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<?php
/*
* This file is part of the PHPASN1 library.
*
* Copyright © Friedrich Große <friedrich.grosse@gmail.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace FG\ASN1;
use FG\ASN1\Exception\ParserException;
/**
* Class ExplicitlyTaggedObject decorate an inner object with an additional tag that gives information about
* its context specific meaning.
*
* Explanation taken from A Layman's Guide to a Subset of ASN.1, BER, and DER:
* >>> An RSA Laboratories Technical Note
* >>> Burton S. Kaliski Jr.
* >>> Revised November 1, 1993
*
* [...]
* Explicitly tagged types are derived from other types by adding an outer tag to the underlying type.
* In effect, explicitly tagged types are structured types consisting of one component, the underlying type.
* Explicit tagging is denoted by the ASN.1 keywords [class number] EXPLICIT (see Section 5.2).
* [...]
*
* @see http://luca.ntop.org/Teaching/Appunti/asn1.html
*/
class ExplicitlyTaggedObject extends ASNObject
{
/** @var \FG\ASN1\ASNObject[] */
private $decoratedObjects;
private $tag;
/**
* @param int $tag
* @param \FG\ASN1\ASNObject $objects,...
*/
public function __construct($tag, /* HH_FIXME[4858]: variadic + strict */ ...$objects)
{
$this->tag = $tag;
$this->decoratedObjects = $objects;
}
protected function calculateContentLength()
{
$length = 0;
foreach ($this->decoratedObjects as $object) {
$length += $object->getObjectLength();
}
return $length;
}
protected function getEncodedValue()
{
$encoded = '';
foreach ($this->decoratedObjects as $object) {
$encoded .= $object->getBinary();
}
return $encoded;
}
public function getContent()
{
return $this->decoratedObjects;
}
public function __toString()
{
switch ($length = count($this->decoratedObjects)) {
case 0:
return "Context specific empty object with tag [{$this->tag}]";
case 1:
$decoratedType = Identifier::getShortName($this->decoratedObjects[0]->getType());
return "Context specific $decoratedType with tag [{$this->tag}]";
default:
return "$length context specific objects with tag [{$this->tag}]";
}
}
public function getType()
{
return ord($this->getIdentifier());
}
public function getIdentifier()
{
$identifier = Identifier::create(Identifier::CLASS_CONTEXT_SPECIFIC, true, $this->tag);
return is_int($identifier) ? chr($identifier) : $identifier;
}
public function getTag()
{
return $this->tag;
}
public static function fromBinary(&$binaryData, &$offsetIndex = 0)
{
$identifier = self::parseBinaryIdentifier($binaryData, $offsetIndex);
$firstIdentifierOctet = ord($identifier);
assert(Identifier::isContextSpecificClass($firstIdentifierOctet), 'identifier octet should indicate context specific class');
assert(Identifier::isConstructed($firstIdentifierOctet), 'identifier octet should indicate constructed object');
$tag = Identifier::getTagNumber($identifier);
$totalContentLength = self::parseContentLength($binaryData, $offsetIndex);
$remainingContentLength = $totalContentLength;
$offsetIndexOfDecoratedObject = $offsetIndex;
$decoratedObjects = [];
while ($remainingContentLength > 0) {
$nextObject = ASNObject::fromBinary($binaryData, $offsetIndex);
$remainingContentLength -= $nextObject->getObjectLength();
$decoratedObjects[] = $nextObject;
}
if ($remainingContentLength != 0) {
throw new ParserException("Context-Specific explicitly tagged object [$tag] starting at offset $offsetIndexOfDecoratedObject specifies a length of $totalContentLength octets but $remainingContentLength remain after parsing the content", $offsetIndexOfDecoratedObject);
}
$parsedObject = new self($tag, ...$decoratedObjects);
$parsedObject->setContentLength($totalContentLength);
return $parsedObject;
}
}
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