CompressionTransform.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Base / MS / Internal / IO / Packaging / CompoundFile / CompressionTransform.cs / 1305600 / CompressionTransform.cs
                        

                        
                            //------------------------------------------------------------------------------ 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//   This class implements IDataTransform for the Compression transform. 
//
// History: 
//  06/04/2002: BruceMac: Initial implementation.
//  05/29/2003: LGolding: Ported to WCP tree.
//  05/17/2005: BruceMac: Port to Office-compatible block-based format
//  05/30/2005: BruceMac: Moved to System.IO.Packaging namespace 
//  12/14/2005: BruceMac: Moved to MS.Internal.IO.Packaging.CompoundFile namespace
// 
//----------------------------------------------------------------------------- 

using System; 
using System.Collections;                       // for IDictionary
using System.IO;                                // for Stream
using System.IO.Packaging;
using System.Globalization;                     // for CultureInfo 
using System.Windows;                           // ExceptionStringTable
 
using MS.Internal.IO.Packaging;                 // CompoundFileEmulationStream 
using MS.Internal.IO.Packaging.CompoundFile;
 
//using System.Windows;

namespace MS.Internal.IO.Packaging.CompoundFile
{ 
    /// 
    /// CompressionTransform for use in Compound File DataSpaces 
    ///  
    internal class CompressionTransform : IDataTransform
    { 
        #region IDataTransform
        /// 
        /// Transform readiness
        ///  
        public bool IsReady
        { 
            get 
            {
                return true; 
            }
        }

        ///  
        /// No configuration parameters for this transform
        ///  
        public bool FixedSettings 
        {
            get 
            {
                return true;
            }
        } 

        ///  
        /// Returns the type name identifier string. 
        /// 
        public object TransformIdentifier 
        {
            get
            {
                return CompressionTransform.ClassTransformIdentifier; 
            }
        } 
 
        /// 
        /// Expose the transform identifier for the use of the DataSpaceManager. 
        /// 
        internal static string ClassTransformIdentifier
        {
            get 
            {
                return "{86DE7F2B-DDCE-486d-B016-405BBE82B8BC}"; 
            } 
        }
 
        //-----------------------------------------------------
        //
        //  Public Methods
        // 
        //-----------------------------------------------------
 
        ///  
        /// Given output stream returns stream for encoding/decoding
        ///  
        /// the encoded stream that this transform acts on
        /// Dictionary object used to store any additional context information
        /// the stream that implements the transform
        ///  
        /// This method is used only by the DataSpaceManager, so we declare it as an explicit
        /// interface implementation to hide it from the public interface. 
        ///  
        Stream
        IDataTransform.GetTransformedStream( 
            Stream encodedStream,
            IDictionary transformContext
            )
        { 
            Stream tempStream = new SparseMemoryStream(_lowWaterMark, _highWaterMark);
            tempStream = new CompressEmulationStream(encodedStream, tempStream, 0, new CompoundFileDeflateTransform()); 
 
            // return a VersionedStream that works with the VersionedStreamOwner
            // to verify/update our FormatVersion info 
            return new VersionedStream(tempStream, _versionedStreamOwner);
        }
        #endregion
 
        /// 
        /// constructor 
        ///  
        /// environment
        /// this should only be used by the DataSpaceManager class 
        public CompressionTransform(TransformEnvironment myEnvironment)
        {
            _transformEnvironment = myEnvironment;
 
            // Create a wrapper that manages persistence and comparison of FormatVersion
            // in our InstanceData stream.  We can read/write to this stream as needed (though CompressionTransform 
            // does not because we don't house any non-FormatVersion data in the instance data stream). 
            // We need to give out our current code version so it can compare with any file version as appropriate.
            _versionedStreamOwner = new VersionedStreamOwner( 
                _transformEnvironment.GetPrimaryInstanceData(),
                new FormatVersion(_featureName, _minimumReaderVersion, _minimumUpdaterVersion, _currentFeatureVersion));
        }
 
        //------------------------------------------------------
        // 
        //  Private Data 
        //
        //----------------------------------------------------- 
        private TransformEnvironment _transformEnvironment;
        private VersionedStreamOwner _versionedStreamOwner;     // our instance data stream wrapped
        private static readonly string _featureName = "Microsoft.Metadata.CompressionTransform";
 
        private static readonly VersionPair _currentFeatureVersion = new VersionPair(1, 0);
        private static readonly VersionPair _minimumReaderVersion = new VersionPair(1, 0); 
        private static readonly VersionPair _minimumUpdaterVersion = new VersionPair(1, 0); 

        private const long _lowWaterMark = 0x19000;     // we definitely would like to keep everything under 100 KB in memory 
        private const long _highWaterMark = 0xA00000;   // we would like to keep everything over 10 MB on disk
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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