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.

Selector for the Base 64 Encoding alphabet used for encoding and decoding. See RFC 4648 Sections 4 and 5.

Base 64 encoded string.

Arbitrary sequences of octets.

Customizes the behaviour of the decode functions.

Customizes the behaviour of the decode functions.

Functions

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.

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.

Decodes a base64 "mime" string encoded using the standard alphabet according to RFC 4648 Section 4 to plain ASCII.

Types

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base64_alphabet()

View Source (not exported)
-type base64_alphabet() :: $A..$Z | $a..$z | $0..$9 | $+ | $/ | $- | $_ | $=.

Base 64 Encoding alphabet, see RFC 4648.

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base64_binary()

View Source (not exported)
-type base64_binary() :: binary().

Base 64 encoded binary.

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base64_mode()

View Source (not exported)
-type base64_mode() :: standard | urlsafe.

Selector for the Base 64 Encoding alphabet used for encoding and decoding. See RFC 4648 Sections 4 and 5.

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base64_string()

View Source (not exported)
-type base64_string() :: [base64_alphabet()].

Base 64 encoded string.

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byte_string()

View Source (not exported)
-type byte_string() :: [byte()].

Arbitrary sequences of octets.

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decode_options()

View Source (not exported)
-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 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, 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.

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encode_options()

View Source (not exported)
-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, #{}).

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decode(Base64, Options)

View Source (since OTP 26.0)
-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>>
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decode_to_string(Base64)

View Source
-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.

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decode_to_string(Base64, Options)

View Source (since OTP 26.0)
-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, #{}).

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encode(Data, Options)

View Source (since OTP 26.0)
-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.

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encode_to_string(Data, Options)

View Source (since OTP 26.0)
-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, #{}).

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mime_decode(Base64, Options)

View Source (since OTP 26.0)
-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>>
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mime_decode_to_string(Base64)

View Source
-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.

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mime_decode_to_string(Base64, Options)

View Source (since OTP 26.0)
-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.