1 files changed, 263 insertions, 0 deletions
diff --git a/libraries/zxing/src/com/google/zxing/common/reedsolomon/GenericGFPoly.java b/libraries/zxing/src/com/google/zxing/common/reedsolomon/GenericGFPoly.java
new file mode 100644
index 000000000..056802287
--- /dev/null
+++ b/libraries/zxing/src/com/google/zxing/common/reedsolomon/GenericGFPoly.java
@@ -0,0 +1,263 @@
+/*
+ * 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.
+ */
+
+package com.google.zxing.common.reedsolomon;
+
+/**
+ * <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 final GenericGF field;
+  private final int[] coefficients;
+
+  /**
+   * @param field the {@link GenericGF} instance representing the field to use
+   * to perform computations
+   * @param coefficients coefficients as ints representing elements of GF(size), arranged
+   * from most significant (highest-power term) coefficient to least significant
+   * @throws IllegalArgumentException 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")
+   */
+  GenericGFPoly(GenericGF field, int[] coefficients) {
+    if (coefficients == null || coefficients.length == 0) {
+      throw new IllegalArgumentException();
+    }
+    this.field = field;
+    int coefficientsLength = coefficients.length;
+    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) {
+        this.coefficients = field.getZero().coefficients;
+      } else {
+        this.coefficients = new int[coefficientsLength - firstNonZero];
+        System.arraycopy(coefficients,
+            firstNonZero,
+            this.coefficients,
+            0,
+            this.coefficients.length);
+      }
+    } else {
+      this.coefficients = coefficients;
+    }
+  }
+
+  int[] getCoefficients() {
+    return coefficients;
+  }
+
+  /**
+   * @return degree of this polynomial
+   */
+  int getDegree() {
+    return coefficients.length - 1;
+  }
+
+  /**
+   * @return true iff this polynomial is the monomial "0"
+   */
+  boolean isZero() {
+    return coefficients[0] == 0;
+  }
+
+  /**
+   * @return coefficient of x^degree term in this polynomial
+   */
+  int getCoefficient(int degree) {
+    return coefficients[coefficients.length - 1 - degree];
+  }
+
+  /**
+   * @return evaluation of this polynomial at a given point
+   */
+  int evaluateAt(int a) {
+    if (a == 0) {
+      // Just return the x^0 coefficient
+      return getCoefficient(0);
+    }
+    int size = coefficients.length;
+    if (a == 1) {
+      // Just the sum of the coefficients
+      int result = 0;
+      for (int i = 0; i < size; i++) {
+        result = GenericGF.addOrSubtract(result, coefficients[i]);
+      }
+      return result;
+    }
+    int result = coefficients[0];
+    for (int i = 1; i < size; i++) {
+      result = GenericGF.addOrSubtract(field.multiply(a, result), coefficients[i]);
+    }
+    return result;
+  }
+
+  GenericGFPoly addOrSubtract(GenericGFPoly other) {
+    if (!field.equals(other.field)) {
+      throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field");
+    }
+    if (isZero()) {
+      return other;
+    }
+    if (other.isZero()) {
+      return this;
+    }
+
+    int[] smallerCoefficients = this.coefficients;
+    int[] largerCoefficients = other.coefficients;
+    if (smallerCoefficients.length > largerCoefficients.length) {
+      int[] temp = smallerCoefficients;
+      smallerCoefficients = largerCoefficients;
+      largerCoefficients = temp;
+    }
+    int[] sumDiff = new int[largerCoefficients.length];
+    int lengthDiff = largerCoefficients.length - smallerCoefficients.length;
+    // Copy high-order terms only found in higher-degree polynomial's coefficients
+    System.arraycopy(largerCoefficients, 0, sumDiff, 0, lengthDiff);
+
+    for (int i = lengthDiff; i < largerCoefficients.length; i++) {
+      sumDiff[i] = GenericGF.addOrSubtract(smallerCoefficients[i - lengthDiff], largerCoefficients[i]);
+    }
+
+    return new GenericGFPoly(field, sumDiff);
+  }
+
+  GenericGFPoly multiply(GenericGFPoly other) {
+    if (!field.equals(other.field)) {
+      throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field");
+    }
+    if (isZero() || other.isZero()) {
+      return field.getZero();
+    }
+    int[] aCoefficients = this.coefficients;
+    int aLength = aCoefficients.length;
+    int[] bCoefficients = other.coefficients;
+    int bLength = bCoefficients.length;
+    int[] product = new int[aLength + bLength - 1];
+    for (int i = 0; i < aLength; i++) {
+      int aCoeff = aCoefficients[i];
+      for (int j = 0; j < bLength; j++) {
+        product[i + j] = GenericGF.addOrSubtract(product[i + j],
+            field.multiply(aCoeff, bCoefficients[j]));
+      }
+    }
+    return new GenericGFPoly(field, product);
+  }
+
+  GenericGFPoly multiply(int scalar) {
+    if (scalar == 0) {
+      return field.getZero();
+    }
+    if (scalar == 1) {
+      return this;
+    }
+    int size = coefficients.length;
+    int[] product = new int[size];
+    for (int i = 0; i < size; i++) {
+      product[i] = field.multiply(coefficients[i], scalar);
+    }
+    return new GenericGFPoly(field, product);
+  }
+
+  GenericGFPoly multiplyByMonomial(int degree, int coefficient) {
+    if (degree < 0) {
+      throw new IllegalArgumentException();
+    }
+    if (coefficient == 0) {
+      return field.getZero();
+    }
+    int size = coefficients.length;
+    int[] product = new int[size + degree];
+    for (int i = 0; i < size; i++) {
+      product[i] = field.multiply(coefficients[i], coefficient);
+    }
+    return new GenericGFPoly(field, product);
+  }
+
+  GenericGFPoly[] divide(GenericGFPoly other) {
+    if (!field.equals(other.field)) {
+      throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field");
+    }
+    if (other.isZero()) {
+      throw new IllegalArgumentException("Divide by 0");
+    }
+
+    GenericGFPoly quotient = field.getZero();
+    GenericGFPoly 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);
+      GenericGFPoly term = other.multiplyByMonomial(degreeDifference, scale);
+      GenericGFPoly iterationQuotient = field.buildMonomial(degreeDifference, scale);
+      quotient = quotient.addOrSubtract(iterationQuotient);
+      remainder = remainder.addOrSubtract(term);
+    }
+
+    return new GenericGFPoly[] { quotient, remainder };
+  }
+
+  public String toString() {
+    StringBuffer result = new StringBuffer(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) {
+          int alphaPower = field.log(coefficient);
+          if (alphaPower == 0) {
+            result.append('1');
+          } else if (alphaPower == 1) {
+            result.append('a');
+          } else {
+            result.append("a^");
+            result.append(alphaPower);
+          }
+        }
+        if (degree != 0) {
+          if (degree == 1) {
+            result.append('x');
+          } else {
+            result.append("x^");
+            result.append(degree);
+          }
+        }
+      }
+    }
+    return result.toString();
+  }
+
+}