204 Zeilen
5.7 KiB
PHP
204 Zeilen
5.7 KiB
PHP
<?php
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/**
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* BaconQrCode
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*
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* @link http://github.com/Bacon/BaconQrCode For the canonical source repository
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* @copyright 2013 Ben 'DASPRiD' Scholzen
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* @license http://opensource.org/licenses/BSD-2-Clause Simplified BSD License
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*/
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namespace BaconQrCode\Common;
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/**
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* Encapsulates a QR Code's format information, including the data mask used and error correction level.
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*/
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class FormatInformation
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{
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/**
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* Mask for format information.
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*/
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private const FORMAT_INFO_MASK_QR = 0x5412;
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/**
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* Lookup table for decoding format information.
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*
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* See ISO 18004:2006, Annex C, Table C.1
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*/
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private const FORMAT_INFO_DECODE_LOOKUP = [
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[0x5412, 0x00],
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[0x5125, 0x01],
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[0x5e7c, 0x02],
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[0x5b4b, 0x03],
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[0x45f9, 0x04],
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[0x40ce, 0x05],
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[0x4f97, 0x06],
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[0x4aa0, 0x07],
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[0x77c4, 0x08],
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[0x72f3, 0x09],
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[0x7daa, 0x0a],
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[0x789d, 0x0b],
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[0x662f, 0x0c],
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[0x6318, 0x0d],
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[0x6c41, 0x0e],
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[0x6976, 0x0f],
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[0x1689, 0x10],
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[0x13be, 0x11],
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[0x1ce7, 0x12],
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[0x19d0, 0x13],
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[0x0762, 0x14],
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[0x0255, 0x15],
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[0x0d0c, 0x16],
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[0x083b, 0x17],
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[0x355f, 0x18],
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[0x3068, 0x19],
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[0x3f31, 0x1a],
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[0x3a06, 0x1b],
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[0x24b4, 0x1c],
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[0x2183, 0x1d],
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[0x2eda, 0x1e],
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[0x2bed, 0x1f],
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];
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/**
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* Offset i holds the number of 1 bits in the binary representation of i.
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*
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* @var array
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*/
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private const BITS_SET_IN_HALF_BYTE = [0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4];
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/**
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* Error correction level.
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*
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* @var ErrorCorrectionLevel
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*/
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private $ecLevel;
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/**
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* Data mask.
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*
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* @var int
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*/
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private $dataMask;
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protected function __construct(int $formatInfo)
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{
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$this->ecLevel = ErrorCorrectionLevel::forBits(($formatInfo >> 3) & 0x3);
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$this->dataMask = $formatInfo & 0x7;
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}
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/**
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* Checks how many bits are different between two integers.
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*/
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public static function numBitsDiffering(int $a, int $b) : int
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{
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$a ^= $b;
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return (
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self::BITS_SET_IN_HALF_BYTE[$a & 0xf]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 4) & 0xf)]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 8) & 0xf)]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 12) & 0xf)]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 16) & 0xf)]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 20) & 0xf)]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 24) & 0xf)]
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+ self::BITS_SET_IN_HALF_BYTE[(BitUtils::unsignedRightShift($a, 28) & 0xf)]
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);
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}
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/**
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* Decodes format information.
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*/
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public static function decodeFormatInformation(int $maskedFormatInfo1, int $maskedFormatInfo2) : ?self
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{
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$formatInfo = self::doDecodeFormatInformation($maskedFormatInfo1, $maskedFormatInfo2);
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if (null !== $formatInfo) {
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return $formatInfo;
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}
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// Should return null, but, some QR codes apparently do not mask this info. Try again by actually masking the
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// pattern first.
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return self::doDecodeFormatInformation(
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$maskedFormatInfo1 ^ self::FORMAT_INFO_MASK_QR,
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$maskedFormatInfo2 ^ self::FORMAT_INFO_MASK_QR
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);
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}
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/**
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* Internal method for decoding format information.
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*/
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private static function doDecodeFormatInformation(int $maskedFormatInfo1, int $maskedFormatInfo2) : ?self
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{
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$bestDifference = PHP_INT_MAX;
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$bestFormatInfo = 0;
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foreach (self::FORMAT_INFO_DECODE_LOOKUP as $decodeInfo) {
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$targetInfo = $decodeInfo[0];
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if ($targetInfo === $maskedFormatInfo1 || $targetInfo === $maskedFormatInfo2) {
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// Found an exact match
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return new self($decodeInfo[1]);
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}
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$bitsDifference = self::numBitsDiffering($maskedFormatInfo1, $targetInfo);
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if ($bitsDifference < $bestDifference) {
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$bestFormatInfo = $decodeInfo[1];
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$bestDifference = $bitsDifference;
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}
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if ($maskedFormatInfo1 !== $maskedFormatInfo2) {
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// Also try the other option
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$bitsDifference = self::numBitsDiffering($maskedFormatInfo2, $targetInfo);
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if ($bitsDifference < $bestDifference) {
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$bestFormatInfo = $decodeInfo[1];
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$bestDifference = $bitsDifference;
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}
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}
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}
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// Hamming distance of the 32 masked codes is 7, by construction, so <= 3 bits differing means we found a match.
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if ($bestDifference <= 3) {
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return new self($bestFormatInfo);
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}
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return null;
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}
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/**
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* Returns the error correction level.
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*/
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public function getErrorCorrectionLevel() : ErrorCorrectionLevel
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{
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return $this->ecLevel;
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}
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/**
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* Returns the data mask.
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*/
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public function getDataMask() : int
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{
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return $this->dataMask;
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}
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/**
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* Hashes the code of the EC level.
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*/
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public function hashCode() : int
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{
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return ($this->ecLevel->getBits() << 3) | $this->dataMask;
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}
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/**
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* Verifies if this instance equals another one.
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*/
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public function equals(self $other) : bool
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{
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return (
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$this->ecLevel === $other->ecLevel
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&& $this->dataMask === $other->dataMask
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);
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}
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}
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