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jake2 ext » jake2 » qcommon » CRC.java
/*
Copyright (C) 1997-2001 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

 */
// Created on 25.01.2004 by RST.
// $Id: CRC.java,v 1.2 2005/01/23 01:19:06 cawe Exp $
package jake2.qcommon;

public class CRC {

  public final static short CRC_INIT_VALUE = (short) 0xffff;
  public final static short CRC_XOR_VALUE = (short) 0x0000;
  private static int crctable[] = {0x0000, 0x1021, 0x2042, 0x3063, 0x4084,
    0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c,
    0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5,
    0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd,
    0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6,
    0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee,
    0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7,
    0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df,
    0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840,
    0x1861, 0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948,
    0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71,
    0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79,
    0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22,
    0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a,
    0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13,
    0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b,
    0xaf3a, 0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c,
    0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004,
    0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d,
    0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235,
    0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e,
    0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466,
    0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f,
    0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657,
    0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8,
    0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0,
    0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9,
    0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1,
    0x1ad0, 0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa,
    0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2,
    0x2c83, 0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b,
    0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93,
    0x3eb2, 0x0ed1, 0x1ef0};

  static int CRC_Block(byte start[], int count) {
    short crc = CRC_INIT_VALUE;

    int ndx = 0;

    while (count-- > 0) {
      crc = (short) ((crc << 8) ^ crctable[0xff & ((crc >> 8) ^ start[ndx++])]);
    }

    // unsigned short
    return crc & 0xFFFF;
  }

  public static void main(String[] args) {
    byte data[] = {
      (byte) 0x71,
      (byte) 0xa9,
      (byte) 0x05,
      (byte) 0xce,
      (byte) 0x8d,
      (byte) 0x75,
      (byte) 0x28,
      (byte) 0xc8,
      (byte) 0xba,
      (byte) 0x97,
      (byte) 0x45,
      (byte) 0xe9,
      (byte) 0x8a,
      (byte) 0xe0,
      (byte) 0x37,
      (byte) 0xbd,
      (byte) 0x6c,
      (byte) 0x6d,
      (byte) 0x67,
      (byte) 0x4a,
      (byte) 0x21};
    System.out.println("crc:" + (CRC_Block(data, 21) & 0xffff));
    System.out.println("----");
    for (int n = 0; n < 5; n++) {
      System.out.println("seq:" + (Com.BlockSequenceCRCByte(data, 0, 21, n * 10) & 0xff));
    }

  }
  /* c test:
   * 
   * D:\Rene\gamesrc\quake2-3.21\qcommon>crc
   * crc=-12353
   * ----
   * seq:215
   * seq:252
   * seq:164
   * seq:202
   * seq:201
   * 
  int main()
  {
  byte data[21] = 
  {  
  0x71,
  0xa9,
  0x05,
  0xce,
  0x8d,
  0x75,
  0x28,
  0xc8,
  0xba,
  0x97,
  
  0x45,
  0xe9,
  0x8a,
  0xe0,
  0x37,
  0xbd,
  0x6c,
  0x6d,
  0x67,
  0x4a, 0x21 };
  int n=0;
  
  printf("crc=%d\n", (short) CRC_Block(&data, 21));
  
  printf("----\n");
  for (n=0; n < 5; n++)
  printf("seq:%d\n", COM_BlockSequenceCRCByte( &data,21, n*10) );
  } 
   */
}
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