Base64 Encoding in Lisp

Here’s the translation of the Base64 Encoding example from Go to Lisp, formatted in Markdown suitable for Hugo:

(defpackage :base64-encoding
  (:use :cl))

(in-package :base64-encoding)

;; We'll use the cl-base64 library for base64 encoding/decoding
(ql:quickload :cl-base64)

(defun main ()
  ;; Here's the string we'll encode/decode
  (let ((data "abc123!?$*&()'-=@~"))
    
    ;; Standard base64 encoding
    (let ((sEnc (cl-base64:string-to-base64-string data)))
      (format t "~A~%" sEnc)
      
      ;; Decoding
      (let ((sDec (cl-base64:base64-string-to-string sEnc)))
        (format t "~A~%~%" sDec)))
    
    ;; URL-safe base64 encoding
    (let ((uEnc (cl-base64:string-to-base64-string data :uri t)))
      (format t "~A~%" uEnc)
      
      ;; Decoding URL-safe base64
      (let ((uDec (cl-base64:base64-string-to-string uEnc :uri t)))
        (format t "~A~%" uDec)))))

(main)

Common Lisp provides base64 encoding/decoding through third-party libraries. In this example, we’re using the cl-base64 library.

First, we define a package and load the cl-base64 library using Quicklisp, a library manager for Common Lisp.

In the main function:

1. We define the string we’ll encode and decode.

2. For standard base64 encoding, we use cl-base64:string-to-base64-string. This function takes a string and returns its base64 encoded version.

3. To decode, we use cl-base64:base64-string-to-string, which takes a base64 encoded string and returns the original string.

4. For URL-safe base64 encoding, we use the same functions but with the :uri t keyword argument. This ensures that the encoding is safe for use in URLs.

5. We print the results of each operation using format.

To run this program, save it to a file (e.g., base64-encoding.lisp), ensure you have Quicklisp installed and configured, then run it using your Common Lisp implementation. For example, with SBCL:

$ sbcl --load base64-encoding.lisp

The output will be similar to:

YWJjMTIzIT8kKiYoKSctPUB+
abc123!?$*&()'-=@~

YWJjMTIzIT8kKiYoKSctPUB-
abc123!?$*&()'-=@~

Note that the standard and URL-safe encodings differ slightly (trailing + vs -), but they both decode to the original string as expected.