LZCodec.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / MS / Internal / Ink / InkSerializedFormat / LZCodec.cs / 1 / LZCodec.cs
                        

                        
                            using MS.Utility; 
using System;
using System.Runtime.InteropServices;
using System.Security;
using System.Globalization; 
using System.Windows;
using System.Windows.Input; 
using System.Windows.Ink; 
using MS.Internal.Ink.InkSerializedFormat;
using MS.Internal.Ink; 
using System.Collections.Generic;
using System.Diagnostics;

 
using SR = MS.Internal.PresentationCore.SR;
using SRID = MS.Internal.PresentationCore.SRID; 
 
namespace MS.Internal.Ink.InkSerializedFormat
{ 
    /// 
    /// LZCodec
    /// 
    internal class LZCodec 
    {
        ///  
        /// LZCodec 
        /// 
        internal LZCodec() 
        {
        }

        ///  
        /// Uncompress
        ///  
        ///  
        /// 
        ///  
        internal byte[] Uncompress(byte[] input, int inputIndex)
        {
            //first things first
            Debug.Assert(input != null); 
            Debug.Assert(input.Length > 1);
            Debug.Assert(inputIndex < input.Length); 
            Debug.Assert(inputIndex >= 0); 

            List output = new List(); 
            BitStreamWriter writer = new BitStreamWriter(output);
            BitStreamReader reader = new BitStreamReader(input, inputIndex);

            //decode 
            int index = 0, countBytes = 0, start = 0;
            byte byte1 = 0, byte2 = 0; 
 
            _maxMatchLength = FirstMaxMatchLength;
 
            // initialize the ring buffer
            for (index = 0; index < RingBufferLength - _maxMatchLength; index++)
            {
                _ringBuffer[index] = 0; 
            }
 
            //initialize decoding globals 
            _flags = 0;
            _currentRingBufferPosition = RingBufferLength - _maxMatchLength; 
            while (!reader.EndOfStream)
            {
                byte1 = reader.ReadByte(Native.BitsPerByte);
 
                // High order byte counts the number of bits used in the low order
                // byte. 
                if (((_flags >>= 1) & 0x100) == 0) 
                {
                    // Set bit mask describing the next 8 bytes. 
                    _flags = (((int)byte1) | 0xff00);

                    byte1 = reader.ReadByte(Native.BitsPerByte);
                } 

                if ((_flags & 1) != 0) 
                { 
                    // Just store the literal byte in the buffer.
                    writer.Write(byte1, Native.BitsPerByte); 

                    _ringBuffer[_currentRingBufferPosition++] = byte1;
                    _currentRingBufferPosition &= RingBufferLength - 1;
                } 
                else
                { 
                    // Extract the offset and count to copy from the ring buffer. 
                    byte2 = reader.ReadByte(Native.BitsPerByte);
 
                    countBytes = (int)byte2;
                    start = (countBytes & 0xf0) << 4 | (int)byte1;
                    countBytes = (countBytes & 0x0f) + MaxLiteralLength;
 
                    for (index = 0; index <= countBytes; index++)
                    { 
                        byte1 = _ringBuffer[(start + index) & (RingBufferLength - 1)]; 
                        writer.Write(byte1, Native.BitsPerByte);
 
                        _ringBuffer[_currentRingBufferPosition++] = byte1;
                        _currentRingBufferPosition &= RingBufferLength - 1;
                    }
                } 
            }
 
            return output.ToArray(); 
        }
 

        /// 
        /// Privates
        ///  
        private byte[] _ringBuffer = new byte[RingBufferLength];
        private int _maxMatchLength = 0; 
        private int _flags = 0; 
        private int _currentRingBufferPosition = 0;
 
        /// 
        /// Statics / constants
        /// 
        private static readonly int FirstMaxMatchLength = 0x10; 
        private static readonly int RingBufferLength = 4069;
        private static readonly int MaxLiteralLength = 2; 
 
    }
} 

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

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