poi/src/main/java/org/apache/poi/hssf/record/RecordFactory.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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package org.apache.poi.hssf.record;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Title:  Record Factory<p>
 * Description:  Takes a stream and outputs an array of Record objects.
 *
 * @see org.apache.poi.hssf.eventmodel.EventRecordFactory
 */
public final class RecordFactory {
    private static final int NUM_RECORDS = 512;

    private RecordFactory() {}

    /**
     * Debug / diagnosis method<p>
     *
     * Gets the POI implementation class for a given {@code sid}.  Only a subset of the BIFF
     * records are actually interpreted by POI.  A few others are known but not interpreted
     * (see {@link UnknownRecord#getBiffName(int)}).
     *
     * @param sid the record sid
     *
     * @return the POI implementation class for the specified record {@code sid}.
     * {@code null} if the specified record is not interpreted by POI.
     */
    public static Class<? extends Record> getRecordClass(int sid) {
        return HSSFRecordTypes.forSID(sid).clazz;
    }

    /**
     * create a record, if there are MUL records than multiple records
     * are returned digested into the non-mul form.
     *
     * @param in the RecordInputStream to read from
     * @return the extracted records
     */
    public static org.apache.poi.hssf.record.Record [] createRecord(RecordInputStream in) {
        Record record = createSingleRecord(in);
        if (record instanceof DBCellRecord) {
            // Not needed by POI.  Regenerated from scratch by POI when spreadsheet is written
            return new Record[] { null, };
        }
        if (record instanceof RKRecord) {
            return new Record[] { convertToNumberRecord((RKRecord) record), };
        }
        if (record instanceof MulRKRecord) {
            return convertRKRecords((MulRKRecord)record);
        }
        return new Record[] { record, };
    }

    public static org.apache.poi.hssf.record.Record createSingleRecord(RecordInputStream in) {
        HSSFRecordTypes rec = HSSFRecordTypes.forSID(in.getSid());
        if (!rec.isParseable()) {
            rec = HSSFRecordTypes.UNKNOWN;
        }
        return rec.recordConstructor.apply(in);
    }

    /**
     * RK record is a slightly smaller alternative to NumberRecord
     * POI likes NumberRecord better
     *
     * @param rk the RK record to convert
     * @return the NumberRecord
     */
    public static NumberRecord convertToNumberRecord(RKRecord rk) {
        NumberRecord num = new NumberRecord();

        num.setColumn(rk.getColumn());
        num.setRow(rk.getRow());
        num.setXFIndex(rk.getXFIndex());
        num.setValue(rk.getRKNumber());
        return num;
    }

    /**
     * Converts a {@link MulRKRecord} into an equivalent array of {@link NumberRecord NumberRecords}
     *
     * @param mrk the MulRKRecord to convert
     * @return the equivalent array of {@link NumberRecord NumberRecords}
     */
    public static NumberRecord[] convertRKRecords(MulRKRecord mrk) {
        NumberRecord[] mulRecs = new NumberRecord[mrk.getNumColumns()];
        for (int k = 0; k < mrk.getNumColumns(); k++) {
            NumberRecord nr = new NumberRecord();

            nr.setColumn((short) (k + mrk.getFirstColumn()));
            nr.setRow(mrk.getRow());
            nr.setXFIndex(mrk.getXFAt(k));
            nr.setValue(mrk.getRKNumberAt(k));
            mulRecs[k] = nr;
        }
        return mulRecs;
    }

    /**
     * Converts a {@link MulBlankRecord} into an equivalent array of {@link BlankRecord BlankRecords}
     *
     * @param mbk the MulBlankRecord to convert
     * @return the equivalent array of {@link BlankRecord BlankRecords}
     */
    public static BlankRecord[] convertBlankRecords(MulBlankRecord mbk) {
        BlankRecord[] mulRecs = new BlankRecord[mbk.getNumColumns()];
        for (int k = 0; k < mbk.getNumColumns(); k++) {
            BlankRecord br = new BlankRecord();

            br.setColumn((short) (k + mbk.getFirstColumn()));
            br.setRow(mbk.getRow());
            br.setXFIndex(mbk.getXFAt(k));
            mulRecs[k] = br;
        }
        return mulRecs;
    }

    /**
     * @return an array of all the SIDS for all known records
     */
    public static short[] getAllKnownRecordSIDs() {
        int[] intSid = Arrays.stream(HSSFRecordTypes.values()).mapToInt(HSSFRecordTypes::getSid).toArray();
        short[] shortSid = new short[intSid.length];
        for (int i=0; i<intSid.length; i++) {
            shortSid[i] = (short)intSid[i];
        }
        return shortSid;
    }

    /**
     * Create an array of records from an input stream
     *
     * @param in the InputStream from which the records will be obtained
     *
     * @return an array of Records created from the InputStream
     *
     * @exception org.apache.poi.util.RecordFormatException on error processing the InputStream
     */
    public static List<org.apache.poi.hssf.record.Record> createRecords(InputStream in) throws org.apache.poi.util.RecordFormatException {

        List<org.apache.poi.hssf.record.Record> records = new ArrayList<>(NUM_RECORDS);

        RecordFactoryInputStream recStream = new RecordFactoryInputStream(in, true);

        Record record;
        while ((record = recStream.nextRecord())!=null) {
            records.add(record);
        }

        return records;
    }
}