/*
 * 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.nifi.provenance.journaling.journals;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;

import org.apache.nifi.stream.io.StreamUtils;

public class StandardJournalMagicHeader {
    private static final byte[] MAGIC_HEADER = "NiFiProvJournal_1".getBytes();
    
    /**
     * Writes the magic header to the output stream
     * @param out
     * @throws IOException
     */
    static void write(final OutputStream out) throws IOException {
        out.write(MAGIC_HEADER);
    }
    
    /**
     * Verifies that the magic header is present on the InputStream
     * @param in
     * @throws IOException
     */
    static void read(final InputStream in) throws IOException {
        final byte[] magicHeaderBuffer = new byte[MAGIC_HEADER.length];
        StreamUtils.fillBuffer(in, magicHeaderBuffer);
        if ( !Arrays.equals(MAGIC_HEADER, magicHeaderBuffer) ) {
            throw new IOException("File is not a Journaling Provenance Repository journal file");
        }
    }
}