CAppleInterface::convertDERSignature

static function convertDERSignature(string $der, int $partLength): string
{
	$hex = unpack('H*', $der)[1];
	if ('30' !== mb_substr($hex, 0, 2, '8bit'))
	{ // SEQUENCE
		throw new RuntimeException();
	}
	if ('81' === mb_substr($hex, 2, 2, '8bit'))
	{ // LENGTH > 128
		$hex = mb_substr($hex, 6, null, '8bit');
	}
	else
	{
		$hex = mb_substr($hex, 4, null, '8bit');
	}
	if ('02' !== mb_substr($hex, 0, 2, '8bit'))
	{ // INTEGER
		throw new RuntimeException();
	}
	$Rl = hexdec(mb_substr($hex, 2, 2, '8bit'));
	$R = self::retrievePositiveInteger(mb_substr($hex, 4, $Rl * 2, '8bit'));
	$R = str_pad($R, $partLength, '0', STR_PAD_LEFT);
	$hex = mb_substr($hex, 4 + $Rl * 2, null, '8bit');
	if ('02' !== mb_substr($hex, 0, 2, '8bit'))
	{ // INTEGER
		throw new RuntimeException();
	}
	$Sl = hexdec(mb_substr($hex, 2, 2, '8bit'));
	$S = self::retrievePositiveInteger(mb_substr($hex, 4, $Sl * 2, '8bit'));
	$S = str_pad($S, $partLength, '0', STR_PAD_LEFT);

	return pack('H*', $R . $S);
}