#!/usr/bin/perl
$_ = shift;
die "usage: base64 -e|-d [file...]" unless /^[^edED]*([edED])[^edED]*$/;
warn "Ignoring extra options" unless /^-?([edED])/;

if($1 =~ /[eE]/) {
	my $to64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	use bytes;
	local $/;
	$_ = <>;
	my $out = "";
	while($_ ne "") {
		if(length >= 3) {
			my $b1 = ord;
			$_ = substr $_,1;
			my $b2 = ord;
			$_ = substr $_,1;
			my $b3 = ord;
			$_ = substr $_,1;
			my $d1 = ($b1 & 0b11111100)>>2,
			   $d2 = ($b1 & 0b00000011)<<4 | ($b2 & 0b11110000)>>4,
			   $d3 = ($b2 & 0b00001111)<<2 | ($b3 & 0b11000000)>>6,
			   $d4 = ($b3 & 0b00111111);
			$out .= substr($to64,$d1,1) . substr($to64,$d2,1) . substr($to64,$d3,1) . substr($to64,$d4,1);
		} elsif(length == 2) {
			my $b1 = ord;
			$_ = substr $_,1;
			my $b2 = ord;
			$_ = substr $_,1;
			my $d1 = ($b1 & 0b11111100)>>2,
			   $d2 = ($b1 & 0b00000011)<<4 | ($b2 & 0b11110000)>>4,
			   $d3 = ($b2 & 0b00001111)<<2;
			$out .= substr($to64,$d1,1) . substr($to64,$d2,1) . substr($to64,$d3,1) . '=';
		} elsif(length == 1) {
			my $b1 = ord;
			$_ = substr $_,1;
			my $d1 = ($b1 & 0b11111100)>>2,
			   $d2 = ($b1 & 0b00000011)<<4;
			$out .= substr($to64,$d1,1) . substr($to64,$d2,1) . '==';
		}
	}
	while(length $out >= 64) {
		print substr($out,0,64), "\x0d\x0a";
		$out = substr $out,64;
	}
	print $out, "\x0d\x0a" if $out ne "";
} else {
#	#             @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_ !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~?
#	my $from64 = '                                           ~   ?tuvwxyz{|}   =   @ABCDEFGHIJKLMNOPQRSTUVWXY      Z[\]^_`abcdefghijklmnopqrs     '
	use bytes;
	local $/;
	$_ = <>;
	s"[^A-Za-z0-9+/=]""g;
	tr"A-Za-z0-9+/=" -?P";
	while($_ ne "") {
		if((length) < 4) {
			warn "Not a multiple of four bytes!";
			$_ .= "P" x (4 - length);
		}
		my $d1 = ord;
		$_ = substr $_,1;
		my $d2 = ord;
		$_ = substr $_,1;
		my $d3 = ord;
		$_ = substr $_,1;
		my $d4 = ord;
		$_ = substr $_,1;
		my $nbytes;
		die "Unexpected =" if $d1>0b00111111 || $d2>0b00111111 || ($d3>0b00111111 && $d4<=0b00111111);
		if($d3>0b00111111) {
			$nbytes = 1;
			$d3 = 0;
			$d4 = 0;
		} elsif($d4>0b00111111) {
			$nbytes = 2;
			$d4 = 0;
		} else {
			$nbytes = 3;
		}
		my $b1 = ($d1 & 0b111111)<<2 | ($d2 & 0b110000)>>4,
		   $b2 = ($d2 & 0b001111)<<4 | ($d3 & 0b111100)>>2,
		   $b3 = ($d3 & 0b000011)<<6 | ($d4 & 0b111111);
		print chr $b1;
		print chr $b2 if $nbytes >= 2;
		print chr $b3 if $nbytes >= 3;
	}
}