89 lines
2.8 KiB
PHP
89 lines
2.8 KiB
PHP
<?php
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/*
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* This file is part of the PHPASN1 library.
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*
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* Copyright © Friedrich Große <friedrich.grosse@gmail.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace FG\ASN1\Universal;
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use Exception;
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use FG\ASN1\Exception\ParserException;
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use FG\ASN1\Parsable;
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use FG\ASN1\Identifier;
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class BitString extends OctetString implements Parsable
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{
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private $nrOfUnusedBits;
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/**
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* Creates a new ASN.1 BitString object.
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*
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* @param string|int $value Either the hexadecimal value as a string (spaces are allowed - leading 0x is optional) or a numeric value
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* @param int $nrOfUnusedBits the number of unused bits in the last octet [optional].
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*
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* @throws Exception if the second parameter is no positive numeric value
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*/
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public function __construct($value, $nrOfUnusedBits = 0)
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{
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parent::__construct($value);
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if (!is_numeric($nrOfUnusedBits) || $nrOfUnusedBits < 0) {
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throw new Exception('BitString: second parameter needs to be a positive number (or zero)!');
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}
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$this->nrOfUnusedBits = $nrOfUnusedBits;
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}
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public function getType()
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{
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return Identifier::BITSTRING;
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}
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protected function calculateContentLength()
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{
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// add one to the length for the first octet which encodes the number of unused bits in the last octet
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return parent::calculateContentLength() + 1;
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}
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protected function getEncodedValue()
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{
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// the first octet determines the number of unused bits
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$nrOfUnusedBitsOctet = chr($this->nrOfUnusedBits);
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$actualContent = parent::getEncodedValue();
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return $nrOfUnusedBitsOctet.$actualContent;
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}
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public function getNumberOfUnusedBits()
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{
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return $this->nrOfUnusedBits;
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}
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public static function fromBinary(&$binaryData, &$offsetIndex = 0)
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{
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self::parseIdentifier($binaryData[$offsetIndex], Identifier::BITSTRING, $offsetIndex++);
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$contentLength = self::parseContentLength($binaryData, $offsetIndex, 2);
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$nrOfUnusedBits = ord($binaryData[$offsetIndex]);
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$value = substr($binaryData, $offsetIndex + 1, $contentLength - 1);
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if ($nrOfUnusedBits > 7 || // no less than 1 used, otherwise non-minimal
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($contentLength - 1) == 1 && $nrOfUnusedBits > 0 || // content length only 1, no
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(ord($value[strlen($value)-1])&((1<<$nrOfUnusedBits)-1)) != 0 // unused bits set
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) {
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throw new ParserException("Can not parse bit string with invalid padding", $offsetIndex);
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}
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$offsetIndex += $contentLength;
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$parsedObject = new self(bin2hex($value), $nrOfUnusedBits);
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$parsedObject->setContentLength($contentLength);
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return $parsedObject;
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}
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}
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