HuffCodec.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / MS / Internal / Ink / InkSerializedFormat / HuffCodec.cs / 1305600 / HuffCodec.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.Collections.Generic; 
using System.Windows.Ink;
using MS.Internal.Ink.InkSerializedFormat; 
using System.Diagnostics;


using SR = MS.Internal.PresentationCore.SR; 
using SRID = MS.Internal.PresentationCore.SRID;
 
namespace MS.Internal.Ink.InkSerializedFormat 
{
    ///  
    /// HuffCodec
    /// 
    internal class HuffCodec
    { 
        /// 
        /// HuffCodec 
        ///  
        /// 
        internal HuffCodec(uint defaultIndex) 
        {
            HuffBits bits = new HuffBits();
            bits.InitBits(defaultIndex);
            InitHuffTable(bits); 
        }
 
        ///  
        /// InitHuffTable
        ///  
        /// 
        private void InitHuffTable(HuffBits huffBits)
        {
            _huffBits = huffBits; 
            uint bitSize = _huffBits.GetSize();
            int lowerBound = 1; 
            _mins[0] = 0; 
            for (uint n = 1; n < bitSize; n++)
            { 
                _mins[n] = (uint)lowerBound;
                lowerBound += (1 << (_huffBits.GetBitsAtIndex(n) - 1));
            }
        } 

        ///  
        /// Compress 
        /// 
        /// can be null 
        /// input array to compress
        /// 
        internal void Compress(DataXform dataXf, int[] input, List compressedData)
        { 
            //
            // use the writer to write to the list 
            // 
            BitStreamWriter writer = new BitStreamWriter(compressedData);
            if (null != dataXf) 
            {
                dataXf.ResetState();
                int xfData = 0;
                int xfExtra = 0; 
                for (uint i = 0; i < input.Length; i++)
                { 
                    dataXf.Transform(input[i], ref xfData, ref xfExtra); 
                    Encode(xfData, xfExtra, writer);
                } 
            }
            else
            {
                for (uint i = 0; i < input.Length; i++) 
                {
                    Encode(input[i], 0, writer); 
                } 
            }
        } 

        /// 
        /// Uncompress
        ///  
        /// 
        ///  
        ///  
        /// 
        internal uint Uncompress(DataXform dtxf, byte[] input, int startIndex, int[] outputBuffer) 
        {
            Debug.Assert(input != null);
            Debug.Assert(input.Length >= 2);
            Debug.Assert(startIndex == 1); 
            Debug.Assert(outputBuffer != null);
            Debug.Assert(outputBuffer.Length != 0); 
 
            BitStreamReader reader = new BitStreamReader(input, startIndex);
            int xfExtra = 0, xfData = 0; 
            int outputBufferIndex = 0;
            if (null != dtxf)
            {
                dtxf.ResetState(); 
                while (!reader.EndOfStream)
                { 
                    Decode(ref xfData, ref xfExtra, reader); 
                    int uncompressed = dtxf.InverseTransform(xfData, xfExtra);
                    Debug.Assert(outputBufferIndex < outputBuffer.Length); 
                    outputBuffer[outputBufferIndex++] = uncompressed;
                    if (outputBufferIndex == outputBuffer.Length)
                    {
                        //only write as much as the outputbuffer can hold 
                        //this is assumed by calling code
                        break; 
                    } 
                }
            } 
            else
            {
                while (!reader.EndOfStream)
                { 
                    Decode(ref xfData, ref xfExtra, reader);
                    Debug.Assert(outputBufferIndex < outputBuffer.Length); 
                    outputBuffer[outputBufferIndex++] = xfData; 
                    if (outputBufferIndex == outputBuffer.Length)
                    { 
                        //only write as much as the outputbuffer can hold
                        //this is assumed by calling code
                        break;
                    } 
                }
            } 
            return (uint)((reader.CurrentIndex + 1) - startIndex); //we include startIndex in the read count 
        }
 
        /// 
        /// Encode
        /// 
        ///  
        /// 
        ///  
        /// number of bits encoded, 0 for failure 
        internal byte Encode(int data, int extra, BitStreamWriter writer)
        { 
            if (writer == null)
            {
                throw new ArgumentNullException("writer");
            } 
            if (data == 0)
            { 
                writer.Write((byte)0, 1); //more efficent 
                return (byte)1;
            } 

            // First, encode extra if non-ZERO
            uint bitSize = _huffBits.GetSize();
            if (0 != extra) 
            {
                // Prefix lenght is 1 more than table size 
                byte extraPrefixLength = (byte)(bitSize + 1); 
                int extraPrefix = ((1 << extraPrefixLength) - 2);
 
                writer.Write((uint)extraPrefix, (int)extraPrefixLength);

                // Encode the extra data first
                byte extraCodeLength = Encode(extra, 0, writer); 
                // Encode the actual data next
                byte dataCodeLength = Encode(data, 0, writer); 
                // Return the total code lenght 
                return (byte)((int)extraPrefixLength + (int)extraCodeLength + (int)dataCodeLength);
            } 
            // Find the absolute value of the data
            // IMPORTANT : It is extremely important that nData is uint, and NOT int
            // If it is int, the LONG_MIN will be encoded erroneaouly
            uint nData = (uint)MathHelper.AbsNoThrow(data); 
            // Find the prefix lenght
            byte nPrefLen = 1; 
            for (; (nPrefLen < bitSize) && (nData >= _mins[nPrefLen]); ++nPrefLen) ; 
            // Get the data length
            uint nDataLen = _huffBits.GetBitsAtIndex((uint)nPrefLen - 1); 

            // Find the prefix
            int nPrefix = ((1 << nPrefLen) - 2);
            // Append the prefix to the bit stream 
            writer.Write((uint)nPrefix, (int)nPrefLen);
            // Find the data offset by lower bound 
            // and append sign bit at LSB 
            Debug.Assert(nDataLen > 0 && nDataLen - 1 <= Int32.MaxValue);
            int dataLenMinusOne = (int)(nDataLen - 1); //can't left shift by a uint, we need to thunk to an int 
            nData = ((((nData - _mins[nPrefLen - 1]) & (uint)((1 << dataLenMinusOne) - 1)) << 1) | (uint)((data < 0) ? 1 : 0));
            // Append data into the bit streamdataLenMinusOne
            Debug.Assert(nDataLen <= Int32.MaxValue);
            writer.Write(nData, (int)nDataLen); 

            return (byte)((uint)nPrefLen + nDataLen); 
        } 

        ///  
        /// Decode
        /// 
        /// 
        ///  
        /// 
        /// number of bits decoded, 0 for error 
        internal void Decode(ref int data, ref int extra, BitStreamReader reader) 
        {
            // Find the prefix length 
            byte prefIndex = 0;
            while (reader.ReadBit())
            {
                prefIndex++; 
            }
            // First indicate there is no extra data 
            extra = 0; 

            // More efficient for 0 
            if (0 == prefIndex)
            {
                data = 0;
                return; 
            }
            else if (prefIndex < _huffBits.GetSize()) 
            { 
                // Find the data lenght
                uint nDataLen = _huffBits.GetBitsAtIndex(prefIndex); 
                // Extract the offset data by lower dound with sign bit at LSB
                long nData = reader.ReadUInt64((int)(byte)nDataLen);
                // Find the sign bit
                bool bNeg = ((nData & 0x01) != 0); 
                // Construct the data
                nData = (nData >> 1) + _mins[prefIndex]; 
                // Adjust the sign bit 
                data = bNeg ? -((int)nData) : (int)nData;
                // return the bit count read from stream 
                return;
            }
            else if (prefIndex == _huffBits.GetSize())
            { 
                // This is the special prefix for extra data.
                // Decode the prefix first 
                int extra2 = 0; 
                int extra2Ignored = 0;
                Decode(ref extra2, ref extra2Ignored, reader); 
                extra = extra2;

                // Following is the actual data
                int data2 = 0; 
                Decode(ref data2, ref extra2Ignored, reader);
                data = data2; 
                return; 
            }
            throw new ArgumentException(StrokeCollectionSerializer.ISFDebugMessage("invalid huffman encoded data")); 
        }

        /// 
        /// Privates 
        /// 
        private HuffBits    _huffBits; 
        private uint[]      _mins = new uint[MaxBAASize]; 

        ///  
        /// Private statics
        /// 
        private static readonly byte MaxBAASize = 10;
 
        /// 
        /// Private helper class 
        ///  
        private class HuffBits
        { 
            /// 
            /// HuffBits
            /// 
            internal HuffBits() 
            {
                _size = 2; 
                _bits[0] = 0; 
                _bits[1] = 32;
                _matchIndex = 0; 
                _prefixCount = 1;
                //_findMatch = true;

            } 

            ///  
            /// InitBits 
            /// 
            ///  
            /// 
            internal bool InitBits(uint defaultIndex)
            {
                if (defaultIndex < DefaultBAACount && DefaultBAASize[defaultIndex] <= MaxBAASize) 
                {
                    _size = DefaultBAASize[defaultIndex]; 
                    _matchIndex = defaultIndex; 
                    _prefixCount = _size;
                    //_findMatch = true; 
                    _bits = DefaultBAAData[defaultIndex];
                    return true;
                }
                return false; 
            }
 
            ///  
            /// GetSize
            ///  
            internal uint GetSize()
            {
                return _size;
            } 

            ///  
            /// GetBitsAtIndex 
            /// 
            internal byte GetBitsAtIndex(uint index) 
            {
                return _bits[(int)index];
            }
 
            /// 
            /// Privates 
            ///  
            private byte[] _bits = new byte[MaxBAASize];
            private uint _size; 
            private uint _matchIndex;
            private uint _prefixCount;
            //private bool _findMatch;
 
            /// 
            /// Private statics 
            ///  
            private static readonly byte MaxBAASize = 10;
            private static readonly byte DefaultBAACount = 8; 
            private static readonly byte[][] DefaultBAAData = new byte[][]
            {
                new byte[]{0, 1,  2,  4,  6,  8, 12, 16, 24, 32},
                new byte[]{0, 1,  1,  2,  4,  8, 12, 16, 24, 32}, 
                new byte[]{0, 1,  1,  1,  2,  4,  8, 14, 22, 32},
                new byte[]{0, 2,  2,  3,  5,  8, 12, 16, 24, 32}, 
                new byte[]{0, 3,  4,  5,  8, 12, 16, 24, 32,  0}, 
                new byte[]{0, 4,  6,  8, 12, 16, 24, 32,  0,  0},
                new byte[]{0, 6,  8, 12, 16, 24, 32,  0,  0,  0}, 
                new byte[]{0, 7,  8, 12, 16, 24, 32,  0,  0,  0},
            };
            private static readonly byte[] DefaultBAASize = new byte[] { 10, 10, 10, 10, 9, 8, 7, 7 };
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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HuffCodec.cs source code in C# .NET

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