Add the cow_qs module for query string parsing and building

Includes functions to encode and decode percent encoded strings
that follow the application/x-www_form_urlencoded format.

Query string parsing should be 3 times faster than the code
that was in Cowboy, and will also create less intermediate
variables.

src/cow_qs.erl

@@ -0,0 +1,571 @@
+%% Copyright (c) 2013, 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.
+
+-module(cow_qs).
+
+-export([parse_qs/1]).
+-export([qs/1]).
+-export([urldecode/1]).
+-export([urlencode/1]).
+
+-type qs_vals() :: [{binary(), binary() | true}].
+
+%% @doc Parse an application/x-www-form-urlencoded string.
+%%
+%% The percent decoding is inlined to greatly improve the performance
+%% by avoiding copying binaries twice (once for extracting, once for
+%% decoding) instead of just extracting the proper representation.
+
+-spec parse_qs(binary()) -> qs_vals().
+parse_qs(B) ->
+	parse_qs_name(B, [], <<>>).
+
+parse_qs_name(<< $%, H, L, Rest/bits >>, Acc, Name) ->
+	C = (unhex(H) bsl 4 bor unhex(L)),
+	parse_qs_name(Rest, Acc, << Name/bits, C >>);
+parse_qs_name(<< $+, Rest/bits >>, Acc, Name) ->
+	parse_qs_name(Rest, Acc, << Name/bits, " " >>);
+parse_qs_name(<< $=, Rest/bits >>, Acc, Name) when Name =/= <<>> ->
+	parse_qs_value(Rest, Acc, Name, <<>>);
+parse_qs_name(<< $&, Rest/bits >>, Acc, Name) ->
+	case Name of
+		<<>> -> parse_qs_name(Rest, Acc, <<>>);
+		_ -> parse_qs_name(Rest, [{Name, true}|Acc], <<>>)
+	end;
+parse_qs_name(<< C, Rest/bits >>, Acc, Name) when C =/= $%, C =/= $= ->
+	parse_qs_name(Rest, Acc, << Name/bits, C >>);
+parse_qs_name(<<>>, Acc, Name) ->
+	case Name of
+		<<>> -> lists:reverse(Acc);
+		_ -> lists:reverse([{Name, true}|Acc])
+	end.
+
+parse_qs_value(<< $%, H, L, Rest/bits >>, Acc, Name, Value) ->
+	C = (unhex(H) bsl 4 bor unhex(L)),
+	parse_qs_value(Rest, Acc, Name, << Value/bits, C >>);
+parse_qs_value(<< $+, Rest/bits >>, Acc, Name, Value) ->
+	parse_qs_value(Rest, Acc, Name, << Value/bits, " " >>);
+parse_qs_value(<< $&, Rest/bits >>, Acc, Name, Value) ->
+	parse_qs_name(Rest, [{Name, Value}|Acc], <<>>);
+parse_qs_value(<< C, Rest/bits >>, Acc, Name, Value) when C =/= $% ->
+	parse_qs_value(Rest, Acc, Name, << Value/bits, C >>);
+parse_qs_value(<<>>, Acc, Name, Value) ->
+	lists:reverse([{Name, Value}|Acc]).
+
+-ifdef(TEST).
+parse_qs_test_() ->
+	Tests = [
+		{<<>>, []},
+		{<<"&">>, []},
+		{<<"a">>, [{<<"a">>, true}]},
+		{<<"a&">>, [{<<"a">>, true}]},
+		{<<"&a">>, [{<<"a">>, true}]},
+		{<<"a&b">>, [{<<"a">>, true}, {<<"b">>, true}]},
+		{<<"a&&b">>, [{<<"a">>, true}, {<<"b">>, true}]},
+		{<<"a&b&">>, [{<<"a">>, true}, {<<"b">>, true}]},
+		{<<"=">>, error},
+		{<<"=b">>, error},
+		{<<"a=">>, [{<<"a">>, <<>>}]},
+		{<<"a=b">>, [{<<"a">>, <<"b">>}]},
+		{<<"a=&b=">>, [{<<"a">>, <<>>}, {<<"b">>, <<>>}]},
+		{<<"a=b&c&d=e">>, [{<<"a">>, <<"b">>},
+			{<<"c">>, true}, {<<"d">>, <<"e">>}]},
+		{<<"a=b=c&d=e=f&g=h=i">>, [{<<"a">>, <<"b=c">>},
+			{<<"d">>, <<"e=f">>}, {<<"g">>, <<"h=i">>}]},
+		{<<"+">>, [{<<" ">>, true}]},
+		{<<"+=+">>, [{<<" ">>, <<" ">>}]},
+		{<<"a+b=c+d">>, [{<<"a b">>, <<"c d">>}]},
+		{<<"+a+=+b+&+c+=+d+">>, [{<<" a ">>, <<" b ">>},
+			{<<" c ">>, <<" d ">>}]},
+		{<<"a%20b=c%20d">>, [{<<"a b">>, <<"c d">>}]},
+		{<<"%25%26%3D=%25%26%3D&_-.=.-_">>, [{<<"%&=">>, <<"%&=">>},
+			{<<"_-.">>, <<".-_">>}]},
+		{<<"for=extend%2Franch">>, [{<<"for">>, <<"extend/ranch">>}]}
+	],
+	[{Qs, fun() ->
+		E = try parse_qs(Qs) of
+			R -> R
+		catch _:_ ->
+			error
+		end
+	end} || {Qs, E} <- Tests].
+
+parse_qs_identity_test_() ->
+	Tests = [
+		<<"+">>,
+		<<"hl=en&q=erlang+cowboy">>,
+		<<"direction=desc&for=extend%2Franch&sort=updated&state=open">>,
+		<<"i=EWiIXmPj5gl6&v=QowBp0oDLQXdd4x_GwiywA&ip=98.20.31.81&"
+			"la=en&pg=New8.undertonebrandsafe.com%2F698a2525065ee2"
+			"60c0b2f2aaad89ab82&re=&sz=1&fc=1&fr=140&br=3&bv=11.0."
+			"696.16&os=3&ov=&rs=vpl&k=cookies%7Csale%7Cbrowser%7Cm"
+			"ore%7Cprivacy%7Cstatistics%7Cactivities%7Cauction%7Ce"
+			"mail%7Cfree%7Cin...&t=112373&xt=5%7C61%7C0&tz=-1&ev=x"
+			"&tk=&za=1&ortb-za=1&zu=&zl=&ax=U&ay=U&ortb-pid=536454"
+			".55&ortb-sid=112373.8&seats=999&ortb-xt=IAB24&ortb-ugc=">>,
+		<<"i=9pQNskA&v=0ySQQd1F&ev=12345678&t=12345&sz=3&ip=67.58."
+			"236.89&la=en&pg=http%3A%2F%2Fwww.yahoo.com%2Fpage1.ht"
+			"m&re=http%3A%2F%2Fsearch.google.com&fc=1&fr=1&br=2&bv"
+			"=3.0.14&os=1&ov=XP&k=cars%2Cford&rs=js&xt=5%7C22%7C23"
+			"4&tz=%2B180&tk=key1%3Dvalue1%7Ckey2%3Dvalue2&zl=4%2C5"
+			"%2C6&za=4&zu=competitor.com&ua=Mozilla%2F5.0+%28Windo"
+			"ws%3B+U%3B+Windows+NT+6.1%3B+en-US%29+AppleWebKit%2F5"
+			"34.13+%28KHTML%2C+like+Gecko%29+Chrome%2F9.0.597.98+S"
+			"afari%2F534.13&ortb-za=1%2C6%2C13&ortb-pid=521732&ort"
+			"b-sid=521732&ortb-xt=IAB3&ortb-ugc=">>
+	],
+	[{V, fun() -> V = qs(parse_qs(V)) end} || V <- Tests].
+-endif.
+
+-ifdef(PERF).
+horse_parse_qs_shorter() ->
+	horse:repeat(20000,
+		parse_qs(<<"hl=en&q=erlang%20cowboy">>)
+	).
+
+horse_parse_qs_short() ->
+	horse:repeat(20000,
+		parse_qs(
+			<<"direction=desc&for=extend%2Franch&sort=updated&state=open">>)
+	).
+
+horse_parse_qs_long() ->
+	horse:repeat(20000,
+		parse_qs(<<"i=EWiIXmPj5gl6&v=QowBp0oDLQXdd4x_GwiywA&ip=98.20.31.81&"
+			"la=en&pg=New8.undertonebrandsafe.com%2F698a2525065ee260c0b2f2a"
+			"aad89ab82&re=&sz=1&fc=1&fr=140&br=3&bv=11.0.696.16&os=3&ov=&rs"
+			"=vpl&k=cookies%7Csale%7Cbrowser%7Cmore%7Cprivacy%7Cstatistics%"
+			"7Cactivities%7Cauction%7Cemail%7Cfree%7Cin...&t=112373&xt=5%7C"
+			"61%7C0&tz=-1&ev=x&tk=&za=1&ortb-za=1&zu=&zl=&ax=U&ay=U&ortb-pi"
+			"d=536454.55&ortb-sid=112373.8&seats=999&ortb-xt=IAB24&ortb-ugc"
+			"=">>)
+	).
+
+horse_parse_qs_longer() ->
+	horse:repeat(20000,
+		parse_qs(<<"i=9pQNskA&v=0ySQQd1F&ev=12345678&t=12345&sz=3&ip=67.58."
+			"236.89&la=en&pg=http%3A%2F%2Fwww.yahoo.com%2Fpage1.htm&re=http"
+			"%3A%2F%2Fsearch.google.com&fc=1&fr=1&br=2&bv=3.0.14&os=1&ov=XP"
+			"&k=cars%2cford&rs=js&xt=5%7c22%7c234&tz=%2b180&tk=key1%3Dvalue"
+			"1%7Ckey2%3Dvalue2&zl=4,5,6&za=4&zu=competitor.com&ua=Mozilla%2"
+			"F5.0%20(Windows%3B%20U%3B%20Windows%20NT%206.1%3B%20en-US)%20A"
+			"ppleWebKit%2F534.13%20(KHTML%2C%20like%20Gecko)%20Chrome%2F9.0"
+			".597.98%20Safari%2F534.13&ortb-za=1%2C6%2C13&ortb-pid=521732&o"
+			"rtb-sid=521732&ortb-xt=IAB3&ortb-ugc=">>)
+	).
+-endif.
+
+%% @doc Build an application/x-www-form-urlencoded string.
+
+-spec qs(qs_vals()) -> binary().
+qs([]) ->
+	<<>>;
+qs(L) ->
+	qs(L, <<>>).
+
+qs([], Acc) ->
+	<< $&, Qs/bits >> = Acc,
+	Qs;
+qs([{Name, true}|Tail], Acc) ->
+	Acc2 = urlencode(Name, << Acc/bits, $& >>),
+	qs(Tail, Acc2);
+qs([{Name, Value}|Tail], Acc) ->
+	Acc2 = urlencode(Name, << Acc/bits, $& >>),
+	Acc3 = urlencode(Value, << Acc2/bits, $= >>),
+	qs(Tail, Acc3).
+
+-define(QS_SHORTER, [
+	{<<"hl">>, <<"en">>},
+	{<<"q">>, <<"erlang cowboy">>}
+]).
+
+-define(QS_SHORT, [
+	{<<"direction">>, <<"desc">>},
+	{<<"for">>, <<"extend/ranch">>},
+	{<<"sort">>, <<"updated">>},
+	{<<"state">>, <<"open">>}
+]).
+
+-define(QS_LONG, [
+	{<<"i">>, <<"EWiIXmPj5gl6">>},
+	{<<"v">>, <<"QowBp0oDLQXdd4x_GwiywA">>},
+	{<<"ip">>, <<"98.20.31.81">>},
+	{<<"la">>, <<"en">>},
+	{<<"pg">>, <<"New8.undertonebrandsafe.com/"
+		"698a2525065ee260c0b2f2aaad89ab82">>},
+	{<<"re">>, <<>>},
+	{<<"sz">>, <<"1">>},
+	{<<"fc">>, <<"1">>},
+	{<<"fr">>, <<"140">>},
+	{<<"br">>, <<"3">>},
+	{<<"bv">>, <<"11.0.696.16">>},
+	{<<"os">>, <<"3">>},
+	{<<"ov">>, <<>>},
+	{<<"rs">>, <<"vpl">>},
+	{<<"k">>, <<"cookies|sale|browser|more|privacy|statistics|"
+		"activities|auction|email|free|in...">>},
+	{<<"t">>, <<"112373">>},
+	{<<"xt">>, <<"5|61|0">>},
+	{<<"tz">>, <<"-1">>},
+	{<<"ev">>, <<"x">>},
+	{<<"tk">>, <<>>},
+	{<<"za">>, <<"1">>},
+	{<<"ortb-za">>, <<"1">>},
+	{<<"zu">>, <<>>},
+	{<<"zl">>, <<>>},
+	{<<"ax">>, <<"U">>},
+	{<<"ay">>, <<"U">>},
+	{<<"ortb-pid">>, <<"536454.55">>},
+	{<<"ortb-sid">>, <<"112373.8">>},
+	{<<"seats">>, <<"999">>},
+	{<<"ortb-xt">>, <<"IAB24">>},
+	{<<"ortb-ugc">>, <<>>}
+]).
+
+-define(QS_LONGER, [
+	{<<"i">>, <<"9pQNskA">>},
+	{<<"v">>, <<"0ySQQd1F">>},
+	{<<"ev">>, <<"12345678">>},
+	{<<"t">>, <<"12345">>},
+	{<<"sz">>, <<"3">>},
+	{<<"ip">>, <<"67.58.236.89">>},
+	{<<"la">>, <<"en">>},
+	{<<"pg">>, <<"http://www.yahoo.com/page1.htm">>},
+	{<<"re">>, <<"http://search.google.com">>},
+	{<<"fc">>, <<"1">>},
+	{<<"fr">>, <<"1">>},
+	{<<"br">>, <<"2">>},
+	{<<"bv">>, <<"3.0.14">>},
+	{<<"os">>, <<"1">>},
+	{<<"ov">>, <<"XP">>},
+	{<<"k">>, <<"cars,ford">>},
+	{<<"rs">>, <<"js">>},
+	{<<"xt">>, <<"5|22|234">>},
+	{<<"tz">>, <<"+180">>},
+	{<<"tk">>, <<"key1=value1|key2=value2">>},
+	{<<"zl">>, <<"4,5,6">>},
+	{<<"za">>, <<"4">>},
+	{<<"zu">>, <<"competitor.com">>},
+	{<<"ua">>, <<"Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) "
+		"AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.98 "
+		"Safari/534.13">>},
+	{<<"ortb-za">>, <<"1,6,13">>},
+	{<<"ortb-pid">>, <<"521732">>},
+	{<<"ortb-sid">>, <<"521732">>},
+	{<<"ortb-xt">>, <<"IAB3">>},
+	{<<"ortb-ugc">>, <<>>}
+]).
+
+-ifdef(TEST).
+qs_test_() ->
+	Tests = [
+		{[<<"a">>], error},
+		{[{<<"a">>, <<"b">>, <<"c">>}], error},
+		{[], <<>>},
+		{[{<<"a">>, true}], <<"a">>},
+		{[{<<"a">>, true}, {<<"b">>, true}], <<"a&b">>},
+		{[{<<"a">>, <<>>}], <<"a=">>},
+		{[{<<"a">>, <<"b">>}], <<"a=b">>},
+		{[{<<"a">>, <<>>}, {<<"b">>, <<>>}], <<"a=&b=">>},
+		{[{<<"a">>, <<"b">>}, {<<"c">>, true}, {<<"d">>, <<"e">>}],
+			<<"a=b&c&d=e">>},
+		{[{<<"a">>, <<"b=c">>}, {<<"d">>, <<"e=f">>}, {<<"g">>, <<"h=i">>}],
+			<<"a=b%3Dc&d=e%3Df&g=h%3Di">>},
+		{[{<<" ">>, true}], <<"+">>},
+		{[{<<" ">>, <<" ">>}], <<"+=+">>},
+		{[{<<"a b">>, <<"c d">>}], <<"a+b=c+d">>},
+		{[{<<" a ">>, <<" b ">>}, {<<" c ">>, <<" d ">>}],
+			<<"+a+=+b+&+c+=+d+">>},
+		{[{<<"%&=">>, <<"%&=">>}, {<<"_-.">>, <<".-_">>}],
+			<<"%25%26%3D=%25%26%3D&_-.=.-_">>},
+		{[{<<"for">>, <<"extend/ranch">>}], <<"for=extend%2Franch">>}
+	],
+	[{lists:flatten(io_lib:format("~p", [Vals])), fun() ->
+		E = try qs(Vals) of
+			R -> R
+		catch _:_ ->
+			error
+		end
+	end} || {Vals, E} <- Tests].
+
+qs_identity_test_() ->
+	Tests = [
+		[{<<"+">>, true}],
+		?QS_SHORTER,
+		?QS_SHORT,
+		?QS_LONG,
+		?QS_LONGER
+	],
+	[{lists:flatten(io_lib:format("~p", [V])), fun() ->
+		V = parse_qs(qs(V))
+	end} || V <- Tests].
+-endif.
+
+-ifdef(PERF).
+horse_qs_shorter() ->
+	horse:repeat(20000, qs(?QS_SHORTER)).
+
+horse_qs_short() ->
+	horse:repeat(20000, qs(?QS_SHORT)).
+
+horse_qs_long() ->
+	horse:repeat(20000, qs(?QS_LONG)).
+
+horse_qs_longer() ->
+	horse:repeat(20000, qs(?QS_LONGER)).
+-endif.
+
+%% @doc Decode a percent encoded string (x-www-form-urlencoded rules).
+
+-spec urldecode(B) -> B when B::binary().
+urldecode(B) ->
+	urldecode(B, <<>>).
+
+urldecode(<< $%, H, L, Rest/bits >>, Acc) ->
+	C = (unhex(H) bsl 4 bor unhex(L)),
+	urldecode(Rest, << Acc/bits, C >>);
+urldecode(<< $+, Rest/bits >>, Acc) ->
+	urldecode(Rest, << Acc/bits, " " >>);
+urldecode(<< C, Rest/bits >>, Acc) when C =/= $% ->
+	urldecode(Rest, << Acc/bits, C >>);
+urldecode(<<>>, Acc) ->
+	Acc.
+
+unhex($0) ->  0;
+unhex($1) ->  1;
+unhex($2) ->  2;
+unhex($3) ->  3;
+unhex($4) ->  4;
+unhex($5) ->  5;
+unhex($6) ->  6;
+unhex($7) ->  7;
+unhex($8) ->  8;
+unhex($9) ->  9;
+unhex($A) -> 10;
+unhex($B) -> 11;
+unhex($C) -> 12;
+unhex($D) -> 13;
+unhex($E) -> 14;
+unhex($F) -> 15;
+unhex($a) -> 10;
+unhex($b) -> 11;
+unhex($c) -> 12;
+unhex($d) -> 13;
+unhex($e) -> 14;
+unhex($f) -> 15.
+
+-ifdef(TEST).
+urldecode_test_() ->
+	Tests = [
+		{<<"%20">>, <<" ">>},
+		{<<"+">>, <<" ">>},
+		{<<"%00">>, <<0>>},
+		{<<"%fF">>, <<255>>},
+		{<<"123">>, <<"123">>},
+		{<<"%i5">>, error},
+		{<<"%5">>, error}
+	],
+	[{Qs, fun() ->
+		E = try urldecode(Qs) of
+			R -> R
+		catch _:_ ->
+			error
+		end
+	end} || {Qs, E} <- Tests].
+
+urldecode_identity_test_() ->
+	Tests = [
+		<<"+">>,
+		<<"nothingnothingnothingnothing">>,
+		<<"Small+fast+modular+HTTP+server">>,
+		<<"Small%2C+fast%2C+modular+HTTP+server.">>,
+		<<"%E3%83%84%E3%82%A4%E3%83%B3%E3%82%BD%E3%82%A6%E3%83"
+			"%AB%E3%80%9C%E8%BC%AA%E5%BB%BB%E3%81%99%E3%82%8B%E6%97%8B%E5"
+			"%BE%8B%E3%80%9C">>
+	],
+	[{V, fun() -> V = urlencode(urldecode(V)) end} || V <- Tests].
+-endif.
+
+-ifdef(PERF).
+horse_urldecode() ->
+	horse:repeat(100000,
+		urldecode(<<"nothingnothingnothingnothing">>)
+	).
+
+horse_urldecode_plus() ->
+	horse:repeat(100000,
+		urldecode(<<"Small+fast+modular+HTTP+server">>)
+	).
+
+horse_urldecode_hex() ->
+	horse:repeat(100000,
+		urldecode(<<"Small%2C%20fast%2C%20modular%20HTTP%20server.">>)
+	).
+
+horse_urldecode_jp_hex() ->
+	horse:repeat(100000,
+		urldecode(<<"%E3%83%84%E3%82%A4%E3%83%B3%E3%82%BD%E3%82%A6%E3%83"
+			"%AB%E3%80%9C%E8%BC%AA%E5%BB%BB%E3%81%99%E3%82%8B%E6%97%8B%E5"
+			"%BE%8B%E3%80%9C">>)
+	).
+
+horse_urldecode_mix() ->
+	horse:repeat(100000,
+		urldecode(<<"Small%2C+fast%2C+modular+HTTP+server.">>)
+	).
+-endif.
+
+%% @doc Percent encode a string (x-www-form-urlencoded rules).
+
+-spec urlencode(B) -> B when B::binary().
+urlencode(B) ->
+	urlencode(B, <<>>).
+
+urlencode(<< $\s, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $+ >>);
+urlencode(<< $-, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $- >>);
+urlencode(<< $., Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $. >>);
+urlencode(<< $0, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $0 >>);
+urlencode(<< $1, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $1 >>);
+urlencode(<< $2, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $2 >>);
+urlencode(<< $3, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $3 >>);
+urlencode(<< $4, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $4 >>);
+urlencode(<< $5, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $5 >>);
+urlencode(<< $6, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $6 >>);
+urlencode(<< $7, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $7 >>);
+urlencode(<< $8, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $8 >>);
+urlencode(<< $9, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $9 >>);
+urlencode(<< $A, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $A >>);
+urlencode(<< $B, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $B >>);
+urlencode(<< $C, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $C >>);
+urlencode(<< $D, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $D >>);
+urlencode(<< $E, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $E >>);
+urlencode(<< $F, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $F >>);
+urlencode(<< $G, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $G >>);
+urlencode(<< $H, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $H >>);
+urlencode(<< $I, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $I >>);
+urlencode(<< $J, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $J >>);
+urlencode(<< $K, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $K >>);
+urlencode(<< $L, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $L >>);
+urlencode(<< $M, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $M >>);
+urlencode(<< $N, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $N >>);
+urlencode(<< $O, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $O >>);
+urlencode(<< $P, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $P >>);
+urlencode(<< $Q, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $Q >>);
+urlencode(<< $R, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $R >>);
+urlencode(<< $S, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $S >>);
+urlencode(<< $T, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $T >>);
+urlencode(<< $U, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $U >>);
+urlencode(<< $V, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $V >>);
+urlencode(<< $W, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $W >>);
+urlencode(<< $X, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $X >>);
+urlencode(<< $Y, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $Y >>);
+urlencode(<< $Z, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $Z >>);
+urlencode(<< $_, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $_ >>);
+urlencode(<< $a, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $a >>);
+urlencode(<< $b, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $b >>);
+urlencode(<< $c, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $c >>);
+urlencode(<< $d, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $d >>);
+urlencode(<< $e, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $e >>);
+urlencode(<< $f, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $f >>);
+urlencode(<< $g, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $g >>);
+urlencode(<< $h, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $h >>);
+urlencode(<< $i, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $i >>);
+urlencode(<< $j, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $j >>);
+urlencode(<< $k, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $k >>);
+urlencode(<< $l, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $l >>);
+urlencode(<< $m, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $m >>);
+urlencode(<< $n, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $n >>);
+urlencode(<< $o, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $o >>);
+urlencode(<< $p, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $p >>);
+urlencode(<< $q, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $q >>);
+urlencode(<< $r, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $r >>);
+urlencode(<< $s, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $s >>);
+urlencode(<< $t, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $t >>);
+urlencode(<< $u, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $u >>);
+urlencode(<< $v, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $v >>);
+urlencode(<< $w, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $w >>);
+urlencode(<< $x, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $x >>);
+urlencode(<< $y, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $y >>);
+urlencode(<< $z, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $z >>);
+urlencode(<< C, Rest/bits >>, Acc) ->
+	H = hex(C bsr 4),
+	L = hex(C band 16#0f),
+	urlencode(Rest, << Acc/bits, $%, H, L >>);
+urlencode(<<>>, Acc) ->
+	Acc.
+
+hex( 0) -> $0;
+hex( 1) -> $1;
+hex( 2) -> $2;
+hex( 3) -> $3;
+hex( 4) -> $4;
+hex( 5) -> $5;
+hex( 6) -> $6;
+hex( 7) -> $7;
+hex( 8) -> $8;
+hex( 9) -> $9;
+hex(10) -> $A;
+hex(11) -> $B;
+hex(12) -> $C;
+hex(13) -> $D;
+hex(14) -> $E;
+hex(15) -> $F.
+
+-ifdef(TEST).
+urlencode_test_() ->
+	Tests = [
+		{<<255, 0>>, <<"%FF%00">>},
+		{<<255, " ">>, <<"%FF+">>},
+		{<<" ">>, <<"+">>},
+		{<<"aBc123">>, <<"aBc123">>},
+		{<<".-_">>, <<".-_">>}
+	],
+	[{V, fun() -> E = urlencode(V) end} || {V, E} <- Tests].
+
+urlencode_identity_test_() ->
+	Tests = [
+		<<"+">>,
+		<<"nothingnothingnothingnothing">>,
+		<<"Small fast modular HTTP server">>,
+		<<"Small, fast, modular HTTP server.">>,
+		<<227,131,132,227,130,164,227,131,179,227,130,189,227,
+			130,166,227,131,171,227,128,156,232,188,170,229,187,187,227,
+			129,153,227,130,139,230,151,139,229,190,139,227,128,156>>
+	],
+	[{V, fun() -> V = urldecode(urlencode(V)) end} || V <- Tests].
+-endif.
+
+-ifdef(PERF).
+horse_urlencode() ->
+	horse:repeat(100000,
+		urlencode(<<"nothingnothingnothingnothing">>)
+	).
+
+horse_urlencode_plus() ->
+	horse:repeat(100000,
+		urlencode(<<"Small fast modular HTTP server">>)
+	).
+
+horse_urlencode_jp() ->
+	horse:repeat(100000,
+		urlencode(<<227,131,132,227,130,164,227,131,179,227,130,189,227,
+			130,166,227,131,171,227,128,156,232,188,170,229,187,187,227,
+			129,153,227,130,139,230,151,139,229,190,139,227,128,156>>)
+	).
+
+horse_urlencode_mix() ->
+	horse:repeat(100000,
+		urlencode(<<"Small, fast, modular HTTP server.">>)
+	).
+-endif.