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<?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
*/
private static $BITS_SET_IN_HALF_BYTE;
private $errorCorrectionLevel;
private $dataMask;
private function __construct($formatInfo)
{
// Bits 3,4
$this->errorCorrectionLevel = ErrorCorrectionLevel::forBits(($formatInfo >> 3) & 0x03);
// Bottom 3 bits
$this->dataMask = ($formatInfo & 0x07);//(byte)
}
public static function Init()
{
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::$FORMAT_INFO_DECODE_LOOKUP = [
[0x5412, 0x00],
[0x5125, 0x01],
[0x5E7C, 0x02],
[0x5B4B, 0x03],
[0x45F9, 0x04],
[0x40CE, 0x05],
[0x4F97, 0x06],
[0x4AA0, 0x07],
[0x77C4, 0x08],
[0x72F3, 0x09],
[0x7DAA, 0x0A],
[0x789D, 0x0B],
[0x662F, 0x0C],
[0x6318, 0x0D],
[0x6C41, 0x0E],
[0x6976, 0x0F],
[0x1689, 0x10],
[0x13BE, 0x11],
[0x1CE7, 0x12],
[0x19D0, 0x13],
[0x0762, 0x14],
[0x0255, 0x15],
[0x0D0C, 0x16],
[0x083B, 0x17],
[0x355F, 0x18],
[0x3068, 0x19],
[0x3F31, 0x1A],
[0x3A06, 0x1B],
[0x24B4, 0x1C],
[0x2183, 0x1D],
[0x2EDA, 0x1E],
[0x2BED, 0x1F],
];
}
/**
* @param maskedFormatInfo1 ; format info indicator, with mask still applied
* @param maskedFormatInfo2 ; second copy of same info; both are checked at the same time
* to establish best match
*
* @return information about the format it specifies, or {@code null}
* if doesn't seem to match any known pattern
*/
public static function decodeFormatInformation($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($bestFormatInfo);
}
return null;
}
public static function numBitsDiffering($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[(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()
{
return $this->errorCorrectionLevel;
}
public function getDataMask()
{
return $this->dataMask;
}
//@Override
public function hashCode()
{
return ($this->errorCorrectionLevel->ordinal() << 3) | (int)($this->dataMask);
}
//@Override
public function equals($o)
{
if (!($o instanceof FormatInformation)) {
return false;
}
$other = $o;
return $this->errorCorrectionLevel == $other->errorCorrectionLevel &&
$this->dataMask == $other->dataMask;
}
}
FormatInformation::Init();
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