/*
 * Copyright (c) 2002, 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.provider;

import java.io.IOException;

/**
 * Seed generator for Windows making use of MS CryptoAPI using native code.
 *
 */
class NativeSeedGenerator extends SeedGenerator {

    /**
     * Create a new CryptoAPI seed generator instances.
     *
     * @exception IOException if CryptoAPI seeds are not available
     * on this platform.
     */
    NativeSeedGenerator() throws IOException {
        super();
        // try generating two random bytes to see if CAPI is available
        if (!nativeGenerateSeed(new byte[2])) {
            throw new IOException("Required native CryptoAPI features not "
                                  + " available on this machine");
        }
    }

    /**
     * Native method to do the actual work.
     */
    private static native boolean nativeGenerateSeed(byte[] result);

    void getSeedBytes(byte[] result) {
        // fill array as a side effect
        if (nativeGenerateSeed(result) == false) {
            // should never happen if constructor check succeeds
            throw new InternalError
                            ("Unexpected CryptoAPI failure generating seed");
        }
    }

    byte getSeedByte() {
        byte[] b = new byte[1];
        getSeedBytes(b);
        return b[0];
    }
}
