speedup cowboy_rest by introducing faster rfc2109 conversion

src/cowboy_clock.erl

@@ -25,7 +25,7 @@
 -export([start_link/0]).
 -export([stop/0]).
 -export([rfc1123/0]).
--export([rfc2109/1]).
+-export([rfc2109/1, rfc2109_fast/1]).
 
 %% gen_server.
 -export([init/1]).
@@ -106,6 +106,21 @@ rfc2109(LocalTime) ->
 	MinBin/binary, ":",
 	SecBin/binary, " GMT">>.
 
+%% @doc Return the current date and time formatted according to RFC-2109.
+%%
+%% This format is used in the <em>set-cookie</em> header sent with
+%% HTTP responses.
+-spec rfc2109_fast(calendar:datetime()) -> binary().
+rfc2109_fast(DateTime) ->
+  {{Year, Month, Day}, {Hour, Minute, Second}} = DateTime,
+  DoW = calendar:day_of_the_week(Year, Month, Day),
+  list_to_binary(io_lib:format(
+      "~s, ~2..0B ~s ~4..0B ~2..0B:~2..0B:~2..0B GMT", [
+      weekday(DoW),
+      Day, month(Month), Year,
+      Hour, Minute, Second
+    ])).
+
 %% gen_server.
 
 %% @private

src/cowboy_rest.erl

@@ -765,7 +765,7 @@ set_resp_body(Req, State=#state{content_type_a={_Type, Fun}}) ->
 		LastModified when is_atom(LastModified) ->
 			Req4 = Req3;
 		LastModified ->
-			LastModifiedStr = httpd_util:rfc1123_date(LastModified),
+			LastModifiedStr = cowboy_clock:rfc2109_fast(LastModified),
 			Req4 = cowboy_req:set_resp_header(
 				<<"Last-Modified">>, LastModifiedStr, Req3)
 	end,
@@ -810,7 +810,7 @@ set_resp_expires(Req, State) ->
 		Expires when is_atom(Expires) ->
 			{Req2, State2};
 		Expires ->
-			ExpiresStr = httpd_util:rfc1123_date(Expires),
+			ExpiresStr = cowboy_clock:rfc2109_fast(Expires),
 			Req3 = cowboy_req:set_resp_header(
 				<<"Expires">>, ExpiresStr, Req2),
 			{Req3, State2}

src/cowboy_static.erl

@@ -238,7 +238,7 @@ rest_init(Req, Opts) ->
 				etag_fun=ETagFunction};
 		ok ->
 			Filepath1 = join_paths(Directory1, Filepath),
-			Fileinfo = file:read_file_info(Filepath1),
+			Fileinfo = file:read_file_info(Filepath1, [{time, universal}]),
 			#state{filepath=Filepath1, fileinfo=Fileinfo, mimetypes=Mimetypes1,
 				etag_fun=ETagFunction}
 	end,