This commit is contained in:
codemasher
2021-01-16 19:25:13 +01:00
parent 043137491a
commit 32b6a5ed77
5 changed files with 456 additions and 2 deletions
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<?php
/**
* Class GF256
*
* @filesource GF256.php
* @created 16.01.2021
* @package chillerlan\QRCode\Common
* @author ZXing Authors
* @author Smiley <smiley@chillerlan.net>
* @copyright 2021 Smiley
* @license Apache-2.0
*/
namespace chillerlan\QRCode\Common;
use InvalidArgumentException;
use function array_fill;
/**
* <p>This class contains utility methods for performing mathematical operations over
* the Galois Fields. Operations use a given primitive polynomial in calculations.</p>
*
* <p>Throughout this package, elements of the GF are represented as an {@code int}
* for convenience and speed (but at the cost of memory).
* </p>
*
* @author Sean Owen
* @author David Olivier
*/
final class GF256{
/**
* irreducible polynomial whose coefficients are represented by the bits of an int,
* where the least-significant bit represents the constant coefficient
*/
# private int $primitive = 0x011D;
private const logTable = [
null, 0, 1, 25, 2, 50, 26, 198, 3, 223, 51, 238, 27, 104, 199, 75,
4, 100, 224, 14, 52, 141, 239, 129, 28, 193, 105, 248, 200, 8, 76, 113,
5, 138, 101, 47, 225, 36, 15, 33, 53, 147, 142, 218, 240, 18, 130, 69,
29, 181, 194, 125, 106, 39, 249, 185, 201, 154, 9, 120, 77, 228, 114, 166,
6, 191, 139, 98, 102, 221, 48, 253, 226, 152, 37, 179, 16, 145, 34, 136,
54, 208, 148, 206, 143, 150, 219, 189, 241, 210, 19, 92, 131, 56, 70, 64,
30, 66, 182, 163, 195, 72, 126, 110, 107, 58, 40, 84, 250, 133, 186, 61,
202, 94, 155, 159, 10, 21, 121, 43, 78, 212, 229, 172, 115, 243, 167, 87,
7, 112, 192, 247, 140, 128, 99, 13, 103, 74, 222, 237, 49, 197, 254, 24,
227, 165, 153, 119, 38, 184, 180, 124, 17, 68, 146, 217, 35, 32, 137, 46,
55, 63, 209, 91, 149, 188, 207, 205, 144, 135, 151, 178, 220, 252, 190, 97,
242, 86, 211, 171, 20, 42, 93, 158, 132, 60, 57, 83, 71, 109, 65, 162,
31, 45, 67, 216, 183, 123, 164, 118, 196, 23, 73, 236, 127, 12, 111, 246,
108, 161, 59, 82, 41, 157, 85, 170, 251, 96, 134, 177, 187, 204, 62, 90,
203, 89, 95, 176, 156, 169, 160, 81, 11, 245, 22, 235, 122, 117, 44, 215,
79, 174, 213, 233, 230, 231, 173, 232, 116, 214, 244, 234, 168, 80, 88, 175,
];
private const expTable = [
1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38,
76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192,
157, 39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159, 35,
70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111, 222, 161,
95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30, 60, 120, 240,
253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223, 163, 91, 182, 113, 226,
217, 175, 67, 134, 17, 34, 68, 136, 13, 26, 52, 104, 208, 189, 103, 206,
129, 31, 62, 124, 248, 237, 199, 147, 59, 118, 236, 197, 151, 51, 102, 204,
133, 23, 46, 92, 184, 109, 218, 169, 79, 158, 33, 66, 132, 21, 42, 84,
168, 77, 154, 41, 82, 164, 85, 170, 73, 146, 57, 114, 228, 213, 183, 115,
230, 209, 191, 99, 198, 145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255,
227, 219, 171, 75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65,
130, 25, 50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166,
81, 162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9,
18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11, 22,
44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71, 142, 1,
];
/**
* Implements both addition and subtraction -- they are the same in GF(size).
*
* @return int sum/difference of a and b
*/
public static function addOrSubtract(int $a, int $b):int{
return $a ^ $b;
}
/**
* @return GenericGFPoly the monomial representing coefficient * x^degree
*/
public static function buildMonomial(int $degree, int $coefficient):GenericGFPoly{
if($degree < 0){
throw new InvalidArgumentException();
}
$coefficients = array_fill(0, $degree + 1, 0);
$coefficients[0] = $coefficient;
return new GenericGFPoly($coefficients);
}
/**
* @return int 2 to the power of a in GF(size)
*/
public static function exp(int $a):int{
if($a < 0){
$a += 255;
}
elseif($a >= 256){
$a -= 255;
}
return self::expTable[$a];
}
/**
* @return int base 2 log of a in GF(size)
*/
public static function log(int $a):int{
if($a < 1){
throw new InvalidArgumentException();
}
return self::logTable[$a];
}
/**
* @return int multiplicative inverse of a
*/
public static function inverse(int $a):int{
if($a === 0){
throw new InvalidArgumentException();
}
return self::expTable[256 - self::logTable[$a] - 1];
}
/**
* @return int product of a and b in GF(size)
*/
public static function multiply(int $a, int $b):int{
if($a === 0 || $b === 0){
return 0;
}
return self::expTable[(self::logTable[$a] + self::logTable[$b]) % 255];
}
}
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<?php
/**
* Class GenericGFPoly
*
* @filesource GenericGFPoly.php
* @created 16.01.2021
* @package chillerlan\QRCode\Common
* @author ZXing Authors
* @author Smiley <smiley@chillerlan.net>
* @copyright 2021 Smiley
* @license Apache-2.0
*/
namespace chillerlan\QRCode\Common;
use InvalidArgumentException;
use function array_fill, array_slice, array_splice, count;
/**
* <p>Represents a polynomial whose coefficients are elements of a GF.
* Instances of this class are immutable.</p>
*
* <p>Much credit is due to William Rucklidge since portions of this code are an indirect
* port of his C++ Reed-Solomon implementation.</p>
*
* @author Sean Owen
*/
final class GenericGFPoly{
private array $coefficients;
/**
* @param array|null $coefficients array coefficients as ints representing elements of GF(size), arranged
* from most significant (highest-power term) coefficient to least significant
* @param int|null $degree
*
* @throws \InvalidArgumentException if argument is null or empty, or if leading coefficient is 0 and this is not a
* constant polynomial (that is, it is not the monomial "0")
*/
public function __construct(array $coefficients, int $degree = null){
$degree ??= 0;
if(empty($coefficients)){
throw new InvalidArgumentException('arg $coefficients is empty');
}
if($degree < 0){
throw new InvalidArgumentException('negative degree');
}
$coefficientsLength = count($coefficients);
// Leading term must be non-zero for anything except the constant polynomial "0"
$firstNonZero = 0;
while($firstNonZero < $coefficientsLength && $coefficients[$firstNonZero] === 0){
$firstNonZero++;
}
if($firstNonZero === $coefficientsLength){
$this->coefficients = [0];
}
else{
$this->coefficients = array_fill(0, $coefficientsLength - $firstNonZero + $degree, 0);
for($i = 0; $i < $coefficientsLength - $firstNonZero; $i++){
$this->coefficients[$i] = $coefficients[$i + $firstNonZero];
}
}
}
/**
* @return int $coefficient of x^degree term in this polynomial
*/
public function getCoefficient(int $degree):int{
return $this->coefficients[count($this->coefficients) - 1 - $degree];
}
/**
* @return int[]
*/
public function getCoefficients():array{
return $this->coefficients;
}
/**
* @return int $degree of this polynomial
*/
public function getDegree():int{
return count($this->coefficients) - 1;
}
/**
* @return bool true if this polynomial is the monomial "0"
*/
public function isZero():bool{
return $this->coefficients[0] === 0;
}
/**
* @return int evaluation of this polynomial at a given point
*/
public function evaluateAt(int $a):int{
if($a === 0){
// Just return the x^0 coefficient
return $this->getCoefficient(0);
}
$result = 0;
foreach($this->coefficients as $c){
// if $a === 1 just the sum of the coefficients
$result = GF256::addOrSubtract(($a === 1 ? $result : GF256::multiply($a, $result)), $c);
}
return $result;
}
/**
* @param \chillerlan\QRCode\Common\GenericGFPoly $other
*
* @return \chillerlan\QRCode\Common\GenericGFPoly
*/
public function multiply(GenericGFPoly $other):GenericGFPoly{
if($this->isZero() || $other->isZero()){
return new self([0]);
}
$product = array_fill(0, count($this->coefficients) + count($other->coefficients) - 1, 0);
foreach($this->coefficients as $i => $aCoeff){
foreach($other->coefficients as $j => $bCoeff){
$product[$i + $j] ^= GF256::multiply($aCoeff, $bCoeff);
}
}
return new self($product);
}
/**
* @param \chillerlan\QRCode\Common\GenericGFPoly $other
*
* @return \chillerlan\QRCode\Common\GenericGFPoly[] [quotient, remainder]
*/
public function divide(GenericGFPoly $other):array{
if($other->isZero()){
throw new InvalidArgumentException('Division by 0');
}
$quotient = new self([0]);
$remainder = clone $this;
$denominatorLeadingTerm = $other->getCoefficient($other->getDegree());
$inverseDenominatorLeadingTerm = GF256::inverse($denominatorLeadingTerm);
while($remainder->getDegree() >= $other->getDegree() && !$remainder->isZero()){
$scale = GF256::multiply($remainder->getCoefficient($remainder->getDegree()), $inverseDenominatorLeadingTerm);
$diff = $remainder->getDegree() - $other->getDegree();
$quotient = $quotient->addOrSubtract(GF256::buildMonomial($diff, $scale));
$remainder = $remainder->addOrSubtract($other->multiplyByMonomial($diff, $scale));
}
return [$quotient, $remainder];
}
/**
* @param int $scalar
*
* @return \chillerlan\QRCode\Common\GenericGFPoly
*/
public function multiplyInt(int $scalar):GenericGFPoly{
if($scalar === 0){
return new self([0]);
}
if($scalar === 1){
return $this;
}
$product = array_fill(0, count($this->coefficients), 0);
foreach($this->coefficients as $i => $c){
$product[$i] = GF256::multiply($c, $scalar);
}
return new self($product);
}
/**
* @param int $degree
* @param int $coefficient
*
* @return \chillerlan\QRCode\Common\GenericGFPoly
*/
public function multiplyByMonomial(int $degree, int $coefficient):GenericGFPoly{
if($degree < 0){
throw new InvalidArgumentException();
}
if($coefficient === 0){
return new self([0]);
}
$product = array_fill(0, count($this->coefficients) + $degree, 0);
foreach($this->coefficients as $i => $c){
$product[$i] = GF256::multiply($c, $coefficient);
}
return new self($product);
}
/**
* @param \chillerlan\QRCode\Common\GenericGFPoly $other
*
* @return \chillerlan\QRCode\Common\GenericGFPoly
*/
public function mod(GenericGFPoly $other):GenericGFPoly{
if(count($this->coefficients) - count($other->coefficients) < 0){
return $this;
}
$ratio = GF256::log($this->coefficients[0]) - GF256::log($other->coefficients[0]);
foreach($other->coefficients as $i => $c){
$this->coefficients[$i] ^= GF256::exp(GF256::log($c) + $ratio);
}
return (new self($this->coefficients))->mod($other);
}
/**
* @param \chillerlan\QRCode\Common\GenericGFPoly $other
*
* @return \chillerlan\QRCode\Common\GenericGFPoly
*/
public function addOrSubtract(GenericGFPoly $other):GenericGFPoly{
if($this->isZero()){
return $other;
}
if($other->isZero()){
return $this;
}
$smallerCoefficients = $this->coefficients;
$largerCoefficients = $other->coefficients;
if(count($smallerCoefficients) > count($largerCoefficients)){
$temp = $smallerCoefficients;
$smallerCoefficients = $largerCoefficients;
$largerCoefficients = $temp;
}
$sumDiff = array_fill(0, count($largerCoefficients), 0);
$lengthDiff = count($largerCoefficients) - count($smallerCoefficients);
// Copy high-order terms only found in higher-degree polynomial's coefficients
array_splice($sumDiff, 0, $lengthDiff, array_slice($largerCoefficients, 0, $lengthDiff));
$countLargerCoefficients = count($largerCoefficients);
for($i = $lengthDiff; $i < $countLargerCoefficients; $i++){
$sumDiff[$i] = GF256::addOrSubtract($smallerCoefficients[$i - $lengthDiff], $largerCoefficients[$i]);
}
return new self($sumDiff);
}
}