org.apache.poi.xssf.binary.XSSFBParser Maven / Gradle / Ivy

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   this work for additional information regarding copyright ownership.
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       http://www.apache.org/licenses/LICENSE-2.0

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package org.apache.poi.xssf.binary;

import java.io.IOException;
import java.io.InputStream;

import com.zaxxer.sparsebits.SparseBitSet;
import org.apache.poi.util.IOUtils;
import org.apache.poi.util.Internal;
import org.apache.poi.util.LittleEndianInputStream;

/**
 * Experimental parser for Microsoft's ooxml xlsb format.
 * Not thread safe, obviously.  Need to create a new one
 * for each thread.
 *
 * @since 3.16-beta3
 */
@Internal
public abstract class XSSFBParser {

    //arbitrarily selected; may need to increase
    private static final int DEFAULT_MAX_RECORD_LENGTH = 1_000_000;
    private static int MAX_RECORD_LENGTH = DEFAULT_MAX_RECORD_LENGTH;

    private final LittleEndianInputStream is;
    private final SparseBitSet records;

    /**
     * @param length the max record length allowed for XSSFBParser
     */
    public static void setMaxRecordLength(int length) {
        MAX_RECORD_LENGTH = length;
    }

    /**
     * @return the max record length allowed for XSSFBParser
     */
    public static int getMaxRecordLength() {
        return MAX_RECORD_LENGTH;
    }

    public XSSFBParser(InputStream is) {
        this.is = new LittleEndianInputStream(is);
        records = null;
    }

    /**
     *
     * @param is inputStream
     * @param bitSet call {@link #handleRecord(int, byte[])} only on those records in this bitSet
     */
    protected XSSFBParser(InputStream is, SparseBitSet bitSet) {
        this.is = new LittleEndianInputStream(is);
        records = bitSet;
    }

    public void parse() throws IOException {

        while (true) {
            int bInt = is.read();
            if (bInt == -1) {
                return;
            }
            readNext((byte) bInt);
        }
    }

    private void readNext(byte b1) throws IOException {
        int recordId = 0;

        //if highest bit == 1
        if ((b1 >> 7 & 1) == 1) {
            byte b2 = is.readByte();
            b1 &= ~(1<<7); //unset highest bit
            b2 &= ~(1<<7); //unset highest bit (if it exists?)
            recordId = ((int)b2 << 7)+(int)b1;
        } else {
            recordId = (int)b1;
        }

        long recordLength = 0;
        int i = 0;
        boolean halt = false;
        while (i < 4 && ! halt) {
            byte b = is.readByte();
            halt = (b >> 7 & 1) == 0; //if highest bit !=1 then continue
            b &= ~(1<<7);
            recordLength += (int)b << (i*7); //multiply by 128^i
            i++;

        }
        if (records == null || records.get(recordId)) {
            byte[] buff = IOUtils.safelyAllocate(recordLength, MAX_RECORD_LENGTH);
            is.readFully(buff);
            handleRecord(recordId, buff);
        } else {
            long length = IOUtils.skipFully(is, recordLength);
            if (length != recordLength) {
                throw new XSSFBParseException("End of file reached before expected.\t"+
                "Tried to skip "+recordLength + ", but only skipped "+length);
            }
        }
    }

    //It hurts, hurts, hurts to create a new byte array for every record.
    //However, on a large Excel spreadsheet, this parser was 1/3 faster than
    //the ooxml sax parser (5 seconds for xssfb and 7.5 seconds for xssf.
    //The code is far cleaner to have the parser read all
    //of the data rather than having every component promise that it will read
    //the correct amount.
    abstract public void handleRecord(int recordType, byte[] data) throws XSSFBParseException;

}