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 * Copyright (c) 1996, 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.util.zip;

import java.nio.ByteBuffer;

/**

 * An interface representing a data checksum.

 *

 * @author David Connelly

 * @since 1.1

 */

public interface Checksum {

    /**

     * Updates the current checksum with the specified byte.

     *

     * @param b the byte to update the checksum with

     */

    public void update(int b);

    /**

     * Updates the current checksum with the specified array of bytes.

     *

     * @implSpec This default implementation is equal to calling

     * {@code update(b, 0, b.length)}.

     *

     * @param b the array of bytes to update the checksum with

     *

     * @throws NullPointerException

     *         if {@code b} is {@code null}

     *

     * @since 9

     */

    default public void update(byte[] b) {

        update(b, 0, b.length);

    }

    /**

     * Updates the current checksum with the specified array of bytes.

     *

     * @param b the byte array to update the checksum with

     * @param off the start offset of the data

     * @param len the number of bytes to use for the update

     */

    public void update(byte[] b, int off, int len);

    /**

     * Updates the current 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.

     *

     * @apiNote For best performance with DirectByteBuffer and other ByteBuffer

     * implementations without a backing array implementers of this interface

     * should override this method.

     *

     * @implSpec The default implementation has the following behavior.<br>

     * For ByteBuffers backed by an accessible byte array.

     * <pre>{@code

     * update(buffer.array(),

     *        buffer.position() + buffer.arrayOffset(),

     *        buffer.remaining());

     * }</pre>

     * For ByteBuffers not backed by an accessible byte array.

     * <pre>{@code

     * 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);

     * }

     * }</pre>

     *

     * @param buffer the ByteBuffer to update the checksum with

     *

     * @throws NullPointerException

     *         if {@code buffer} is {@code null}

     *

     * @since 9

     */

    default 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.hasArray()) {

            update(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);

    }

    /**

     * Returns the current checksum value.

     *

     * @return the current checksum value

     */

    public long getValue();

    /**

     * Resets the checksum to its initial value.

     */

    public void reset();

}