DeflateEmulationStream.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 / DeflateEmulationStream.cs / 1305600 / DeflateEmulationStream.cs
                        

                        
                            //------------------------------------------------------------------------------ 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//  Implementation of a helper class that provides a fully functional Stream on a restricted functionality 
//  Compression stream (System.IO.Compression.DeflateStream).
// 
// History:
//  10/05/2005: BruceMac: Split out from CompressEmulationStream
//-----------------------------------------------------------------------------
 
using System;
using System.IO; 
using System.IO.Compression;                // for DeflateStream 
using System.Diagnostics;
 
using System.IO.Packaging;
using System.Windows;

namespace MS.Internal.IO.Packaging 
{
    //----------------------------------------------------- 
    // 
    //  Internal Members
    // 
    //-----------------------------------------------------
    /// 
    /// Emulates a fully functional stream using restricted functionality DeflateStream
    ///  
    internal class DeflateEmulationTransform : IDeflateTransform
    { 
        ///  
        /// Extract from DeflateStream to temp stream
        ///  
        /// Caller is responsible for correctly positioning source and sink stream pointers before calling.
        public void Decompress(Stream source, Stream sink)
        {
            // for non-empty stream create deflate stream that can 
            // actually decompress
            using (DeflateStream deflateStream = new DeflateStream( 
                source,                    // source of compressed data 
                CompressionMode.Decompress,     // compress or decompress
                true))                          // leave base stream open when the deflate stream is closed 
            {
                int bytesRead = 0;
                do
                { 
                    bytesRead = deflateStream.Read(Buffer, 0, Buffer.Length);
                    if (bytesRead > 0) 
                        sink.Write(Buffer, 0, bytesRead); 

                } while (bytesRead > 0); 
            }
        }

        ///  
        /// Compress from the temp stream into the base stream
        ///  
        /// Caller is responsible for correctly positioning source and sink stream pointers before calling. 
        public void Compress(Stream source, Stream sink)
        { 
            // create deflate stream that can actually compress or decompress
            using (DeflateStream deflateStream = new DeflateStream(
                sink,                       // destination for compressed data
                CompressionMode.Compress,   // compress or decompress 
                true))                      // leave base stream open when the deflate stream is closed
            { 
                // persist to deflated stream from working stream 
                int bytesRead = 0;
                do 
                {
                    bytesRead = source.Read(Buffer, 0, Buffer.Length);
                    if (bytesRead > 0)
                        deflateStream.Write(Buffer, 0, bytesRead); 
                } while (bytesRead > 0);
            } 
 
            // truncate if necessary and possible
            if (sink.CanSeek) 
                sink.SetLength(sink.Position);
        }

        //------------------------------------------------------ 
        //
        //  Private Properties 
        // 
        //-----------------------------------------------------
        private byte[] Buffer 
        {
            get
            {
                if (_buffer == null) 
                    _buffer = new byte[0x1000];     // 4k
 
                return _buffer; 
            }
        } 

        //------------------------------------------------------
        //
        //  Private Members 
        //
        //------------------------------------------------------ 
        private byte[] _buffer;     // alloc and re-use to reduce memory fragmentation 
                                    // this is safe because we are not thread-safe
    } 
}

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

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