#!/usr/bin/newlisp
#
# Base64 decoder - tested with newLisp 8.3.2
#
# Due to the nature of newLISP, this is the smallest 
# BASE64 decoder I've ever written.
#
# March 2, 2004 - PvE.
#-------------------------------------------------------

# Setup base64 encode string
(set 'BASE64 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")

# Get input from argument
(set 'dat (nth 2 (main-args)))
(if (= (nth 1 (main-args)) dat) (begin
	(println "Usage: ./b64dec.lsp <string>")
	(exit)
))

# Initialize result variable to string
(set 'res "")

# Mainloop
(while (> (length dat) 0) (begin

	# Find the indexnumber in the BASE64 definition
	(set 'byte1 (find (nth 0 dat) BASE64))
	(if (= byte1 nil)(set 'byte1 0))
	(set 'byte2 (find (nth 1 dat) BASE64))
	(if (= byte2 nil)(set 'byte2 0))
	(set 'byte3 (find (nth 2 dat) BASE64))
	(if (= byte3 nil)(set 'byte3 0))
	(set 'byte4 (find (nth 3 dat) BASE64))
	(if (= byte4 nil)(set 'byte4 0))

	# Recalculate to ASCII value
	(set 'res (append res (char (+ (* (& byte1 63) 4) (/ (& byte2 48) 16)))))
	(set 'res (append res (char (+ (* (& byte2 15) 16) (/ (& byte3 60) 4)))))
	(set 'res (append res (char (+ (* (& byte3 3) 64) byte4))))

	# Decrease string with 4
	(set 'dat (slice dat 4))
))

# Print resulting string
(println "Decoded from BASE64: " res)

# Exit
(exit)