org.xiph.speex
Class OggCrc

java.lang.Object
  org.xiph.speex.OggCrc

public class OggCrc

extends java.lang.Object

Calculates the CRC checksum for Ogg packets.

Ogg uses the same generator polynomial as ethernet, although with an unreflected alg and an init/final of 0, not 0xffffffff.

Version:

$Revision: 1.5 $

Author:

Jim Lawrence, helloNetwork.com, Marc Gimpel, Wimba S.A. (marc@wimba.com)

Field Summary

private static int[]

crc_lookup CRC checksum lookup table

Constructor Summary

OggCrc()

Method Summary

static int

checksum(int crc, byte[] data, int offset, int length) Calculates the checksum on the given data, from the give offset and for the given length, using the given initial value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

crc_lookup

private static int[] crc_lookup

CRC checksum lookup table

Constructor Detail

OggCrc

public OggCrc()

Method Detail

checksum

public static int checksum(int crc,
                           byte[] data,
                           int offset,
                           int length)

Calculates the checksum on the given data, from the give offset and for the given length, using the given initial value. This allows on to calculate the checksum iteratively, by reinjecting the last returned value as the initial value when the function is called for the next data chunk. The initial value should be 0 for the first iteration.

Parameters:

crc - - the initial value

data - - the data

offset - - the offset at which to start calculating the checksum.

length - - the length of data over which to calculate the checksum.

Returns:

the checksum.