#!/bin/bash

LANG=C

B64=({A..Z} {a..z} {0..9} + /)

printf -v ascii \\%o {32..126}
printf -v ascii "$ascii"

printf -v cntrl %-20sE abtnvfr

pkt=()
lne=
while IFS= read -r -d '' -n 1 car ;do
    if [ "$car" ] ;then
	printf -v car "%q" "$car"
	case ${#car} in
	 1|2 ) car=${ascii%$car*};pkt+=($((${#car}+32)));;
	   7 ) car=${car#*\'\\};pkt+=($((8#${car%\'})));;
	   5 ) car=${car#*\'\\};car=${cntrl%${car%\'}*};pkt+=($((${#car}+7)));;
	   * ) echo >&2 ERROR: $car;;
	esac
      else
	pkt+=(0)
      fi
    if [ ${#pkt[@]} -gt 2 ] ;then
	car=$((pkt<<16|${pkt[1]}<<8|${pkt[2]}))
	lne+=${B64[car>>18]}${B64[car>>12&63]}${B64[car>>6&63]}${B64[car&63]}
	if [ "${#lne}" -gt 72 ] ;then
	    echo $lne
	    lne=
	  fi
	pkt=()
      fi
  done

if [ "$pkt" ] ;then
    f=0
    while [ ${#pkt[@]} -lt 3 ] ;do
	pkt+=(0)
	((f++))
    done
    car=$((pkt<<16|${pkt[1]}<<8|${pkt[2]}))
    lne+=${B64[car>>18]}${B64[car>>12&63]}${B64[car>>6&63]}${B64[car&63]}
    lne=${lne:0:${#lne}-f}
    printf -v f %${f}s
    lne+=${f// /=}
fi
[ "$lne" ] && echo $lne