PHP Decode

<?php
/*
 * Copyright 2007 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Zxing\Qrcode\Decoder;

/**
 * <p>Encapsulates a QR Code's format information, including the data mask used and
 * error correction level.</p>
 *
 * @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
  * @var int[]|null
  */
	private static ?array $BITS_SET_IN_HALF_BYTE = null;

	private readonly \Zxing\Qrcode\Decoder\ErrorCorrectionLevel $errorCorrectionLevel;
	private readonly int $dataMask;

	private function __construct($formatInfo)
	{
		// Bits 3,4
		$this->errorCorrectionLevel = ErrorCorrectionLevel::forBits(($formatInfo >> 3) & 0x03);
		// Bottom 3 bits
		$this->dataMask = ($formatInfo & 0x07);//(byte)
	}

	public static function Init(): void
	{
		self::$FORMAT_INFO_MASK_QR = 0x5412;
		self::$BITS_SET_IN_HALF_BYTE = [0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4];
		self::$FORMAT_INFO_DECODE_LOOKUP = [
			[0x5412, 0x00],
			[0x5125, 0x01],
			[0x5E7C, 0x02],
			[0x5B4B, 0x03],
			[0x45F9, 0x04],
			[0x40CE, 0x05],
			[0x4F97, 0x06],
			[0x4AA0, 0x07],
			[0x77C4, 0x08],
			[0x72F3, 0x09],
			[0x7DAA, 0x0A],
			[0x789D, 0x0B],
			[0x662F, 0x0C],
			[0x6318, 0x0D],
			[0x6C41, 0x0E],
			[0x6976, 0x0F],
			[0x1689, 0x10],
			[0x13BE, 0x11],
			[0x1CE7, 0x12],
			[0x19D0, 0x13],
			[0x0762, 0x14],
			[0x0255, 0x15],
			[0x0D0C, 0x16],
			[0x083B, 0x17],
			[0x355F, 0x18],
			[0x3068, 0x19],
			[0x3F31, 0x1A],
			[0x3A06, 0x1B],
			[0x24B4, 0x1C],
			[0x2183, 0x1D],
			[0x2EDA, 0x1E],
			[0x2BED, 0x1F],
		];
	}

	/**
	 * @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 FormatInformation|null information about the format it specifies, or {@code null}
	 *  if doesn't seem to match any known pattern
	 *
	 * @psalm-param 0|1 $maskedFormatInfo1
	 * @psalm-param 0|1 $maskedFormatInfo2
	 */
	public static function decodeFormatInformation(int $maskedFormatInfo1, int $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
		);
	}

	/**
	 * @psalm-param 0|1 $maskedFormatInfo1
	 * @psalm-param 0|1 $maskedFormatInfo2
	 */
	private static function doDecodeFormatInformation(int $maskedFormatInfo1, int $maskedFormatInfo2): self|null
	{
		// 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;
	}

	/**
	 * @psalm-param 0|1 $a
	 */
	public static function numBitsDiffering(int $a, $b): int
	{
		$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[(int)(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)];
	}

	public function getErrorCorrectionLevel(): ErrorCorrectionLevel
	{
		return $this->errorCorrectionLevel;
	}

	public function getDataMask(): int
	{
		return $this->dataMask;
	}

	
	public function hashCode()
	{
		return ($this->errorCorrectionLevel->ordinal() << 3) | (int)($this->dataMask);
	}

	
	public function equals($o): bool
	{
		if (!($o instanceof FormatInformation)) {
			return false;
		}
		$other = $o;

		return $this->errorCorrectionLevel == $other->errorCorrectionLevel &&
			$this->dataMask == $other->dataMask;
	}
}

FormatInformation::Init();
 ?>