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handler.ex
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handler.ex
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defmodule Plug.Cowboy.Handler do
@moduledoc false
@connection Plug.Cowboy.Conn
@already_sent {:plug_conn, :sent}
def init(req, {plug, opts}) do
conn = @connection.conn(req)
try do
conn
|> plug.call(opts)
|> maybe_send(plug)
|> case do
%Plug.Conn{adapter: {@connection, %{upgrade: {:websocket, websocket_args}} = req}} = conn ->
{handler, state, connection_opts} = websocket_args
cowboy_opts =
connection_opts
|> Enum.flat_map(fn
{:timeout, timeout} -> [idle_timeout: timeout]
{:compress, _} = opt -> [opt]
{:max_frame_size, _} = opt -> [opt]
_other -> []
end)
|> Map.new()
{__MODULE__, copy_resp_headers(conn, req), {handler, state}, cowboy_opts}
%Plug.Conn{adapter: {@connection, req}} ->
{:ok, req, {plug, opts}}
end
catch
kind, reason ->
exit_on_error(kind, reason, __STACKTRACE__, {plug, :call, [conn, opts]})
after
receive do
@already_sent -> :ok
after
0 -> :ok
end
end
end
def upgrade(req, env, __MODULE__, {handler, state}, opts) do
:cowboy_websocket.upgrade(req, env, handler, state, opts)
end
defp copy_resp_headers(%Plug.Conn{} = conn, req) do
Enum.reduce(conn.resp_headers, req, fn {key, val}, acc ->
:cowboy_req.set_resp_header(key, val, acc)
end)
end
defp exit_on_error(
:error,
%Plug.Conn.WrapperError{kind: kind, reason: reason, stack: stack},
_stack,
call
) do
exit_on_error(kind, reason, stack, call)
end
defp exit_on_error(:error, value, stack, call) do
exception = Exception.normalize(:error, value, stack)
:erlang.raise(:exit, {{exception, stack}, call}, [])
end
defp exit_on_error(:throw, value, stack, call) do
:erlang.raise(:exit, {{{:nocatch, value}, stack}, call}, [])
end
defp exit_on_error(:exit, value, _stack, call) do
:erlang.raise(:exit, {value, call}, [])
end
defp maybe_send(%Plug.Conn{state: :unset}, _plug), do: raise(Plug.Conn.NotSentError)
defp maybe_send(%Plug.Conn{state: :set} = conn, _plug), do: Plug.Conn.send_resp(conn)
defp maybe_send(%Plug.Conn{} = conn, _plug), do: conn
defp maybe_send(other, plug) do
raise "Cowboy2 adapter expected #{inspect(plug)} to return Plug.Conn but got: " <>
inspect(other)
end
end