Encode and Decode Crockford's BASE32 in pure shell

crockford-base32

#! /bin/sh

# Encode and decode Crockford's BASE32
# Copyright (C) 2022 Matous Jan Fialka, <https://mjf.cz/>
# Released under the terms of the "MIT" license

# DO NOT USE FOR ANY REASON! This was just for some quick testing.

use() {
	printf -- '%s -d <enc> | <dec>\n' "${0##*/}"
	exit $1
}
loc() {
	for val in ${sym[@]}; do
		if [ $val = $1 ]; then
			printf -- '%d' $ind
			break
		fi
		ind=$((ind + 1))
	done
}

[ $# -eq 0 ] && use
sym=({0..9} {A..H} J K M N {P..T} {V..Z}) bas=${#sym[@]}
if [ "$1" = '-d' ]; then
	[ $# -ne 2 ] &&	use 1 >&2
	str="$2" num=0 len=${#str}
	while [ $len -gt 0 ]; do
		chr="${str:$((${#str} - $len)):1}"
		len=$(($len - 1))
		num=$(($num*$bas + $(loc "$chr")))
	done
	printf -- '%d\n' $num
else
	[ $# -ne 1 ] && use 1 >&2
	num=$1 str=''
	while [ $num -gt 0 ]; do
		rem=$(($num%$bas))
		num=$(($num/$bas))
		str="${sym[$rem]}$str"
	done
	printf -- '%s\n' "$str"
fi

# vi:ft=sh