Codec.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 / Core / CSharp / MS / Internal / Ink / InkSerializedFormat / Codec.cs / 1305600 / Codec.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 SR = MS.Internal.PresentationCore.SR;
using SRID = MS.Internal.PresentationCore.SRID;
 
namespace MS.Internal.Ink.InkSerializedFormat
{ 
    ///  
    /// A Math helper class.
    ///  
    internal static class MathHelper
    {
        /// 
        /// Returns the absolute value of a 32-bit signed integer. 
        /// Unlike Math.Abs, this method doesn't throw OverflowException
        /// when the signed integer equals int.MinValue (-2,147,483,648/0x80000000). 
        /// It will return the same value (-2,147,483,648). 
        /// In this case, value can be casted to unsigned value which will be positive (2,147,483,648)
        ///  
        /// 
        /// 
        internal static int AbsNoThrow(int data)
        { 
            // This behavior is desired for ISF decoder. Please refer to the below macro in old native code (codec.h).
            //  template{typename DataType} 
            //  inline DataType Abs(DataType data) { return (data < 0) ? -data : data; }; 
            return (data < 0) ? -data : data;
        } 

        /// 
        /// Returns the absolute value of a 64-bit signed integer.
        /// Unlike Math.Abs, this method doesn't throw OverflowException 
        /// when the signed integer equals int.MinValue (-9,223,372,036,854,775,808/0x8000000000000000).
        /// It will return the same value -9,223,372,036,854,775,808 instead. 
        /// In this case, value can be casted to unsigned value which will be positive (9,223,372,036,854,775,808) 
        /// 
        ///  
        /// 
        internal static long AbsNoThrow(long data)
        {
            // This behavior is desired for ISF decoder. Please refer to the below macro in old native code (codec.h). 
            //  template{typename DataType}
            //  inline DataType Abs(DataType data) { return (data < 0) ? -data : data; }; 
            return (data < 0) ? -data : data; 
        }
    } 

    /// 
    /// Abstact base class for DeltaDelta and some others
    ///  
    internal abstract class DataXform
    { 
        internal abstract void Transform(int data, ref int xfData, ref int extra); 
        internal abstract void ResetState();
        internal abstract int InverseTransform(int xfData, int extra); 
    }
    /// 
    /// Oddly named because we have unmanged code we keep in [....] with this that
    /// has this name. 
    /// 
    internal class DeltaDelta : DataXform 
    { 
        private long _d_i_1 = 0;
        private long _d_i_2 = 0; 

        internal DeltaDelta()
        {
        } 

        ///  
        /// Your guess is as good as mine 
        /// 
        ///  
        /// 
        /// 
        internal override void Transform(int data, ref int xfData, ref int extra)
        { 
            // Find out the delta delta of the number
            // Its absolute value could potentially be more than LONG_MAX 
            long llxfData = (data + _d_i_2 - (_d_i_1 << 1)); 
            // Save the state info for next number
            _d_i_2 = _d_i_1; 
            _d_i_1 = data;
            // Most of the cases, the delta delta will be less than LONG_MAX
            if ( Int32.MaxValue >= MathHelper.AbsNoThrow(llxfData) )
            { 
                // In those cases, we set 0 to nExtra and
                // assign the delta delta to xfData 
                extra = 0; 
                xfData = (int)llxfData;
            } 
            else
            {
                long absLxfData = MathHelper.AbsNoThrow(llxfData);
                // Additional bits in most significant 32 bits 
                extra = (int)(absLxfData >> (sizeof(int) << 3));
                // Left sift one bit and append sign bit the the LSB 
                extra = (extra << 1) | ((llxfData < 0) ? 1 : 0); 
                // Save least significant 32 bits in xfData
                xfData = (int)((unchecked((uint)~0 & absLxfData))); 
            }
        }

        ///  
        ///
        ///  
        internal override void ResetState() 
        {
            _d_i_1 = 0; 
            _d_i_2 = 0;
        }

        ///  
        /// Your guess is as good as mine
        ///  
        ///  
        /// 
        ///  
        internal override int InverseTransform(int xfData, int extra)
        {
            long llxfData;
            // Find out whether the original delta delta exceeded the limit 
            if (0 != extra)
            { 
                // Yes, we had |delta delta| more than LONG_MAX 
                // Find out the original delta delta was negative
                bool negative = ((extra & 0x01) != 0); 
                // Construct the |DelDel| from xfData and nExtra
                llxfData = (((long)extra >> 1) << (sizeof(int) << 3)) | (unchecked((uint)~0) & xfData);
                // Do the sign adjustment
                llxfData = (negative) ? -llxfData : llxfData; 
            }
            else 
            { 
                llxfData = xfData;
            } 
            // Reconstruct the number from delta delta
            long orgData = (llxfData - _d_i_2 + (_d_i_1 << 1));
            _d_i_2 = _d_i_1;
            _d_i_1 = orgData; 
            // Typecast to LONG and return it
            return (int)orgData; 
        } 
    }
} 

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

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