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view GZip/GzipOutputStream.cs @ 10:627dcbca86fc default tip
* Update standard .csproj with MonoDevelop-initiated cleanup
* Add Mono for Android version of .csproj file
author | IBBoard <dev@ibboard.co.uk> |
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date | Sat, 14 Jul 2012 15:25:26 +0100 |
parents | 94e25b786321 |
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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; /// using ICSharpCode.SharpZipLib.Core; /// /// class MainClass /// { /// public static void Main(string[] args) /// { /// using (Stream s = new GZipOutputStream(File.Create(args[0] + ".gz"))) /// using (FileStream fs = File.OpenRead(args[0])) { /// byte[] writeData = new byte[4096]; /// Streamutils.Copy(s, fs, writeData); /// } /// } /// } /// } /// </code> /// </example> public class GZipOutputStream : DeflaterOutputStream { enum OutputState { Header, Footer, Finished, Closed, }; #region Instance Fields /// <summary> /// CRC-32 value for uncompressed data /// </summary> protected Crc32 crc = new Crc32(); OutputState state_ = OutputState.Header; #endregion #region 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) { } #endregion #region Public API /// <summary> /// Sets the active compression level (1-9). The new level will be activated /// immediately. /// </summary> /// <param name="level">The compression level to set.</param> /// <exception cref="ArgumentOutOfRangeException"> /// Level specified is not supported. /// </exception> /// <see cref="Deflater"/> public void SetLevel(int level) { if (level < Deflater.BEST_SPEED) { throw new ArgumentOutOfRangeException("level"); } deflater_.SetLevel(level); } /// <summary> /// Get the current compression level. /// </summary> /// <returns>The current compression level.</returns> public int GetLevel() { return deflater_.GetLevel(); } #endregion #region Stream overrides /// <summary> /// Write given buffer to output updating crc /// </summary> /// <param name="buffer">Buffer to write</param> /// <param name="offset">Offset of first byte in buf to write</param> /// <param name="count">Number of bytes to write</param> public override void Write(byte[] buffer, int offset, int count) { if ( state_ == OutputState.Header ) { WriteHeader(); } if( state_!=OutputState.Footer ) { throw new InvalidOperationException("Write not permitted in current state"); } crc.Update(buffer, offset, count); base.Write(buffer, offset, count); } /// <summary> /// Writes remaining compressed output data to the output stream /// and closes it. /// </summary> public override void Close() { try { Finish(); } finally { if ( state_ != OutputState.Closed ) { state_ = OutputState.Closed; if( IsStreamOwner ) { baseOutputStream_.Close(); } } } } #endregion #region DeflaterOutputStream overrides /// <summary> /// Finish compression and write any footer information required to stream /// </summary> public override void Finish() { // If no data has been written a header should be added. if ( state_ == OutputState.Header ) { WriteHeader(); } if( state_ == OutputState.Footer) { state_=OutputState.Finished; base.Finish(); uint totalin=(uint)(deflater_.TotalIn&0xffffffff); uint crcval=(uint)(crc.Value&0xffffffff); byte[] gzipFooter; unchecked { gzipFooter=new byte[] { (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); } } #endregion #region Support Routines void WriteHeader() { if ( state_ == OutputState.Header ) { state_=OutputState.Footer; int mod_time = (int)((DateTime.Now.Ticks - new DateTime(1970, 1, 1).Ticks) / 10000000L); // Ticks give back 100ns intervals byte[] gzipHeader = { // The two magic bytes (byte) (GZipConstants.GZIP_MAGIC >> 8), (byte) (GZipConstants.GZIP_MAGIC & 0xff), // 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); } } #endregion } }