
{OK, Socket, Data} ->
websocket_data(State, Req, HandlerState,
<< SoFar/binary, Data/binary >>);
{Closed, Socket} ->
handler_terminate(State, Req, HandlerState, {error, closed});
{Error, Socket, Reason} ->
handler_terminate(State, Req, HandlerState, {error, Reason});
{timeout, TRef, ?MODULE} ->
websocket_close(State, Req, HandlerState, {normal, timeout});
{timeout, OlderTRef, ?MODULE} when is_reference(OlderTRef) ->
handler_loop(State, Req, HandlerState, SoFar);
Message ->
handler_call(State, Req, HandlerState,
SoFar, websocket_info, Message, fun handler_before_loop/4)
end.

-spec websocket_data(#state{}, cowboy_req:req(), any(), binary()) -> closed.
%% No more data.
websocket_data(State, Req, HandlerState, <<>>) ->
handler_before_loop(State, Req, HandlerState, <<>>);
%% hixie-76 close frame.
websocket_data(State=#state{version=0}, Req, HandlerState,
<< 255, 0, _Rest/binary >>) ->
websocket_close(State, Req, HandlerState, {normal, closed});
%% hixie-76 data frame. We only support the frame type 0, same as the specs.
websocket_data(State=#state{version=0, eop=EOP}, Req, HandlerState,
Data = << 0, _/binary >>) ->
case binary:match(Data, EOP) of
{Pos, 1} ->
Pos2 = Pos - 1,
<< 0, Payload:Pos2/binary, 255, Rest/bits >> = Data,
handler_call(State, Req, HandlerState,
Rest, websocket_handle, {text, Payload}, fun websocket_data/4);
nomatch ->
%% @todo We probably should allow limiting frame length.
handler_before_loop(State, Req, HandlerState, Data)
end;
%% incomplete hybi data frame.
websocket_data(State=#state{version=Version}, Req, HandlerState, Data)
when Version =/= 0, byte_size(Data) =:= 1 ->
handler_before_loop(State, Req, HandlerState, Data);
%% 7 bit payload length prefix exists
websocket_data(State, Req, HandlerState,
<< Fin:1, Rsv:3, Opcode:4, Mask:1, PayloadLen:7, Rest/bits >>
= Data) when PayloadLen < 126 ->
websocket_data(State, Req, HandlerState,
Fin, Rsv, Opcode, Mask, PayloadLen, Rest, Data);
%% 7+16 bits payload length prefix exists
websocket_data(State, Req, HandlerState,
<< Fin:1, Rsv:3, Opcode:4, Mask:1, 126:7, PayloadLen:16, Rest/bits >>
= Data) when PayloadLen > 125 ->
websocket_data(State, Req, HandlerState,
Fin, Rsv, Opcode, Mask, PayloadLen, Rest, Data);
%% 7+16 bits payload length prefix missing
websocket_data(State, Req, HandlerState,
<< _Fin:1, _Rsv:3, _Opcode:4, _Mask:1, 126:7, Rest/bits >>
= Data) when byte_size(Rest) < 2 ->
handler_before_loop(State, Req, HandlerState, Data);
%% 7+64 bits payload length prefix exists
websocket_data(State, Req, HandlerState,
<< Fin:1, Rsv:3, Opcode:4, Mask:1, 127:7, 0:1, PayloadLen:63,
Rest/bits >> = Data) when PayloadLen > 16#FFFF ->
websocket_data(State, Req, HandlerState,
Fin, Rsv, Opcode, Mask, PayloadLen, Rest, Data);
%% 7+64 bits payload length prefix missing
websocket_data(State, Req, HandlerState,
<< _Fin:1, _Rsv:3, _Opcode:4, _Mask:1, 127:7, Rest/bits >>
= Data) when byte_size(Rest) < 8 ->
handler_before_loop(State, Req, HandlerState, Data);
%% invalid payload length prefix.
websocket_data(State, Req, HandlerState, _Data) ->
websocket_close(State, Req, HandlerState, {error, badframe}).

-spec websocket_data(#state{}, cowboy_req:req(), any(), non_neg_integer(),
non_neg_integer(), non_neg_integer(), non_neg_integer(),
non_neg_integer(), binary(), binary()) -> closed.
%% A fragmented message MUST start a non-zero opcode.
websocket_data(State=#state{frag_state=undefined}, Req, HandlerState,
_Fin=0, _Rsv=0, _Opcode=0, _Mask, _PayloadLen, _Rest, _Buffer) ->
websocket_close(State, Req, HandlerState, {error, badframe});
%% A control message MUST NOT be fragmented.
websocket_data(State, Req, HandlerState, _Fin=0, _Rsv=0, Opcode, _Mask,
_PayloadLen, _Rest, _Buffer) when Opcode >= 8 ->
websocket_close(State, Req, HandlerState, {error, badframe});
%% The opcode is only included in the first message fragment.
websocket_data(State=#state{frag_state=undefined}, Req, HandlerState,
_Fin=0, _Rsv=0, Opcode, Mask, PayloadLen, Rest, Data) ->
websocket_before_unmask(
State#state{frag_state={nofin, Opcode}}, Req, HandlerState,
Data, Rest, 0, Mask, PayloadLen);
%% non-control opcode when expecting control message or next fragment.
websocket_data(State=#state{frag_state={nofin, _, _}}, Req, HandlerState, _Fin,
_Rsv=0, Opcode, _Mask, _Ln, _Rest, _Data) when Opcode > 0, Opcode < 8 ->
websocket_close(State, Req, HandlerState, {error, badframe});
%% If the first message fragment was incomplete, retry unmasking.
websocket_data(State=#state{frag_state={nofin, Opcode}}, Req, HandlerState,
_Fin=0, _Rsv=0, Opcode, Mask, PayloadLen, Rest, Data) ->
websocket_before_unmask(
State#state{frag_state={nofin, Opcode}}, Req, HandlerState,
Data, Rest, 0, Mask, PayloadLen);
%% if the opcode is zero and the fin flag is zero, unmask and await next.
websocket_data(State=#state{frag_state={nofin, _Opcode, _Payloads}}, Req,
HandlerState, _Fin=0, _Rsv=0, _Opcode2=0, Mask, PayloadLen, Rest,
Data) ->
websocket_before_unmask(
State, Req, HandlerState, Data, Rest, 0, Mask, PayloadLen);
%% when the last fragment is seen. Update the fragmentation status.
websocket_data(State=#state{frag_state={nofin, Opcode, Payloads}}, Req,
HandlerState, _Fin=1, _Rsv=0, _Opcode=0, Mask, PayloadLen, Rest,
Data) ->
websocket_before_unmask(
State#state{frag_state={fin, Opcode, Payloads}},
Req, HandlerState, Data, Rest, 0, Mask, PayloadLen);
%% control messages MUST NOT use 7+16 bits or 7+64 bits payload length prefixes
websocket_data(State, Req, HandlerState, _Fin, _Rsv, Opcode, _Mask, PayloadLen,
_Rest, _Data) when Opcode >= 8, PayloadLen > 125 ->
websocket_close(State, Req, HandlerState, {error, badframe});
%% unfragmented message. unmask and dispatch the message.
websocket_data(State=#state{version=Version}, Req, HandlerState, _Fin=1, _Rsv=0,
Opcode, Mask, PayloadLen, Rest, Data) when Version =/= 0 ->
websocket_before_unmask(
State, Req, HandlerState, Data, Rest, Opcode, Mask, PayloadLen);
%% Something was wrong with the frame. Close the connection.
websocket_data(State, Req, HandlerState, _Fin, _Rsv, _Opcode, _Mask,
_PayloadLen, _Rest, _Data) ->
websocket_close(State, Req, HandlerState, {error, badframe}).

%% hybi routing depending on whether unmasking is needed.
-spec websocket_before_unmask(#state{}, cowboy_req:req(), any(), binary(),
binary(), opcode(), 0 | 1, non_neg_integer() | undefined) -> closed.
websocket_before_unmask(State, Req, HandlerState, Data,
Rest, Opcode, Mask, PayloadLen) ->
case {Mask, PayloadLen} of
{0, 0} ->
websocket_dispatch(State, Req, HandlerState, Rest, Opcode, <<>>);
{1, N} when N + 4 > byte_size(Rest); N =:= undefined ->
%% @todo We probably should allow limiting frame length.
handler_before_loop(State, Req, HandlerState, Data);
{1, _N} ->
<< MaskKey:32, Payload:PayloadLen/binary, Rest2/bits >> = Rest,
websocket_unmask(State, Req, HandlerState, Rest2,
Opcode, Payload, MaskKey)
end.

%% hybi unmasking.
-spec websocket_unmask(#state{}, cowboy_req:req(), any(), binary(),
opcode(), binary(), mask_key()) -> closed.
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, Payload, MaskKey) ->
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, Payload, MaskKey, <<>>).

-spec websocket_unmask(#state{}, cowboy_req:req(), any(), binary(),
opcode(), binary(), mask_key(), binary()) -> closed.
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, << O:32, Rest/bits >>, MaskKey, Acc) ->
T = O bxor MaskKey,
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, Rest, MaskKey, << Acc/binary, T:32 >>);
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, << O:24 >>, MaskKey, Acc) ->
<< MaskKey2:24, _:8 >> = << MaskKey:32 >>,
T = O bxor MaskKey2,
websocket_dispatch(State, Req, HandlerState, RemainingData,
Opcode, << Acc/binary, T:24 >>);
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, << O:16 >>, MaskKey, Acc) ->
<< MaskKey2:16, _:16 >> = << MaskKey:32 >>,
T = O bxor MaskKey2,
websocket_dispatch(State, Req, HandlerState, RemainingData,
Opcode, << Acc/binary, T:16 >>);
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, << O:8 >>, MaskKey, Acc) ->
<< MaskKey2:8, _:24 >> = << MaskKey:32 >>,
T = O bxor MaskKey2,
websocket_dispatch(State, Req, HandlerState, RemainingData,
Opcode, << Acc/binary, T:8 >>);
websocket_unmask(State, Req, HandlerState, RemainingData,
Opcode, <<>>, _MaskKey, Acc) ->
websocket_dispatch(State, Req, HandlerState, RemainingData,
Opcode, Acc).

%% hybi dispatching.
-spec websocket_dispatch(#state{}, cowboy_req:req(), any(), binary(),
opcode(), binary()) -> closed.
%% First frame of a fragmented message unmasked. Expect intermediate or last.
websocket_dispatch(State=#state{frag_state={nofin, Opcode}}, Req, HandlerState,
RemainingData, 0, Payload) ->
websocket_data(State#state{frag_state={nofin, Opcode, Payload}},
Req, HandlerState, RemainingData);
%% Intermediate frame of a fragmented message unmasked. Add payload to buffer.
websocket_dispatch(State=#state{frag_state={nofin, Opcode, Payloads}}, Req,
HandlerState, RemainingData, 0, Payload) ->
websocket_data(State#state{frag_state={nofin, Opcode,
<<Payloads/binary, Payload/binary>>}}, Req, HandlerState,
RemainingData);
%% Last frame of a fragmented message unmasked. Dispatch to handler.
websocket_dispatch(State=#state{frag_state={fin, Opcode, Payloads}}, Req,
HandlerState, RemainingData, 0, Payload) ->
websocket_dispatch(State#state{frag_state=undefined}, Req, HandlerState,
RemainingData, Opcode, <<Payloads/binary, Payload/binary>>);
%% Text frame.
websocket_dispatch(State, Req, HandlerState, RemainingData, 1, Payload) ->
handler_call(State, Req, HandlerState, RemainingData,
websocket_handle, {text, Payload}, fun websocket_data/4);
%% Binary frame.
websocket_dispatch(State, Req, HandlerState, RemainingData, 2, Payload) ->
handler_call(State, Req, HandlerState, RemainingData,
websocket_handle, {binary, Payload}, fun websocket_data/4);
%% Close control frame.
%% @todo Handle the optional Payload.
websocket_dispatch(State, Req, HandlerState, _RemainingData, 8, _Payload) ->
websocket_close(State, Req, HandlerState, {normal, closed});
%% Ping control frame. Send a pong back and forward the ping to the handler.
websocket_dispatch(State=#state{socket=Socket, transport=Transport},
Req, HandlerState, RemainingData, 9, Payload) ->
Len = hybi_payload_length(byte_size(Payload)),
Transport:send(Socket, << 1:1, 0:3, 10:4, 0:1, Len/bits, Payload/binary >>),
handler_call(State, Req, HandlerState, RemainingData,
websocket_handle, {ping, Payload}, fun websocket_data/4);
%% Pong control frame.
websocket_dispatch(State, Req, HandlerState, RemainingData, 10, Payload) ->
handler_call(State, Req, HandlerState, RemainingData,
websocket_handle, {pong, Payload}, fun websocket_data/4).

-spec handler_call(#state{}, cowboy_req:req(), any(), binary(),
atom(), any(), fun()) -> closed.
handler_call(State=#state{handler=Handler, opts=Opts}, Req, HandlerState,
RemainingData, Callback, Message, NextState) ->
try Handler:Callback(Message, Req, HandlerState) of
{ok, Req2, HandlerState2} ->
NextState(State, Req2, HandlerState2, RemainingData);
{ok, Req2, HandlerState2, hibernate} ->
NextState(State#state{hibernate=true},
Req2, HandlerState2, RemainingData);
{reply, Payload, Req2, HandlerState2}
when is_tuple(Payload) ->
ok = websocket_send(Payload, State),
NextState(State, Req2, HandlerState2, RemainingData);
{reply, Payload, Req2, HandlerState2, hibernate}
when is_tuple(Payload) ->
ok = websocket_send(Payload, State),
NextState(State#state{hibernate=true},
Req2, HandlerState2, RemainingData);
{reply, Payload, Req2, HandlerState2}
when is_list(Payload) ->
ok = websocket_send_many(Payload, State),
NextState(State, Req2, HandlerState2, RemainingData);
{reply, Payload, Req2, HandlerState2, hibernate}
when is_list(Payload) ->
ok = websocket_send_many(Payload, State),
NextState(State#state{hibernate=true},
Req2, HandlerState2, RemainingData);
{shutdown, Req2, HandlerState2} ->
websocket_close(State, Req2, HandlerState2, {normal, shutdown})
catch Class:Reason ->
PLReq = cowboy_req:to_list(Req),
error_logger:error_msg(
"** Handler ~p terminating in ~p/3~n"
" for the reason ~p:~p~n** Message was ~p~n"
"** Options were ~p~n** Handler state was ~p~n"
"** Request was ~p~n** Stacktrace: ~p~n~n",
[Handler, Callback, Class, Reason, Message, Opts,
HandlerState, PLReq, erlang:get_stacktrace()]),
websocket_close(State, Req, HandlerState, {error, handler})
end.

-spec websocket_send({text | binary | ping | pong, binary()}, #state{})
-> ok | {error, atom()}.
%% hixie-76 text frame.
websocket_send({text, Payload}, #state{
socket=Socket, transport=Transport, version=0}) ->
Transport:send(Socket, [0, Payload, 255]);
%% Ignore all unknown frame types for compatibility with hixie 76.
websocket_send(_Any, #state{version=0}) ->
ok;
websocket_send({Type, Payload}, #state{socket=Socket, transport=Transport}) ->
Opcode = case Type of
text -> 1;
binary -> 2;
ping -> 9;
pong -> 10
end,
Len = hybi_payload_length(iolist_size(Payload)),
Transport:send(Socket, [<< 1:1, 0:3, Opcode:4, 0:1, Len/bits >>,
Payload]).

-spec websocket_send_many([{text | binary | ping | pong, binary()}], #state{})
-> ok | {error, atom()}.
websocket_send_many([], _) ->
ok;
websocket_send_many([Frame|Tail], State) ->
ok = websocket_send(Frame, State),
websocket_send_many(Tail, State).

-spec websocket_close(#state{}, cowboy_req:req(), any(), {atom(), atom()})
-> closed.
websocket_close(State=#state{socket=Socket, transport=Transport, version=0},
Req, HandlerState, Reason) ->
Transport:send(Socket, << 255, 0 >>),
handler_terminate(State, Req, HandlerState, Reason);
%% @todo Send a Payload? Using Reason is usually good but we're quite careless.
websocket_close(State=#state{socket=Socket, transport=Transport},
Req, HandlerState, Reason) ->
Transport:send(Socket, << 1:1, 0:3, 8:4, 0:8 >>),
handler_terminate(State, Req, HandlerState, Reason).

-spec handler_terminate(#state{}, cowboy_req:req(),
any(), atom() | {atom(), atom()}) -> closed.
handler_terminate(#state{handler=Handler, opts=Opts},
Req, HandlerState, TerminateReason) ->
try
Handler:websocket_terminate(TerminateReason, Req, HandlerState)
catch Class:Reason ->
PLReq = cowboy_req:to_list(Req),
error_logger:error_msg(
"** Handler ~p terminating in websocket_terminate/3~n"
" for the reason ~p:~p~n** Initial reason was ~p~n"
"** Options were ~p~n** Handler state was ~p~n"
"** Request was ~p~n** Stacktrace: ~p~n~n",
[Handler, Class, Reason, TerminateReason, Opts,
HandlerState, PLReq, erlang:get_stacktrace()])
end,
closed.

%% hixie-76 specific.

-spec hixie76_challenge(binary(), binary(), binary()) -> binary().
hixie76_challenge(Key1, Key2, Key3) ->
IntKey1 = hixie76_key_to_integer(Key1),
IntKey2 = hixie76_key_to_integer(Key2),
erlang:md5(<< IntKey1:32, IntKey2:32, Key3/binary >>).

-spec hixie76_key_to_integer(binary()) -> integer().
hixie76_key_to_integer(Key) ->
Number = list_to_integer([C || << C >> <= Key, C >= $0, C =< $9]),
Spaces = length([C || << C >> <= Key, C =:= 32]),
Number div Spaces.

%% hybi specific.

-spec hybi_challenge(binary()) -> binary().
hybi_challenge(Key) ->
Bin = << Key/binary, "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" >>,
base64:encode(crypto:sha(Bin)).

-spec hybi_payload_length(0..16#7fffffffffffffff)
-> << _:7 >> | << _:23 >> | << _:71 >>.
hybi_payload_length(N) ->
case N of
N when N =< 125 -> << N:7 >>;
N when N =< 16#ffff -> << 126:7, N:16 >>;
N when N =< 16#7fffffffffffffff -> << 127:7, N:64 >>
end.
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