private function fromBin($str)
{
if (strlen($str) % 8 > 0) {
throw new \InvalidArgumentException('Length must be divisible by 8');
}
if (!preg_match('/^[01]+$/', $str)) {
throw new \InvalidArgumentException('Only 0\'s and 1\'s are permitted');
}
// Base32 works on the first 5 bits of a byte, so we insert blanks to pad it out
$str = preg_replace('/(.{5})/', '000$1', $str);
// We need a string divisible by 5
$length = strlen($str);
$rbits = $length & 7;
if ($rbits > 0) {
// Excessive bits need to be padded
$ebits = substr($str, $length - $rbits);
$str = substr($str, 0, $length - $rbits);
$str .= "000{$ebits}" . str_repeat('0', 5 - strlen($ebits));
}
preg_match_all('/.{8}/', $str, $chrs);
$chrs = array_map(array($this, 'mapCharset'), $chrs[0]);
return join('', $chrs);
}
