.TH base64 3erl "stdlib 5.2.2" "Ericsson AB" "Erlang Module Definition"
.SH NAME
base64 \- Provides base64 encode and decode, see
    RFC 2045.
.SH DESCRIPTION
.LP
Provides base64 encode and decode, see RFC 2045\&.
.SH DATA TYPES
.nf

\fBbase64_alphabet()\fR\& = 
.br
    65\&.\&.90 | 97\&.\&.122 | 48\&.\&.57 | 43 | 47 | 45 | 95 | 61
.br
.fi
.RS
.LP
Base 64 Encoding alphabet, see RFC 4648\&.
.RE

.nf

\fBbase64_mode()\fR\& = standard | urlsafe
.br
.fi
.RS
.LP
Selector for the Base 64 Encoding alphabet used for encoding and decoding\&. See RFC 4648 Sections 4 and 5\&.
.RE

.nf

\fBoptions()\fR\& = #{padding => boolean(), mode => base64_mode()}
.br
.fi
.RS
.LP
Customises the behaviour of the encode and decode functions\&. Default value if omitted entirely or partially is \fI#{mode => standard, padding => true}\fR\&\&.
.RE

.nf

\fBbase64_string()\fR\& = [base64_alphabet()]
.br
.fi
.RS
.LP
Base 64 encoded string\&.
.RE

.nf

\fBbase64_binary()\fR\& = binary()
.br
.fi
.RS
.LP
Base 64 encoded binary\&.
.RE

.nf

\fBbyte_string()\fR\& = [byte()]
.br
.fi
.RS
.LP
Arbitrary sequences of octets\&.
.RE

.SH EXPORTS
.LP
.nf

.B
decode(Base64) -> Data
.br
.fi
.br
.nf

.B
decode_to_string(Base64) -> DataString
.br
.fi
.br
.nf

.B
mime_decode(Base64) -> Data
.br
.fi
.br
.nf

.B
mime_decode_to_string(Base64) -> DataString
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Base64 = base64_string() | base64_binary()
.br
Data = binary()
.br
DataString = byte_string()
.br
.RE
.RE
.RS
.LP
Decodes a base64 string encoded using the standard alphabet according to RFC 4648 Section 4 to plain ASCII\&.
.LP
\fImime_decode/1\fR\& and \fImime_decode_to_string/1\fR\& strip away illegal characters, while \fIdecode/1\fR\& and \fIdecode_to_string/1\fR\& only strip away whitespace characters\&.
.LP
Checks the correct number of \fI=\fR\& padding characters at the end of the encoded string\&.
.RE

.LP
.nf

.B
decode(Base64, Options) -> Data
.br
.fi
.br
.nf

.B
decode_to_string(Base64, Options) -> DataString
.br
.fi
.br
.nf

.B
mime_decode(Base64, Options) -> Data
.br
.fi
.br
.nf

.B
mime_decode_to_string(Base64, Options) -> DataString
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Base64 = base64_string() | base64_binary()
.br
Options = options()
.br
Data = binary()
.br
DataString = byte_string()
.br
.RE
.RE
.RS
.LP
Decodes a base64 string encoded using the alphabet indicated by the \fImode\fR\& option to plain ASCII\&.
.LP
\fImime_decode/2\fR\& and \fImime_decode_to_string/2\fR\& strip away illegal characters, while \fIdecode/2\fR\& and \fIdecode_to_string/2\fR\& only strip away whitespace characters\&.
.LP
The \fImode\fR\& option can be one of the following:
.RS 2
.TP 2
.B
\fIstandard\fR\&:
Default\&. Decode the given string using the standard base64 alphabet according to RFC 4648 Section 4, that is \fI"+"\fR\& and \fI"/"\fR\& are representing bytes \fI62\fR\& and \fI63\fR\& respectively, while \fI"-"\fR\& and \fI"_"\fR\& are illegal characters\&.
.TP 2
.B
\fIurlsafe\fR\&:
Decode the given string using the alternative "URL and Filename safe" base64 alphabet according to RFC 4648 Section 5, that is \fI"-"\fR\& and \fI"_"\fR\& are representing bytes \fI62\fR\& and \fI63\fR\& respectively, while \fI"+"\fR\& and \fI"/"\fR\& are illegal characters\&.
.RE
.LP
The \fIpadding\fR\& option can be one of the following:
.RS 2
.TP 2
.B
\fItrue\fR\&:
Default\&. Checks the correct number of \fI=\fR\& padding characters at the end of the encoded string\&.
.TP 2
.B
\fIfalse\fR\&:
Accepts an encoded string with missing \fI=\fR\& padding characters at the end\&.
.RE
.RE

.LP
.nf

.B
encode(Data) -> Base64
.br
.fi
.br
.nf

.B
encode_to_string(Data) -> Base64String
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Data = byte_string() | binary()
.br
Base64 = base64_binary()
.br
Base64String = base64_string()
.br
.RE
.RE
.RS
.LP
Encodes a plain ASCII string into base64 using the standard alphabet according to RFC 4648 Section 4\&. The result is 33% larger than the data\&.
.LP
Always appends correct number of \fI=\fR\& padding characters to the encoded string\&.
.RE

.LP
.nf

.B
encode(Data, Options) -> Base64
.br
.fi
.br
.nf

.B
encode_to_string(Data, Options) -> Base64String
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Data = byte_string() | binary()
.br
Options = options()
.br
Base64 = base64_binary()
.br
Base64String = base64_string()
.br
.RE
.RE
.RS
.LP
Encodes a plain ASCII string into base64 using the alphabet indicated by the \fImode\fR\& option\&. The result is 33% larger than the data\&.
.LP
The \fImode\fR\& option can be one of the following:
.RS 2
.TP 2
.B
\fIstandard\fR\&:
Default\&. Encode the given string using the standard base64 alphabet according to RFC 4648 Section 4\&.
.TP 2
.B
\fIurlsafe\fR\&:
Encode the given string using the alternative "URL and Filename safe" base64 alphabet according to RFC 4648 Section 5\&.
.RE
.LP
The \fIpadding\fR\& option can be one of the following:
.RS 2
.TP 2
.B
\fItrue\fR\&:
Default\&. Appends correct number of \fI=\fR\& padding characters to the encoded string\&.
.TP 2
.B
\fIfalse\fR\&:
Skips appending \fI=\fR\& padding characters to the encoded string\&.
.RE
.RE