93 lines
1.7 KiB
C++
93 lines
1.7 KiB
C++
/*
|
|
* Copyright 2016 Nu-book Inc.
|
|
* Copyright 2016 ZXing authors
|
|
*/
|
|
// SPDX-License-Identifier: Apache-2.0
|
|
|
|
#pragma once
|
|
|
|
#include "PDFModulusPoly.h"
|
|
#include "ZXConfig.h"
|
|
|
|
#include <stdexcept>
|
|
#include <vector>
|
|
|
|
namespace ZXing {
|
|
namespace Pdf417 {
|
|
|
|
/**
|
|
* <p>A field based on powers of a generator integer, modulo some modulus.< / p>
|
|
*
|
|
* @author Sean Owen
|
|
* @see com.google.zxing.common.reedsolomon.GenericGF
|
|
*/
|
|
class ModulusGF
|
|
{
|
|
int _modulus;
|
|
std::vector<short> _expTable;
|
|
std::vector<short> _logTable;
|
|
ModulusPoly _zero;
|
|
ModulusPoly _one;
|
|
|
|
// avoid using the '%' modulo operator => ReedSolomon computation is more than twice as fast
|
|
// see also https://stackoverflow.com/a/33333636/2088798
|
|
static int fast_mod(int a, int d) { return a < d ? a : a - d; }
|
|
|
|
public:
|
|
ModulusGF(int modulus, int generator);
|
|
|
|
const ModulusPoly& zero() const {
|
|
return _zero;
|
|
}
|
|
|
|
const ModulusPoly& one() const {
|
|
return _one;
|
|
}
|
|
|
|
ModulusPoly buildMonomial(int degree, int coefficient) const;
|
|
|
|
int add(int a, int b) const {
|
|
return fast_mod(a + b, _modulus);
|
|
}
|
|
|
|
int subtract(int a, int b) const {
|
|
return fast_mod(_modulus + a - b, _modulus);
|
|
}
|
|
|
|
int exp(int a) const {
|
|
return _expTable.at(a);
|
|
}
|
|
|
|
int log(int a) const {
|
|
if (a == 0) {
|
|
throw std::invalid_argument("a == 0");
|
|
}
|
|
return _logTable[a];
|
|
}
|
|
|
|
int inverse(int a) const {
|
|
if (a == 0) {
|
|
throw std::invalid_argument("a == 0");
|
|
}
|
|
return _expTable[_modulus - _logTable[a] - 1];
|
|
}
|
|
|
|
int multiply(int a, int b) const {
|
|
if (a == 0 || b == 0) {
|
|
return 0;
|
|
}
|
|
#ifdef ZX_REED_SOLOMON_USE_MORE_MEMORY_FOR_SPEED
|
|
return _expTable[_logTable[a] + _logTable[b]];
|
|
#else
|
|
return _expTable[fast_mod(_logTable[a] + _logTable[b], _modulus - 1)];
|
|
#endif
|
|
}
|
|
|
|
int size() const {
|
|
return _modulus;
|
|
}
|
|
};
|
|
|
|
} // Pdf417
|
|
} // ZXing
|