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package java.util.zip;

import java.nio.ByteBuffer;
import sun.nio.ch.DirectBuffer;

import jdk.internal.HotSpotIntrinsicCandidate;

A class that can be used to compute the Adler-32 checksum of a data
stream. An Adler-32 checksum is almost as reliable as a CRC-32 but
can be computed much faster.
 Passing a null argument to a method in this class will cause a NullPointerException to be thrown.
Author:
     David Connelly
Since:
1.1/**
 * A class that can be used to compute the Adler-32 checksum of a data
 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but
 * can be computed much faster.
 *
 * <p> Passing a {@code null} argument to a method in this class will cause
 * a {@link NullPointerException} to be thrown.</p>
 *
 * @author      David Connelly
 * @since 1.1
 */
public
class Adler32 implements Checksum {

    private int adler = 1;

    
Creates a new Adler32 object.
/**
     * Creates a new Adler32 object.
     */
    public Adler32() {
    }

    
Updates the checksum with the specified byte (the low eight
bits of the argument b).
/**
     * Updates the checksum with the specified byte (the low eight
     * bits of the argument b).
     */
    @Override
    public void update(int b) {
        adler = update(adler, b);
    }

    
Updates the checksum with the specified array of bytes.
Throws:
ArrayIndexOutOfBoundsException –  if off is negative, or len is negative, or off+len is negative or greater than the length of the array b./**
     * Updates the checksum with the specified array of bytes.
     *
     * @throws ArrayIndexOutOfBoundsException
     *         if {@code off} is negative, or {@code len} is negative, or
     *         {@code off+len} is negative or greater than the length of
     *         the array {@code b}.
     */
    @Override
    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();
        }
        adler = updateBytes(adler, b, off, len);
    }

    
Updates the checksum with the bytes from the specified buffer.
The checksum is updated with the remaining bytes in the buffer, starting
at the buffer's position. Upon return, the buffer's position will be
updated to its limit; its limit will not have been changed.
Since:
1.8/**
     * Updates the checksum with the bytes from the specified buffer.
     *
     * The checksum is updated with the remaining bytes in the buffer, starting
     * at the buffer's position. Upon return, the buffer's position will be
     * updated to its limit; its limit will not have been changed.
     *
     * @since 1.8
     */
    @Override
    public void update(ByteBuffer buffer) {
        int pos = buffer.position();
        int limit = buffer.limit();
        assert (pos <= limit);
        int rem = limit - pos;
        if (rem <= 0)
            return;
        if (buffer instanceof DirectBuffer) {
            adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem);
        } else if (buffer.hasArray()) {
            adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem);
        } else {
            byte[] b = new byte[Math.min(buffer.remaining(), 4096)];
            while (buffer.hasRemaining()) {
                int length = Math.min(buffer.remaining(), b.length);
                buffer.get(b, 0, length);
                update(b, 0, length);
            }
        }
        buffer.position(limit);
    }

    
Resets the checksum to initial value.
/**
     * Resets the checksum to initial value.
     */
    @Override
    public void reset() {
        adler = 1;
    }

    
Returns the checksum value.
/**
     * Returns the checksum value.
     */
    @Override
    public long getValue() {
        return (long)adler & 0xffffffffL;
    }

    private static native int update(int adler, int b);

    @HotSpotIntrinsicCandidate
    private static native int updateBytes(int adler, byte[] b, int off,
                                          int len);
    @HotSpotIntrinsicCandidate
    private static native int updateByteBuffer(int adler, long addr,
                                               int off, int len);

    static {
        ZipUtils.loadLibrary();
    }
}