1 files changed, 188 insertions, 0 deletions
diff --git a/OpenPGP-Keychain/src/com/google/zxing/common/reedsolomon/GenericGF.java b/OpenPGP-Keychain/src/com/google/zxing/common/reedsolomon/GenericGF.java
new file mode 100644
index 000000000..859c379ee
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+++ b/OpenPGP-Keychain/src/com/google/zxing/common/reedsolomon/GenericGF.java
@@ -0,0 +1,188 @@
+/*
+ * 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>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</code>
+ * for convenience and speed (but at the cost of memory).
+ * </p>
+ *
+ * @author Sean Owen
+ * @author David Olivier
+ */
+public final class GenericGF {
+
+  public static final GenericGF AZTEC_DATA_12 = new GenericGF(0x1069, 4096); // x^12 + x^6 + x^5 + x^3 + 1
+  public static final GenericGF AZTEC_DATA_10 = new GenericGF(0x409, 1024); // x^10 + x^3 + 1
+  public static final GenericGF AZTEC_DATA_6 = new GenericGF(0x43, 64); // x^6 + x + 1
+  public static final GenericGF AZTEC_PARAM = new GenericGF(0x13, 16); // x^4 + x + 1
+  public static final GenericGF QR_CODE_FIELD_256 = new GenericGF(0x011D, 256); // x^8 + x^4 + x^3 + x^2 + 1
+  public static final GenericGF DATA_MATRIX_FIELD_256 = new GenericGF(0x012D, 256); // x^8 + x^5 + x^3 + x^2 + 1
+  public static final GenericGF AZTEC_DATA_8 = DATA_MATRIX_FIELD_256;
+
+  private static final int INITIALIZATION_THRESHOLD = 0;
+
+  private int[] expTable;
+  private int[] logTable;
+  private GenericGFPoly zero;
+  private GenericGFPoly one;
+  private final int size;
+  private final int primitive;
+  private boolean initialized = false;
+
+  /**
+   * Create a representation of GF(size) using the given primitive polynomial.
+   *
+   * @param primitive irreducible polynomial whose coefficients are represented by
+   *  the bits of an int, where the least-significant bit represents the constant
+   *  coefficient
+   */
+  public GenericGF(int primitive, int size) {
+  	this.primitive = primitive;
+    this.size = size;
+    
+    if (size <= INITIALIZATION_THRESHOLD){
+    	initialize();
+    }
+  }
+
+  private void initialize(){
+    expTable = new int[size];
+    logTable = new int[size];
+    int x = 1;
+    for (int i = 0; i < size; i++) {
+      expTable[i] = x;
+      x <<= 1; // x = x * 2; we're assuming the generator alpha is 2
+      if (x >= size) {
+        x ^= primitive;
+        x &= size-1;
+      }
+    }
+    for (int i = 0; i < size-1; i++) {
+      logTable[expTable[i]] = i;
+    }
+    // logTable[0] == 0 but this should never be used
+    zero = new GenericGFPoly(this, new int[]{0});
+    one = new GenericGFPoly(this, new int[]{1});
+    initialized = true;
+  }
+  
+  private void checkInit(){
+  	if (!initialized) {
+      initialize();
+    }
+  }
+  
+  GenericGFPoly getZero() {
+  	checkInit();
+  	
+    return zero;
+  }
+
+  GenericGFPoly getOne() {
+  	checkInit();
+  	
+    return one;
+  }
+
+  /**
+   * @return the monomial representing coefficient * x^degree
+   */
+  GenericGFPoly buildMonomial(int degree, int coefficient) {
+  	checkInit();
+  	
+    if (degree < 0) {
+      throw new IllegalArgumentException();
+    }
+    if (coefficient == 0) {
+      return zero;
+    }
+    int[] coefficients = new int[degree + 1];
+    coefficients[0] = coefficient;
+    return new GenericGFPoly(this, coefficients);
+  }
+
+  /**
+   * Implements both addition and subtraction -- they are the same in GF(size).
+   *
+   * @return sum/difference of a and b
+   */
+  static int addOrSubtract(int a, int b) {
+    return a ^ b;
+  }
+
+  /**
+   * @return 2 to the power of a in GF(size)
+   */
+  int exp(int a) {
+  	checkInit();
+  	
+    return expTable[a];
+  }
+
+  /**
+   * @return base 2 log of a in GF(size)
+   */
+  int log(int a) {
+  	checkInit();
+  	
+    if (a == 0) {
+      throw new IllegalArgumentException();
+    }
+    return logTable[a];
+  }
+
+  /**
+   * @return multiplicative inverse of a
+   */
+  int inverse(int a) {
+  	checkInit();
+  	
+    if (a == 0) {
+      throw new ArithmeticException();
+    }
+    return expTable[size - logTable[a] - 1];
+  }
+
+  /**
+   * @param a
+   * @param b
+   * @return product of a and b in GF(size)
+   */
+  int multiply(int a, int b) {
+  	checkInit();
+  	
+    if (a == 0 || b == 0) {
+      return 0;
+    }
+    
+    if (a<0 || b <0 || a>=size || b >=size){
+    	a++;
+    }
+    
+    int logSum = logTable[a] + logTable[b];
+    return expTable[(logSum % size) + logSum / size];
+  }
+
+  public int getSize(){
+  	return size;
+  }
+  
+}