/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.sshd.common.random;

import java.security.SecureRandom;

import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.Random;

/**
 * A <code>Random</code> implementation using the built-in {@link SecureRandom} PRNG. 
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public class JceRandom implements Random {

    /**
     * Named factory for the BouncyCastle <code>Random</code>
     */
    public static class Factory implements NamedFactory<Random> {

        public String getName() {
            return "default";
        }

        public Random create() {
            return new JceRandom();
        }

    }

    private byte[] tmp = new byte[16];
    private SecureRandom random = null;

    public JceRandom() {
      random = new SecureRandom();
    }

    public synchronized void fill(byte[] foo, int start, int len) {
        if (start == 0 && len == foo.length) {
            random.nextBytes(foo);
        } else {
            synchronized (this) {
                if (len > tmp.length) {
                      tmp = new byte[len];
                }
                random.nextBytes(tmp);
                System.arraycopy(tmp, 0, foo, start, len);
            }
        }
    }

    public synchronized int random(int n) {
        return random.nextInt(n);
    }

}
