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Thread: CRC algorithm

  1. #1
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    Default CRC algorithm

    I have a code CRC but I don't know how to use it. Cause I don't know why the code is working
    I new in Java programming.

    can other tell me how the code is working and how to use it?

    import java.util.zip.Checksum;
     
    public class crc implements Checksum {
     
    	public crc(){
    		crc = 0;
    	}
     
      private int crc;
     
     
      private static int[] crc_table = make_crc_table();
     
     
      private static int[] make_crc_table ()
      {
        int[] crc_table = new int[256];
        for (int n = 0; n < 256; n++)
          {
            int c = n;
            for (int k = 8;  --k >= 0; )
              {
                if ((c & 1) != 0)
                    c = 0xedb88320 ^ (c >>> 1); 
                else
                  c = c >>> 1;
              }
            crc_table[n] = c;
          }
        return crc_table;
      }
     
     
      public long getValue ()
      {
        return (long) crc & 0xffffffffL;
      }
     
      public void reset () { crc = 0; }
     
      public void update (int bval)
      {
        int c = ~crc;
        c = crc_table[(c ^ bval) & 0xff] ^ (c >>> 8);
        crc = ~c;
      }
     
      public void update (byte[] buf, int off, int len)
      {
        int c = ~crc;
     
        while (--len >= 0)
     
          c = crc_table[(c ^ buf[off++]) & 0xff] ^ (c >>> 8);
        crc = ~c;
      }
      public void printCRCTable(){
    	  int count = 0;
    	for(int printcrc :crc_table){
    	}
      }
     
      public void update (byte[] buf) { update(buf, 0, buf.length); }
     
    }

    thanks for your attention


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: CRC algorithm

    The comments in the code should tell you how it works and how to use it.
    Or you could read the API doc that came with it.
    Or you could ask the author.

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