________________________________________________________________________

This file is part of Logtalk <https://logtalk.org/>  
SPDX-FileCopyrightText: 1998-2025 Paulo Moura <pmoura@logtalk.org>  
SPDX-License-Identifier: Apache-2.0

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.
________________________________________________________________________


`base64`
========

The `base64` library provides predicates for parsing and generating data in
the Base64 and Base64URL formats as per the specification found at:

https://www.rfc-editor.org/rfc/rfc4648


API documentation
-----------------

Open the [../../docs/library_index.html#base64](../../docs/library_index.html#base64)
link in a web browser.


Loading
-------

To load all entities in this library, load the `loader.lgt` utility file:

	| ?- logtalk_load(base64(loader)).


Testing
-------

To test this library predicates, load the `tester.lgt` file:

	| ?- logtalk_load(base64(tester)).


Encoding
--------

Encoding a list of bytes in Base64 format is accomplished by the
`base64::generate/2` predicate. For example:

	| ?- atom_codes('Hello world!', Bytes),
	     base64::generate(atom(Base64), Bytes).
	Base64 = 'SGVsbG8gd29ybGQh'
	Bytes = [72,101,108,108,111,32,119,111,114,108,100,33]
	yes

	| ?- atom_codes('Hello world!', Bytes),
	     base64::generate(codes(Base64), Bytes).
	Base64 = [83,71,86,115,98,71,56,103,100,50,57,121,98,71,81,104]
	Bytes = [72,101,108,108,111,32,119,111,114,108,100,33]
	yes

The Base64 result can also be represented using a list of chars, written to
a file or to a stream. See the API documentation for details.

For safe encoding of URLs, use instead the Base64URL format. For example:

	| ?- base64url::generate(atom(Base64URL), 'https://logtalk.org').
	Base64URL == 'aHR0cHM6Ly9sb2d0YWxrLm9yZw'
	yes

The Base64URL can also be represented using a list of chars or a list of codes.
The input URL should be in the same format.	


Decoding
--------

Decoding of Base64 data is accomplished using the `base64::parse/2` predicate.
For example:

	| ?- base64::parse(atom('SGVsbG8gd29ybGQh'), Bytes),
	     atom_codes(Atom, Bytes).
	Atom = 'Hello world!'
	Bytes = [72,101,108,108,111,32,119,111,114,108,100,33]
	yes

	| ?- base64::parse(chars(['S','G','V',s,b,'G','8',g,d,'2','9',y,b,'G','Q',h]), Bytes),
	     atom_codes(Atom, Bytes).
	Atom = 'Hello world!'
	Bytes = [72,101,108,108,111,32,119,111,114,108,100,33]
	yes

The `base64::parse/2` predicate accepts other input source such as a file or a
stream. See the API documentation for details.

For decoding of URLs in the Base64URL format, use the `base64url::parse/2`
predicate. For example:

	| ?- base64url::parse(atom('aHR0cHM6Ly9sb2d0YWxrLm9yZw'), URL).
	URL == 'https://logtalk.org'
	yes

The `base64url::parse/2` predicate also accepts a list of chars or a list of
codes as input. See the API documentation for details.
