NET Framework 2.0 中新增的两个压缩类(转载)

System.IO.Compression 命名空间
注意：此命名空间在 .NET Framework 2.0 版中是新增的。
System.IO.Compression 命名空间包含提供基本的流压缩和解压缩服务的类。
(downmoon原作)
类 说明
DeflateStream 提供用于使用 Deflate 算法压缩和解压缩流的方法和属性。
GZipStream 提供用于压缩和解压缩流的方法和属性。
枚举 说明
CompressionMode 指定是否压缩或解压缩基础流。

下面以 GZipStream 为例说明

注意：此类在 .NET Framework 2.0 版中是新增的。

提供用于压缩和解压缩流的方法和属性。
命名空间:System.IO.Compression
程序集:System（在 system.dll 中）
语法
Visual Basic（声明）
Public Class GZipStream
Inherits Stream
Visual Basic（用法）
Dim instance As GZipStream

C#
public class GZipStream : Stream

C++
public ref class GZipStream : public Stream

J#
public class GZipStream extends Stream

JScript
public class GZipStream extends Stream

备注
此类表示 GZip 数据格式，它使用无损压缩和解压缩文件的行业标准算法。
这种格式包括一个检测数据损坏的循环冗余校验值。GZip 数据格式使用的算法与 DeflateStream 类的算法相同
，但它可以扩展以使用其他压缩格式。这种格式可以通过不涉及专利使用权的方式轻松实现。
 gzip 的格式可以从 RFC 1952“GZIP file format specification 4.3（GZIP 文件格式规范 4.3）
 GZIP file format specification 4.3（GZIP 文件格式规范 4.3）”中获得。此类不能用于压缩大于 4 GB 的文件。

给继承者的说明 当从 GZipStream 继承时，必须重写下列成员：CanSeek、CanWrite 和 CanRead。

下面提供 一个完整的压缩与解压类(downmoon原作 )：

 

class clsZip
 ...{
 public void CompressFile ( string sourceFile, string destinationFile )
 ...{
 // make sure the source file is there
 if ( File.Exists ( sourceFile ) == false )
 throw new FileNotFoundException ( );

 // Create the streams and byte arrays needed
 byte[] buffer = null;
 FileStream sourceStream = null;
 FileStream destinationStream = null;
 GZipStream compressedStream = null;

 try
 ...{
 // Read the bytes from the source file into a byte array
 sourceStream = new FileStream ( sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read );

 // Read the source stream values into the buffer
 buffer = new byte[sourceStream.Length];
 int checkCounter = sourceStream.Read ( buffer, 0, buffer.Length );

 if ( checkCounter != buffer.Length )
 ...{
 throw new ApplicationException ( );
 }

 // Open the FileStream to write to
 destinationStream = new FileStream ( destinationFile, FileMode.OpenOrCreate, FileAccess.Write );

 // Create a compression stream pointing to the destiantion stream
 compressedStream = new GZipStream ( destinationStream, CompressionMode.Compress, true );

 // Now write the compressed data to the destination file
 compressedStream.Write ( buffer, 0, buffer.Length );
 }
 catch ( ApplicationException ex )
 ...{
 MessageBox.Show ( ex.Message, "压缩文件时发生错误：", MessageBoxButtons.OK, MessageBoxIcon.Error );
 }
 finally
 ...{
 // Make sure we allways close all streams
 if ( sourceStream != null )
 sourceStream.Close ( );

 if ( compressedStream != null )
 compressedStream.Close ( );

 if ( destinationStream != null )
 destinationStream.Close ( );
 }
 }

 public void DecompressFile ( string sourceFile, string destinationFile )
 ...{
 // make sure the source file is there
 if ( File.Exists ( sourceFile ) == false )
 throw new FileNotFoundException ( );

 // Create the streams and byte arrays needed
 FileStream sourceStream = null;
 FileStream destinationStream = null;
 GZipStream decompressedStream = null;
 byte[] quartetBuffer = null;

 try
 ...{
 // Read in the compressed source stream
 sourceStream = new FileStream ( sourceFile, FileMode.Open );

 // Create a compression stream pointing to the destiantion stream
 decompressedStream = new GZipStream ( sourceStream, CompressionMode.Decompress, true );

 // Read the footer to determine the length of the destiantion file
 quartetBuffer = new byte[4];
 int position = (int)sourceStream.Length - 4;
 sourceStream.Position = position;
 sourceStream.Read ( quartetBuffer, 0, 4 );
 sourceStream.Position = 0;
 int checkLength = BitConverter.ToInt32 ( quartetBuffer, 0 );

 byte[] buffer = new byte[checkLength + 100];

 int offset = 0;
 int total = 0;

 // Read the compressed data into the buffer
 while ( true )
 ...{
 int bytesRead = decompressedStream.Read ( buffer, offset, 100 );

 if ( bytesRead == 0 )
 break;

 offset += bytesRead;
 total += bytesRead;
 }

 // Now write everything to the destination file
 destinationStream = new FileStream ( destinationFile, FileMode.Create );
 destinationStream.Write ( buffer, 0, total );

 // and flush everyhting to clean out the buffer
 destinationStream.Flush ( );
 }
 catch ( ApplicationException ex )
 ...{
 MessageBox.Show(ex.Message, "解压文件时发生错误：", MessageBoxButtons.OK, MessageBoxIcon.Error);
 }
 finally
 ...{
 // Make sure we allways close all streams
 if ( sourceStream != null )
 sourceStream.Close ( );

 if ( decompressedStream != null )
 decompressedStream.Close ( );

 if ( destinationStream != null )
 destinationStream.Close ( );
 }

 }
 }