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 * 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 sun.security.provider;

import java.security.MessageDigestSpi;

import java.security.DigestException;

import java.security.ProviderException;

/**

 * Common base message digest implementation for the Sun provider.

 * It implements all the JCA methods as suitable for a Java message digest

 * implementation of an algorithm based on a compression function (as all

 * commonly used algorithms are). The individual digest subclasses only need to

 * implement the following methods:

 *

 *  . abstract void implCompress(byte[] b, int ofs);

 *  . abstract void implDigest(byte[] out, int ofs);

 *  . abstract void implReset();

 *

 * See the inline documentation for details.

 *

 * @since   1.5

 * @author  Andreas Sterbenz

 */

abstract class DigestBase extends MessageDigestSpi implements Cloneable {

    // one element byte array, temporary storage for update(byte)

    private byte[] oneByte;

    // algorithm name to use in the exception message

    private final String algorithm;

    // length of the message digest in bytes

    private final int digestLength;

    // size of the input to the compression function in bytes

    private final int blockSize;

    // buffer to store partial blocks, blockSize bytes large

    // Subclasses should not access this array directly except possibly in their

    // implDigest() method. See MD5.java as an example.

    byte[] buffer;

    // offset into buffer

    private int bufOfs;

    // number of bytes processed so far. subclasses should not modify

    // this value.

    // also used as a flag to indicate reset status

    // -1: need to call engineReset() before next call to update()

    //  0: is already reset

    long bytesProcessed;

    /**

     * Main constructor.

     */

    DigestBase(String algorithm, int digestLength, int blockSize) {

        super();

        this.algorithm = algorithm;

        this.digestLength = digestLength;

        this.blockSize = blockSize;

        buffer = new byte[blockSize];

    }

    // return digest length. See JCA doc.

    protected final int engineGetDigestLength() {

        return digestLength;

    }

    // single byte update. See JCA doc.

    protected final void engineUpdate(byte b) {

        if (oneByte == null) {

            oneByte = new byte[1];

        }

        oneByte[0] = b;

        engineUpdate(oneByte, 0, 1);

    }

    // array update. See JCA doc.

    protected final void engineUpdate(byte[] b, int ofs, int len) {

        if (len == 0) {

            return;

        }

        if ((ofs < 0) || (len < 0) || (ofs > b.length - len)) {

            throw new ArrayIndexOutOfBoundsException();

        }

        if (bytesProcessed < 0) {

            engineReset();

        }

        bytesProcessed += len;

        // if buffer is not empty, we need to fill it before proceeding

        if (bufOfs != 0) {

            int n = Math.min(len, blockSize - bufOfs);

            System.arraycopy(b, ofs, buffer, bufOfs, n);

            bufOfs += n;

            ofs += n;

            len -= n;

            if (bufOfs >= blockSize) {

                // compress completed block now

                implCompress(buffer, 0);

                bufOfs = 0;

            }

        }

        // compress complete blocks

        while (len >= blockSize) {

            implCompress(b, ofs);

            len -= blockSize;

            ofs += blockSize;

        }

        // copy remainder to buffer

        if (len > 0) {

            System.arraycopy(b, ofs, buffer, 0, len);

            bufOfs = len;

        }

    }

    // reset this object. See JCA doc.

    protected final void engineReset() {

        if (bytesProcessed == 0) {

            // already reset, ignore

            return;

        }

        implReset();

        bufOfs = 0;

        bytesProcessed = 0;

    }

    // return the digest. See JCA doc.

    protected final byte[] engineDigest() {

        byte[] b = new byte[digestLength];

        try {

            engineDigest(b, 0, b.length);

        } catch (DigestException e) {

            throw (ProviderException)

                new ProviderException("Internal error").initCause(e);

        }

        return b;

    }

    // return the digest in the specified array. See JCA doc.

    protected final int engineDigest(byte[] out, int ofs, int len)

            throws DigestException {

        if (len < digestLength) {

            throw new DigestException("Length must be at least "

                + digestLength + " for " + algorithm + "digests");

        }

        if ((ofs < 0) || (len < 0) || (ofs > out.length - len)) {

            throw new DigestException("Buffer too short to store digest");

        }

        if (bytesProcessed < 0) {

            engineReset();

        }

        implDigest(out, ofs);

        bytesProcessed = -1;

        return digestLength;

    }

    /**

     * Core compression function. Processes blockSize bytes at a time

     * and updates the state of this object.

     */

    abstract void implCompress(byte[] b, int ofs);

    /**

     * Return the digest. Subclasses do not need to reset() themselves,

     * DigestBase calls implReset() when necessary.

     */

    abstract void implDigest(byte[] out, int ofs);

    /**

     * Reset subclass specific state to their initial values. DigestBase

     * calls this method when necessary.

     */

    abstract void implReset();

    public Object clone() throws CloneNotSupportedException {

        DigestBase copy = (DigestBase) super.clone();

        copy.buffer = copy.buffer.clone();

        return copy;

    }

    // padding used for the MD5, and SHA-* message digests

    static final byte[] padding;

    static {

        // we need 128 byte padding for SHA-384/512

        // and an additional 8 bytes for the high 8 bytes of the 16

        // byte bit counter in SHA-384/512

        padding = new byte[136];

        padding[0] = (byte)0x80;

    }

}