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%% @author Bob Ippolito <bob@mochimedia.com>
%% @copyright 2013 Mochi Media, Inc.
%%
%% Permission is hereby granted, free of charge, to any person obtaining a
%% copy of this software and associated documentation files (the "Software"),
%% to deal in the Software without restriction, including without limitation
%% the rights to use, copy, modify, merge, publish, distribute, sublicense,
%% and/or sell copies of the Software, and to permit persons to whom the
%% Software is furnished to do so, subject to the following conditions:
%%
%% The above copyright notice and this permission notice shall be included in
%% all copies or substantial portions of the Software.
%%
%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
%% THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
%% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
%% DEALINGS IN THE SOFTWARE.
-module(mochiweb_base64url).
-export([encode/1, decode/1]).
%% @doc URL and filename safe base64 variant with no padding,
%% also known as "base64url" per RFC 4648.
%%
%% This differs from base64 in the following ways:
%% '-' is used in place of '+' (62),
%% '_' is used in place of '/' (63),
%% padding is implicit rather than explicit ('=').
-spec encode(iolist() | binary()) -> binary().
encode(B) when is_binary(B) ->
encode_binary(B);
encode(L) when is_list(L) ->
encode_binary(iolist_to_binary(L)).
-spec decode(iolist() | binary()) -> binary().
decode(B) when is_binary(B) ->
decode_binary(B);
decode(L) when is_list(L) ->
decode_binary(iolist_to_binary(L)).
%% Implementation, derived from stdlib base64.erl
%% One-based decode map.
-define(DECODE_MAP,
{bad,bad,bad,bad,bad,bad,bad,bad,ws,ws,bad,bad,ws,bad,bad, %1-15
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad, %16-31
ws,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,62,bad,bad, %32-47
52,53,54,55,56,57,58,59,60,61,bad,bad,bad,bad,bad,bad, %48-63
bad,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14, %64-79
15,16,17,18,19,20,21,22,23,24,25,bad,bad,bad,bad,63, %80-95
bad,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40, %96-111
41,42,43,44,45,46,47,48,49,50,51,bad,bad,bad,bad,bad, %112-127
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad}).
encode_binary(Bin) ->
Split = 3*(byte_size(Bin) div 3),
<<Main0:Split/binary,Rest/binary>> = Bin,
Main = << <<(b64e(C)):8>> || <<C:6>> <= Main0 >>,
case Rest of
<<A:6,B:6,C:4>> ->
<<Main/binary,(b64e(A)):8,(b64e(B)):8,(b64e(C bsl 2)):8>>;
<<A:6,B:2>> ->
<<Main/binary,(b64e(A)):8,(b64e(B bsl 4)):8>>;
<<>> ->
Main
end.
decode_binary(Bin) ->
Main = << <<(b64d(C)):6>> || <<C>> <= Bin,
(C =/= $\t andalso C =/= $\s andalso
C =/= $\r andalso C =/= $\n) >>,
case bit_size(Main) rem 8 of
0 ->
Main;
N ->
Split = byte_size(Main) - 1,
<<Result:Split/bytes, _:N>> = Main,
Result
end.
%% accessors
b64e(X) ->
element(X+1,
{$A, $B, $C, $D, $E, $F, $G, $H, $I, $J, $K, $L, $M, $N,
$O, $P, $Q, $R, $S, $T, $U, $V, $W, $X, $Y, $Z,
$a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n,
$o, $p, $q, $r, $s, $t, $u, $v, $w, $x, $y, $z,
$0, $1, $2, $3, $4, $5, $6, $7, $8, $9, $-, $_}).
b64d(X) ->
b64d_ok(element(X, ?DECODE_MAP)).
b64d_ok(I) when is_integer(I) -> I.