%% %% %CopyrightBegin% %% %% Copyright Ericsson AB 2007-2011. All Rights Reserved. %% %% The contents of this file are subject to the Erlang Public License, %% Version 1.1, (the "License"); you may not use this file except in %% compliance with the License. You should have received a copy of the %% Erlang Public License along with this software. If not, it can be %% retrieved online at http://www.erlang.org/. %% %% Software distributed under the License is distributed on an "AS IS" %% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See %% the License for the specific language governing rights and limitations %% under the License. %% %% %CopyrightEnd% %% %% Description: Implements base 64 encode and decode. See RFC4648. -module(base64). -export([encode/1, decode/1, mime_decode/1, encode_to_string/1, decode_to_string/1, mime_decode_to_string/1]). %%------------------------------------------------------------------------- %% The following type is a subtype of string() for return values %% of (some) functions of this module. %%------------------------------------------------------------------------- -type ascii_string() :: [1..255]. %%------------------------------------------------------------------------- %% encode_to_string(ASCII) -> Base64String %% ASCII - string() | binary() %% Base64String - string() %% %% Description: Encodes a plain ASCII string (or binary) into base64. %%------------------------------------------------------------------------- -spec encode_to_string(Data) -> Base64String when Data :: string() | binary(), Base64String :: ascii_string(). encode_to_string(Bin) when is_binary(Bin) -> encode_to_string(binary_to_list(Bin)); encode_to_string(List) when is_list(List) -> encode_l(List). %%------------------------------------------------------------------------- %% encode(ASCII) -> Base64 %% ASCII - string() | binary() %% Base64 - binary() %% %% Description: Encodes a plain ASCII string (or binary) into base64. %%------------------------------------------------------------------------- -spec encode(Data) -> Base64 when Data :: string() | binary(), Base64 :: binary(). encode(Bin) when is_binary(Bin) -> encode_binary(Bin); encode(List) when is_list(List) -> list_to_binary(encode_l(List)). -spec encode_l(string()) -> ascii_string(). encode_l([]) -> []; encode_l([A]) -> [b64e(A bsr 2), b64e((A band 3) bsl 4), $=, $=]; encode_l([A,B]) -> [b64e(A bsr 2), b64e(((A band 3) bsl 4) bor (B bsr 4)), b64e((B band 15) bsl 2), $=]; encode_l([A,B,C|Ls]) -> BB = (A bsl 16) bor (B bsl 8) bor C, [b64e(BB bsr 18), b64e((BB bsr 12) band 63), b64e((BB bsr 6) band 63), b64e(BB band 63) | encode_l(Ls)]. encode_binary(Bin) -> Split = 3*(byte_size(Bin) div 3), <<Main0:Split/binary,Rest/binary>> = Bin, Main = << <<(b64e(C)):8>> || <<C:6>> <= Main0 >>, case Rest of <<A:6,B:6,C:4>> -> <<Main/binary,(b64e(A)):8,(b64e(B)):8,(b64e(C bsl 2)):8,$=:8>>; <<A:6,B:2>> -> <<Main/binary,(b64e(A)):8,(b64e(B bsl 4)):8,$=:8,$=:8>>; <<>> -> Main end. %%------------------------------------------------------------------------- %% mime_decode(Base64) -> ASCII %% decode(Base64) -> ASCII %% Base64 - string() | binary() %% ASCII - binary() %% %% Description: Decodes an base64 encoded string to plain ASCII. %% mime_decode strips away all characters not Base64 before converting, %% whereas decode crashes if an illegal character is found %%------------------------------------------------------------------------- -spec decode(Base64) -> Data when Base64 :: string() | binary(), Data :: binary(). decode(Bin) when is_binary(Bin) -> decode_binary(<<>>, Bin); decode(List) when is_list(List) -> list_to_binary(decode_l(List)). -spec mime_decode(Base64) -> Data when Base64 :: string() | binary(), Data :: binary(). mime_decode(Bin) when is_binary(Bin) -> mime_decode_binary(<<>>, Bin); mime_decode(List) when is_list(List) -> mime_decode(list_to_binary(List)). -spec decode_l(string()) -> string(). decode_l(List) -> L = strip_spaces(List, []), decode(L, []). -spec mime_decode_l(string()) -> string(). mime_decode_l(List) -> L = strip_illegal(List, [], 0), decode(L, []). %%------------------------------------------------------------------------- %% mime_decode_to_string(Base64) -> ASCII %% decode_to_string(Base64) -> ASCII %% Base64 - string() | binary() %% ASCII - binary() %% %% Description: Decodes an base64 encoded string to plain ASCII. %% mime_decode strips away all characters not Base64 before converting, %% whereas decode crashes if an illegal character is found %%------------------------------------------------------------------------- -spec decode_to_string(Base64) -> DataString when Base64 :: string() | binary(), DataString :: string(). decode_to_string(Bin) when is_binary(Bin) -> decode_to_string(binary_to_list(Bin)); decode_to_string(List) when is_list(List) -> decode_l(List). -spec mime_decode_to_string(Base64) -> DataString when Base64 :: string() | binary(), DataString :: string(). mime_decode_to_string(Bin) when is_binary(Bin) -> mime_decode_to_string(binary_to_list(Bin)); mime_decode_to_string(List) when is_list(List) -> mime_decode_l(List). %% 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,62,bad,bad,bad,63, %32-47 52,53,54,55,56,57,58,59,60,61,bad,bad,bad,eq,bad,bad, %48-63 bad,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14, 15,16,17,18,19,20,21,22,23,24,25,bad,bad,bad,bad,bad, bad,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40, 41,42,43,44,45,46,47,48,49,50,51,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,bad,bad,bad,bad,bad}). decode_binary(Result0, <<C:8,T0/bits>>) -> case element(C, ?DECODE_MAP) of bad -> erlang:error({badarg,C}); ws -> decode_binary(Result0, T0); eq -> case strip_ws(T0) of <<$=:8,T/binary>> -> <<>> = strip_ws(T), Split = byte_size(Result0) - 1, <<Result:Split/bytes,_:4>> = Result0, Result; T -> <<>> = strip_ws(T), Split = byte_size(Result0) - 1, <<Result:Split/bytes,_:2>> = Result0, Result end; Bits -> decode_binary(<<Result0/bits,Bits:6>>, T0) end; decode_binary(Result, <<>>) -> true = is_binary(Result), Result. %% Skipping pad character if not at end of string. Also liberal about %% excess padding and skipping of other illegal (non-base64 alphabet) %% characters. See section 3.3 of RFC4648 mime_decode_binary(Result, <<0:8,T/bits>>) -> mime_decode_binary(Result, T); mime_decode_binary(Result0, <<C:8,T/bits>>) -> case element(C, ?DECODE_MAP) of Bits when is_integer(Bits) -> mime_decode_binary(<<Result0/bits,Bits:6>>, T); eq -> case tail_contains_more(T, false) of {<<>>, Eq} -> %% No more valid data. case bit_size(Result0) rem 8 of 0 -> %% '====' is not uncommon. Result0; 4 when Eq -> %% enforce at least one more '=' only ignoring illegals and spacing Split = byte_size(Result0) - 1, <<Result:Split/bytes,_:4>> = Result0, Result; 2 -> %% remove 2 bits Split = byte_size(Result0) - 1, <<Result:Split/bytes,_:2>> = Result0, Result end; {More, _} -> %% More valid data, skip the eq as invalid mime_decode_binary(Result0, More) end; _ -> mime_decode_binary(Result0, T) end; mime_decode_binary(Result, <<>>) -> true = is_binary(Result), Result. decode([], A) -> A; decode([$=,$=,C2,C1|Cs], A) -> Bits2x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12), Octet1 = Bits2x6 bsr 16, decode(Cs, [Octet1|A]); decode([$=,C3,C2,C1|Cs], A) -> Bits3x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12) bor (b64d(C3) bsl 6), Octet1 = Bits3x6 bsr 16, Octet2 = (Bits3x6 bsr 8) band 16#ff, decode(Cs, [Octet1,Octet2|A]); decode([C4,C3,C2,C1| Cs], A) -> Bits4x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12) bor (b64d(C3) bsl 6) bor b64d(C4), Octet1 = Bits4x6 bsr 16, Octet2 = (Bits4x6 bsr 8) band 16#ff, Octet3 = Bits4x6 band 16#ff, decode(Cs, [Octet1,Octet2,Octet3|A]). %%%======================================================================== %%% Internal functions %%%======================================================================== strip_spaces([], A) -> A; strip_spaces([$\s|Cs], A) -> strip_spaces(Cs, A); strip_spaces([$\t|Cs], A) -> strip_spaces(Cs, A); strip_spaces([$\r|Cs], A) -> strip_spaces(Cs, A); strip_spaces([$\n|Cs], A) -> strip_spaces(Cs, A); strip_spaces([C|Cs], A) -> strip_spaces(Cs, [C | A]). strip_ws(<<$\t,T/binary>>) -> strip_ws(T); strip_ws(<<$\n,T/binary>>) -> strip_ws(T); strip_ws(<<$\r,T/binary>>) -> strip_ws(T); strip_ws(<<$\s,T/binary>>) -> strip_ws(T); strip_ws(T) -> T. %% Skipping pad character if not at end of string. Also liberal about %% excess padding and skipping of other illegal (non-base64 alphabet) %% characters. See section 3.3 of RFC4648 strip_illegal([], A, _Cnt) -> A; strip_illegal([0|Cs], A, Cnt) -> strip_illegal(Cs, A, Cnt); strip_illegal([C|Cs], A, Cnt) -> case element(C, ?DECODE_MAP) of bad -> strip_illegal(Cs, A, Cnt); ws -> strip_illegal(Cs, A, Cnt); eq -> case {tail_contains_more(Cs, false), Cnt rem 4} of {{[], _}, 0} -> A; %% Ignore extra = {{[], true}, 2} -> [$=|[$=|A]]; %% 'XX==' {{[], _}, 3} -> [$=|A]; %% 'XXX=' {{[H|T], _}, _} -> %% more data, skip equals strip_illegal(T, [H|A], Cnt+1) end; _ -> strip_illegal(Cs, [C|A], Cnt+1) end. %% Search the tail for more valid data and remember if we saw %% another equals along the way. tail_contains_more([], Eq) -> {[], Eq}; tail_contains_more(<<>>, Eq) -> {<<>>, Eq}; tail_contains_more([C|T]=More, Eq) -> case element(C, ?DECODE_MAP) of bad -> tail_contains_more(T, Eq); ws -> tail_contains_more(T, Eq); eq -> tail_contains_more(T, true); _ -> {More, Eq} end; tail_contains_more(<<C:8,T/bits>> =More, Eq) -> case element(C, ?DECODE_MAP) of bad -> tail_contains_more(T, Eq); ws -> tail_contains_more(T, Eq); eq -> tail_contains_more(T, true); _ -> {More, Eq} end. %% accessors b64e(X) -> element(X+1, {$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.