Add cow_uri:urlencode/1 and cow_uri:urldecode/1

These are expected to be used on path components,
unlike cow_qs:url{en,de}code/1 which are for query strings.

2 files changed, 347 insertions, 1 deletions

diff --git a/ebin/cowlib.app b/ebin/cowlib.app
index db04923..83ff3cc 100644
--- a/ebin/cowlib.app
+++ b/ebin/cowlib.app
@@ -1 +1,8 @@
-{application, cowlib, [ {description, "Support library for manipulating Web protocols."}, {vsn, "1.3.0"}, {id, "1.3.0-6-gad39742-dirty"}, {modules, [cow_cookie,cow_date,cow_hpack,cow_http,cow_http2,cow_http_hd,cow_http_te,cow_mimetypes,cow_multipart,cow_qs,cow_spdy,cow_ws]}, {registered, []}, {applications, [kernel,stdlib,crypto]}]}.
+{application, cowlib, [
+	{description, "Support library for manipulating Web protocols."},
+	{vsn, "1.3.0"},
+	{id, "1.3.0-18-g41949dd-dirty"},
+	{modules, ['cow_cookie','cow_date','cow_hpack','cow_http','cow_http2','cow_http_hd','cow_http_te','cow_mimetypes','cow_multipart','cow_qs','cow_spdy','cow_uri','cow_ws']},
+	{registered, []},
+	{applications, [kernel,stdlib,crypto]}
+]}.
\ No newline at end of file
diff --git a/src/cow_uri.erl b/src/cow_uri.erl
new file mode 100644
index 0000000..ccbb7b1
--- /dev/null
+++ b/src/cow_uri.erl
@@ -0,0 +1,339 @@
+%% Copyright (c) 2016, Loïc Hoguin <[email protected]>
+%%
+%% 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_uri).
+
+-export([urldecode/1]).
+-export([urlencode/1]).
+
+%% @doc Decode a percent encoded string. (RFC3986 2.1)
+
+-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(<< $$, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $$ >>);
+urldecode(<< $&, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $& >>);
+urldecode(<< $', Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $' >>);
+urldecode(<< $(, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $( >>);
+urldecode(<< $), Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $) >>);
+urldecode(<< $*, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $* >>);
+urldecode(<< $+, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $+ >>);
+urldecode(<< $,, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $, >>);
+urldecode(<< $-, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $- >>);
+urldecode(<< $., Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $. >>);
+urldecode(<< $0, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $0 >>);
+urldecode(<< $1, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $1 >>);
+urldecode(<< $2, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $2 >>);
+urldecode(<< $3, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $3 >>);
+urldecode(<< $4, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $4 >>);
+urldecode(<< $5, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $5 >>);
+urldecode(<< $6, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $6 >>);
+urldecode(<< $7, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $7 >>);
+urldecode(<< $8, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $8 >>);
+urldecode(<< $9, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $9 >>);
+urldecode(<< $:, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $: >>);
+urldecode(<< $;, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $; >>);
+urldecode(<< $=, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $= >>);
+urldecode(<< $@, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $@ >>);
+urldecode(<< $A, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $A >>);
+urldecode(<< $B, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $B >>);
+urldecode(<< $C, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $C >>);
+urldecode(<< $D, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $D >>);
+urldecode(<< $E, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $E >>);
+urldecode(<< $F, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $F >>);
+urldecode(<< $G, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $G >>);
+urldecode(<< $H, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $H >>);
+urldecode(<< $I, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $I >>);
+urldecode(<< $J, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $J >>);
+urldecode(<< $K, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $K >>);
+urldecode(<< $L, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $L >>);
+urldecode(<< $M, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $M >>);
+urldecode(<< $N, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $N >>);
+urldecode(<< $O, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $O >>);
+urldecode(<< $P, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $P >>);
+urldecode(<< $Q, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $Q >>);
+urldecode(<< $R, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $R >>);
+urldecode(<< $S, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $S >>);
+urldecode(<< $T, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $T >>);
+urldecode(<< $U, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $U >>);
+urldecode(<< $V, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $V >>);
+urldecode(<< $W, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $W >>);
+urldecode(<< $X, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $X >>);
+urldecode(<< $Y, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $Y >>);
+urldecode(<< $Z, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $Z >>);
+urldecode(<< $_, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $_ >>);
+urldecode(<< $a, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $a >>);
+urldecode(<< $b, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $b >>);
+urldecode(<< $c, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $c >>);
+urldecode(<< $d, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $d >>);
+urldecode(<< $e, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $e >>);
+urldecode(<< $f, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $f >>);
+urldecode(<< $g, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $g >>);
+urldecode(<< $h, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $h >>);
+urldecode(<< $i, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $i >>);
+urldecode(<< $j, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $j >>);
+urldecode(<< $k, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $k >>);
+urldecode(<< $l, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $l >>);
+urldecode(<< $m, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $m >>);
+urldecode(<< $n, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $n >>);
+urldecode(<< $o, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $o >>);
+urldecode(<< $p, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $p >>);
+urldecode(<< $q, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $q >>);
+urldecode(<< $r, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $r >>);
+urldecode(<< $s, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $s >>);
+urldecode(<< $t, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $t >>);
+urldecode(<< $u, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $u >>);
+urldecode(<< $v, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $v >>);
+urldecode(<< $w, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $w >>);
+urldecode(<< $x, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $x >>);
+urldecode(<< $y, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $y >>);
+urldecode(<< $z, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $z >>);
+urldecode(<< $~, Rest/bits >>, Acc) -> urldecode(Rest, << Acc/bits, $~ >>);
+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 = [
+		<<"%20">>,
+		<<"+">>,
+		<<"nothingnothingnothingnothing">>,
+		<<"Small+fast+modular+HTTP+server">>,
+		<<"Small%20fast%20modular%20HTTP%20server">>,
+		<<"Small%2F+fast%2F+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].
+
+horse_urldecode() ->
+	horse:repeat(100000,
+		urldecode(<<"nothingnothingnothingnothing">>)
+	).
+
+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">>)
+	).
+-endif.
+
+%% @doc Percent encode a string. (RFC3986 2.1)
+%%
+%% This function is meant to be used for path components.
+
+-spec urlencode(B) -> B when B::binary().
+urlencode(B) ->
+	urlencode(B, <<>>).
+
+urlencode(<< $!, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $! >>);
+urlencode(<< $$, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $$ >>);
+urlencode(<< $&, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $& >>);
+urlencode(<< $', Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $' >>);
+urlencode(<< $(, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $( >>);
+urlencode(<< $), Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $) >>);
+urlencode(<< $*, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $* >>);
+urlencode(<< $+, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $+ >>);
+urlencode(<< $,, 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(<< $:, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $: >>);
+urlencode(<< $;, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $; >>);
+urlencode(<< $=, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $= >>);
+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(<< $_, 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(<< $~, Rest/bits >>, Acc) -> urlencode(Rest, << Acc/bits, $~ >>);
+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) -> $F.
+
+-ifdef(TEST).
+urlencode_test_() ->
+	Tests = [
+		{<<255, 0>>, <<"%FF%00">>},
+		{<<255, " ">>, <<"%FF%20">>},
+		{<<"+">>, <<"+">>},
+		{<<"aBc123">>, <<"aBc123">>},
+		{<<"!$&'()*+,:;=@-._~">>, <<"!$&'()*+,:;=@-._~">>}
+	],
+	[{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].
+
+horse_urlencode() ->
+	horse:repeat(100000,
+		urlencode(<<"nothingnothingnothingnothing">>)
+	).
+
+horse_urlencode_spaces() ->
+	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.