Encapsulates a QR Code's format information, including the data mask used and * error correction level.

* * @author Sean Owen * @see DataMask * @see ErrorCorrectionLevel */ final class FormatInformation { public static $FORMAT_INFO_MASK_QR; /** * See ISO 18004:2006, Annex C, Table C.1 */ public static $FORMAT_INFO_DECODE_LOOKUP; /** * Offset i holds the number of 1 bits in the binary representation of i */ private static $BITS_SET_IN_HALF_BYTE; private $errorCorrectionLevel; private $dataMask; public static function Init(){ self::$FORMAT_INFO_MASK_QR= 0x5412; self::$BITS_SET_IN_HALF_BYTE = array(0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4); self::$FORMAT_INFO_DECODE_LOOKUP = array( array(0x5412, 0x00), array (0x5125, 0x01), array(0x5E7C, 0x02), array(0x5B4B, 0x03), array(0x45F9, 0x04), array(0x40CE, 0x05), array(0x4F97, 0x06), array(0x4AA0, 0x07), array(0x77C4, 0x08), array(0x72F3, 0x09), array(0x7DAA, 0x0A), array(0x789D, 0x0B), array(0x662F, 0x0C), array(0x6318, 0x0D), array(0x6C41, 0x0E), array(0x6976, 0x0F), array(0x1689, 0x10), array(0x13BE, 0x11), array(0x1CE7, 0x12), array(0x19D0, 0x13), array(0x0762, 0x14), array(0x0255, 0x15), array(0x0D0C, 0x16), array(0x083B, 0x17), array(0x355F, 0x18), array(0x3068, 0x19), array(0x3F31, 0x1A), array(0x3A06, 0x1B), array(0x24B4, 0x1C), array(0x2183, 0x1D), array(0x2EDA, 0x1E), array(0x2BED, 0x1F), ); } private function __construct($formatInfo) { // Bits 3,4 $this->errorCorrectionLevel = ErrorCorrectionLevel::forBits(($formatInfo >> 3) & 0x03); // Bottom 3 bits $this->dataMask = ($formatInfo & 0x07);//(byte) } static function numBitsDiffering($a, $b) { $a ^= $b; // a now has a 1 bit exactly where its bit differs with b's // Count bits set quickly with a series of lookups: return self::$BITS_SET_IN_HALF_BYTE[$a & 0x0F] + self::$BITS_SET_IN_HALF_BYTE[intval(uRShift($a, 4) & 0x0F)] + self::$BITS_SET_IN_HALF_BYTE[(uRShift($a ,8) & 0x0F)] + self::$BITS_SET_IN_HALF_BYTE[(uRShift($a , 12) & 0x0F)] + self::$BITS_SET_IN_HALF_BYTE[(uRShift($a, 16) & 0x0F)] + self::$BITS_SET_IN_HALF_BYTE[(uRShift($a , 20) & 0x0F)] + self::$BITS_SET_IN_HALF_BYTE[(uRShift($a, 24) & 0x0F)] + self::$BITS_SET_IN_HALF_BYTE[(uRShift($a ,28) & 0x0F)]; } /** * @param maskedFormatInfo1; format info indicator, with mask still applied * @param maskedFormatInfo2; second copy of same info; both are checked at the same time * to establish best match * @return information about the format it specifies, or {@code null} * if doesn't seem to match any known pattern */ static function decodeFormatInformation($maskedFormatInfo1, $maskedFormatInfo2) { $formatInfo = self::doDecodeFormatInformation($maskedFormatInfo1, $maskedFormatInfo2); if ($formatInfo != null) { return $formatInfo; } // Should return null, but, some QR codes apparently // do not mask this info. Try again by actually masking the pattern // first return self::doDecodeFormatInformation($maskedFormatInfo1 ^ self::$FORMAT_INFO_MASK_QR, $maskedFormatInfo2 ^ self::$FORMAT_INFO_MASK_QR); } private static function doDecodeFormatInformation($maskedFormatInfo1, $maskedFormatInfo2) { // Find the int in FORMAT_INFO_DECODE_LOOKUP with fewest bits differing $bestDifference = PHP_INT_MAX; $bestFormatInfo = 0; foreach (self::$FORMAT_INFO_DECODE_LOOKUP as $decodeInfo ) { $targetInfo = $decodeInfo[0]; if ($targetInfo == $maskedFormatInfo1 || $targetInfo == $maskedFormatInfo2) { // Found an exact match return new FormatInformation($decodeInfo[1]); } $bitsDifference = self::numBitsDiffering($maskedFormatInfo1, $targetInfo); if ($bitsDifference < $bestDifference) { $bestFormatInfo = $decodeInfo[1]; $bestDifference = $bitsDifference; } if ($maskedFormatInfo1 != $maskedFormatInfo2) { // also try the other option $bitsDifference = self::numBitsDiffering($maskedFormatInfo2, $targetInfo); if ($bitsDifference < $bestDifference) { $bestFormatInfo = $decodeInfo[1]; $bestDifference = $bitsDifference; } } } // Hamming distance of the 32 masked codes is 7, by construction, so <= 3 bits // differing means we found a match if ($bestDifference <= 3) { return new FormatInformation($bestFormatInfo); } return null; } function getErrorCorrectionLevel() { return $this->errorCorrectionLevel; } function getDataMask() { return $this->dataMask; } //@Override public function hashCode() { return ($this->errorCorrectionLevel->ordinal() << 3) | intval($this->dataMask); } //@Override public function equals($o) { if (!($o instanceof FormatInformation)) { return false; } $other =$o; return $this->errorCorrectionLevel == $other->errorCorrectionLevel && $this->dataMask == $other->dataMask; } } FormatInformation::Init();