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

/* ====================================================================
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   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.
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package org.apache.poi.hssf.record;

import java.util.ArrayList;
import java.util.Map;
import java.util.function.Supplier;
import java.util.stream.Stream;

import org.apache.poi.common.usermodel.GenericRecord;
import org.apache.poi.hssf.record.cont.ContinuableRecord;
import org.apache.poi.hssf.record.cont.ContinuableRecordOutput;
import org.apache.poi.util.GenericRecordUtil;
import org.apache.poi.util.LittleEndianOutput;

/**
 * Extended Static String Table (0x00FF)<p>
 * 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.
 */
public final class ExtSSTRecord extends ContinuableRecord {
    public static final 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;


    public static final class InfoSubRecord implements GenericRecord {
    	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;

        /**
         * Creates new ExtSSTInfoSubRecord
         *
         * @param streamPos stream pointer to the SST record
         * @param bucketSstOffset ... don't really understand this yet
         */
        public InfoSubRecord(int streamPos, int bucketSstOffset) {
            field_1_stream_pos        = streamPos;
            field_2_bucket_sst_offset = bucketSstOffset;
        }

        public InfoSubRecord(InfoSubRecord other) {
            field_1_stream_pos        = other.field_1_stream_pos;
            field_2_bucket_sst_offset = other.field_2_bucket_sst_offset;
            field_3_zero              = other.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);
        }

        @Override
        public Map<String, Supplier<?>> getGenericProperties() {
            return GenericRecordUtil.getGenericProperties(
                "streamPos", this::getStreamPos,
                "bucketSSTOffset", this::getBucketSSTOffset
            );
        }
    }


    private short _stringsPerBucket;
    private InfoSubRecord[] _sstInfos;


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

    public ExtSSTRecord(ExtSSTRecord other) {
        _stringsPerBucket = other._stringsPerBucket;
        _sstInfos = (other._sstInfos == null) ? null
            : Stream.of(other._sstInfos).map(InfoSubRecord::new).toArray(InfoSubRecord[]::new);
    }

    public ExtSSTRecord(RecordInputStream in) {
        _stringsPerBucket = in.readShort();

        int nInfos = in.remaining() / InfoSubRecord.ENCODED_SIZE;
        ArrayList<InfoSubRecord> lst = new ArrayList<>(nInfos);

        while (in.available() > 0) {
            InfoSubRecord info = new InfoSubRecord(in);
            lst.add(info);

            if(in.available() == 0 && in.hasNextRecord() && in.getNextSid() == ContinueRecord.sid) {
                in.nextRecord();
            }
        }
        _sstInfos = lst.toArray(new InfoSubRecord[0]);
    }

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

    public void serialize(ContinuableRecordOutput out) {
        out.writeShort(_stringsPerBucket);
        for (InfoSubRecord sstInfo : _sstInfos) {
            sstInfo.serialize(out);
        }
    }

    int getDataSize() {
    	return 2 + InfoSubRecord.ENCODED_SIZE*_sstInfos.length;
    }

    InfoSubRecord[] getInfoSubRecords() {
        return _sstInfos;
    }

    public static 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;
    }

    /**
     * Given a number of strings (in the sst), returns the size of the extsst record
     *
     * @param numStrings the number of strings
     *
     * @return the size of the extsst record
     */
    public static int getRecordSizeForStrings(int numStrings) {
        return 4 + 2 + getNumberOfInfoRecsForStrings(numStrings) * 8;
    }

    public short getSid() {
        return sid;
    }

    public void setBucketOffsets(int[] bucketAbsoluteOffsets, int[] bucketRelativeOffsets) {
    	// TODO - replace no-arg constructor with this logic
        _sstInfos = new InfoSubRecord[bucketAbsoluteOffsets.length];
        for (int i = 0; i < bucketAbsoluteOffsets.length; i++) {
            _sstInfos[i] = new InfoSubRecord(bucketAbsoluteOffsets[i], bucketRelativeOffsets[i]);
        }
    }

    @Override
    public ExtSSTRecord copy() {
        return new ExtSSTRecord(this);
    }

    @Override
    public HSSFRecordTypes getGenericRecordType() {
        return HSSFRecordTypes.EXT_SST;
    }

    @Override
    public Map<String, Supplier<?>> getGenericProperties() {
        return GenericRecordUtil.getGenericProperties(
            "dataSize", this::getDataSize,
            "infoSubRecords", this::getInfoSubRecords
        );
    }
}