poi/src/main/java/org/apache/poi/hssf/record/StandardRecord.java

/* ====================================================================
   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.poi.hssf.record;

import java.io.IOException;

import org.apache.poi.util.LittleEndianByteArrayOutputStream;
import org.apache.poi.util.LittleEndianOutput;

/**
 * Subclasses of this class (the majority of BIFF records) are non-continuable.
 * This allows for some simplification of serialization logic
 */
public abstract class StandardRecord extends Record {
    protected abstract int getDataSize();

    protected StandardRecord() {}

    protected StandardRecord(StandardRecord other) {}

    @Override
    public final int getRecordSize() {
        return 4 + getDataSize();
    }

    /**
     * Write the data content of this BIFF record including the sid and record
     * length.
     * <p>
     * The subclass must write the exact number of bytes as reported by
     * {@link org.apache.poi.hssf.record.Record#getRecordSize()}}
     */
    @Override
    public final int serialize(int offset, byte[] data) {
        int dataSize = getDataSize();
        int recSize = 4 + dataSize;
        try (LittleEndianByteArrayOutputStream out =
                new LittleEndianByteArrayOutputStream(data, offset, recSize)) {
            out.writeShort(getSid());
            out.writeShort(dataSize);
            serialize(out);
            if (out.getWriteIndex() - offset != recSize) {
                throw new IllegalStateException("Error in serialization of (" + getClass().getName() + "): "
                        + "Incorrect number of bytes written - expected " + recSize + " but got "
                        + (out.getWriteIndex() - offset));
            }
        } catch (IOException ioe) {
            // should never happen in practice
            throw new IllegalStateException(ioe);
        }
        return recSize;
    }

    /**
     * Write the data content of this BIFF record. The 'ushort sid' and 'ushort
     * size' header fields have already been written by the superclass.
     * <p>
     * The number of bytes written must equal the record size reported by
     * {@link org.apache.poi.hssf.record.Record#getRecordSize()}} minus four (
     * record header consisting of a 'ushort sid' and 'ushort reclength' has
     * already been written by their superclass).
     *
     * @param out
     *            the output object
     */
    protected abstract void serialize(LittleEndianOutput out);

    public abstract StandardRecord copy();
}