Remove the dependency on httpd_util

Add the function cowboy_clock:rfc1123/1 that formats the given
date to the RFC1123 format.

src/cowboy_clock.erl

@@ -25,6 +25,7 @@
 -export([start_link/0]).
 -export([stop/0]).
 -export([rfc1123/0]).
+-export([rfc1123/1]).
 -export([rfc2109/1]).
 
 %% gen_server.
@@ -61,12 +62,15 @@ stop() ->
 	gen_server:call(?SERVER, stop).
 
 %% @doc Return the current date and time formatted according to RFC-1123.
-%%
-%% This format is used in the <em>date</em> header sent with HTTP responses.
 -spec rfc1123() -> binary().
 rfc1123() ->
 	ets:lookup_element(?TABLE, rfc1123, 2).
 
+%% @doc Return the given date and time formatted according to RFC-1123.
+-spec rfc1123(calendar:datetime()) -> binary().
+rfc1123(DateTime) ->
+	update_rfc1123(<<>>, undefined, DateTime).
+
 %% @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

src/cowboy_rest.erl

@@ -778,9 +778,9 @@ set_resp_body(Req, State=#state{handler=Handler, handler_state=HandlerState,
 		LastModified when is_atom(LastModified) ->
 			Req3;
 		LastModified ->
-			LastModifiedStr = httpd_util:rfc1123_date(LastModified),
+			LastModifiedBin = cowboy_clock:rfc1123(LastModified),
 			cowboy_req:set_resp_header(
-				<<"last-modified">>, LastModifiedStr, Req3)
+				<<"last-modified">>, LastModifiedBin, Req3)
 	end,
 	{Req5, State4} = set_resp_expires(Req4, State3),
 	case call(Req5, State4, Fun) of
@@ -831,9 +831,9 @@ set_resp_expires(Req, State) ->
 		Expires when is_atom(Expires) ->
 			{Req2, State2};
 		Expires ->
-			ExpiresStr = httpd_util:rfc1123_date(Expires),
+			ExpiresBin = cowboy_clock:rfc1123(Expires),
 			Req3 = cowboy_req:set_resp_header(
-				<<"expires">>, ExpiresStr, Req2),
+				<<"expires">>, ExpiresBin, Req2),
 			{Req3, State2}
 	end.