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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

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/* ====================================================================
   Licensed to the Apache Software Foundation (ASF) under one or more
   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.
==================================================================== */

package org.apache.poi.poifs.crypt;

import java.io.IOException;
import java.nio.charset.StandardCharsets;

import org.apache.poi.EncryptedDocumentException;
import org.apache.poi.poifs.crypt.standard.EncryptionRecord;
import org.apache.poi.poifs.filesystem.DirectoryEntry;
import org.apache.poi.poifs.filesystem.DocumentEntry;
import org.apache.poi.poifs.filesystem.POIFSWriterEvent;
import org.apache.poi.poifs.filesystem.POIFSWriterListener;
import org.apache.poi.util.IOUtils;
import org.apache.poi.util.LittleEndianByteArrayOutputStream;
import org.apache.poi.util.LittleEndianConsts;
import org.apache.poi.util.LittleEndianInput;
import org.apache.poi.util.LittleEndianOutput;
import org.apache.poi.util.StringUtil;

public class DataSpaceMapUtils {

    //arbitrarily selected; may need to increase
    private static final int MAX_RECORD_LENGTH = 100_000;

    public static void addDefaultDataSpace(DirectoryEntry dir) throws IOException {
        DataSpaceMapEntry dsme = new DataSpaceMapEntry(
                new int[]{ 0 }
              , new String[]{ Decryptor.DEFAULT_POIFS_ENTRY }
              , "StrongEncryptionDataSpace"
          );
          DataSpaceMap dsm = new DataSpaceMap(new DataSpaceMapEntry[]{dsme});
          createEncryptionEntry(dir, "\u0006DataSpaces/DataSpaceMap", dsm);

          DataSpaceDefinition dsd = new DataSpaceDefinition(new String[]{ "StrongEncryptionTransform" });
          createEncryptionEntry(dir, "\u0006DataSpaces/DataSpaceInfo/StrongEncryptionDataSpace", dsd);

          TransformInfoHeader tih = new TransformInfoHeader(
                1
              , "{FF9A3F03-56EF-4613-BDD5-5A41C1D07246}"
              , "Microsoft.Container.EncryptionTransform"
              , 1, 0, 1, 0, 1, 0
          );
          IRMDSTransformInfo irm = new IRMDSTransformInfo(tih, 0, null);
          createEncryptionEntry(dir, "\u0006DataSpaces/TransformInfo/StrongEncryptionTransform/\u0006Primary", irm);
          
          DataSpaceVersionInfo dsvi = new DataSpaceVersionInfo("Microsoft.Container.DataSpaces", 1, 0, 1, 0, 1, 0);
          createEncryptionEntry(dir, "\u0006DataSpaces/Version", dsvi);
    }
    
    public static DocumentEntry createEncryptionEntry(DirectoryEntry dir, String path, EncryptionRecord out) throws IOException {
        String[] parts = path.split("/");
        for (int i=0; i 0) {
            for (int i=0; i<(4-scratchedBytes); i++) {
                is.readByte();
            }
        }

        return new String(data, 0, data.length, StandardCharsets.UTF_8);
    }
    
    public static void writeUtf8LPP4(LittleEndianOutput os, String str) {
        if (str == null || str.isEmpty()) {
            os.writeInt(str == null ? 0 : 4);
            os.writeInt(0);
        } else {
            byte[] buf = str.getBytes(StandardCharsets.UTF_8);
            os.writeInt(buf.length);
            os.write(buf);
            int scratchBytes = buf.length%4;
            if (scratchBytes > 0) {
                for (int i=0; i<(4-scratchBytes); i++) {
                    os.writeByte(0);
                }
            }
        }        
    }

}