+++ /dev/null
-/*\r
-* Licensed under the Apache License, Version 2.0 (the "License");\r
-* you may not use this file except in compliance with the License.\r
-* You may obtain a copy of the License at\r
-*\r
-* http://www.apache.org/licenses/LICENSE-2.0\r
-*\r
-* Unless required by applicable law or agreed to in writing, software\r
-* distributed under the License is distributed on an "AS IS" BASIS,\r
-* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
-* See the License for the specific language governing permissions and\r
-* limitations under the License.\r
-*/\r
-\r
-using System;\r
-namespace com.google.zxing.common.reedsolomon\r
-{\r
-\r
- /// <summary> <p>This class contains utility methods for performing mathematical operations over\r
- /// the Galois Field GF(256). Operations use the primitive polynomial\r
- /// x^8 + x^4 + x^3 + x^2 + 1 in calculations.</p>\r
- /// \r
- /// <p>Throughout this package, elements of GF(256) are represented as an <code>int</code>\r
- /// for convenience and speed (but at the cost of memory).\r
- /// Only the bottom 8 bits are really used.</p>\r
- /// \r
- /// </summary>\r
- /// <author> srowen@google.com (Sean Owen)\r
- /// </author>\r
- public sealed class GF256\r
- { \r
- public static GF256 QR_CODE_FIELD = new GF256(0x011D); // x^8 + x^4 + x^3 + x^2 + 1\r
- public static GF256 DATA_MATRIX_FIELD = new GF256(0x012D); // x^8 + x^5 + x^3 + x^2 + 1\r
-\r
- private int[] expTable;\r
- private int[] logTable;\r
- private GF256Poly zero;\r
- private GF256Poly one;\r
-\r
- /**\r
- * Create a representation of GF(256) using the given primitive polynomial.\r
- *\r
- * @param primitive irreducible polynomial whose coefficients are represented by\r
- * the bits of an int, where the least-significant bit represents the constant\r
- * coefficient\r
- */\r
- private GF256(int primitive) {\r
- expTable = new int[256];\r
- logTable = new int[256];\r
- int x = 1;\r
- for (int i = 0; i < 256; i++) {\r
- expTable[i] = x;\r
- x <<= 1; // x = x * 2; we're assuming the generator alpha is 2\r
- if (x >= 0x100) {\r
- x ^= primitive;\r
- }\r
- }\r
- for (int i = 0; i < 255; i++) {\r
- logTable[expTable[i]] = i;\r
- }\r
- // logTable[0] == 0 but this should never be used\r
- zero = new GF256Poly(this, new int[]{0});\r
- one = new GF256Poly(this, new int[]{1});\r
- }\r
-\r
- public GF256Poly getZero() {\r
- return zero;\r
- }\r
-\r
- public GF256Poly getOne()\r
- {\r
- return one;\r
- }\r
-\r
- /**\r
- * @return the monomial representing coefficient * x^degree\r
- */\r
- public GF256Poly buildMonomial(int degree, int coefficient)\r
- {\r
- if (degree < 0) {\r
- throw new ArgumentException();\r
- }\r
- if (coefficient == 0) {\r
- return zero;\r
- }\r
- int[] coefficients = new int[degree + 1];\r
- coefficients[0] = coefficient;\r
- return new GF256Poly(this, coefficients);\r
- }\r
-\r
- /**\r
- * Implements both addition and subtraction -- they are the same in GF(256).\r
- *\r
- * @return sum/difference of a and b\r
- */\r
- public static int addOrSubtract(int a, int b) {\r
- return a ^ b;\r
- }\r
-\r
- /**\r
- * @return 2 to the power of a in GF(256)\r
- */\r
- public int exp(int a)\r
- {\r
- return expTable[a];\r
- }\r
-\r
- /**\r
- * @return base 2 log of a in GF(256)\r
- */\r
- public int log(int a)\r
- {\r
- if (a == 0) {\r
- throw new ArgumentException();\r
- }\r
- return logTable[a];\r
- }\r
-\r
- /**\r
- * @return multiplicative inverse of a\r
- */\r
- public int inverse(int a)\r
- {\r
- if (a == 0) {\r
- throw new ArithmeticException();\r
- }\r
- return expTable[255 - logTable[a]];\r
- }\r
-\r
- /**\r
- * @param a\r
- * @param b\r
- * @return product of a and b in GF(256)\r
- */\r
- public int multiply(int a, int b)\r
- {\r
- if (a == 0 || b == 0) {\r
- return 0;\r
- }\r
- if (a == 1) {\r
- return b;\r
- }\r
- if (b == 1) {\r
- return a;\r
- }\r
- return expTable[(logTable[a] + logTable[b]) % 255];\r
- }\r
- \r
- \r
- }\r
-}
\ No newline at end of file
projects / zxing.git / blobdiff