/*
 * Copyright (C)2009 - SSHJ Contributors
 *
 * Licensed 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 net.schmizz.sshj.transport.random;

import java.security.SecureRandom;

/** A {@link Random} implementation using the built-in {@link SecureRandom} PRNG. */
public class JCERandom
        implements Random {

    /** Named factory for the JCE {@link Random} */
    public static class Factory
            implements net.schmizz.sshj.common.Factory.Named<Random> {

        @Override
        public Random create() {
            return new JCERandom();
        }

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

    }

    private byte[] tmp = new byte[16];
    private final SecureRandom random = new SecureRandom();

    /**
     * Fill the given byte-array with random bytes from this PRNG.
     *
     * @param foo   the byte-array
     * @param start the offset to start at
     * @param len   the number of bytes to fill
     */
    @Override
    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);
            }
    }

}
