Creating gzip file using jzlib

Question

I am trying to create a gzip file using jzlib which is an open source. The Java GZIPOutputStream is a bit problemtic, the CPU got higher and never released.

The problem with the JZlib that the file cannot be open by winrar, it seems like missing header. Any idea how to solve it?

Answer 1

JZlib does not support the Gzip data format (RFC 1952), only zlib (RFC 1950) and plain deflate (RFC 1951).

These formats differ only by the header and a checksum at the end:

• gzip is deflate with a header containing file meta information and a CRC32 checksum at the end,
• zlib is deflate with a tiny compression method header and an Adler32 checksum at the end.

Thus you can write your own wrapper around jzlib's deflate compressing stream (using nowrap=true to avoid the zlib header), adding your metadata and the CRC32 checksum. Or you take a look if someone else already did this. (Looks like bestsss' answer does about this.)

Answer 2

This is skimmed version of the class; Hopefully it can serve.
This version still retains proper flush() implementation.

The original version has optimizations for in-mem process (hopefully it still works after cutting some part). The source contains CRC32 from Apache and proper notice to the License.

package bestsss.util;


import java.io.EOFException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.Deflater;

import com.jcraft.jzlib.JZlib;
import com.jcraft.jzlib.ZStream;

import java.util.zip.Checksum;
/**
 * GZipOutputStream replacement, faster than optimized (not any more here)
 * @author XXX XXX
 *
 */
public class JGZipOutputStream extends OutputStream{
  /*
   * GZIP header magic number.
   */
  private final static int GZIP_MAGIC = 0x8b1f;

  /*
   * Trailer size in bytes.
   *
   */
  private final static int TRAILER_SIZE = 8;

    private OutputStream out;
    private byte[] buf;
    private CRC32 crc;
    private ZStream zip;
    private boolean closed;
    private boolean finished;


    public JGZipOutputStream(OutputStream out, byte[] buf) throws IOException{
        this.out = out;
        this.buf = buf;

        if (buf==null){
                throw new NullPointerException("buf");          
        }
        this.crc = new CRC32();     
        zip = new ZStream();
        initZStream(zip);


        writeHeader();
    }

    protected int initZStream(ZStream zip) {
        return zip.deflateInit(JZlib.Z_BEST_COMPRESSION-1, true);
    }

  /*
   * Writes GZIP member header.
   */

  private final static byte[] header = {
      (byte) GZIP_MAGIC,                // Magic number (short)
      (byte)(GZIP_MAGIC >> 8),          // Magic number (short)
      Deflater.DEFLATED,                // Compression method (CM)
      0,                                // Flags (FLG)
      0,                                // Modification time MTIME (int)
      0,                                // Modification time MTIME (int)
      0,                                // Modification time MTIME (int)
      0,                                // Modification time MTIME (int)
      0,                                // Extra flags (XFLG)
      0                                 // Operating system (OS)
  };

  private void writeHeader() throws IOException {
    out.write(header);
  }

  public void write(byte[] buf, int off, int len) throws IOException{
    if (off < 0 || len < 0 || off > buf.length - len) 
        throw new ArrayIndexOutOfBoundsException();
      if (finished)
        throw new EOFException();
    zip.next_in = buf;
    zip.next_in_index = off;
    zip.avail_in = len;

    deflate(JZlib.Z_NO_FLUSH);

    crc.update(buf, off, len);
  }

    private void deflate(int flushMode) throws IOException {
        final boolean force =  JZlib.Z_NO_FLUSH!=flushMode;
        while (zip.avail_in>0 || force){
        byte[] b = this.buf;
        int remaining;
        {
            zip.next_out_index = 0;
            remaining = b.length;           
        }                   

        zip.next_out = b;
        zip.avail_out =remaining;
        deflate(zip, this.finished?JZlib.Z_FINISH:flushMode);
        int len = remaining - zip.avail_out;

            out.write(this.buf, 0, len);

        if (force)
            return;
    }
    }

    private static void deflate(ZStream z, int flushMode) throws IOException {
        int err=z.deflate(flushMode); 
    if (err!=JZlib.Z_OK){
        boolean finish = JZlib.Z_FINISH==flushMode;
        if (finish && err == JZlib.Z_STREAM_END)
            return;

        throw new IOException(String.format("Deflate exception:[%s]  msg: %s", err, z.msg));
    }
    }

    public void flush() throws IOException {
        deflate(JZlib.Z_SYNC_FLUSH);
    }

    public void fullFlush() throws IOException {
        deflate(JZlib.Z_FULL_FLUSH);
    }

    public void finish() throws IOException {
        if (!finished) {
            finished = true;
            zip.avail_in=0;              

            do{
                deflate(JZlib.Z_FINISH);
            }while(zip.avail_out==0);               

            int err = zip.deflateEnd();     
            if (JZlib.Z_OK !=   err){
                throw new IOException(String.format("Deflate exception, finish error:[%s]  msg: %s", err, zip.msg));
            }

            writeTrailer(buf, 0);
            out.write(buf, 0 , TRAILER_SIZE);

        }
    }

  /*
   * Writes GZIP member trailer to a byte array, starting at a given
   * offset.
   */
  private void writeTrailer(byte[] buf, int offset) throws IOException {
      writeInt((int)crc.getValue(), buf, offset); // CRC-32 of uncompr. data
      writeInt((int)zip.total_in, buf, offset + 4); // Number of uncompr. bytes
  }

  /*
   * Writes integer in Intel byte order to a byte array, starting at a
   * given offset.
   */
  private void writeInt(int i, byte[] buf, int offset) throws IOException {
      writeShort(i & 0xffff, buf, offset);
      writeShort((i >> 16) & 0xffff, buf, offset + 2);
  }

  /*
   * Writes short integer in Intel byte order to a byte array, starting
   * at a given offset
   */
  private void writeShort(int s, byte[] buf, int offset) throws IOException {
      buf[offset] = (byte)(s & 0xff);
      buf[offset + 1] = (byte)((s >> 8) & 0xff);
  }

  public void close() throws IOException {
    if (!closed) {
        finish();
        out.close();
        closed = true;
    }
  }

  public void reset(){
    zip.free();
    initZStream(zip);
    crc.reset();
    this.finished = false;
    this.closed = false;
  }

    @Override
    public void write(int b) throws IOException {           
        write(new byte[]{(byte) b});
    }



    /**
     * 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.
     */

    //from
    //https://issues.apache.org/jira/secure/attachment/12413610/PureJavaCrc32NewLoop.java



    /**
     * A pure-java implementation of the CRC32 checksum that uses
     * the same polynomial as the built-in native CRC32.
     *
     * This is to avoid the JNI overhead for certain uses of Checksumming
     * where many small pieces of data are checksummed in succession.
     *
     * The current version is ~10x to 1.8x as fast as Sun's native
     * java.util.zip.CRC32 in Java 1.6
     *
     * @see java.util.zip.CRC32
     */
    public static class CRC32 implements Checksum {

      /** the current CRC value, bit-flipped */
      int crc;

      /** {@inheritDoc} */
      public CRC32() {
        reset();
      }

      /** {@inheritDoc} */
      public long getValue() {
        return (~crc) & 0xffffffffL;
      }

      /** {@inheritDoc} */
      public void reset() {
        crc = ~0;
      }

      /** {@inheritDoc} */
      public void update(byte[] b, int off, final int len) {
        for(final int end = off + (len & ~3); off < end; ) {
          crc = T4[((crc) ^ b[off]) & 0xFF] 
                ^ T3[((crc >>> 8) ^ b[off+1]) & 0xFF] 
                ^ T2[((crc >>> 16) ^ b[off+2]) & 0xFF] 
                ^ T1[((crc >>> 24) ^ b[off+3]) & 0xFF];
          off +=4;
        }

        for(final int end = off + (len & 3); off < end; ) {
          crc = (crc >>> 8) ^ T1[(crc ^ b[off++]) & 0xff];
        }
      }

      /** {@inheritDoc} */
      final public void update(int b) {
        crc = (crc >>> 8) ^ T1[(crc ^ b) & 0xff];
      }

      /**
       * Pre-generated lookup tables. For the code to generate these tables
       * please see HDFS-297.
       */

      /** T1[x] is ~CRC(x) */
      private static final int[] T1 = new int[] {
        0x0, 0x77073096, 0xee0e612c, 0x990951ba,
        0x76dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
        0xedb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
        0x9b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
        0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
        0x1adad47d, 0x6ffffde4eb, 0xf4d4b551, 0x83d385c7,
        0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
        0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
        0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
        0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
        0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
        0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
        0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
        0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
        0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
        0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
        0x76dc4190, 0x1db7106, 0x98d220bc, 0xefd5102a,
        0x71b18589, 0x6b6b51f, 0x9fbfe4a5, 0xe8b8d433,
        0x7807c9a2, 0xf00f934, 0x9609a88e, 0xe10e9818,
        0x7f6a0dbb, 0x86d3d2d, 0x91646c97, 0xe6635c01,
        0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
        0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
        0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
        0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
        0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
        0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
        0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
        0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
        0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
        0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
        0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
        0xedb88320, 0x9abfb3b6, 0x3b6e20c, 0x74b1d29a,
        0xead54739, 0x9dd277af, 0x4db2615, 0x73dc1683,
        0xe3630b12, 0x94643b84, 0xd6d6a3e, 0x7a6a5aa8,
        0xe40ecf0b, 0x9309ff9d, 0xa00ae27, 0x7d079eb1,
        0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
        0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
        0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
        0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
        0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
        0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
        0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
        0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
        0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
        0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
        0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
        0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
        0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x26d930a,
        0x9c0906a9, 0xeb0e363f, 0x72076785, 0x5005713,
        0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0xcb61b38,
        0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0xbdbdf21,
        0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
        0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
        0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
        0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
        0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
        0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
        0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
        0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
        0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
        0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
        0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
      };

      /** T2[x] is ~CRC(x followed by one 0x00 byte) */
      private static final int[] T2 = new int[] {
        0x0, 0x191b3141, 0x32366282, 0x2b2d53c3,
        0x646cc504, 0x7d77f445, 0x565aa786, 0x4f4196c7,
        0xc8d98a08, 0xd1c2bb49, 0xfaefe88a, 0xe3f4d9cb,
        0xacb54f0c, 0xb5ae7e4d, 0x9e832d8e, 0x87981ccf,
        0x4ac21251, 0x53d92310, 0x78f470d3, 0x61ef4192,
        0x2eaed755, 0x37b5e614, 0x1c98b5d7, 0x5838496,
        0x821b9859, 0x9b00a918, 0xb02dfadb, 0xa936cb9a,
        0xe6775d5d, 0xff6c6c1c, 0xd4413fdf, 0xcd5a0e9e,
        0x958424a2, 0x8c9f15e3, 0xa7b24620, 0xbea97761,
        0xf1e8e1a6, 0xe8f3d0e7, 0xc3de8324, 0xdac5b265,
        0x5d5daeaa, 0x44469feb, 0x6f6bcc28, 0x7670fd69,
        0x39316bae, 0x202a5aef, 0xb07092c, 0x121c386d,
        0xdf4636f3, 0xc65d07b2, 0xed705471, 0xf46b6530,
        0xbb2af3f7, 0xa231c2b6, 0x891c9175, 0x9007a034,
        0x179fbcfb, 0xe848dba, 0x25a9de79, 0x3cb2ef38,
        0x73f379ff, 0x6ae848be, 0x41c51b7d, 0x58de2a3c,
        0xf0794f05, 0xe9627e44, 0xc24f2d87, 0xdb541cc6,
        0x94158a01, 0x8d0ebb40, 0xa623e883, 0xbf38d9c2,
        0x38a0c50d, 0x21bbf44c, 0xa96a78f, 0x138d96ce,
        0x5ccc0009, 0x45d73148, 0x6efa628b, 0x77e153ca,
        0xbabb5d54, 0xa3a06c15, 0x888d3fd6, 0x91960e97,
        0xded79850, 0xc7cca911, 0xece1fad2, 0xf5facb93,
        0x7262d75c, 0x6b79e61d, 0x4054b5de, 0x594f849f,
        0x160e1258, 0xf152319, 0x243870da, 0x3d23419b,
        0x65fd6ba7, 0x7ce65ae6, 0x57cb0925, 0x4ed03864,
        0x191aea3, 0x188a9fe2, 0x33a7cc21, 0x2abcfd60,
        0xad24e1af, 0xb43fd0ee, 0x9f12832d, 0x8609b26c,
        0xc94824ab, 0xd05315ea, 0xfb7e4629, 0xe2657768,
        0x2f3f79f6, 0x362448b7, 0x1d091b74, 0x4122a35,
        0x4b53bcf2, 0x52488db3, 0x7965de70, 0x607eef31,
        0xe7e6f3fe, 0xfefdc2bf, 0xd5d0917c, 0xcccba03d,
        0x838a36fa, 0x9a9107bb, 0xb1bc5478, 0xa8a76539,
        0x3b83984b, 0x2298a90a, 0x9b5fac9, 0x10aecb88,
        0x5fef5d4f, 0x46f46c0e, 0x6dd93fcd, 0x74c20e8c,
        0xf35a1243, 0xea412302, 0xc16c70c1, 0xd8774180,
        0x9736d747, 0x8e2de606, 0xa500b5c5, 0xbc1b8484,
        0x71418a1a, 0x685abb5b, 0x4377e898, 0x5a6cd9d9,
        0x152d4f1e, 0xc367e5f, 0x271b2d9c, 0x3e001cdd,
        0xb9980012, 0xa0833153, 0x8bae6290, 0x92b553d1,
        0xddf4c516, 0xc4eff457, 0xefc2a794, 0xf6d996d5,
        0xae07bce9, 0xb71c8da8, 0x9c31de6b, 0x852aef2a,
        0xca6b79ed, 0xd37048ac, 0xf85d1b6f, 0xe1462a2e,
        0x66de36e1, 0x7fc507a0, 0x54e85463, 0x4df36522,
        0x2b2f3e5, 0x1ba9c2a4, 0x30849167, 0x299fa026,
        0xe4c5aeb8, 0xfdde9ff9, 0xd6f3cc3a, 0xcfe8fd7b,
        0x80a96bbc, 0x99b25afd, 0xb29f093e, 0xab84387f,
        0x2c1c24b0, 0x350715f1, 0x1e2a4632, 0x7317773,
        0x4870e1b4, 0x516bd0f5, 0x7a468336, 0x635db277,
        0xcbfad74e, 0xd2e1e60f, 0xf9ccb5cc, 0xe0d7848d,
        0xaf96124a, 0xb68d230b, 0x9da070c8, 0x84bb4189,
        0x3235d46, 0x1a386c07, 0x31153fc4, 0x280e0e85,
        0x674f9842, 0x7e54a903, 0x5579fac0, 0x4c62cb81,
        0x8138c51f, 0x9823f45e, 0xb30ea79d, 0xaa1596dc,
        0xe554001b, 0xfc4f315a, 0xd7626299, 0xce7953d8,
        0x49e14f17, 0x50fa7e56, 0x7bd72d95, 0x62cc1cd4,
        0x2d8d8a13, 0x3496bb52, 0x1fbbe891, 0x6a0d9d0,
        0x5e7ef3ec, 0x4765c2ad, 0x6c48916e, 0x7553a02f,
        0x3a1236e8, 0x230907a9, 0x824546a, 0x113f652b,
        0x96a779e4, 0x8fbc48a5, 0xa4911b66, 0xbd8a2a27,
        0xf2cbbce0, 0xebd08da1, 0xc0fdde62, 0xd9e6ef23,
        0x14bce1bd, 0xda7d0fc, 0x268a833f, 0x3f91b27e,
        0x70d024b9, 0x69cb15f8, 0x42e6463b, 0x5bfd777a,
        0xdc656bb5, 0xc57e5af4, 0xee530937, 0xf7483876,
        0xb809aeb1, 0xa1129ff0, 0x8a3fcc33, 0x9324fd72
      };

      /** T3[x] is ~CRC(x followed by two 0x00 bytes) */
      private static final int[] T3 = new int[] {
        0x0, 0x1c26a37, 0x384d46e, 0x246be59,
        0x709a8dc, 0x6cbc2eb, 0x48d7cb2, 0x54f1685,
        0xe1351b8, 0xfd13b8f, 0xd9785d6, 0xc55efe1,
        0x91af964, 0x8d89353, 0xa9e2d0a, 0xb5c473d,
        0x1c26a370, 0x1de4c947, 0x1fa2771e, 0x1e601d29,
        0x1b2f0bac, 0x1aed619b, 0x18abdfc2, 0x1969b5f5,
        0x1235f2c8, 0x13f798ff, 0x11b126a6, 0x10734c91,
        0x153c5a14, 0x14fe3023, 0x16b88e7a, 0x177ae44d,
        0x384d46e0, 0x398f2cd7, 0x3bc9928e, 0x3a0bf8b9,
        0x3f44ee3c, 0x3e86840b, 0x3cc03a52, 0x3d025065,
        0x365e1758, 0x379c7d6f, 0x35dac336, 0x3418a901,
        0x3157bf84, 0x3095d5b3, 0x32d36bea, 0x331101dd,
        0x246be590, 0x25a98fa7, 0x27ef31fe, 0x262d5bc9,
        0x23624d4c, 0x22a0277b, 0x20e69922, 0x2124f315,
        0x2a78b428, 0x2bbade1f, 0x29fc6046, 0x283e0a71,
        0x2d711cf4, 0x2cb376c3, 0x2ef5c89a, 0x2f37a2ad,
        0x709a8dc0, 0x7158e7f7, 0x731e59ae, 0x72dc3399,
        0x7793251c, 0x76514f2b, 0x7417f172, 0x75d59b45,
        0x7e89dc78, 0x7f4bb64f, 0x7d0d0816, 0x7ccf6221,
        0x798074a4, 0x78421e93, 0x7a04a0ca, 0x7bc6cafd,
        0x6cbc2eb0, 0x6d7e4487, 0x6f38fade, 0x6efa90e9,
        0x6bb5866c, 0x6a77ec5b, 0x68315202, 0x69f33835,
        0x62af7f08, 0x636d153f, 0x612bab66, 0x60e9c151,
        0x65a6d7d4, 0x6464bde3, 0x662203ba, 0x67e0698d,
        0x48d7cb20, 0x4915a117, 0x4b531f4e, 0x4a917579,
        0x4fde63fc, 0x4e1c09cb, 0x4c5ab792, 0x4d98dda5,
        0x46c49a98, 0x4706f0af, 0x45404ef6, 0x448224c1,
        0x41cd3244, 0x400f5873, 0x4249e62a, 0x438b8c1d,
        0x54f16850, 0x55330267, 0x5775bc3e, 0x56b7d609,
        0x53f8c08c, 0x523aaabb, 0x507c14e2, 0x51be7ed5,
        0x5ae239e8, 0x5b2053df, 0x5966ed86, 0x58a487b1,
        0x5deb9134, 0x5c29fb03, 0x5e6f455a, 0x5fad2f6d,
        0xe1351b80, 0xe0f771b7, 0xe2b1cfee, 0xe373a5d9,
        0xe63cb35c, 0xe7fed96b, 0xe5b86732, 0xe47a0d05,
        0xef264a38, 0xeee4200f, 0xeca29e56, 0xed60f461,
        0xe82fe2e4, 0xe9ed88d3, 0xebab368a, 0xea695cbd,
        0xfd13b8f0, 0xfcd1d2c7, 0xfe976c9e, 0xff5506a9,
        0xfa1a102c, 0xfbd87a1b, 0xf99ec442, 0xf85cae75,
        0xf300e948, 0xf2c2837f, 0xf0843d26, 0xf1465711,
        0xf4094194, 0xf5cb2ba3, 0xf78d95fa, 0xf64fffcd,
        0xd9785d60, 0xd8ba3757, 0xdafc890e, 0xdb3ee339,
        0xde71f5bc, 0xdfb39f8b, 0xddf521d2, 0xdc374be5,
        0xd76b0cd8, 0xd6a966ef, 0xd4efd8b6, 0xd52db281,
        0xd062a404, 0xd1a0ce33, 0xd3e6706a, 0xd2241a5d,
        0xc55efe10, 0xc49c9427, 0xc6da2a7e, 0xc7184049,
        0xc25756cc, 0xc3953cfb, 0xc1d382a2, 0xc011e895,
        0xcb4dafa8, 0xca8fc59f, 0xc8c97bc6, 0xc90b11f1,
        0xcc440774, 0xcd866d43, 0xcfc0d31a, 0xce02b92d,
        0x91af9640, 0x906dfc77, 0x922b422e, 0x93e92819,
        0x96a63e9c, 0x976454ab, 0x9522eaf2, 0x94e080c5,
        0x9fbcc7f8, 0x9e7eadcf, 0x9c381396, 0x9dfa79a1,
        0x98b56f24, 0x99770513, 0x9b31bb4a, 0x9af3d17d,
        0x8d893530, 0x8c4b5f07, 0x8e0de15e, 0x8fcf8b69,
        0x8a809dec, 0x8b42f7db, 0x89044982, 0x88c623b5,
        0x839a6488, 0x82580ebf, 0x801eb0e6, 0x81dcdad1,
        0x8493cc54, 0x8551a663, 0x8717183a, 0x86d5720d,
        0xa9e2d0a0, 0xa820ba97, 0xaa6604ce, 0xaba46ef9,
        0xaeeb787c, 0xaf29124b, 0xad6fac12, 0xacadc625,
        0xa7f18118, 0xa633eb2f, 0xa4755576, 0xa5b73f41,
        0xa0f829c4, 0xa13a43f3, 0xa37cfdaa, 0xa2be979d,
        0xb5c473d0, 0xb40619e7, 0xb640a7be, 0xb782cd89,
        0xb2cddb0c, 0xb30fb13b, 0xb1490f62, 0xb08b6555,
        0xbbd72268, 0xba15485f, 0xb853f606, 0xb9919c31,
        0xbcde8ab4, 0xbd1ce083, 0xbf5a5eda, 0xbe9834ed
      };

      /** T4[x] is ~CRC(x followed by three 0x00 bytes) */
      private static final int[] T4 = new int[] {
        0x0, 0xb8bc6765, 0xaa09c88b, 0x12b5afee,
        0x8f629757, 0x37def032, 0x256b5fdc, 0x9dd738b9,
        0xc5b428ef, 0x7d084f8a, 0x6fbde064, 0xd7018701,
        0x4ad6bfb8, 0xf26ad8dd, 0xe0df7733, 0x58631056,
        0x5019579f, 0xe8a530fa, 0xfa109f14, 0x42acf871,
        0xdf7bc0c8, 0x67c7a7ad, 0x75720843, 0xcdce6f26,
        0x95ad7f70, 0x2d111815, 0x3fa4b7fb, 0x8718d09e,
        0x1acfe827, 0xa2738f42, 0xb0c620ac, 0x87a47c9,
        0xa032af3e, 0x188ec85b, 0xa3b67b5, 0xb28700d0,
        0x2f503869, 0x97ec5f0c, 0x8559f0e2, 0x3de59787,
        0x658687d1, 0xdd3ae0b4, 0xcf8f4f5a, 0x7733283f,
        0xeae41086, 0x525877e3, 0x40edd80d, 0xf851bf68,
        0xf02bf8a1, 0x48979fc4, 0x5a22302a, 0xe29e574f,
        0x7f496ff6, 0xc7f50893, 0xd540a77d, 0x6dfcc018,
        0x359fd04e, 0x8d23b72b, 0x9f9618c5, 0x272a7fa0,
        0xbafd4719, 0x241207c, 0x10f48f92, 0xa848e8f7,
        0x9b14583d, 0x23a83f58, 0x311d90b6, 0x89a1f7d3,
        0x1476cf6a, 0xaccaa80f, 0xbe7f07e1, 0x6c36084,
        0x5ea070d2, 0xe61c17b7, 0xf4a9b859, 0x4c15df3c,
        0xd1c2e785, 0x697e80e0, 0x7bcb2f0e, 0xc377486b,
        0xcb0d0fa2, 0x73b168c7, 0x6104c729, 0xd9b8a04c,
        0x446f98f5, 0xfcd3ff90, 0xee66507e, 0x56da371b,
        0xeb9274d, 0xb6054028, 0xa4b0efc6, 0x1c0c88a3,
        0x81dbb01a, 0x3967d77f, 0x2bd27891, 0x936e1ff4,
        0x3b26f703, 0x839a9066, 0x912f3f88, 0x299358ed,
        0xb4446054, 0xcf80731, 0x1e4da8df, 0xa6f1cfba,
        0xfe92dfec, 0x462eb889, 0x549b1767, 0xec277002,
        0x71f048bb, 0xc94c2fde, 0xdbf98030, 0x6345e755,
        0x6b3fa09c, 0xd383c7f9, 0xc1366817, 0x798a0f72,
        0xe45d37cb, 0x5ce150ae, 0x4e54ff40, 0xf6e89825,
        0xae8b8873, 0x1637ef16, 0x48240f8, 0xbc3e279d,
        0x21e91f24, 0x99557841, 0x8be0d7af, 0x335cb0ca,
        0xed59b63b, 0x55e5d15e, 0x47507eb0, 0xffec19d5,
        0x623b216c, 0xda874609, 0xc832e9e7, 0x708e8e82,
        0x28ed9ed4, 0x9051f9b1, 0x82e4565f, 0x3a58313a,
        0xa78f0983, 0x1f336ee6, 0xd86c108, 0xb53aa66d,
        0xbd40e1a4, 0x5fc86c1, 0x1749292f, 0xaff54e4a,
        0x322276f3, 0x8a9e1196, 0x982bbe78, 0x2097d91d,
        0x78f4c94b, 0xc048ae2e, 0xd2fd01c0, 0x6a4166a5,
        0xf7965e1c, 0x4f2a3979, 0x5d9f9697, 0xe523f1f2,
        0x4d6b1905, 0xf5d77e60, 0xe762d18e, 0x5fdeb6eb,
        0xc2098e52, 0x7ab5e937, 0x680046d9, 0xd0bc21bc,
        0x88df31ea, 0x3063568f, 0x22d6f961, 0x9a6a9e04,
        0x7bda6bd, 0xbf01c1d8, 0xadb46e36, 0x15080953,
        0x1d724e9a, 0xa5ce29ff, 0xb77b8611, 0xfc7e174,
        0x9210d9cd, 0x2aacbea8, 0x38191146, 0x80a57623,
        0xd8c66675, 0x607a0110, 0x72cfaefe, 0xca73c99b,
        0x57a4f122, 0xef189647, 0xfdad39a9, 0x45115ecc,
        0x764dee06, 0xcef18963, 0xdc44268d, 0x64f841e8,
        0xf92f7951, 0x41931e34, 0x5326b1da, 0xeb9ad6bf,
        0xb3f9c6e9, 0xb45a18c, 0x19f00e62, 0xa14c6907,
        0x3c9b51be, 0x842736db, 0x96929935, 0x2e2efe50,
        0x2654b999, 0x9ee8defc, 0x8c5d7112, 0x34e11677,
        0xa9362ece, 0x118a49ab, 0x33fe645, 0xbb838120,
        0xe3e09176, 0x5b5cf613, 0x49e959fd, 0xf1553e98,
        0x6c820621, 0xd43e6144, 0xc68bceaa, 0x7e37a9cf,
        0xd67f4138, 0x6ec3265d, 0x7c7689b3, 0xc4caeed6,
        0x591dd66f, 0xe1a1b10a, 0xf3141ee4, 0x4ba87981,
        0x13cb69d7, 0xab770eb2, 0xb9c2a15c, 0x17ec639,
        0x9ca9fe80, 0x241599e5, 0x36a0360b, 0x8e1c516e,
        0x866616a7, 0x3eda71c2, 0x2c6fde2c, 0x94d3b949,
        0x90481f0, 0xb1b8e695, 0xa30d497b, 0x1bb12e1e,
        0x43d23e48, 0xfb6e592d, 0xe9dbf6c3, 0x516791a6,
        0xccb0a91f, 0x740cce7a, 0x66b96194, 0xde0506f1
      };


    }

}

Answer 3

Since JZlib 1.1.0, it has supported gzip file format. Try com.jcraft.jzlib.GZIPOutputStream class