DecoderFallback.cs source code in C# .NET

                        Code:
                         / FXUpdate3074 / FXUpdate3074 / 1.1 / untmp / whidbey / QFE / ndp / clr / src / BCL / System / Text / DecoderFallback.cs / 1 / DecoderFallback.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
//
using System; 
using System.Threading; 
using System.Globalization;
 
namespace System.Text
{
    [Serializable]
    public abstract class DecoderFallback 
    {
        internal bool                  bIsMicrosoftBestFitFallback = false; 
 
        private static DecoderFallback replacementFallback; // Default fallback, uses no best fit & "?"
        private static DecoderFallback exceptionFallback; 

        // Private object for locking instead of locking on a internal 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; 
            }
        } 
 
        // Get each of our generic fallbacks.
 
        public static DecoderFallback ReplacementFallback
        {
            get
            { 
                if (replacementFallback == null)
                    lock(InternalSyncObject) 
                        if (replacementFallback == null) 
                            replacementFallback = new DecoderReplacementFallback();
 
                return replacementFallback;
            }
        }
 

        public static DecoderFallback ExceptionFallback 
        { 
            get
            { 
                if (exceptionFallback == null)
                    lock(InternalSyncObject)
                        if (exceptionFallback == null)
                            exceptionFallback = new DecoderExceptionFallback(); 

                return exceptionFallback; 
            } 
        }
 
        // Fallback
        //
        // Return the appropriate unicode string alternative to the character that need to fall back.
        // Most implimentations will be: 
        //      return new MyCustomDecoderFallbackBuffer(this);
 
        public abstract DecoderFallbackBuffer CreateFallbackBuffer(); 

        // Maximum number of characters that this instance of this fallback could return 

        public abstract int MaxCharCount { get; }

        internal bool IsMicrosoftBestFitFallback 
        {
            get 
            { 
                return bIsMicrosoftBestFitFallback;
            } 
        }
    }

 
    public abstract class DecoderFallbackBuffer
    { 
        // Most implimentations will probably need an implimenation-specific constructor 

        // internal methods that cannot be overriden that let us do our fallback thing 
        // These wrap the internal methods so that we can

        public abstract bool Fallback(byte[] bytesUnknown, int index);
 
        // Get next character
 
        public abstract char GetNextChar(); 

        // Back up a character 

        public abstract bool MovePrevious();

        // How many chars left in this fallback? 

        public abstract int Remaining { get; } 
 
        // Clear the buffer
 
        public virtual void Reset()
        {
            while (GetNextChar() != (char)0);
        } 

        // Internal items to help us figure out what we're doing as far as error messages, etc. 
        // These help us with our performance and messages internally 
        internal     unsafe byte*    byteStart = null;
        internal     unsafe char*    charEnd = null; 

        // Internal Reset
        internal unsafe void InternalReset()
        { 
            byteStart = null;
            Reset(); 
        } 

        // Set the above values 
        // This can't be part of the constructor because DecoderFallbacks would have to know how to impliment these.
        internal unsafe void InternalInitialize(byte* byteStart, char* charEnd)
        {
            this.byteStart = byteStart; 
            this.charEnd = charEnd;
        } 
 
        // Fallback the current byte by sticking it into the remaining char buffer.
        // This can only be called by our encodings (other have to use the public fallback methods), so 
        // we can use our DecoderNLS here too (except we don't).
        // Returns true if we are successful, false if we can't fallback the character (no buffer space)
        // So caller needs to throw buffer space if return false.
        // Right now this has both bytes and bytes[], which is ----, but we might have extra bytes, hence the 
        // array, and we might need the index, hence the byte*
        // Don't touch ref chars unless we succeed 
        internal unsafe virtual bool InternalFallback(byte[] bytes, byte* pBytes, ref char* chars) 
        {
            // Copy bytes to array (slow, but right now that's what we get to do. 
          //  byte[] bytesUnknown = new byte[count];
//            for (int i = 0; i < count; i++)
//                bytesUnknown[i] = *(bytes++);
 
            BCLDebug.Assert(byteStart != null, "[DecoderFallback.InternalFallback]Used InternalFallback without calling InternalInitialize");
 
            // See if there's a fallback character and we have an output buffer then copy our string. 
            if (this.Fallback(bytes, (int)(pBytes - byteStart - bytes.Length)))
            { 
                // Copy the chars to our output
                char ch;
                char* charTemp = chars;
                bool bHighSurrogate = false; 
                while ((ch = GetNextChar()) != 0)
                { 
                    // Make sure no mixed up surrogates 
                    if (Char.IsSurrogate(ch))
                    { 
                        if (Char.IsHighSurrogate(ch))
                        {
                            // High Surrogate
                            if (bHighSurrogate) 
                                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex"));
                            bHighSurrogate = true; 
                        } 
                        else
                        { 
                            // Low surrogate
                            if (bHighSurrogate == false)
                                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex"));
                            bHighSurrogate = false; 
                        }
                    } 
 
                    if (charTemp >= charEnd)
                    { 
                        // No buffer space
                        return false;
                    }
 
                    *(charTemp++) = ch;
                } 
 
                // Need to make sure that bHighSurrogate isn't true
                if (bHighSurrogate) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex"));

                // Now we aren't going to be false, so its OK to update chars
                chars = charTemp; 
            }
 
            return true; 
        }
 
        // This version just counts the fallback and doesn't actually copy anything.
        internal unsafe virtual int InternalFallback(byte[] bytes, byte* pBytes)
        // Right now this has both bytes and bytes[], which is ----, but we might have extra bytes, hence the
        // array, and we might need the index, hence the byte* 
        {
            // Copy bytes to array (slow, but right now that's what we get to do. 
//            byte[] bytesUnknown = new byte[count]; 
//            for (int i = 0; i < count; i++)
  //              bytesUnknown[i] = *(bytes++); 

            BCLDebug.Assert(byteStart != null, "[DecoderFallback.InternalFallback]Used InternalFallback without calling InternalInitialize");

            // See if there's a fallback character and we have an output buffer then copy our string. 
            if (this.Fallback(bytes, (int)(pBytes - byteStart - bytes.Length)))
            { 
                int count = 0; 

                char ch; 
                bool bHighSurrogate = false;
                while ((ch = GetNextChar()) != 0)
                {
                    // Make sure no mixed up surrogates 
                    if (Char.IsSurrogate(ch))
                    { 
                        if (Char.IsHighSurrogate(ch)) 
                        {
                            // High Surrogate 
                            if (bHighSurrogate)
                                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex"));
                            bHighSurrogate = true;
                        } 
                        else
                        { 
                            // Low surrogate 
                            if (bHighSurrogate == false)
                                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex")); 
                            bHighSurrogate = false;
                        }
                    }
 
                    count++;
                } 
 
                // Need to make sure that bHighSurrogate isn't true
                if (bHighSurrogate) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex"));

                return count;
            } 

            // If no fallback return 0 
            return 0; 
        }
 
        // private helper methods
        internal void ThrowLastBytesRecursive(byte[] bytesUnknown)
        {
            // Create a string representation of our bytes. 
            StringBuilder strBytes = new StringBuilder(bytesUnknown.Length * 3);
            int i; 
            for (i = 0; i < bytesUnknown.Length && i < 20; i++) 
            {
                if (strBytes.Length > 0) 
                    strBytes.Append(" ");
                strBytes.Append(String.Format(CultureInfo.InvariantCulture, "\\x{0:X2}", bytesUnknown[i]));
            }
            // In case the string's really long 
            if (i == 20)
                strBytes.Append(" ..."); 
 
            // Throw it, using our complete bytes
            throw new ArgumentException( 
                Environment.GetResourceString("Argument_RecursiveFallbackBytes",
                    strBytes.ToString()), "bytesUnknown");
        }
 
    }
} 

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