/*

 * Copyright (c) 2005, 2013, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.security.mscapi;

import java.security.ProviderException;

import java.security.SecureRandomSpi;

/**

 * Native PRNG implementation for Windows using the Microsoft Crypto API.

 *

 * @since 1.6

 */

public final class PRNG extends SecureRandomSpi

    implements java.io.Serializable {

    private static final long serialVersionUID = 4129268715132691532L;

    /*

     * The CryptGenRandom function fills a buffer with cryptographically random

     * bytes.

     */

    private static native byte[] generateSeed(int length, byte[] seed);

    /**

     * Creates a random number generator.

     */

    public PRNG() {

    }

    /**

     * Reseeds this random object. The given seed supplements, rather than

     * replaces, the existing seed. Thus, repeated calls are guaranteed

     * never to reduce randomness.

     *

     * @param seed the seed.

     */

    @Override

    protected void engineSetSeed(byte[] seed) {

        if (seed != null) {

            generateSeed(-1, seed);

        }

    }

    /**

     * Generates a user-specified number of random bytes.

     *

     * @param bytes the array to be filled in with random bytes.

     */

    @Override

    protected void engineNextBytes(byte[] bytes) {

        if (bytes != null) {

            if (generateSeed(0, bytes) == null) {

                throw new ProviderException("Error generating random bytes");

            }

        }

    }

    /**

     * Returns the given number of seed bytes.  This call may be used to

     * seed other random number generators.

     *

     * @param numBytes the number of seed bytes to generate.

     *

     * @return the seed bytes.

     */

    @Override

    protected byte[] engineGenerateSeed(int numBytes) {

        byte[] seed = generateSeed(numBytes, null);

        if (seed == null) {

            throw new ProviderException("Error generating seed bytes");

        }

        return seed;

    }

}