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base64.erl
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base64.erl
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%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2007-2024. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
%% Description: Implements base 64 encode and decode. See RFC4648.
-module(base64).
-moduledoc """
Provides base64 encode and decode, see
[RFC 2045](https://www.ietf.org/rfc/rfc2045.txt).
""".
-export([encode/1, encode/2,
decode/1, decode/2,
mime_decode/1, mime_decode/2,
encode_to_string/1, encode_to_string/2,
decode_to_string/1, decode_to_string/2,
mime_decode_to_string/1, mime_decode_to_string/2,
format_error/2]).
%% RFC 4648: Base 64 Encoding alphabet
-doc """
Base 64 Encoding alphabet, see
[RFC 4648](https://datatracker.ietf.org/doc/html/rfc4648).
""".
-type base64_alphabet() :: $A..$Z | $a..$z | $0..$9 | $+ | $/ | $- | $_ | $=.
%% Selector for the Base 64 alphabet, `standard' for RFC 4648
%% Section 4, `urlsafe' for RFC 4648 Section 5.
-doc """
Selector for the Base 64 Encoding alphabet used for [encoding](`encode/2`) and
[decoding](`decode/2`). See
[RFC 4648](https://datatracker.ietf.org/doc/html/rfc4648) Sections
[4](https://datatracker.ietf.org/doc/html/rfc4648#section-4) and
[5](https://datatracker.ietf.org/doc/html/rfc4648#section-5).
""".
-type base64_mode() :: 'standard' | 'urlsafe'.
-doc """
Customizes the behaviour of the decode functions.
Default value if omitted entirely or partially is `#{mode => standard, padding => true}`.
The `mode` option can be one of the following:
- **`standard`** - Default. Decode the given string using the standard base64
alphabet according to
[RFC 4648 Section 4](https://datatracker.ietf.org/doc/html/rfc4648#section-4),
that is `"+"` and `"/"` are representing bytes `62` and `63` respectively,
while `"-"` and `"_"` are illegal characters.
- **`urlsafe`** - Decode the given string using the alternative "URL and
Filename safe" base64 alphabet according to
[RFC 4648 Section 5](https://datatracker.ietf.org/doc/html/rfc4648#section-5),
that is `"-"` and `"_"` are representing bytes `62` and `63` respectively,
while `"+"` and `"/"` are illegal characters.
The `padding` option can be one of the following:
- **`true`** - Default. Checks the correct number of `=` padding characters at
the end of the encoded string.
- **`false`** - Accepts an encoded string with missing `=` padding characters at
the end.
""".
-type decode_options() :: #{padding => boolean(), mode => base64_mode()}.
-doc """
Customizes the behaviour of the decode functions.
Default value if omitted entirely or partially is `#{mode => standard, padding => true}`.
The `mode` option can be one of the following:
- **`standard`** - Default. Encode the given string using the standard base64
alphabet according to
[RFC 4648 Section 4](https://datatracker.ietf.org/doc/html/rfc4648#section-4).
- **`urlsafe`** - Encode the given string using the alternative "URL and
Filename safe" base64 alphabet according to
[RFC 4648 Section 5](https://datatracker.ietf.org/doc/html/rfc4648#section-5).
The `padding` option can be one of the following:
- **`true`** - Default. Appends correct number of `=` padding characters to the
encoded string.
- **`false`** - Skips appending `=` padding characters to the encoded string.
""".
-type encode_options() :: #{padding => boolean(), mode => base64_mode()}.
%% The following type is a subtype of string() for return values
%% of encoding functions.
-doc "Base 64 encoded string.".
-type base64_string() :: [base64_alphabet()].
-doc "Base 64 encoded binary.".
-type base64_binary() :: binary().
%% Decoded sequence of octets
-doc "Arbitrary sequences of octets.".
-type byte_string() :: [byte()].
-doc """
Equivalent to [`encode(Data)`](`encode/1`), but returns a `t:byte_string/0`.
""".
-spec encode_to_string(Data) -> Base64String when
Data :: byte_string() | binary(),
Base64String :: base64_string().
encode_to_string(Data) ->
encode_to_string(Data, #{}).
-doc """
Equivalent to [`encode(Data, Options)`](`encode/2`), but returns a `t:byte_string/0`.
""".
-doc(#{since => <<"OTP 26.0">>}).
-spec encode_to_string(Data, Options) -> Base64String when
Data :: byte_string() | binary(),
Options :: encode_options(),
Base64String :: base64_string().
encode_to_string(Bin, Options) when is_binary(Bin), is_map(Options) ->
encode_to_string(binary_to_list(Bin), Options);
encode_to_string(List, Options) when is_list(List), is_map(Options) ->
encode_list_to_string(get_encoding_offset(Options), get_padding(Options), List).
-doc(#{ equiv => encode(Data, #{}) }).
-spec encode(Data) -> Base64 when
Data :: byte_string() | binary(),
Base64 :: base64_binary().
encode(Data) ->
encode(Data, #{}).
-doc """
Encodes a plain ASCII string into base64 using the alphabet indicated by the
`mode` option. The result is 33% larger than the data.
See `t:encode_options/0` for details on which options can be passed.
""".
-doc(#{since => <<"OTP 26.0">>}).
-spec encode(Data, Options) -> Base64 when
Data :: byte_string() | binary(),
Options :: encode_options(),
Base64 :: base64_binary().
encode(Bin, Options) when is_binary(Bin), is_map(Options) ->
encode_binary(get_encoding_offset(Options), get_padding(Options), Bin, <<>>);
encode(List, Options) when is_list(List) ->
encode_list(get_encoding_offset(Options), get_padding(Options), List, <<>>).
encode_list_to_string(_ModeOffset, _Padding, []) ->
[];
encode_list_to_string(ModeOffset, Padding, [B1]) ->
[b64e(B1 bsr 2, ModeOffset),
b64e((B1 band 3) bsl 4, ModeOffset) |
case Padding of
true -> "==";
false -> ""
end];
encode_list_to_string(ModeOffset, Padding, [B1,B2]) ->
[b64e(B1 bsr 2, ModeOffset),
b64e(((B1 band 3) bsl 4) bor (B2 bsr 4), ModeOffset),
b64e((B2 band 15) bsl 2, ModeOffset) |
case Padding of
true -> "=";
false -> ""
end];
encode_list_to_string(ModeOffset, Padding, [B1,B2,B3|Ls]) ->
BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
[b64e(BB bsr 18, ModeOffset),
b64e((BB bsr 12) band 63, ModeOffset),
b64e((BB bsr 6) band 63, ModeOffset),
b64e(BB band 63, ModeOffset) | encode_list_to_string(ModeOffset, Padding, Ls)].
encode_binary(ModeOffset, Padding, <<B1:6, B2:6, B3:6, B4:6, B5:6, B6:6, B7:6, B8:6, Ls/bits>>, A) ->
encode_binary(ModeOffset,
Padding,
Ls,
<<A/bits,
(b64e(B1, ModeOffset)):8,
(b64e(B2, ModeOffset)):8,
(b64e(B3, ModeOffset)):8,
(b64e(B4, ModeOffset)):8,
(b64e(B5, ModeOffset)):8,
(b64e(B6, ModeOffset)):8,
(b64e(B7, ModeOffset)):8,
(b64e(B8, ModeOffset)):8>>);
encode_binary(_ModeOffset, _Padding, <<>>, A) ->
A;
encode_binary(ModeOffset, Padding, <<B1:6, B2:6, B3:6, B4:6, Ls/bits>>, A) ->
encode_binary(ModeOffset,
Padding,
Ls,
<<A/bits,
(b64e(B1, ModeOffset)):8,
(b64e(B2, ModeOffset)):8,
(b64e(B3, ModeOffset)):8,
(b64e(B4, ModeOffset)):8>>);
encode_binary(ModeOffset, Padding, <<B1:6, B2:2>>, A) ->
E1 = b64e(B1, ModeOffset),
E2 = b64e(B2 bsl 4, ModeOffset),
case Padding of
true -> <<A/bits,E1,E2,$=,$=>>;
_ -> <<A/bits,E1,E2>>
end;
encode_binary(ModeOffset, Padding, <<B1:6, B2:6, B3:4>>, A) ->
E1 = b64e(B1, ModeOffset),
E2 = b64e(B2, ModeOffset),
E3 = b64e(B3 bsl 2, ModeOffset),
case Padding of
true -> <<A/bits,E1,E2,E3,$=>>;
_ -> <<A/bits,E1,E2,E3>>
end.
encode_list(_ModeOffset, _Padding, [], A) ->
A;
encode_list(ModeOffset, Padding, [B1], A) ->
E1 = b64e(B1 bsr 2, ModeOffset),
E2 = b64e((B1 band 3) bsl 4, ModeOffset),
case Padding of
true -> <<A/bits,E1,E2,$=,$=>>;
false -> <<A/bits,E1,E2>>
end;
encode_list(ModeOffset, Padding, [B1,B2], A) ->
E1 = b64e(B1 bsr 2, ModeOffset),
E2 = b64e(((B1 band 3) bsl 4) bor (B2 bsr 4), ModeOffset),
E3 = b64e((B2 band 15) bsl 2, ModeOffset),
case Padding of
true -> <<A/bits,E1,E2,E3,$=>>;
false -> <<A/bits,E1,E2,E3>>
end;
encode_list(ModeOffset, Padding, [B1,B2,B3|Ls], A) ->
BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
encode_list(ModeOffset,
Padding,
Ls,
<<A/bits,(b64e(BB bsr 18, ModeOffset)):8,
(b64e((BB bsr 12) band 63, ModeOffset)):8,
(b64e((BB bsr 6) band 63, ModeOffset)):8,
(b64e(BB band 63, ModeOffset)):8>>).
%% mime_decode strips away all characters not Base64 before
%% converting, whereas decode crashes if an illegal character is found
-doc(#{equiv => decode(Base64, #{})}).
-spec decode(Base64) -> Data when
Base64 :: base64_string() | base64_binary(),
Data :: binary().
decode(Base64) ->
decode(Base64, #{}).
-doc """
Decodes a base64 string encoded using the standard alphabet according to
[RFC 4648 Section 4](https://datatracker.ietf.org/doc/html/rfc4648#section-4) to
plain ASCII.
The function will strips away any whitespace characters and check for the
the correct number of `=` padding characters at the end of the encoded string.
See `t:decode_options/0` for details on which options can be passed.
_Example_:
```erlang
1> base64:decode("AQIDBA==").
<<1,2,3,4>>
2> base64:decode("AQ ID BA==").
<<1,2,3,4>>
3> base64:decode("AQIDBA=").
** exception error: missing_padding
in function base64:decode_list/7 (base64.erl, line 734)
*** data to decode is missing final = padding characters, if this is intended, use the `padding => false` option
4> base64:decode("AQIDBA=", #{ padding => false }).
<<1,2,3,4>>
```
""".
-doc(#{since => <<"OTP 26.0">>}).
-spec decode(Base64, Options) -> Data when
Base64 :: base64_string() | base64_binary(),
Options :: decode_options(),
Data :: binary().
decode(Bin, Options) when is_binary(Bin) ->
decode_binary(get_decoding_offset(Options), get_padding(Options), Bin, <<>>);
decode(List, Options) when is_list(List) ->
decode_list(get_decoding_offset(Options), get_padding(Options), List, <<>>).
-doc(#{equiv => mime_decode_to_string(Base64, #{})}).
-spec mime_decode(Base64) -> Data when
Base64 :: base64_string() | base64_binary(),
Data :: binary().
mime_decode(Base64) ->
mime_decode(Base64, #{}).
-doc """
Decodes a base64 "mime" string encoded using the standard alphabet according to
[RFC 4648 Section 4](https://datatracker.ietf.org/doc/html/rfc4648#section-4) to
plain ASCII.
The function will strips away any illegal characters. It does *not* check for the
the correct number of `=` padding characters at the end of the encoded string.
See `t:decode_options/0` for details on which options can be passed.
_Example_:
```erlang
1> base64:mime_decode("AQIDBA==").
<<1,2,3,4>>
2> base64:mime_decode("AQIDB=A=").
<<1,2,3,4>>
```
""".
-doc(#{since => <<"OTP 26.0">>}).
-spec mime_decode(Base64, Options) -> Data when
Base64 :: base64_string() | base64_binary(),
Options :: decode_options(),
Data :: binary().
mime_decode(Bin, Options) when is_binary(Bin) ->
mime_decode_binary(get_decoding_offset(Options), get_padding(Options), Bin, <<>>);
mime_decode(List, Options) when is_list(List) ->
mime_decode_list(get_decoding_offset(Options), get_padding(Options), List, <<>>).
%% mime_decode_to_string strips away all characters not Base64 before
%% converting, whereas decode_to_string crashes if an illegal
%% character is found
-doc "Equivalent to [`decode(Base64)`](`decode/1`), but returns a `t:byte_string/0`.".
-spec decode_to_string(Base64) -> DataString when
Base64 :: base64_string() | base64_binary(),
DataString :: byte_string().
decode_to_string(Base64) ->
decode_to_string(Base64, #{}).
-doc "Equivalent to [`decode(Base64, Options)`](`decode/2`), but returns a `t:byte_string/0`.".
-doc(#{since => <<"OTP 26.0">>}).
-spec decode_to_string(Base64, Options) -> DataString when
Base64 :: base64_string() | base64_binary(),
Options :: decode_options(),
DataString :: byte_string().
decode_to_string(Bin, Options) when is_binary(Bin) ->
decode_to_string(binary_to_list(Bin), Options);
decode_to_string(List, Options) when is_list(List) ->
decode_list_to_string(get_decoding_offset(Options), get_padding(Options), List).
-doc """
Equivalent to [`mime_decode(Base64)`](`mime_decode/1`),
but returns a `t:byte_string/0`.
""".
-spec mime_decode_to_string(Base64) -> DataString when
Base64 :: base64_string() | base64_binary(),
DataString :: byte_string().
mime_decode_to_string(Base64) ->
mime_decode_to_string(Base64, #{}).
-doc """
Equivalent to [`mime_decode(Base64, Options)`](`mime_decode/2`),
but returns a `t:byte_string/0`.
""".
-doc(#{since => <<"OTP 26.0">>}).
-spec mime_decode_to_string(Base64, Options) -> DataString when
Base64 :: base64_string() | base64_binary(),
Options :: decode_options(),
DataString :: byte_string().
mime_decode_to_string(Bin, Options) when is_binary(Bin) ->
mime_decode_to_string(binary_to_list(Bin), Options);
mime_decode_to_string(List, Options) when is_list(List) ->
mime_decode_list_to_string(get_decoding_offset(Options), get_padding(Options), List).
%% 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_list(ModeOffset, Padding, [C1 | Cs], A) ->
case b64d(C1, ModeOffset) of
B1 when is_integer(B1) -> mime_decode_list(ModeOffset, Padding, Cs, A, B1);
_ -> mime_decode_list(ModeOffset, Padding, Cs, A) % eq is padding
end;
mime_decode_list(_ModeOffset, _Padding, [], A) ->
A.
mime_decode_list(ModeOffset, Padding, [C2 | Cs], A, B1) ->
case b64d(C2, ModeOffset) of
B2 when is_integer(B2) ->
mime_decode_list(ModeOffset, Padding, Cs, A, B1, B2);
_ -> mime_decode_list(ModeOffset, Padding, Cs, A, B1) % eq is padding
end.
mime_decode_list(ModeOffset, Padding, [C3 | Cs], A, B1, B2) ->
case b64d(C3, ModeOffset) of
B3 when is_integer(B3) ->
mime_decode_list(ModeOffset, Padding, Cs, A, B1, B2, B3);
eq=B3 ->
mime_decode_list_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3);
_ -> mime_decode_list(ModeOffset, Padding, Cs, A, B1, B2)
end;
mime_decode_list(ModeOffset, Padding, [], A, B1, B2) ->
case Padding of
true -> missing_padding_error();
false -> mime_decode_list_after_eq(ModeOffset, Padding, [], A, B1, B2, eq)
end.
mime_decode_list(ModeOffset, Padding, [C4 | Cs], A, B1, B2, B3) ->
case b64d(C4, ModeOffset) of
B4 when is_integer(B4) ->
mime_decode_list(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>);
eq ->
mime_decode_list_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3);
_ -> mime_decode_list(ModeOffset, Padding, Cs, A, B1, B2, B3)
end;
mime_decode_list(ModeOffset, Padding, [], A, B1, B2, B3) ->
case Padding of
true -> missing_padding_error();
false -> mime_decode_list_after_eq(ModeOffset, Padding, [], A, B1, B2, B3)
end.
mime_decode_list_after_eq(ModeOffset, Padding, [C | Cs], A, B1, B2, B3) ->
case b64d(C, ModeOffset) of
B when is_integer(B) ->
%% More valid data, skip the eq as invalid
case B3 of
eq -> mime_decode_list(ModeOffset, Padding, Cs, A, B1, B2, B);
_ -> mime_decode_list(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B:6>>)
end;
_ -> mime_decode_list_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3)
end;
mime_decode_list_after_eq(_ModeOffset, _Padding, [], A, B1, B2, eq) ->
<<A/bits,B1:6,(B2 bsr 4):2>>;
mime_decode_list_after_eq(_ModeOffset, _Padding, [], A, B1, B2, B3) ->
<<A/bits,B1:6,B2:6,(B3 bsr 2):4>>.
mime_decode_binary(ModeOffset, Padding, <<C1:8, Cs/bits>>, A) ->
case b64d(C1, ModeOffset) of
B1 when is_integer(B1) -> mime_decode_binary(ModeOffset, Padding, Cs, A, B1);
_ -> mime_decode_binary(ModeOffset, Padding, Cs, A) % eq is padding
end;
mime_decode_binary(_ModeOffset, _Padding, <<>>, A) ->
A.
mime_decode_binary(ModeOffset, Padding, <<C2:8, Cs/bits>>, A, B1) ->
case b64d(C2, ModeOffset) of
B2 when is_integer(B2) ->
mime_decode_binary(ModeOffset, Padding, Cs, A, B1, B2);
_ -> mime_decode_binary(ModeOffset, Padding, Cs, A, B1) % eq is padding
end.
mime_decode_binary(ModeOffset, Padding, <<C3:8, Cs/bits>>, A, B1, B2) ->
case b64d(C3, ModeOffset) of
B3 when is_integer(B3) ->
mime_decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B3);
eq=B3 ->
mime_decode_binary_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3);
_ -> mime_decode_binary(ModeOffset, Padding, Cs, A, B1, B2)
end;
mime_decode_binary(ModeOffset, Padding, <<Cs/bits>>, A, B1, B2) ->
case Padding of
true -> missing_padding_error();
false -> mime_decode_binary_after_eq(ModeOffset, Padding, Cs, A, B1, B2, eq)
end.
mime_decode_binary(ModeOffset, Padding, <<C4:8, Cs/bits>>, A, B1, B2, B3) ->
case b64d(C4, ModeOffset) of
B4 when is_integer(B4) ->
mime_decode_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>);
eq ->
mime_decode_binary_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3);
_ -> mime_decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B3)
end;
mime_decode_binary(ModeOffset, Padding, <<Cs/bits>>, A, B1, B2, B3) ->
case Padding of
true -> missing_padding_error();
false -> mime_decode_binary_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3)
end.
mime_decode_binary_after_eq(ModeOffset, Padding, <<C:8, Cs/bits>>, A, B1, B2, B3) ->
case b64d(C, ModeOffset) of
B when is_integer(B) ->
%% More valid data, skip the eq as invalid
case B3 of
eq -> mime_decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B);
_ -> mime_decode_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B:6>>)
end;
_ -> mime_decode_binary_after_eq(ModeOffset, Padding, Cs, A, B1, B2, B3)
end;
mime_decode_binary_after_eq(_ModeOffset, _Padding, <<>>, A, B1, B2, eq) ->
<<A/bits,B1:6,(B2 bsr 4):2>>;
mime_decode_binary_after_eq(_ModeOffset, _Padding, <<>>, A, B1, B2, B3) ->
<<A/bits,B1:6,B2:6,(B3 bsr 2):4>>.
mime_decode_list_to_string(ModeOffset, Padding, [C1 | Cs]) ->
case b64d(C1, ModeOffset) of
B1 when is_integer(B1) -> mime_decode_list_to_string(ModeOffset, Padding, Cs, B1);
_ -> mime_decode_list_to_string(ModeOffset, Padding, Cs) % eq is padding
end;
mime_decode_list_to_string(_ModeOffset, _Padding, []) ->
[].
mime_decode_list_to_string(ModeOffset, Padding, [C2 | Cs], B1) ->
case b64d(C2, ModeOffset) of
B2 when is_integer(B2) ->
mime_decode_list_to_string(ModeOffset, Padding, Cs, B1, B2);
_ -> mime_decode_list_to_string(ModeOffset, Padding, Cs, B1) % eq is padding
end.
mime_decode_list_to_string(ModeOffset, Padding, [C3 | Cs], B1, B2) ->
case b64d(C3, ModeOffset) of
B3 when is_integer(B3) ->
mime_decode_list_to_string(ModeOffset, Padding, Cs, B1, B2, B3);
eq=B3 -> mime_decode_list_to_string_after_eq(ModeOffset, Padding, Cs, B1, B2, B3);
_ -> mime_decode_list_to_string(ModeOffset, Padding, Cs, B1, B2)
end;
mime_decode_list_to_string(ModeOffset, Padding, [], B1, B2) ->
case Padding of
true -> missing_padding_error();
false -> mime_decode_list_to_string_after_eq(ModeOffset, Padding, [], B1, B2, eq)
end.
mime_decode_list_to_string(ModeOffset, Padding, [C4 | Cs], B1, B2, B3) ->
case b64d(C4, ModeOffset) of
B4 when is_integer(B4) ->
Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B4,
Octet1 = Bits4x6 bsr 16,
Octet2 = (Bits4x6 bsr 8) band 16#ff,
Octet3 = Bits4x6 band 16#ff,
[Octet1, Octet2, Octet3 | mime_decode_list_to_string(ModeOffset, Padding, Cs)];
eq ->
mime_decode_list_to_string_after_eq(ModeOffset, Padding, Cs, B1, B2, B3);
_ -> mime_decode_list_to_string(ModeOffset, Padding, Cs, B1, B2, B3)
end;
mime_decode_list_to_string(ModeOffset, Padding, [], B1, B2, B3) ->
case Padding of
true -> missing_padding_error();
false -> mime_decode_list_to_string_after_eq(ModeOffset, Padding, [], B1, B2, B3)
end.
mime_decode_list_to_string_after_eq(ModeOffset, Padding, [C | Cs], B1, B2, B3) ->
case b64d(C, ModeOffset) of
B when is_integer(B) ->
%% More valid data, skip the eq as invalid
case B3 of
eq -> mime_decode_list_to_string(ModeOffset, Padding, Cs, B1, B2, B);
_ ->
Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B,
Octet1 = Bits4x6 bsr 16,
Octet2 = (Bits4x6 bsr 8) band 16#ff,
Octet3 = Bits4x6 band 16#ff,
[Octet1, Octet2, Octet3 | mime_decode_list_to_string(ModeOffset, Padding, Cs)]
end;
_ -> mime_decode_list_to_string_after_eq(ModeOffset, Padding, Cs, B1, B2, B3)
end;
mime_decode_list_to_string_after_eq(_ModeOffset, _Padding, [], B1, B2, eq) ->
binary_to_list(<<B1:6,(B2 bsr 4):2>>);
mime_decode_list_to_string_after_eq(_ModeOffset, _Padding, [], B1, B2, B3) ->
binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>).
decode_list(ModeOffset, Padding, [C1 | Cs], A) ->
case b64d(C1, ModeOffset) of
ws -> decode_list(ModeOffset, Padding, Cs, A);
B1 -> decode_list(ModeOffset, Padding, Cs, A, B1)
end;
decode_list(_ModeOffset, _Padding, [], A) ->
A.
decode_list(ModeOffset, Padding, [C2 | Cs], A, B1) ->
case b64d(C2, ModeOffset) of
ws -> decode_list(ModeOffset, Padding, Cs, A, B1);
B2 -> decode_list(ModeOffset, Padding, Cs, A, B1, B2)
end.
decode_list(ModeOffset, Padding, [C3 | Cs], A, B1, B2) ->
case b64d(C3, ModeOffset) of
ws -> decode_list(ModeOffset, Padding, Cs, A, B1, B2);
B3 -> decode_list(ModeOffset, Padding, Cs, A, B1, B2, B3)
end;
decode_list(ModeOffset, Padding, [], A, B1, B2) ->
case Padding of
true -> missing_padding_error();
false -> decode_list(ModeOffset, Padding, [], A, B1, B2, eq)
end.
decode_list(ModeOffset, Padding, [C4 | Cs], A, B1, B2, B3) ->
case b64d(C4, ModeOffset) of
ws -> decode_list(ModeOffset, Padding, Cs, A, B1, B2, B3);
eq when B3 =:= eq -> only_ws(ModeOffset, Padding, Cs, <<A/bits,B1:6,(B2 bsr 4):2>>);
eq -> only_ws(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,(B3 bsr 2):4>>);
B4 -> decode_list(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>)
end;
decode_list(_ModeOffset, Padding, [], A, B1, B2, B3) ->
case Padding of
true -> missing_padding_error();
false when B3 == eq -> <<A/bits,B1:6,(B2 bsr 4):2>>;
false -> <<A/bits,B1:6,B2:6,(B3 bsr 2):4>>
end.
decode_binary(ModeOffset, Padding, <<C1:8, C2:8, C3:8, C4:8, Cs/bits>>, A) ->
case {b64d(C1, ModeOffset), b64d(C2, ModeOffset), b64d(C3, ModeOffset), b64d(C4, ModeOffset)} of
{B1, B2, B3, B4} when is_integer(B1), is_integer(B2),
is_integer(B3), is_integer(B4) ->
decode_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>);
{B1, B2, B3, B4} ->
dec_bin(ModeOffset, Padding, Cs, B1, B2, B3, B4, A)
end;
decode_binary(_ModeOffset, _Padding, <<>>, A) ->
A;
decode_binary(ModeOffset, Padding, <<C1:8, Cs/bits>>, A) ->
case b64d(C1, ModeOffset) of
ws -> decode_binary(ModeOffset, Padding, Cs, A);
B1 -> decode_binary(ModeOffset, Padding, Cs, A, B1)
end.
dec_bin(ModeOffset, Padding, Cs, ws, B2, B3, B4, A) ->
dec_bin(ModeOffset, Padding, Cs, B2, B3, B4, A);
dec_bin(ModeOffset, Padding, Cs, B1, ws, B3, B4, A) ->
dec_bin(ModeOffset, Padding, Cs, B1, B3, B4, A);
dec_bin(ModeOffset, Padding, Cs, B1, B2, ws, B4, A) ->
dec_bin(ModeOffset, Padding, Cs, B1, B2, B4, A);
dec_bin(ModeOffset, Padding, Cs, B1, B2, B3, B4, A) ->
case B4 of
ws -> decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B3);
eq when B3 =:= eq -> only_ws_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,(B2 bsr 4):2>>);
eq -> only_ws_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,(B3 bsr 2):4>>);
B4 -> decode_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>)
end.
dec_bin(ModeOffset, Padding, Cs, ws, B2, B3, A) ->
dec_bin(ModeOffset, Padding, Cs, B2, B3, A);
dec_bin(ModeOffset, Padding, Cs, B1, ws, B3, A) ->
dec_bin(ModeOffset, Padding, Cs, B1, B3, A);
dec_bin(ModeOffset, Padding, Cs, B1, B2, ws, A) ->
dec_bin(ModeOffset, Padding, Cs, B1, B2, A);
dec_bin(ModeOffset, Padding, Cs, B1, B2, B3, A) ->
decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B3).
dec_bin(ModeOffset, Padding, Cs, ws, B2, A) ->
dec_bin(ModeOffset, Padding, Cs, B2, A);
dec_bin(ModeOffset, Padding, Cs, B1, ws, A) ->
dec_bin(ModeOffset, Padding, Cs, B1, A);
dec_bin(ModeOffset, Padding, Cs, B1, B2, A) ->
decode_binary(ModeOffset, Padding, Cs, A, B1, B2).
dec_bin(ModeOffset, Padding, Cs, ws, A) ->
decode_binary(ModeOffset, Padding, Cs, A);
dec_bin(ModeOffset, Padding, Cs, B1, A) ->
decode_binary(ModeOffset, Padding,Cs, A, B1).
decode_binary(ModeOffset, Padding, <<C2:8, Cs/bits>>, A, B1) ->
case b64d(C2, ModeOffset) of
ws -> decode_binary(ModeOffset, Padding, Cs, A, B1);
B2 -> decode_binary(ModeOffset, Padding, Cs, A, B1, B2)
end.
decode_binary(ModeOffset, Padding, <<C3:8, Cs/bits>>, A, B1, B2) ->
case b64d(C3, ModeOffset) of
ws -> decode_binary(ModeOffset, Padding, Cs, A, B1, B2);
B3 -> decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B3)
end;
decode_binary(ModeOffset, Padding, <<Cs/bits>>, A, B1, B2) ->
case Padding of
true -> missing_padding_error();
false -> decode_binary(ModeOffset, Padding, Cs, A, B1, B2, eq)
end.
decode_binary(ModeOffset, Padding, <<C4:8, Cs/bits>>, A, B1, B2, B3) ->
case b64d(C4, ModeOffset) of
ws -> decode_binary(ModeOffset, Padding, Cs, A, B1, B2, B3);
eq when B3 =:= eq -> only_ws_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,(B2 bsr 4):2>>);
eq -> only_ws_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,(B3 bsr 2):4>>);
B4 -> decode_binary(ModeOffset, Padding, Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>)
end;
decode_binary(_ModeOffset, Padding, <<>>, A, B1, B2, B3) ->
case Padding of
true -> missing_padding_error();
false when B3 =:= eq -> <<A/bits,B1:6,(B2 bsr 4):2>>;
false -> <<A/bits,B1:6,B2:6,(B3 bsr 2):4>>
end.
only_ws_binary(_ModeOffset, _Padding, <<>>, A) ->
A;
only_ws_binary(ModeOffset, Padding, <<C:8, Cs/bits>>, A) ->
case b64d(C, ModeOffset) of
ws -> only_ws_binary(ModeOffset, Padding, Cs, A)
end.
decode_list_to_string(ModeOffset, Padding, [C1 | Cs]) ->
case b64d(C1, ModeOffset) of
ws -> decode_list_to_string(ModeOffset, Padding, Cs);
B1 -> decode_list_to_string(ModeOffset, Padding, Cs, B1)
end;
decode_list_to_string(_ModeOffset, _Padding, []) ->
[].
decode_list_to_string(ModeOffset, Padding, [C2 | Cs], B1) ->
case b64d(C2, ModeOffset) of
ws -> decode_list_to_string(ModeOffset, Padding, Cs, B1);
B2 -> decode_list_to_string(ModeOffset, Padding, Cs, B1, B2)
end.
decode_list_to_string(ModeOffset, Padding, [C3 | Cs], B1, B2) ->
case b64d(C3, ModeOffset) of
ws -> decode_list_to_string(ModeOffset, Padding, Cs, B1, B2);
B3 -> decode_list_to_string(ModeOffset, Padding, Cs, B1, B2, B3)
end;
decode_list_to_string(ModeOffset, Padding, [], B1, B2) ->
case Padding of
true -> missing_padding_error();
false -> decode_list_to_string(ModeOffset, Padding, [], B1, B2, eq)
end.
decode_list_to_string(ModeOffset, Padding, [C4 | Cs], B1, B2, B3) ->
case b64d(C4, ModeOffset) of
ws ->
decode_list_to_string(ModeOffset, Padding, Cs, B1, B2, B3);
eq when B3 =:= eq ->
only_ws(ModeOffset, Padding, Cs, binary_to_list(<<B1:6,(B2 bsr 4):2>>));
eq ->
only_ws(ModeOffset, Padding, Cs, binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>));
B4 ->
Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B4,
Octet1 = Bits4x6 bsr 16,
Octet2 = (Bits4x6 bsr 8) band 16#ff,
Octet3 = Bits4x6 band 16#ff,
[Octet1, Octet2, Octet3 | decode_list_to_string(ModeOffset, Padding, Cs)]
end;
decode_list_to_string(_ModeOffset, Padding, [], B1, B2, B3) ->
case Padding of
true -> missing_padding_error();
false when B3 =:= eq -> binary_to_list(<<B1:6,(B2 bsr 4):2>>);
false -> binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>)
end.
only_ws(_ModeOffset, _Padding, [], A) ->
A;
only_ws(ModeOffset, Padding, [C | Cs], A) ->
case b64d(C, ModeOffset) of
ws -> only_ws(ModeOffset, Padding, Cs, A)
end.
%%%========================================================================
%%% Error handling functions
%%%========================================================================
% always inlined for useful stacktraces when called in tail position
-compile({inline, missing_padding_error/0}).
missing_padding_error() ->
error(missing_padding, none, [{error_info, #{}}]).
-doc false.
format_error(missing_padding, _) ->
#{general => "data to decode is missing final = padding characters, if this is intended, use the `padding => false` option"};
format_error(_, _) ->
#{}.
%%%========================================================================
%%% Internal functions
%%%========================================================================
%% accessors
get_padding(#{padding := Bool}) when is_boolean(Bool) -> Bool;
get_padding(#{}) -> true.
get_decoding_offset(#{mode := standard}) -> 1;
get_decoding_offset(#{mode := urlsafe}) -> 257;
get_decoding_offset(#{}) -> 1.
-compile({inline, [{b64d, 2}]}).
b64d(X, Off) ->
element(X + Off,
{
%% standard base64 alphabet (RFC 4648 Section 4)
bad,bad,bad,bad,bad,bad,bad,bad,bad,ws,ws,bad,bad,ws,bad,bad, %0-15
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, %48-61
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,
%% alternative base64url alphabet (RFC 4648 Section 5)
bad,bad,bad,bad,bad,bad,bad,bad,bad,ws,ws,bad,bad,ws,bad,bad, %0-15
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,eq,bad,bad, %48-61
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,63,
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}).
get_encoding_offset(#{mode := standard}) -> 1;
get_encoding_offset(#{mode := urlsafe}) -> 65;
get_encoding_offset(#{}) -> 1.
-compile({inline, [{b64e, 2}]}).
b64e(X, Off) ->
element(X + Off,
{
%% standard base64 alphabet (RFC 4648 Section 4)
$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, $+, $/,
%% alternative base64url alphabet (RFC 4648 Section 5)
$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, $-, $_}).