ExtSSTRecord.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

   Unless required by applicable law or agreed to in writing, software
   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
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package org.apache.poi.hssf.record;

import org.apache.poi.util.LittleEndianOutput;

/**
 * Title:        Extended Static String Table (0x00FF)<p/>
 * Description: This record is used for a quick lookup into the SST record. This
 *              record breaks the SST table into a set of buckets. The offsets
 *              to these buckets within the SST record are kept as well as the
 *              position relative to the start of the SST record.
 * REFERENCE:  PG 313 Microsoft Excel 97 Developer's Kit (ISBN: 1-57231-498-2)<P>
 * @author Andrew C. Oliver (acoliver at apache dot org)
 * @author Jason Height (jheight at apache dot org)
 */
public final class ExtSSTRecord extends StandardRecord {
    public final static short sid = 0x00FF;
    public static final int DEFAULT_BUCKET_SIZE = 8;
    //Can't seem to find this documented but from the biffviewer it is clear that
    //Excel only records the indexes for the first 128 buckets.
    public static final int MAX_BUCKETS = 128;
    
    
    private static final class InfoSubRecord {
    	public static final int ENCODED_SIZE = 8;
        private int field_1_stream_pos;          // stream pointer to the SST record
        private int field_2_bucket_sst_offset;   // don't really understand this yet.
        /** unused - supposed to be zero */
        private short field_3_zero;


        public InfoSubRecord(RecordInputStream in)
        {
            field_1_stream_pos        = in.readInt();
            field_2_bucket_sst_offset = in.readShort();
            field_3_zero              = in.readShort();
        }

        public int getStreamPos() {
            return field_1_stream_pos;
        }

        public int getBucketSSTOffset() {
            return field_2_bucket_sst_offset;
        }

        public void serialize(LittleEndianOutput out) {
            out.writeInt(field_1_stream_pos);
            out.writeShort(field_2_bucket_sst_offset);
            out.writeShort(field_3_zero);
        }
    }
    
    
    private short _stringsPerBucket;
    private InfoSubRecord[] _sstInfos;


    public ExtSSTRecord() {
    	_stringsPerBucket = DEFAULT_BUCKET_SIZE;
        _sstInfos = new InfoSubRecord[0];
    }

    public ExtSSTRecord(RecordInputStream in) { // NO_UCD
        _stringsPerBucket = in.readShort();
        int nInfos = in.remaining() / InfoSubRecord.ENCODED_SIZE;
        _sstInfos = new InfoSubRecord[nInfos];
        for (int i = 0; i < _sstInfos.length; i++) {
            _sstInfos[i] = new InfoSubRecord(in);
        }
    }

    public void setNumStringsPerBucket(short numStrings) {
        _stringsPerBucket = numStrings;
    }

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

        buffer.append("[EXTSST]\n");
        buffer.append("    .dsst           = ")
            .append(Integer.toHexString(_stringsPerBucket))
            .append("\n");
        buffer.append("    .numInfoRecords = ").append(_sstInfos.length)
            .append("\n");
        for (int k = 0; k < _sstInfos.length; k++)
        {
            buffer.append("    .inforecord     = ").append(k).append("\n");
            buffer.append("    .streampos      = ")
                .append(Integer
                .toHexString(_sstInfos[k].getStreamPos())).append("\n");
            buffer.append("    .sstoffset      = ")
                .append(Integer
                .toHexString(_sstInfos[k].getBucketSSTOffset()))
                    .append("\n");
        }
        buffer.append("[/EXTSST]\n");
        return buffer.toString();
    }

    public void serialize(LittleEndianOutput out) {
        out.writeShort(_stringsPerBucket);
        for (int k = 0; k < _sstInfos.length; k++) {
            _sstInfos[k].serialize(out);
        }
    }
    protected int getDataSize() {
    	return 2 + InfoSubRecord.ENCODED_SIZE*_sstInfos.length;
    }

    public static final int getNumberOfInfoRecsForStrings(int numStrings) {
      int infoRecs = (numStrings / DEFAULT_BUCKET_SIZE);
      if ((numStrings % DEFAULT_BUCKET_SIZE) != 0)
        infoRecs ++;
      //Excel seems to max out after 128 info records.
      //This isn't really documented anywhere...
      if (infoRecs > MAX_BUCKETS)
        infoRecs = MAX_BUCKETS;
      return infoRecs;
    }


    public short getSid() {
        return sid;
    }

}