org.ttzero.excel.entity.e3.BOFParser Maven / Gradle / Ivy

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/*
 * Copyright (c) 2019-2020, [email protected] All Rights Reserved.
 *
 * Licensed 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.
 */

package org.ttzero.excel.entity.e3;

import org.ttzero.excel.entity.e3.enums.BIFFVerEnum;
import org.ttzero.excel.entity.e3.enums.StreamTypeEnum;
import org.ttzero.excel.reader.ExcelReadException;

/**
 * 5.8 BOF – Beginning of File
 * 
 * The BOF record is the first record of any kind of stream or sub-stream:
 * 

 *     The Worksheet Stream (➜4.1.1) and the Chart Stream (➜7.1.1)
 *     All sub-streams in the Workbook Stream (the Sheet Sub-stream
 *     and the Workbook Globals Sub-stream, ➜4.1.2,
 *     and the Chart Sub-stream, ➜7.1.2)
 *     The Workspace Stream
 * 
 * A BOF record will never be encrypted, regardless of
 * its type and position in the stream.
 * 
 * If a BIFF8 version of Excel (Excel 8.0 and newer) writes
 * a BIFF5 workbook, it writes a wrong BIFF version in BOF
 * records of the Sheet Sub-streams. Only the leading BOF
 * record of the Workbook Globals Sub-stream contains the
 * correct value and should be used to determine the BIFF
 * version for the entire stream.
 *
 * @author guanquan.wang at 2019-01-31 15:19
 */
public class BOFParser {

    public static BOF get(Block block) {
        // Mark the ready flag
        block.ready();
        // BIFF version (always 0600H for BIFF8)
        short version = block.nextShort();
        if (version != 0x0600) {
            // version error.
            throw new ExcelReadException("Only support BIFF8.");
        }
        // Type of the following data
        short type = block.nextShort();
        StreamTypeEnum streamType = StreamTypeEnum.of(type);
        if (streamType == null) {
            throw new ExcelReadException("Unknown stream type." + type);
        }
        // Build identifier, must not be 0
        short identifier = block.nextShort();
        if (identifier == 0) {
            throw new ExcelReadException("Build identifier must not be zero.");
        }
        // Build year, must not be 0
        short year = block.nextShort();
        if (year == 0) {
            throw new ExcelReadException("Build year must not be zero.");
        }
        // File history flags
        int history = block.nextInt();
        // Lowest Excel version that can read all records in this file
        int supportLowestVersion = block.nextInt();

        BIFFVerEnum lowVer = null;
        for (BIFFVerEnum ver : BIFFVerEnum.values()) {
            if (ver.getValue() > supportLowestVersion) {
                lowVer = ver;
                break;
            }
        }

        // Block end of read
        block.commit();

        BOF bof = new BOF();
        bof.version = version;
        bof.type = streamType;
        bof.identifier = identifier;
        bof.year = year;
        bof.supportLowestVersion = lowVer;
        bof.history = history;

        return bof;
    }

    public static short getId() {
        return ParserIdentifier.BOF;
    }

    public static class BOF {
        short version;
        StreamTypeEnum type;
        short identifier;
        short year;
        int history;
        BIFFVerEnum supportLowestVersion;

        @Override
        public String toString() {
            return
                "Version: " + version +
                    " Type: " + type +
                    " Identifier: " + identifier +
                    " Build year: " + year +
                    " History: " + history +
                    " SupportLowestVersion: " + supportLowestVersion;
        }
    }
}