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OggCRCFactory.javaAPI DocJaudiotagger 2.0.42729Wed Mar 30 16:11:54 BST 2011org.jaudiotagger.audio.ogg.util

OggCRCFactory

public class OggCRCFactory extends Object
OffCRC Calculations

$Id: OggCRCFactory.java 836 2009-11-12 15:44:07Z paultaylor $

author
Raphael Slinckx (KiKiDonK)
version
19 d�cembre 2003

Fields Summary
public static Logger
logger
private static long[]
crc_lookup
private static boolean
init
Constructors Summary
Methods Summary
public booleancheckCRC(byte[] data, byte[] crc)

        return new String(crc).equals(new String(computeCRC(data)));
public static byte[]computeCRC(byte[] data)


        if (!init)
        {
            init();
        }

        long crc_reg = 0;

        for (byte aData : data)
        {
            int tmp = (int) (((crc_reg >>> 24) & 0xff) ^ u(aData));

            crc_reg = (crc_reg << 8) ^ crc_lookup[tmp];
            crc_reg &= 0xffffffff;
        }

        byte[] sum = new byte[4];

        sum[0] = (byte) (crc_reg & 0xffL);
        sum[1] = (byte) ((crc_reg >>> 8) & 0xffL);
        sum[2] = (byte) ((crc_reg >>> 16) & 0xffL);
        sum[3] = (byte) ((crc_reg >>> 24) & 0xffL);

        return sum;
public static voidinit()



       
    
        for (int i = 0; i < 256; i++)
        {
            long r = i << 24;

            for (int j = 0; j < 8; j++)
            {
                if ((r & 0x80000000L) != 0)
                {
                    r = (r << 1) ^ 0x04c11db7L;
                }
                else
                {
                    r <<= 1;
                }
            }

            crc_lookup[i] = (r);
        }
        init = true;
private static intu(int n)

        return n & 0xff;