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// GzipOutputStream.cs
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program 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
// of the License, or (at your option) any later version.
//
// This program 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 this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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.
using System;
using System.IO;
using ICSharpCode.SharpZipLib.Checksums;
using ICSharpCode.SharpZipLib.Zip.Compression;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
namespace ICSharpCode.SharpZipLib.GZip
{
/// <summary>
/// This filter stream is used to compress a stream into a "GZIP" stream.
/// The "GZIP" format is described in RFC 1952.
///
/// author of the original java version : John Leuner
/// </summary>
/// <example> This sample shows how to gzip a file
/// <code>
/// using System;
/// using System.IO;
///
/// using ICSharpCode.SharpZipLib.GZip; // -jr- corrected
///
/// class MainClass
/// {
/// public static void Main(string[] args)
/// {
/// Stream s = new GZipOutputStream(File.Create(args[0] + ".gz"));
/// FileStream fs = File.OpenRead(args[0]);
/// byte[] writeData = new byte[fs.Length];
/// fs.Read(writeData, 0, (int)fs.Length);
/// s.Write(writeData, 0, writeData.Length);
/// s.Close();
/// }
/// }
/// </code>
/// </example>
public class GZipOutputStream : DeflaterOutputStream
{
//Variables
/// <summary>
/// CRC-32 value for uncompressed data
/// </summary>
protected Crc32 crc = new Crc32();
// Constructors
/// <summary>
/// Creates a GzipOutputStream with the default buffer size
/// </summary>
/// <param name="baseOutputStream">
/// The stream to read data (to be compressed) from
/// </param>
public GZipOutputStream(Stream baseOutputStream) : this(baseOutputStream, 4096)
{
}
/// <summary>
/// Creates a GZIPOutputStream with the specified buffer size
/// </summary>
/// <param name="baseOutputStream">
/// The stream to read data (to be compressed) from
/// </param>
/// <param name="size">
/// Size of the buffer to use
/// </param>
public GZipOutputStream(Stream baseOutputStream, int size) : base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size)
{
WriteHeader();
// System.err.println("wrote GZIP header (" + gzipHeader.length + " bytes )");
}
void WriteHeader()
{
int mod_time = (int)(DateTime.Now.Ticks / 10000L); // Ticks give back 100ns intervals
byte[] gzipHeader = {
/* The two magic bytes */
(byte) (GZipConstants.GZIP_MAGIC >> 8), (byte) GZipConstants.GZIP_MAGIC,
/* 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
};
baseOutputStream.Write(gzipHeader, 0, gzipHeader.Length);
}
public override void Write(byte[] buf, int off, int len)
{
crc.Update(buf, off, len);
base.Write(buf, off, len);
}
/// <summary>
/// Writes remaining compressed output data to the output stream
/// and closes it.
/// </summary>
public override void Close()
{
Finish();
baseOutputStream.Close();
}
public override void Finish()
{
base.Finish();
int totalin = def.TotalIn;
int crcval = (int) (crc.Value & 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)
};
baseOutputStream.Write(gzipFooter, 0, gzipFooter.Length);
// System.err.println("wrote GZIP trailer (" + gzipFooter.length + " bytes )");
}
}
}
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