base64.pl -- Base64 encoding and decoding

Prolog-based base64 encoding using DCG rules. Encoding according to rfc2045. For example:

1 ?- base64('Hello World', X).
X = 'SGVsbG8gV29ybGQ='.

2 ?- base64(H, 'SGVsbG8gV29ybGQ=').
H = 'Hello World'.

The Base64URL encoding provides a URL and file name friendly alternative to base64. Base64URL encoded strings do not contain white space.

bug

- Base64 only works with bytes. The grammars do not check the input to be in the range 0..255.

To be done

- Stream I/O

- White-space introduction and parsing

- Encoding support (notably UTF-8)

 base64_encoded(+Plain, -Encoded, +Options) is det

base64_encoded(-Plain, +Encoded, +Options) is det

General the base64 encoding and decoding. This predicate subsumes base64/2 and base64url/2, providing control over padding, the characters used for encoding and the output type. Options:

charset(+Charset)

Define the encoding character set to use. The (default) classic uses the classical rfc2045 characters. The value url uses URL and file name friendly characters. See base64url/2. The value openbsd uses the OpenBSD password-file alphabet.

padding(+Boolean)

If true (default), the output is padded with = characters.

as(+Type)

Defines the type of the output. One of string (default) or atom.

encoding(+Encoding)

Encoding to use for translation between (Unicode) text and bytes (Base64 is an encoding for bytes). Default is utf8.

Arguments:

Plain	- is an atom or string containing the unencoded (plain) text.
Encoded	- is an atom or string containing the base64 encoded version of Plain.

 base64(+Plain, -Encoded) is det

base64(-Plain, +Encoded) is det

Equivalent to base64_encoded/3 using the options as(atom) and encoding(iso_latin_1).

deprecated

- New code should use base64_encoded/3. Notably the iso_latin_1 should be utf8 in most today's applications.

 base64url(+Plain, -Encoded) is det

base64url(-Plain, +Encoded) is det

Translates between plaintext and base64url encoded atom or string. Base64URL encoded values can safely be used as URLs and file names. The use "-" instead of "+", "_" instead of "/" and do not use padding. This implies that the encoded value cannot be embedded inside a longer string.

Equivalent to base64_encoded/3 using the options as(atom), encoding(utf8) and charset(url).

 base64_encoded(+PlainText, +Options)// is det

base64_encoded(-PlainText, +Options)// is det

 base64(+PlainText)// is det

base64(-PlainText)// is det

Encode/decode list of character codes using base64. See also base64/2.

 base64url(+PlainText)// is det

base64url(-PlainText)// is det

Encode/decode list of character codes using Base64URL. See also base64url/2.