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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.xssf.streaming;

import org.apache.poi.xssf.streaming.Zip64Impl.Entry;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.*;

/**
 * ZIP64 OutputStream implementation compatible with MS Excel.
 * Drop in replacement for `java.util.ZipOutputStream`.
 *
 * For more information see https://github.com/rzymek/opczip
 *
 * @author Krzysztof Rzymkowski
 */
class OpcOutputStream extends DeflaterOutputStream {

    private final Zip64Impl spec;
    private final List entries = new ArrayList<>();
    private final CRC32 crc = new CRC32();
    private Entry current;
    private int written = 0;
    private boolean finished = false;

    /**
     * Creates ZIP64 output stream
     *
     * @param out target stream to write compressed data to
     */
    public OpcOutputStream(OutputStream out) {
        super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true));
        this.spec = new Zip64Impl(out);
    }

    /**
     * @see Deflater#setLevel(int)
     */
    public void setLevel(int level) {
        super.def.setLevel(level);
    }

    /**
     * @see ZipOutputStream#putNextEntry(ZipEntry)
     */
    public void putNextEntry(String name) throws IOException {
        if (current != null) {
            closeEntry();
        }
        current = new Entry(name);
        current.offset = written;
        written += spec.writeLFH(current);
        entries.add(current);
    }

    /**
     * @see ZipOutputStream#closeEntry()
     */
    public void closeEntry() throws IOException {
        if (current == null) {
            throw new IllegalStateException("not current zip current");
        }
        def.finish();
        while (!def.finished()) {
            deflate();
        }

        current.size = def.getBytesRead();
        current.compressedSize = Math.toIntExact(def.getBytesWritten());
        current.crc = crc.getValue();

        written += current.compressedSize;
        written += spec.writeDAT(current);
        current = null;
        def.reset();
        crc.reset();
    }


    /**
     * @see ZipOutputStream#finish()
     */
    @Override
    public void finish() throws IOException {
        if(finished){
            return;
        }
        if(current != null) {
            closeEntry();
        }
        int offset = written;
        for (Entry entry : entries) {
            written += spec.writeCEN(entry);
        }
        written += spec.writeEND(entries.size(), offset, written - offset);
        finished = true;
    }

    /**
     * @see ZipOutputStream#write(byte[], int, int)
     */
    @Override
    public synchronized void write(byte[] b, int off, int len) throws IOException {
        if (off < 0 || len < 0 || off > b.length - len) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }
        super.write(b, off, len);
        crc.update(b, off, len);
    }

    /**
     * @see ZipOutputStream#close()
     */
    @Override
    public void close() throws IOException {
        finish();
        out.close();
    }
}