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<?php |
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declare(strict_types = 1); |
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namespace ASN1\Component; |
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use ASN1\Exception\DecodeException; |
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use ASN1\Feature\Encodable; |
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/** |
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* Class to represent BER/DER length octets. |
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*/ |
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class Length implements Encodable |
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{ |
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/** |
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* Length. |
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* |
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* @var int|string |
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*/ |
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private $_length; |
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/** |
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* Whether length is indefinite. |
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* |
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* @var boolean |
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*/ |
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private $_indefinite; |
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/** |
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* Constructor. |
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* |
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* @param int|string $length Length |
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* @param boolean $indefinite Whether length is indefinite |
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*/ |
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public function __construct($length, bool $indefinite = false) |
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{ |
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309 |
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$this->_length = $length; |
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$this->_indefinite = $indefinite; |
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} |
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/** |
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* Decode length component from DER data. |
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* |
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* @param string $data DER encoded data |
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* @param int|null $offset Reference to the variable that contains offset |
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* into the data where to start parsing. Variable is updated to |
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* the offset next to the parsed length component. If null, start |
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* from offset 0. |
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* @throws DecodeException If decoding fails |
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* @return self |
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*/ |
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public static function fromDER(string $data, int &$offset = null): self |
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{ |
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$idx = $offset ? $offset : 0; |
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$datalen = strlen($data); |
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if ($idx >= $datalen) { |
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1 |
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throw new DecodeException("Invalid offset."); |
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} |
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$indefinite = false; |
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$byte = ord($data[$idx++]); |
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// bits 7 to 1 |
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$length = (0x7f & $byte); |
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// long form |
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if (0x80 & $byte) { |
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if (!$length) { |
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$indefinite = true; |
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} else { |
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if ($idx + $length > $datalen) { |
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1 |
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throw new DecodeException("Too many length octets."); |
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} |
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7 |
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$length = self::_decodeLongFormLength($length, $data, $idx); |
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} |
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} |
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if (isset($offset)) { |
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$offset = $idx; |
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} |
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return new self($length, $indefinite); |
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} |
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/** |
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* Decode long form length. |
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* |
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* @param int $length Number of octets |
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* @param string $data Data |
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* @param int $offset Reference to the variable containing offset to the |
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* data. |
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* @throws DecodeException If decoding fails |
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* @return string Integer as a string |
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*/ |
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private static function _decodeLongFormLength(int $length, string $data, |
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int &$offset): string |
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{ |
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// first octet must not be 0xff (spec 8.1.3.5c) |
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if ($length == 127) { |
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1 |
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throw new DecodeException("Invalid number of length octets."); |
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} |
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$num = gmp_init(0, 10); |
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while (--$length >= 0) { |
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$byte = ord($data[$offset++]); |
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$num <<= 8; |
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$num |= $byte; |
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} |
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return gmp_strval($num); |
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} |
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/** |
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* Decode length from DER. |
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* |
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* Throws an exception if length doesn't match with expected or if data |
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* doesn't contain enough bytes. |
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* |
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* @see self::fromDER |
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* @param string $data DER data |
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* @param int $offset Reference to the offset variable |
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* @param int|null $expected Expected length, null to bypass checking |
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* @throws DecodeException If decoding or expectation fails |
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* @return self |
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*/ |
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public static function expectFromDER(string $data, int &$offset, |
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int $expected = null): self |
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{ |
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$idx = $offset; |
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$length = self::fromDER($data, $idx); |
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// DER encoding must have definite length (spec 10.1) |
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if ($length->isIndefinite()) { |
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1 |
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throw new DecodeException("DER encoding must have definite length."); |
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} |
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// if certain length was expected |
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if (isset($expected) && $expected != $length->_length) { |
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throw new DecodeException( |
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sprintf("Expected length %d, got %d.", $expected, |
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$length->_length)); |
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} |
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// check that enough data is available |
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if (strlen($data) < $idx + $length->_length) { |
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throw new DecodeException( |
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sprintf("Length %d overflows data, %d bytes left.", |
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$length->_length, strlen($data) - $idx)); |
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} |
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$offset = $idx; |
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return $length; |
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} |
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/** |
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* |
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* @see Encodable::toDER() |
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* @throws \DomainException If length is too large to encode |
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* @return string |
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*/ |
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public function toDER(): string |
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{ |
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$bytes = []; |
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if ($this->_indefinite) { |
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1 |
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$bytes[] = 0x80; |
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} else { |
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$num = gmp_init($this->_length, 10); |
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// long form |
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if ($num > 127) { |
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$octets = []; |
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for (; $num > 0; $num >>= 8) { |
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$octets[] = gmp_intval(0xff & $num); |
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} |
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7 |
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$count = count($octets); |
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// first octet must not be 0xff |
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7 |
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if ($count >= 127) { |
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throw new \DomainException("Too many length octets."); |
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} |
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$bytes[] = 0x80 | $count; |
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foreach (array_reverse($octets) as $octet) { |
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$bytes[] = $octet; |
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} |
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} else { // short form |
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$bytes[] = gmp_intval($num); |
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} |
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} |
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return pack("C*", ...$bytes); |
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} |
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/** |
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* Get the length. |
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* |
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* @throws \LogicException If length is indefinite |
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* @return int|string |
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*/ |
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public function length() |
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{ |
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5 |
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if ($this->_indefinite) { |
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1 |
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throw new \LogicException("Length is indefinite."); |
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} |
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4 |
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return $this->_length; |
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} |
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/** |
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* @return int |
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*/ |
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public function intVal(): int |
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{ |
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if ($this->_indefinite) { |
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1 |
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throw new \LogicException("Length is indefinite."); |
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} |
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if (gmp_cmp(gmp_init($this->_length, 10), gmp_init(PHP_INT_MAX, 10)) >= 0) { |
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1 |
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throw new \LogicException("Integer length too large"); |
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} |
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return (int) $this->_length; |
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} |
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/** |
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* Whether length is indefinite. |
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* |
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* @return boolean |
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*/ |
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public function isIndefinite(): bool |
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{ |
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return $this->_indefinite; |
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} |
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} |
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sop /
asn1
