| /******************************************************************************* |
| * Copyright 2014 Trevor Robinson |
| * |
| * 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.scurrilous.circe.crc; |
| |
| /** |
| * Implements a "reflected" LSB-first long-width CRC function using a lookup |
| * table. |
| */ |
| final class ReflectedLongCrc extends AbstractLongCrc { |
| |
| private final long[] table = new long[256]; |
| |
| ReflectedLongCrc(String algorithm, int width, long poly, long init, long xorOut) { |
| super(algorithm, width, init, xorOut); |
| |
| poly = reflect(poly); |
| for (int i = 0; i < 256; ++i) { |
| long crc = i; |
| for (int j = 0; j < 8; ++j) |
| crc = (crc & 1) != 0 ? (crc >>> 1) ^ poly : crc >>> 1; |
| table[i] = crc; |
| } |
| } |
| |
| @Override |
| protected long initial() { |
| return reflect(super.initial()); |
| } |
| |
| @Override |
| protected long resumeRaw(long crc, byte[] input, int index, int length) { |
| for (int i = 0; i < length; ++i) |
| crc = table[(int) (crc ^ input[index + i]) & 0xff] ^ (crc >>> 8); |
| return crc; |
| } |
| } |