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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2023 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.