poi/src/java/org/apache/poi/hssf/record/ObjRecord.java

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   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
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       http://www.apache.org/licenses/LICENSE-2.0

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   distributed under the License is distributed on an "AS IS" BASIS,
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   See the License for the specific language governing permissions and
   limitations under the License.
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package org.apache.poi.hssf.record;

import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.poi.util.HexDump;
import org.apache.poi.util.LittleEndian;
import org.apache.poi.util.LittleEndianByteArrayOutputStream;
import org.apache.poi.util.LittleEndianInputStream;

/**
 * OBJRECORD (0x005D)<p/>
 * 
 * The obj record is used to hold various graphic objects and controls.
 *
 * @author Glen Stampoultzis (glens at apache.org)
 */
public final class ObjRecord extends Record {
	public final static short sid = 0x005D;

	private static final int NORMAL_PAD_ALIGNMENT = 2;
	private static int MAX_PAD_ALIGNMENT = 4;
	
	private List<SubRecord> subrecords;
	/** used when POI has no idea what is going on */
	private final byte[] _uninterpretedData;
	/**
	 * Excel seems to tolerate padding to quad or double byte length
	 */
	private boolean _isPaddedToQuadByteMultiple;

	//00000000 15 00 12 00 01 00 01 00 11 60 00 00 00 00 00 0D .........`......
	//00000010 26 01 00 00 00 00 00 00 00 00                   &.........


	public ObjRecord() {
		subrecords = new ArrayList<SubRecord>(2);
		// TODO - ensure 2 sub-records (ftCmo 15h, and ftEnd 00h) are always created
		_uninterpretedData = null;
	}

	public ObjRecord(RecordInputStream in) {
		// TODO - problems with OBJ sub-records stream
		// MS spec says first sub-record is always CommonObjectDataSubRecord,
		// and last is
		// always EndSubRecord. OOO spec does not mention ObjRecord(0x005D).
		// Existing POI test data seems to violate that rule. Some test data
		// seems to contain
		// garbage, and a crash is only averted by stopping at what looks like
		// the 'EndSubRecord'

		// Check if this can be continued, if so then the
		// following wont work properly
		byte[] subRecordData = in.readRemainder();
		if (LittleEndian.getUShort(subRecordData, 0) != CommonObjectDataSubRecord.sid) {
			// seems to occur in just one junit on "OddStyleRecord.xls" (file created by CrystalReports)
			// Excel tolerates the funny ObjRecord, and replaces it with a corrected version
			// The exact logic/reasoning is not yet understood
			_uninterpretedData = subRecordData;
			subrecords = null;
			return;
		}

        //YK: files produced by OO violate the condition below
        /*
        if (subRecordData.length % 2 != 0) {
			String msg = "Unexpected length of subRecordData : " + HexDump.toHex(subRecordData);
			throw new RecordFormatException(msg);
		}
        */

		subrecords = new ArrayList<SubRecord>();
		ByteArrayInputStream bais = new ByteArrayInputStream(subRecordData);
		LittleEndianInputStream subRecStream = new LittleEndianInputStream(bais);
		CommonObjectDataSubRecord cmo = (CommonObjectDataSubRecord)SubRecord.createSubRecord(subRecStream, 0);
        subrecords.add(cmo);
        while (true) {
			SubRecord subRecord = SubRecord.createSubRecord(subRecStream, cmo.getObjectType());
			subrecords.add(subRecord);
			if (subRecord.isTerminating()) {
				break;
			}
		}
		int nRemainingBytes = bais.available();
		if (nRemainingBytes > 0) {
			// At present (Oct-2008), most unit test samples have (subRecordData.length % 2 == 0)
			_isPaddedToQuadByteMultiple = subRecordData.length % MAX_PAD_ALIGNMENT == 0;
			if (nRemainingBytes >= (_isPaddedToQuadByteMultiple ? MAX_PAD_ALIGNMENT : NORMAL_PAD_ALIGNMENT)) {
				if (!canPaddingBeDiscarded(subRecordData, nRemainingBytes)) {
					String msg = "Leftover " + nRemainingBytes 
						+ " bytes in subrecord data " + HexDump.toHex(subRecordData);
					throw new RecordFormatException(msg);
				}
				_isPaddedToQuadByteMultiple = false;
			}

        } else {
			_isPaddedToQuadByteMultiple = false;
		}
		_uninterpretedData = null;
	}

	/**
	 * Some XLS files have ObjRecords with nearly 8Kb of excessive padding. These were probably
	 * written by a version of POI (around 3.1) which incorrectly interpreted the second short of
	 * the ftLbs subrecord (0x1FEE) as a length, and read that many bytes as padding (other bugs
	 * helped allow this to occur).
	 * 
	 * Excel reads files with this excessive padding OK, truncating the over-sized ObjRecord back
	 * to the its proper size.  POI does the same.
	 */
	private static boolean canPaddingBeDiscarded(byte[] data, int nRemainingBytes) {
        // make sure none of the padding looks important
		for(int i=data.length-nRemainingBytes; i<data.length; i++) {
			if (data[i] != 0x00) {
				return false;
			}
		}
		return true;
	}

	public String toString() {
		StringBuffer sb = new StringBuffer();

		sb.append("[OBJ]\n");
		for (int i = 0; i < subrecords.size(); i++) {
			SubRecord record = subrecords.get(i);
			sb.append("SUBRECORD: ").append(record.toString());
		}
		sb.append("[/OBJ]\n");
		return sb.toString();
	}
	
	public int getRecordSize() {
		if (_uninterpretedData != null) {
			return _uninterpretedData.length + 4;
		}
		int size = 0;
		for (int i=subrecords.size()-1; i>=0; i--) {
			SubRecord record = subrecords.get(i);
			size += record.getDataSize()+4;
		}
		if (_isPaddedToQuadByteMultiple) {
			while (size % MAX_PAD_ALIGNMENT != 0) {
				size++;
			}
		} else {
			while (size % NORMAL_PAD_ALIGNMENT != 0) {
				size++;
			}
		}
		return size + 4;
	}

	public int serialize(int offset, byte[] data) {
		int recSize = getRecordSize();
		int dataSize = recSize - 4;
		LittleEndianByteArrayOutputStream out = new LittleEndianByteArrayOutputStream(data, offset, recSize);

		out.writeShort(sid);
		out.writeShort(dataSize);

		if (_uninterpretedData == null) {

			for (int i = 0; i < subrecords.size(); i++) {
				SubRecord record = subrecords.get(i);
				record.serialize(out);
			}
			int expectedEndIx = offset+dataSize;
			// padding
			while (out.getWriteIndex() < expectedEndIx) {
				out.writeByte(0);
			}
		} else {
			out.write(_uninterpretedData);
		}
		return recSize;
	}

	public short getSid() {
		return sid;
	}

	public List<SubRecord> getSubRecords() {
		return subrecords;
	}

	public void clearSubRecords() {
		subrecords.clear();
	}

	public void addSubRecord(int index, SubRecord element) {
		subrecords.add(index, element);
	}

	public boolean addSubRecord(SubRecord o) {
		return subrecords.add(o);
	}

	public Object clone() {
		ObjRecord rec = new ObjRecord();

		for (int i = 0; i < subrecords.size(); i++) {
			SubRecord record = subrecords.get(i);
			rec.addSubRecord((SubRecord) record.clone());
		}
		return rec;
	}
}