content: /*******************************************************************************
   * 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 int-width CRC function using a lookup
   * table.
   */
  final class ReflectedIntCrc extends AbstractIntCrc {
  
      private final int[] table = new int[256];
  
      ReflectedIntCrc(String algorithm, int width, int poly, int init, int xorOut) {
          super(algorithm, width, init, xorOut);
  
          poly = reflect(poly);
          for (int i = 0; i < 256; ++i) {
              int crc = i;
              for (int j = 0; j < 8; ++j)
                  crc = (crc & 1) != 0 ? (crc >>> 1) ^ poly : crc >>> 1;
              table[i] = crc;
          }
      }
  
      @Override
      protected int initial() {
          return reflect(super.initial());
      }
  
      @Override
      protected int resumeRaw(int crc, byte[] input, int index, int length) {
          for (int i = 0; i < length; ++i)
              crc = table[(crc ^ input[index + i]) & 0xff] ^ (crc >>> 8);
          return crc;
      }
  }
  