[Summary view] [Print] [Text view]

   1  <?php
   2  /*
   3   * This file is part of the PHPASN1 library.
   4   *
   5   * Copyright © Friedrich Große <[email protected]>
   6   *
   7   * For the full copyright and license information, please view the LICENSE
   8   * file that was distributed with this source code.
   9   */
  10  
  11  namespace FG\ASN1\Universal;
  12  
  13  use Exception;
  14  use FG\ASN1\Exception\ParserException;
  15  use FG\ASN1\Parsable;
  16  use FG\ASN1\Identifier;
  17  
  18  class BitString extends OctetString implements Parsable
  19  {
  20      private $nrOfUnusedBits;
  21  
  22      /**
  23       * Creates a new ASN.1 BitString object.
  24       *
  25       * @param string|int $value Either the hexadecimal value as a string (spaces are allowed - leading 0x is optional) or a numeric value
  26       * @param int $nrOfUnusedBits the number of unused bits in the last octet [optional].
  27       *
  28       * @throws Exception if the second parameter is no positive numeric value
  29       */
  30      public function __construct($value, $nrOfUnusedBits = 0)
  31      {
  32          parent::__construct($value);
  33  
  34          if (!is_numeric($nrOfUnusedBits) || $nrOfUnusedBits < 0) {
  35              throw new Exception('BitString: second parameter needs to be a positive number (or zero)!');
  36          }
  37  
  38          $this->nrOfUnusedBits = $nrOfUnusedBits;
  39      }
  40  
  41      public function getType()
  42      {
  43          return Identifier::BITSTRING;
  44      }
  45  
  46      protected function calculateContentLength()
  47      {
  48          // add one to the length for the first octet which encodes the number of unused bits in the last octet
  49          return parent::calculateContentLength() + 1;
  50      }
  51  
  52      protected function getEncodedValue()
  53      {
  54          // the first octet determines the number of unused bits
  55          $nrOfUnusedBitsOctet = chr($this->nrOfUnusedBits);
  56          $actualContent = parent::getEncodedValue();
  57  
  58          return $nrOfUnusedBitsOctet.$actualContent;
  59      }
  60  
  61      public function getNumberOfUnusedBits()
  62      {
  63          return $this->nrOfUnusedBits;
  64      }
  65  
  66      public static function fromBinary(&$binaryData, &$offsetIndex = 0)
  67      {
  68          self::parseIdentifier($binaryData[$offsetIndex], Identifier::BITSTRING, $offsetIndex++);
  69          $contentLength = self::parseContentLength($binaryData, $offsetIndex, 2);
  70  
  71          $nrOfUnusedBits = ord($binaryData[$offsetIndex]);
  72          $value = substr($binaryData, $offsetIndex + 1, $contentLength - 1);
  73  
  74          if ($nrOfUnusedBits > 7 || // no less than 1 used, otherwise non-minimal
  75              ($contentLength - 1) == 1 && $nrOfUnusedBits > 0 || // content length only 1, no
  76              (ord($value[strlen($value)-1])&((1<<$nrOfUnusedBits)-1)) != 0 // unused bits set
  77          ) {
  78              throw new ParserException("Can not parse bit string with invalid padding", $offsetIndex);
  79          }
  80  
  81          $offsetIndex += $contentLength;
  82  
  83          $parsedObject = new self(bin2hex($value), $nrOfUnusedBits);
  84          $parsedObject->setContentLength($contentLength);
  85  
  86          return $parsedObject;
  87      }
  88  }