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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.8 and up. The APIs are designed primarily to be used in conjunction with the BC LTS provider but may also be used with other providers providing cryptographic services.

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package org.bouncycastle.cms;

import java.io.IOException;
import java.io.OutputStream;

import org.bouncycastle.asn1.ASN1Integer;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.BERSequenceGenerator;
import org.bouncycastle.asn1.cms.CMSObjectIdentifiers;
import org.bouncycastle.operator.OutputCompressor;

/**
 * General class for generating a compressed CMS message stream.
 * 
 * A simple example of usage.
 * 
 *  *      CMSCompressedDataStreamGenerator gen = new CMSCompressedDataStreamGenerator();
 *      
 *      OutputStream cOut = gen.open(outputStream, new ZlibCompressor());
 *      
 *      cOut.write(data);
 *      
 *      cOut.close();
 * 
 */
public class CMSCompressedDataStreamGenerator
{
    public static final String ZLIB = CMSObjectIdentifiers.zlibCompress.getId();

    private int _bufferSize;
    
    /**
     * base constructor
     */
    public CMSCompressedDataStreamGenerator()
    {
    }

    /**
     * Set the underlying string size for encapsulated data
     *
     * @param bufferSize length of octet strings to buffer the data.
     */
    public void setBufferSize(
        int bufferSize)
    {
        _bufferSize = bufferSize;
    }

    /**
     * Open a compressing output stream with the PKCS#7 content type OID of "data".
     *
     * @param out the stream to encode to.
     * @param compressor the type of compressor to use.
     * @return an output stream to write the data be compressed to.
     * @throws IOException
     */
    public OutputStream open(
        OutputStream out,
        OutputCompressor compressor)
        throws IOException
    {
        return open(CMSObjectIdentifiers.data, out, compressor);
    }

    /**
     * Open a compressing output stream.
     *
     * @param contentOID the content type OID.
     * @param out the stream to encode to.
     * @param compressor the type of compressor to use.
     * @return an output stream to write the data be compressed to.
     * @throws IOException
     */
    public OutputStream open(
        ASN1ObjectIdentifier contentOID,
        OutputStream out,
        OutputCompressor compressor)
        throws IOException
    {
        BERSequenceGenerator sGen = new BERSequenceGenerator(out);

        sGen.addObject(CMSObjectIdentifiers.compressedData);

        //
        // Compressed Data
        //
        BERSequenceGenerator cGen = new BERSequenceGenerator(sGen.getRawOutputStream(), 0, true);

        cGen.addObject(new ASN1Integer(0));

        //
        // AlgorithmIdentifier
        //
        cGen.addObject(compressor.getAlgorithmIdentifier());

        //
        // Encapsulated ContentInfo
        //
        BERSequenceGenerator eiGen = new BERSequenceGenerator(cGen.getRawOutputStream());

        eiGen.addObject(contentOID);

        OutputStream octetStream = CMSUtils.createBEROctetOutputStream(
            eiGen.getRawOutputStream(), 0, true, _bufferSize);

        return new CmsCompressedOutputStream(
            compressor.getOutputStream(octetStream), sGen, cGen, eiGen);
    }

    private static class CmsCompressedOutputStream
        extends OutputStream
    {
        private OutputStream _out;
        private BERSequenceGenerator _sGen;
        private BERSequenceGenerator _cGen;
        private BERSequenceGenerator _eiGen;
        
        CmsCompressedOutputStream(
            OutputStream out,
            BERSequenceGenerator sGen,
            BERSequenceGenerator cGen,
            BERSequenceGenerator eiGen)
        {
            _out = out;
            _sGen = sGen;
            _cGen = cGen;
            _eiGen = eiGen;
        }
        
        public void write(
            int b)
            throws IOException
        {
            _out.write(b); 
        }
        
        
        public void write(
            byte[] bytes,
            int    off,
            int    len)
            throws IOException
        {
            _out.write(bytes, off, len);
        }
        
        public void write(
            byte[] bytes)
            throws IOException
        {
            _out.write(bytes);
        }
        
        public void close()
            throws IOException
        {
            _out.close();
            _eiGen.close();
            _cGen.close();
            _sGen.close();
        }
    }
}