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<?php |
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declare(strict_types=1); |
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namespace unreal4u\MQTT; |
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use LogicException; |
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use OutOfRangeException; |
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use unreal4u\MQTT\Exceptions\MessageTooBig; |
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use function chr; |
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use function dechex; |
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use function hexdec; |
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use function ord; |
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/** |
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* Functionality that is shared across the entire package |
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* @package unreal4u\MQTT |
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*/ |
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final class Utilities |
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{ |
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/** |
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* Swaps the given number from endian format (INT16, not to be confused with UINT16) |
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* |
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* @param int $number |
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* @return int |
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* @throws OutOfRangeException |
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*/ |
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public static function convertEndianness(int $number): int |
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{ |
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if ($number > 65535) { |
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1 |
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throw new OutOfRangeException('This is an INT16 conversion, so the maximum is 65535'); |
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} |
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$finalNumber = hexdec( |
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// Invert first byte and make it a complete hexadecimal number |
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str_pad(dechex($number & 255), 2, '0', STR_PAD_LEFT) . |
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// Invert second byte and make a complete hexadecimal number |
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str_pad(dechex($number >> 8), 2, '0', STR_PAD_LEFT) |
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); |
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return (int)$finalNumber; |
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} |
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/** |
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* Converts a number to a binary string that the MQTT protocol understands |
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* |
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* @param int $number |
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* @return string |
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* @throws OutOfRangeException |
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*/ |
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public static function convertNumberToBinaryString(int $number): string |
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{ |
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if ($number > 65535) { |
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throw new OutOfRangeException('This is an INT16 conversion, so the maximum is 65535'); |
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} |
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return chr($number >> 8) . chr($number & 255); |
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} |
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/** |
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* Converts a binary representation of a number to an actual int |
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* |
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* @param string $binaryString |
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* @return int |
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* @throws OutOfRangeException |
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*/ |
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public static function convertBinaryStringToNumber(string $binaryString): int |
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{ |
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return self::convertEndianness((ord($binaryString{1}) << 8) + (ord($binaryString{0}) & 255)); |
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} |
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/** |
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* Returns the correct format for the length in bytes of the remaining bytes |
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* |
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* Original pseudo-code algorithm as per the documentation: |
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* <pre> |
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* do |
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* encodedByte = X MOD 128 |
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* X = X DIV 128 |
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* // if there are more data to encode, set the top bit of this byte |
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* if ( X > 0 ) |
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* encodedByte = encodedByte OR 128 |
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* endif |
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* 'output' encodedByte |
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* while ( X > 0 ) |
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* </pre> |
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* @see http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/errata01/os/mqtt-v3.1.1-errata01-os-complete.html#_Toc385349213 |
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* |
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* @param int $lengthInBytes |
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* @return string |
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* @throws MessageTooBig |
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*/ |
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public static function formatRemainingLengthOutput(int $lengthInBytes): string |
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{ |
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if ($lengthInBytes > 268435455) { |
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throw new MessageTooBig('The message cannot exceed 268435455 bytes in length'); |
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} |
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$x = $lengthInBytes; |
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$outputString = ''; |
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do { |
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$encodedByte = $x % 128; |
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$x >>= 7; // Shift 7 bytes |
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// if there are more data to encode, set the top bit of this byte |
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if ($x > 0) { |
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$encodedByte |= 128; |
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} |
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$outputString .= chr($encodedByte); |
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} while ($x > 0); |
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return $outputString; |
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} |
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/** |
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* The remaining length of a message is encoded in this specific way, the opposite of formatRemainingLengthOutput |
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* |
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* Many thanks to Peter's blog for your excellent examples and knowledge. |
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* @see http://indigoo.com/petersblog/?p=263 |
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* |
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* Original pseudo-algorithm as per the documentation: |
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* <pre> |
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* multiplier = 1 |
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* value = 0 |
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* do |
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* encodedByte = 'next byte from stream' |
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* value += (encodedByte & 127) * multiplier |
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* if (multiplier > 128*128*128) |
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* throw Error(Malformed Remaining Length) |
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* multiplier *= 128 |
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* while ((encodedByte & 128) != 0) |
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* </pre> |
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* |
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* @see http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/errata01/os/mqtt-v3.1.1-errata01-os-complete.html#_Toc385349213 |
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* @see Utilities::formatRemainingLengthOutput() |
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* |
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* @param string $remainingLengthField |
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* @return int |
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*/ |
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public static function convertRemainingLengthStringToInt(string $remainingLengthField): int |
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{ |
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$multiplier = 128; |
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$value = 0; |
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$iteration = 0; |
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do { |
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// Extract the next byte in the sequence |
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$encodedByte = ord($remainingLengthField{$iteration}); |
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// Add the current multiplier^iteration * first half of byte |
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$value += ($encodedByte & 127) * ($multiplier ** $iteration); |
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if ($multiplier > 128 ** 3) { |
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throw new LogicException('Malformed remaining length field'); |
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} |
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// Prepare for the next iteration |
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$iteration++; |
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} while (($encodedByte & 128) !== 0); |
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return $value; |
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} |
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} |
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unreal4u /
mqtt
