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/* GZIPOutputStream.java - Create a file in gzip format

   Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package java.util.zip;

import java.io.IOException;

import java.io.OutputStream;

/**

 * This filter stream is used to compress a stream into a "GZIP" stream.

 * The "GZIP" format is described in RFC 1952.

 *

 * @author John Leuner

 * @author Tom Tromey

 * @since JDK 1.1

 */

/* Written using on-line Java Platform 1.2 API Specification

 * and JCL book.

 * Believed complete and correct.

 */

public class GZIPOutputStream extends DeflaterOutputStream

{

  /**

   * CRC-32 value for uncompressed data

   */

  protected CRC32 crc;

  /**

   * Creates a GZIPOutputStream with the default buffer size

   *

   * @param out The stream to read data (to be compressed) from

   *

   */

  public GZIPOutputStream(OutputStream out) throws IOException

  {

    this(out, 4096);

  }

  /**

   * Creates a GZIPOutputStream with the specified buffer size

   *

   * @param out The stream to read compressed data from

   * @param size Size of the buffer to use

   */

  public GZIPOutputStream(OutputStream out, int size) throws IOException

  {

    super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size);

    crc = new CRC32();

    int mod_time = (int) (System.currentTimeMillis() / 1000L);

    byte[] gzipHeader =

      {

        /* The two magic bytes */

        (byte) GZIPInputStream.GZIP_MAGIC,

        (byte) (GZIPInputStream.GZIP_MAGIC >> 8),

        /* The compression type */

        (byte) Deflater.DEFLATED,

        /* The flags (not set) */

        0,

        /* The modification time */

        (byte) mod_time, (byte) (mod_time >> 8),

        (byte) (mod_time >> 16), (byte) (mod_time >> 24),

        /* The extra flags */

        0,

        /* The OS type (unknown) */

        (byte) 255

      };

    out.write(gzipHeader);

    //    System.err.println("wrote GZIP header (" + gzipHeader.length + " bytes )");

  }

  public synchronized void write(byte[] buf, int off, int len)

    throws IOException

  {

    super.write(buf, off, len);

    crc.update(buf, off, len);

  }

  /**

   * Writes remaining compressed output data to the output stream

   * and closes it.

   */

  public void close() throws IOException

  {

    finish();

    out.close();

  }

  public void finish() throws IOException

  {

    super.finish();

    int totalin = def.getTotalIn();

    int crcval = (int) (crc.getValue() & 0xffffffff);

    //    System.err.println("CRC val is " + Integer.toHexString( crcval )                     + " and length " + Integer.toHexString(totalin));

    byte[] gzipFooter =

      {

        (byte) crcval, (byte) (crcval >> 8),

        (byte) (crcval >> 16), (byte) (crcval >> 24),

        (byte) totalin, (byte) (totalin >> 8),

        (byte) (totalin >> 16), (byte) (totalin >> 24)

      };

    out.write(gzipFooter);

  //    System.err.println("wrote GZIP trailer (" + gzipFooter.length + " bytes )");

  }

}