EncoderBestFitFallback.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 / ndp / clr / src / BCL / System / Text / EncoderBestFitFallback.cs / 1305376 / EncoderBestFitFallback.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// EncoderBestFitFallback.cs
// 
// This is used internally to create best fit behavior as per the original windows best fit behavior. 
//
namespace System.Text 
{
    using System;
    using System.Globalization;
    using System.Text; 
    using System.Threading;
    using System.Diagnostics.Contracts; 
 
    [Serializable]
    internal class InternalEncoderBestFitFallback : EncoderFallback 
    {
        // Our variables
        internal Encoding encoding = null;
        internal char[]   arrayBestFit = null; 

        internal InternalEncoderBestFitFallback(Encoding encoding) 
        { 
            // Need to load our replacement characters table.
            this.encoding = encoding; 
            this.bIsMicrosoftBestFitFallback = true;
        }

        public override EncoderFallbackBuffer CreateFallbackBuffer() 
        {
            return new InternalEncoderBestFitFallbackBuffer(this); 
        } 

        // Maximum number of characters that this instance of this fallback could return 
        public override int MaxCharCount
        {
            get
            { 
                return 1;
            } 
        } 

        public override bool Equals(Object value) 
        {
            InternalEncoderBestFitFallback that = value as InternalEncoderBestFitFallback;
            if (that != null)
            { 
                return (this.encoding.CodePage == that.encoding.CodePage);
            } 
            return (false); 
        }
 
        public override int GetHashCode()
        {
            return this.encoding.CodePage;
        } 
    }
 
    internal sealed class InternalEncoderBestFitFallbackBuffer : EncoderFallbackBuffer 
    {
        // Our variables 
        private char                    cBestFit = '\0';
        private InternalEncoderBestFitFallback  oFallback;
        private int                     iCount = -1;
        private int                     iSize; 

        // Private object for locking instead of locking on a public type for SQL reliability work. 
        private static Object s_InternalSyncObject; 
        private static Object InternalSyncObject
        { 
            get
            {
                if (s_InternalSyncObject == null)
                { 
                    Object o = new Object();
                    Interlocked.CompareExchange(ref s_InternalSyncObject, o, null); 
                } 
                return s_InternalSyncObject;
            } 
        }

        // Constructor
        public InternalEncoderBestFitFallbackBuffer(InternalEncoderBestFitFallback fallback) 
        {
            this.oFallback = fallback; 
 
            if (oFallback.arrayBestFit == null)
            { 
                // Lock so we don't confuse ourselves.
                lock(InternalSyncObject)
                {
                    // Double check before we do it again. 
                    if (oFallback.arrayBestFit == null)
                        oFallback.arrayBestFit = fallback.encoding.GetBestFitUnicodeToBytesData(); 
                } 
            }
        } 

        // Fallback methods
        public override bool Fallback(char charUnknown, int index)
        { 
            // If we had a buffer already we're being recursive, throw, it's probably at the suspect
            // character in our array. 
            // Shouldn't be able to get here for all of our code pages, table would have to be messed up. 
            Contract.Assert(iCount < 1, "[InternalEncoderBestFitFallbackBuffer.Fallback(non surrogate)] Fallback char " + ((int)cBestFit).ToString("X4", CultureInfo.InvariantCulture) + " caused recursive fallback");
 
            iCount = iSize = 1;
            cBestFit = TryBestFit(charUnknown);
            if (cBestFit == '\0')
                cBestFit = '?'; 

            return true; 
        } 

        public override bool Fallback(char charUnknownHigh, char charUnknownLow, int index) 
        {
            // Double check input surrogate pair
            if (!Char.IsHighSurrogate(charUnknownHigh))
                throw new ArgumentOutOfRangeException("charUnknownHigh", 
                    Environment.GetResourceString("ArgumentOutOfRange_Range",
                    0xD800, 0xDBFF)); 
 
            if (!Char.IsLowSurrogate(charUnknownLow))
                throw new ArgumentOutOfRangeException("CharUnknownLow", 
                    Environment.GetResourceString("ArgumentOutOfRange_Range",
                    0xDC00, 0xDFFF));
            Contract.EndContractBlock();
 
            // If we had a buffer already we're being recursive, throw, it's probably at the suspect
            // character in our array.  0 is processing last character, < 0 is not falling back 
            // Shouldn't be able to get here, table would have to be messed up. 
            Contract.Assert(iCount < 1, "[InternalEncoderBestFitFallbackBuffer.Fallback(surrogate)] Fallback char " + ((int)cBestFit).ToString("X4", CultureInfo.InvariantCulture) + " caused recursive fallback");
 
            // Go ahead and get our fallback, surrogates don't have best fit
            cBestFit = '?';
            iCount = iSize = 2;
 
            return true;
        } 
 
        // Default version is overridden in EncoderReplacementFallback.cs
        public override char GetNextChar() 
        {
            // We want it to get < 0 because == 0 means that the current/last character is a fallback
            // and we need to detect recursion.  We could have a flag but we already have this counter.
            iCount--; 

            // Do we have anything left? 0 is now last fallback char, negative is nothing left 
            if (iCount < 0) 
                return '\0';
 
            // Need to get it out of the buffer.
            // Make sure it didn't wrap from the fast count-- path
            if (iCount == int.MaxValue)
            { 
                iCount = -1;
                return '\0'; 
            } 

            // Return the best fit character 
            return cBestFit;
        }

        public override bool MovePrevious() 
        {
            // Exception fallback doesn't have anywhere to back up to. 
            if (iCount >= 0) 
                iCount++;
 
            // Return true if we could do it.
            return (iCount >= 0 && iCount <= iSize);
        }
 

        // How many characters left to output? 
        public override int Remaining 
        {
            get 
            {
                return (iCount > 0) ? iCount : 0;
            }
        } 

        // Clear the buffer 
        [System.Security.SecuritySafeCritical] // overrides public transparent member 
        public override unsafe void Reset()
        { 
            iCount = -1;
            charStart = null;
            bFallingBack = false;
        } 

        // private helper methods 
        private char TryBestFit(char cUnknown) 
        {
            // Need to figure out our best fit character, low is beginning of array, high is 1 AFTER end of array 
            int lowBound = 0;
            int highBound = oFallback.arrayBestFit.Length;
            int index;
 
            // Binary search the array
            int iDiff; 
            while ((iDiff = (highBound - lowBound)) > 6) 
            {
                // Look in the middle, which is complicated by the fact that we have 2 #s for each pair, 
                // so we don't want index to be odd because we want to be on word boundaries.
                // Also note that index can never == highBound (because diff is rounded down)
                index = ((iDiff / 2) + lowBound) & 0xFFFE;
 
                char cTest = oFallback.arrayBestFit[index];
                if (cTest == cUnknown) 
                { 
                    // We found it
                    Contract.Assert(index + 1 < oFallback.arrayBestFit.Length, 
                        "[InternalEncoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
                    return oFallback.arrayBestFit[index + 1];
                }
                else if (cTest < cUnknown) 
                {
                    // We weren't high enough 
                    lowBound = index; 
                }
                else 
                {
                    // We weren't low enough
                    highBound = index;
                } 
            }
 
            for (index = lowBound; index < highBound; index += 2) 
            {
                if (oFallback.arrayBestFit[index] == cUnknown) 
                {
                    // We found it
                    Contract.Assert(index + 1 < oFallback.arrayBestFit.Length,
                        "[InternalEncoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array"); 
                    return oFallback.arrayBestFit[index + 1];
                } 
            } 

            // Char wasn't in our table 
            return '\0';
        }
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.


                        

                        

                        
                        
                    
                    

                        
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