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package java.util.zip;

A class that can be used to compute the CRC-32 of a data stream.
Author:
     David Connelly
See Also:
Checksum/**
 * A class that can be used to compute the CRC-32 of a data stream.
 *
 * @see         Checksum
 * @author      David Connelly
 */
public
class CRC32 implements Checksum {
    private int crc;

    
Creates a new CRC32 object.
/**
     * Creates a new CRC32 object.
     */
    public CRC32() {
    }


    
Updates the CRC-32 checksum with the specified byte (the low
eight bits of the argument b).
Params:
b – the byte to update the checksum with/**
     * Updates the CRC-32 checksum with the specified byte (the low
     * eight bits of the argument b).
     *
     * @param b the byte to update the checksum with
     */
    public void update(int b) {
        crc = update(crc, b);
    }

    
Updates the CRC-32 checksum with the specified array of bytes.
/**
     * Updates the CRC-32 checksum with the specified array of bytes.
     */
    public void update(byte[] b, int off, int len) {
        if (b == null) {
            throw new NullPointerException();
        }
        if (off < 0 || len < 0 || off > b.length - len) {
            throw new ArrayIndexOutOfBoundsException();
        }
        crc = updateBytes(crc, b, off, len);
    }

    
Updates the CRC-32 checksum with the specified array of bytes.
Params:
b – the array of bytes to update the checksum with/**
     * Updates the CRC-32 checksum with the specified array of bytes.
     *
     * @param b the array of bytes to update the checksum with
     */
    public void update(byte[] b) {
        crc = updateBytes(crc, b, 0, b.length);
    }

    
Resets CRC-32 to initial value.
/**
     * Resets CRC-32 to initial value.
     */
    public void reset() {
        crc = 0;
    }

    
Returns CRC-32 value.
/**
     * Returns CRC-32 value.
     */
    public long getValue() {
        return (long)crc & 0xffffffffL;
    }

    private native static int update(int crc, int b);
    private native static int updateBytes(int crc, byte[] b, int off, int len);
}