View Source base64 (stdlib v6.0)
Provides base64 encode and decode, see RFC 2045.
Summary
Types
Base 64 Encoding alphabet, see RFC 4648.
Base 64 encoded binary.
Base 64 encoded string.
Arbitrary sequences of octets.
Customizes the behaviour of the decode functions.
Customizes the behaviour of the decode functions.
Functions
Equivalent to decode(Base64, #{}).
Decodes a base64 string encoded using the standard alphabet according to RFC 4648 Section 4 to plain ASCII.
Equivalent to decode(Base64), but returns a byte_string/0.
Equivalent to decode(Base64, Options), but returns a byte_string/0.
Equivalent to encode(Data, #{}).
Encodes a plain ASCII string into base64 using the alphabet indicated by the
mode option. The result is 33% larger than the data.
Equivalent to encode(Data), but returns a byte_string/0.
Equivalent to encode(Data, Options), but returns a byte_string/0.
Equivalent to mime_decode_to_string(Base64, #{}).
Decodes a base64 "mime" string encoded using the standard alphabet according to RFC 4648 Section 4 to plain ASCII.
Equivalent to mime_decode(Base64),
but returns a byte_string/0.
Equivalent to mime_decode(Base64, Options),
but returns a byte_string/0.
Types
-type base64_alphabet() :: $A..$Z | $a..$z | $0..$9 | $+ | $/ | $- | $_ | $=.
Base 64 Encoding alphabet, see RFC 4648.
-type base64_binary() :: binary().
Base 64 encoded binary.
-type base64_mode() :: standard | urlsafe.
Selector for the Base 64 Encoding alphabet used for encoding and decoding. See RFC 4648 Sections 4 and 5.
-type base64_string() :: [base64_alphabet()].
Base 64 encoded string.
-type byte_string() :: [byte()].
Arbitrary sequences of octets.
-type decode_options() :: #{padding => boolean(), mode => base64_mode()}.
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, that is"+"and"/"are representing bytes62and63respectively, 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, that is"-"and"_"are representing bytes62and63respectively, 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 encode_options() :: #{padding => boolean(), mode => base64_mode()}.
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.urlsafe- Encode the given string using the alternative "URL and Filename safe" base64 alphabet according to RFC 4648 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.
Functions
-spec decode(Base64) -> Data when Base64 :: base64_string() | base64_binary(), Data :: binary().
Equivalent to decode(Base64, #{}).
-spec decode(Base64, Options) -> Data when Base64 :: base64_string() | base64_binary(), Options :: decode_options(), Data :: binary().
Decodes a base64 string encoded using the standard alphabet according to RFC 4648 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 decode_options/0 for details on which options can be passed.
Example:
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>>-spec decode_to_string(Base64) -> DataString when Base64 :: base64_string() | base64_binary(), DataString :: byte_string().
Equivalent to decode(Base64), but returns a byte_string/0.
-spec decode_to_string(Base64, Options) -> DataString when Base64 :: base64_string() | base64_binary(), Options :: decode_options(), DataString :: byte_string().
Equivalent to decode(Base64, Options), but returns a byte_string/0.
-spec encode(Data) -> Base64 when Data :: byte_string() | binary(), Base64 :: base64_binary().
Equivalent to encode(Data, #{}).
-spec encode(Data, Options) -> Base64 when Data :: byte_string() | binary(), Options :: encode_options(), Base64 :: base64_binary().
Encodes a plain ASCII string into base64 using the alphabet indicated by the
mode option. The result is 33% larger than the data.
See encode_options/0 for details on which options can be passed.
-spec encode_to_string(Data) -> Base64String when Data :: byte_string() | binary(), Base64String :: base64_string().
Equivalent to encode(Data), but returns a byte_string/0.
-spec encode_to_string(Data, Options) -> Base64String when Data :: byte_string() | binary(), Options :: encode_options(), Base64String :: base64_string().
Equivalent to encode(Data, Options), but returns a byte_string/0.
-spec mime_decode(Base64) -> Data when Base64 :: base64_string() | base64_binary(), Data :: binary().
Equivalent to mime_decode_to_string(Base64, #{}).
-spec mime_decode(Base64, Options) -> Data when Base64 :: base64_string() | base64_binary(), Options :: decode_options(), Data :: binary().
Decodes a base64 "mime" string encoded using the standard alphabet according to RFC 4648 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 decode_options/0 for details on which options can be passed.
Example:
1> base64:mime_decode("AQIDBA==").
<<1,2,3,4>>
2> base64:mime_decode("AQIDB=A=").
<<1,2,3,4>>-spec mime_decode_to_string(Base64) -> DataString when Base64 :: base64_string() | base64_binary(), DataString :: byte_string().
Equivalent to mime_decode(Base64),
but returns a byte_string/0.
-spec mime_decode_to_string(Base64, Options) -> DataString when Base64 :: base64_string() | base64_binary(), Options :: decode_options(), DataString :: byte_string().
Equivalent to mime_decode(Base64, Options),
but returns a byte_string/0.