GZipOutputStream.cs


1:	// GzipOutputStream.cs
2:	// Copyright (C) 2001 Mike Krueger
3:	//
4:	// This file was translated from java, it was part of the GNU Classpath
5:	// Copyright (C) 2001 Free Software Foundation, Inc.
6:	//
7:	// This program is free software; you can redistribute it and/or
8:	// modify it under the terms of the GNU General Public License
9:	// as published by the Free Software Foundation; either version 2
10:	// of the License, or (at your option) any later version.
11:	//
12:	// This program is distributed in the hope that it will be useful,
13:	// but WITHOUT ANY WARRANTY; without even the implied warranty of
14:	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15:	// GNU General Public License for more details.
16:	//
17:	// You should have received a copy of the GNU General Public License
18:	// along with this program; if not, write to the Free Software
19:	// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
20:	//
21:	// Linking this library statically or dynamically with other modules is
22:	// making a combined work based on this library. Thus, the terms and
23:	// conditions of the GNU General Public License cover the whole
24:	// combination.
25:	//
26:	// As a special exception, the copyright holders of this library give you
27:	// permission to link this library with independent modules to produce an
28:	// executable, regardless of the license terms of these independent
29:	// modules, and to copy and distribute the resulting executable under
30:	// terms of your choice, provided that you also meet, for each linked
31:	// independent module, the terms and conditions of the license of that
32:	// module. An independent module is a module which is not derived from
33:	// or based on this library. If you modify this library, you may extend
34:	// this exception to your version of the library, but you are not
35:	// obligated to do so. If you do not wish to do so, delete this
36:	// exception statement from your version.
37:
38:	using System;
39:	using System.IO;
40:
41:	using ICSharpCode.SharpZipLib.Checksums;
42:	using ICSharpCode.SharpZipLib.Zip.Compression;
43:	using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
44:
45:	namespace ICSharpCode.SharpZipLib.GZip {
46:
47:	/// <summary>
48:	/// This filter stream is used to compress a stream into a "GZIP" stream.
49:	/// The "GZIP" format is described in RFC 1952.
50:	///
51:	/// author of the original java version : John Leuner
52:	/// </summary>
53:	/// <example> This sample shows how to gzip a file
54:	/// <code>
55:	/// using System;
56:	/// using System.IO;
57:	///
58:	/// using NZlib.GZip;
59:	///
60:	/// class MainClass
61:	/// {
62:	/// public static void Main(string[] args)
63:	/// {
64:	/// Stream s = new GZipOutputStream(File.Create(args[0] + ".gz"));
65:	/// FileStream fs = File.OpenRead(args[0]);
66:	/// byte[] writeData = new byte[fs.Length];
67:	/// fs.Read(writeData, 0, (int)fs.Length);
68:	/// s.Write(writeData, 0, writeData.Length);
69:	/// s.Close();
70:	/// }
71:	/// }
72:	/// </code>
73:	/// </example>
74:	public class GZipOutputStream : DeflaterOutputStream
75:	{
76:	//Variables
77:
78:	/// <summary>
79:	/// CRC-32 value for uncompressed data
80:	/// </summary>
81:	protected Crc32 crc = new Crc32();
82:
83:	// Constructors
84:
85:	/// <summary>
86:	/// Creates a GzipOutputStream with the default buffer size
87:	/// </summary>
88:	/// <param name="baseOutputStream">
89:	/// The stream to read data (to be compressed) from
90:	/// </param>
91:	public GZipOutputStream(Stream baseOutputStream) : this(baseOutputStream, 4096)
92:	{
93:	}
94:
95:	/// <summary>
96:	/// Creates a GZIPOutputStream with the specified buffer size
97:	/// </summary>
98:	/// <param name="baseOutputStream">
99:	/// The stream to read data (to be compressed) from
100:	/// </param>
101:	/// <param name="size">
102:	/// Size of the buffer to use
103:	/// </param>
104:	public GZipOutputStream(Stream baseOutputStream, int size) : base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size)
105:	{
106:	// TODO : find out correctness, orgininally this was : (int) (System.currentTimeMillis() / 1000L);
107:	int mod_time = (int)(DateTime.Now.Ticks / 10000L); // Ticks give back 100ns intervals
108:	byte[] gzipHeader = {
109:	/* The two magic bytes */
110:	(byte) (GZipConstants.GZIP_MAGIC >> 8), (byte) GZipConstants.GZIP_MAGIC,
111:
112:	/* The compression type */
113:	(byte) Deflater.DEFLATED,
114:
115:	/* The flags (not set) */
116:	0,
117:
118:	/* The modification time */
119:	(byte) mod_time, (byte) (mod_time >> 8),
120:	(byte) (mod_time >> 16), (byte) (mod_time >> 24),
121:
122:	/* The extra flags */
123:	0,
124:
125:	/* The OS type (unknown) */
126:	(byte) 255
127:	};
128:
129:	baseOutputStream.Write(gzipHeader, 0, gzipHeader.Length);
130:	// System.err.println("wrote GZIP header (" + gzipHeader.length + " bytes )");
131:	}
132:
133:	public override void Write(byte[] buf, int off, int len)
134:	{
135:	crc.Update(buf, off, len);
136:	base.Write(buf, off, len);
137:	}
138:
139:	/// <summary>
140:	/// Writes remaining compressed output data to the output stream
141:	/// and closes it.
142:	/// </summary>
143:	public override void Close()
144:	{
145:	Finish();
146:	baseOutputStream.Close();
147:	}
148:
149:	public override void Finish()
150:	{
151:	base.Finish();
152:
153:	int totalin = def.TotalIn;
154:	int crcval = (int) (crc.Value & 0xffffffff);
155:
156:	// System.err.println("CRC val is " + Integer.toHexString( crcval ) + " and length " + Integer.toHexString(totalin));
157:
158:	byte[] gzipFooter = {
159:	(byte) crcval, (byte) (crcval >> 8),
160:	(byte) (crcval >> 16), (byte) (crcval >> 24),
161:
162:	(byte) totalin, (byte) (totalin >> 8),
163:	(byte) (totalin >> 16), (byte) (totalin >> 24)
164:	};
165:
166:	baseOutputStream.Write(gzipFooter, 0, gzipFooter.Length);
167:	// System.err.println("wrote GZIP trailer (" + gzipFooter.length + " bytes )");
168:	}
169:	}
170:	}