qzxing/source/zxing/pdf417/decoder/ec/ModulusPoly.cpp

// -*- mode:c++; tab-width:2; indent-tabs-mode:nil; c-basic-offset:2 -*-
/*
 * Copyright 2012 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.
 *
 * 2012-09-19 HFN translation from Java into C++
 */

#include <zxing/pdf417/decoder/ec/ModulusPoly.h>
#include <zxing/pdf417/decoder/ec/ModulusGF.h>

using zxing::Ref;
using zxing::ArrayRef;
using zxing::pdf417::decoder::ec::ModulusGF;
using zxing::pdf417::decoder::ec::ModulusPoly;

/**
 * @author Sean Owen
 * @see com.google.zxing.common.reedsolomon.GenericGFPoly
 */

ModulusPoly::ModulusPoly(ModulusGF& field, ArrayRef<int> coefficients)
    : field_(field)
{
  if (coefficients->size() == 0) {
    throw IllegalArgumentException("no coefficients!");
  }
  int coefficientsLength = coefficients->size();
  if (coefficientsLength > 1 && coefficients[0] == 0) {
    // Leading term must be non-zero for anything except the constant polynomial "0"
    int firstNonZero = 1;
    while (firstNonZero < coefficientsLength && coefficients[firstNonZero] == 0) {
      firstNonZero++;
    }
    if (firstNonZero == coefficientsLength) {
	    coefficientsLength = field_.getZero()->getCoefficients()->size();
      coefficients_.reset(new Array<int> (coefficientsLength));
      *coefficients_ = *(field_.getZero()->getCoefficients());
    } else {
      ArrayRef<int> c(coefficients);
      coefficientsLength -= firstNonZero;
      coefficients_.reset(new Array<int> (coefficientsLength));
      for (int i = 0; i < coefficientsLength; i++) {
        coefficients_[i] = c[i + firstNonZero];
      }
      /*
        coefficientsLength -= firstNonZero;
        coefficients_.reset(new Array<int>(coefficientsLength - firstNonZero));
        for (int i = 0; i < coefficientsLength; i++) {
        coefficients_[i] = coefficients[i + firstNonZero];
        }
      */
    }
  } else {
    coefficients_ = coefficients;
  }
}

ArrayRef<int> ModulusPoly::getCoefficients() {
  return coefficients_;
}

/**
 * @return degree of this polynomial
 */
int ModulusPoly::getDegree() {
  return coefficients_->size() - 1;
}

/**
 * @return true iff this polynomial is the monomial "0"
 */
bool ModulusPoly::isZero() {
  return coefficients_[0] == 0;
}

/**
 * @return coefficient of x^degree term in this polynomial
 */
int ModulusPoly::getCoefficient(int degree) {
  return coefficients_[coefficients_->size() - 1 - degree];
}

/**
 * @return evaluation of this polynomial at a given point
 */
int ModulusPoly::evaluateAt(int a) {
	int i;
  if (a == 0) {
    // Just return the x^0 coefficient
    return getCoefficient(0);
  }
  int size = coefficients_->size();
  if (a == 1) {
    // Just the sum of the coefficients
    int result = 0;
	  for (i = 0; i < size; i++) {
      result = field_.add(result, coefficients_[i]);
	  }
    return result;
  }
  int result = coefficients_[0];
  for (i = 1; i < size; i++) {
    result = field_.add(field_.multiply(a, result), coefficients_[i]);
  }
  return result;
}

Ref<ModulusPoly> ModulusPoly::add(Ref<ModulusPoly> other) {
  if (&field_ != &other->field_) {
    throw IllegalArgumentException("ModulusPolys do not have same ModulusGF field");
  }
  if (isZero()) {
    return other;
  }
  if (other->isZero()) {
    return Ref<ModulusPoly>(this);
  }

  ArrayRef<int> smallerCoefficients = coefficients_;
  ArrayRef<int> largerCoefficients = other->coefficients_;
  if (smallerCoefficients->size() > largerCoefficients->size()) {
    ArrayRef<int> temp(smallerCoefficients);
    smallerCoefficients = largerCoefficients;
    largerCoefficients = temp;
  }
  ArrayRef<int>  sumDiff (new Array<int>(largerCoefficients->size()));
  int lengthDiff = largerCoefficients->size() - smallerCoefficients->size();
  // Copy high-order terms only found in higher-degree polynomial's coefficients
	for (int i = 0; i < lengthDiff; i++) {
		sumDiff[i] = largerCoefficients[i];
	}

  for (int i = lengthDiff; i < largerCoefficients->size(); i++) {
    sumDiff[i] = field_.add(smallerCoefficients[i - lengthDiff], largerCoefficients[i]);
  }

  return Ref<ModulusPoly>(new ModulusPoly(field_, sumDiff));
}

Ref<ModulusPoly> ModulusPoly::subtract(Ref<ModulusPoly> other) {
  if (&field_ != &other->field_) {
    throw new IllegalArgumentException("ModulusPolys do not have same ModulusGF field");
  }
  if (other->isZero()) {
    return Ref<ModulusPoly>(this);
  }
  return add(other->negative());
}

Ref<ModulusPoly> ModulusPoly::multiply(Ref<ModulusPoly> other) {
  if (&field_ != &other->field_) {
    throw new IllegalArgumentException("ModulusPolys do not have same ModulusGF field");
  }
  if (isZero() || other->isZero()) {
    return field_.getZero();
  }
	int i,j;
  ArrayRef<int> aCoefficients = coefficients_;
  int aLength = aCoefficients->size();
  ArrayRef<int> bCoefficients = other->coefficients_;
  int bLength = bCoefficients->size();
  ArrayRef<int> product (new Array<int>(aLength + bLength - 1));
  for (i = 0; i < aLength; i++) {
    int aCoeff = aCoefficients[i];
    for (j = 0; j < bLength; j++) {
      product[i + j] = field_.add(product[i + j], field_.multiply(aCoeff, bCoefficients[j]));
    }
  }
  return Ref<ModulusPoly>(new ModulusPoly(field_, product));
}

Ref<ModulusPoly> ModulusPoly::negative() {
  int size = coefficients_->size();
  ArrayRef<int> negativeCoefficients (new Array<int>(size));
  for (int i = 0; i < size; i++) {
    negativeCoefficients[i] = field_.subtract(0, coefficients_[i]);
  }
  return Ref<ModulusPoly>(new ModulusPoly(field_, negativeCoefficients));
}

Ref<ModulusPoly> ModulusPoly::multiply(int scalar) {
  if (scalar == 0) {
    return field_.getZero();
  }
  if (scalar == 1) {
    return Ref<ModulusPoly>(this);
  }
  int size = coefficients_->size();
  ArrayRef<int> product( new Array<int>(size));
  for (int i = 0; i < size; i++) {
    product[i] = field_.multiply(coefficients_[i], scalar);
  }
  return Ref<ModulusPoly>(new ModulusPoly(field_, product));
}

Ref<ModulusPoly> ModulusPoly::multiplyByMonomial(int degree, int coefficient) {
  if (degree < 0) {
    throw new IllegalArgumentException("negative degree!");
  }
  if (coefficient == 0) {
    return field_.getZero();
  }
  int size = coefficients_->size();
  ArrayRef<int> product (new Array<int>(size + degree));
  for (int i = 0; i < size; i++) {
    product[i] = field_.multiply(coefficients_[i], coefficient);
  }
  return Ref<ModulusPoly>(new ModulusPoly(field_, product));
}

std::vector<Ref<ModulusPoly> > ModulusPoly::divide(Ref<ModulusPoly> other) {
  if (&field_ != &other->field_) {
    throw new IllegalArgumentException("ModulusPolys do not have same ModulusGF field");
  }
  if (other->isZero()) {
    throw new IllegalArgumentException("Divide by 0");
  }

  Ref<ModulusPoly> quotient (field_.getZero());
  Ref<ModulusPoly> remainder (this);

  int denominatorLeadingTerm = other->getCoefficient(other->getDegree());
  int inverseDenominatorLeadingTerm = field_.inverse(denominatorLeadingTerm);

  while (remainder->getDegree() >= other->getDegree() && !remainder->isZero()) {
    int degreeDifference = remainder->getDegree() - other->getDegree();
    int scale = field_.multiply(remainder->getCoefficient(remainder->getDegree()), inverseDenominatorLeadingTerm);
    Ref<ModulusPoly> term (other->multiplyByMonomial(degreeDifference, scale));
    Ref<ModulusPoly> iterationQuotient (field_.buildMonomial(degreeDifference, scale));
    quotient = quotient->add(iterationQuotient);
    remainder = remainder->subtract(term);
  }

	std::vector<Ref<ModulusPoly> > result(2);
	result[0] = quotient;
	result[1] = remainder;
  return result;
}

#if 0
@Override
public String toString() {
  StringBuilder result = new StringBuilder(8 * getDegree());
  for (int degree = getDegree(); degree >= 0; degree--) {
    int coefficient = getCoefficient(degree);
    if (coefficient != 0) {
      if (coefficient < 0) {
        result.append(" - ");
        coefficient = -coefficient;
      } else {
        if (result.length() > 0) {
          result.append(" + ");
        }
      }
      if (degree == 0 || coefficient != 1) {
        result.append(coefficient);
      }
      if (degree != 0) {
        if (degree == 1) {
          result.append('x');
        } else {
          result.append("x^");
          result.append(degree);
        }
      }
    }
  }
  return result.toString();
}
#endif

ModulusPoly::~ModulusPoly() {}