Decoder::decodeBitStream()   C
last analyzed

Complexity

Conditions 13
Paths 4

Size

Total Lines 62
Code Lines 39

Duplication

Lines 0
Ratio 0 %

Importance

Changes 6
Bugs 0 Features 0
Metric Value
cc 13
eloc 39
nc 4
nop 1
dl 0
loc 62
rs 6.6166
c 6
b 0
f 0

How to fix   Long Method    Complexity   

Long Method

Small methods make your code easier to understand, in particular if combined with a good name. Besides, if your method is small, finding a good name is usually much easier.

For example, if you find yourself adding comments to a method's body, this is usually a good sign to extract the commented part to a new method, and use the comment as a starting point when coming up with a good name for this new method.

Commonly applied refactorings include:

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<?php
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/**
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 * Class Decoder
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 *
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 * @created      17.01.2021
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 * @author       ZXing Authors
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 * @author       Smiley <[email protected]>
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 * @copyright    2021 Smiley
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 * @license      Apache-2.0
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 */
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namespace chillerlan\QRCode\Decoder;
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use chillerlan\QRCode\Common\{BitBuffer, EccLevel, MaskPattern, Mode, ReedSolomonDecoder, Version};
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use chillerlan\QRCode\Data\{AlphaNum, Byte, ECI, Hanzi, Kanji, Number};
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use chillerlan\QRCode\Detector\Detector;
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use Throwable;
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use function chr, str_replace;
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/**
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 * The main class which implements QR Code decoding -- as opposed to locating and extracting
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 * the QR Code from an image.
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 *
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 * @author Sean Owen
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 */
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final class Decoder{
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	private ?Version     $version = null;
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	private ?EccLevel    $eccLevel = null;
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	private ?MaskPattern $maskPattern = null;
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	private BitBuffer    $bitBuffer;
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	/**
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	 * Decodes a QR Code represented as a BitMatrix.
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	 * A 1 or "true" is taken to mean a black module.
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	 *
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	 * @throws \Throwable|\chillerlan\QRCode\Decoder\QRCodeDecoderException
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	 */
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	public function decode(LuminanceSourceInterface $source):DecoderResult{
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		$matrix = (new Detector($source))->detect();
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		try{
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			// clone the BitMatrix to avoid errors in case we run into mirroring
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			return $this->decodeMatrix(clone $matrix);
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		}
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		catch(Throwable $e){
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			try{
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				/*
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				 * Prepare for a mirrored reading.
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				 *
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				 * Since we're here, this means we have successfully detected some kind
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				 * of version and format information when mirrored. This is a good sign,
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				 * that the QR code may be mirrored, and we should try once more with a
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				 * mirrored content.
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				 */
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				return $this->decodeMatrix($matrix->resetVersionInfo()->mirrorDiagonal());
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			}
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			catch(Throwable $f){
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				// Throw the exception from the original reading
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				throw $e;
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			}
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		}
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	}
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	/**
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	 * @throws \chillerlan\QRCode\Decoder\QRCodeDecoderException
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	 */
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	private function decodeMatrix(BitMatrix $matrix):DecoderResult{
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		// Read raw codewords
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		$rawCodewords      = $matrix->readCodewords();
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		$this->version     = $matrix->getVersion();
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		$this->eccLevel    = $matrix->getEccLevel();
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		$this->maskPattern = $matrix->getMaskPattern();
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		if($this->version === null || $this->eccLevel === null || $this->maskPattern === null){
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			throw new QRCodeDecoderException('unable to read version or format info'); // @codeCoverageIgnore
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		}
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		$resultBytes = (new ReedSolomonDecoder($this->version, $this->eccLevel))->decode($rawCodewords);
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		return $this->decodeBitStream($resultBytes);
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	}
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	/**
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	 * Decode the contents of that stream of bytes
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	 *
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	 * @throws \chillerlan\QRCode\Decoder\QRCodeDecoderException
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	 */
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	private function decodeBitStream(BitBuffer $bitBuffer):DecoderResult{
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		$this->bitBuffer  = $bitBuffer;
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		$versionNumber    = $this->version->getVersionNumber();
0 ignored issues
show
Bug introduced by
The method getVersionNumber() does not exist on null. ( Ignorable by Annotation )

If this is a false-positive, you can also ignore this issue in your code via the ignore-call  annotation

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		/** @scrutinizer ignore-call */ 
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  $versionNumber    = $this->version->getVersionNumber();

This check looks for calls to methods that do not seem to exist on a given type. It looks for the method on the type itself as well as in inherited classes or implemented interfaces.

This is most likely a typographical error or the method has been renamed.

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		$symbolSequence   = -1;
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		$parityData       = -1;
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		$fc1InEffect      = false;
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		$result           = '';
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		// While still another segment to read...
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		while($this->bitBuffer->available() >= 4){
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			$datamode = $this->bitBuffer->read(4); // mode is encoded by 4 bits
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			// OK, assume we're done
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			if($datamode === Mode::TERMINATOR){
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				break;
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			}
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			elseif($datamode === Mode::NUMBER){
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				$result .= Number::decodeSegment($this->bitBuffer, $versionNumber);
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			}
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			elseif($datamode === Mode::ALPHANUM){
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				$result .= $this->decodeAlphanumSegment($versionNumber, $fc1InEffect);
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			}
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			elseif($datamode === Mode::BYTE){
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				$result .= Byte::decodeSegment($this->bitBuffer, $versionNumber);
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			}
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			elseif($datamode === Mode::KANJI){
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				$result .= Kanji::decodeSegment($this->bitBuffer, $versionNumber);
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			}
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			elseif($datamode === Mode::STRCTURED_APPEND){
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				if($this->bitBuffer->available() < 16){
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					throw new QRCodeDecoderException('structured append: not enough bits left');
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				}
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				// sequence number and parity is added later to the result metadata
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				// Read next 8 bits (symbol sequence #) and 8 bits (parity data), then continue
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				$symbolSequence = $this->bitBuffer->read(8);
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				$parityData     = $this->bitBuffer->read(8);
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			}
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			elseif($datamode === Mode::FNC1_FIRST || $datamode === Mode::FNC1_SECOND){
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				// We do little with FNC1 except alter the parsed result a bit according to the spec
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				$fc1InEffect = true;
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			}
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			elseif($datamode === Mode::ECI){
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				$result .= ECI::decodeSegment($this->bitBuffer, $versionNumber);
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			}
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			elseif($datamode === Mode::HANZI){
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				$result .= Hanzi::decodeSegment($this->bitBuffer, $versionNumber);
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			}
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			else{
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				throw new QRCodeDecoderException('invalid data mode');
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			}
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		}
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		return new DecoderResult([
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			'rawBytes'                 => $this->bitBuffer,
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			'data'                     => $result,
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			'version'                  => $this->version,
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			'eccLevel'                 => $this->eccLevel,
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			'maskPattern'              => $this->maskPattern,
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			'structuredAppendParity'   => $parityData,
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			'structuredAppendSequence' => $symbolSequence,
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		]);
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	}
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	/**
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	 *
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	 */
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	private function decodeAlphanumSegment(int $versionNumber, bool $fc1InEffect):string{
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		$str = AlphaNum::decodeSegment($this->bitBuffer, $versionNumber);
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		// See section 6.4.8.1, 6.4.8.2
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		if($fc1InEffect){ // ???
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			// We need to massage the result a bit if in an FNC1 mode:
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			$str = str_replace(chr(0x1d), '%', $str);
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			$str = str_replace('%%', '%', $str);
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		}
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		return $str;
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	}
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}
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