%% Copyright (c) 2017, 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.
%% This module implements "base64url" following the algorithm
%% found in Appendix C of RFC7515. The option #{padding => false}
%% must be given to reproduce this variant exactly. The default
%% will leave the padding characters.
-module(cow_base64url).
-export([decode/1]).
-export([decode/2]).
-export([encode/1]).
-export([encode/2]).
-ifdef(TEST).
-include_lib("proper/include/proper.hrl").
-endif.
decode(Enc) ->
decode(Enc, #{}).
decode(Enc0, Opts) ->
Enc1 = << << case C of
$- -> $+;
$_ -> $/;
_ -> C
end >> || << C >> <= Enc0 >>,
Enc = case Opts of
#{padding := false} ->
case byte_size(Enc1) rem 4 of
0 -> Enc1;
2 -> << Enc1/binary, "==" >>;
3 -> << Enc1/binary, "=" >>
end;
_ ->
Enc1
end,
base64:decode(Enc).
encode(Dec) ->
encode(Dec, #{}).
encode(Dec, Opts) ->
encode(base64:encode(Dec), Opts, <<>>).
encode(<<$+, R/bits>>, Opts, Acc) -> encode(R, Opts, <<Acc/binary, $->>);
encode(<<$/, R/bits>>, Opts, Acc) -> encode(R, Opts, <<Acc/binary, $_>>);
encode(<<$=, _/bits>>, #{padding := false}, Acc) -> Acc;
encode(<<C, R/bits>>, Opts, Acc) -> encode(R, Opts, <<Acc/binary, C>>);
encode(<<>>, _, Acc) -> Acc.
-ifdef(TEST).
rfc7515_test() ->
Dec = <<3,236,255,224,193>>,
Enc = <<"A-z_4ME">>,
Pad = <<"A-z_4ME=">>,
Dec = decode(<<Enc/binary,$=>>),
Dec = decode(Enc, #{padding => false}),
Pad = encode(Dec),
Enc = encode(Dec, #{padding => false}),
ok.
prop_identity() ->
?FORALL(B, binary(), B =:= decode(encode(B))).
prop_identity_no_padding() ->
?FORALL(B, binary(), B =:= decode(encode(B, #{padding => false}), #{padding => false})).
-endif.
