EncoderFallback.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 / EncoderFallback.cs / 1305376 / EncoderFallback.cs

                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
using System;
using System.Threading; 
using System.Diagnostics.Contracts; 

namespace System.Text 
{
    [Serializable]
    public abstract class EncoderFallback
    { 
// disable csharp compiler warning #0414: field assigned unused value
#pragma warning disable 0414 
        internal bool                 bIsMicrosoftBestFitFallback = false; 
#pragma warning restore 0414
 
        private static EncoderFallback replacementFallback; // Default fallback, uses no best fit & "?"
        private static EncoderFallback exceptionFallback;

        // 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; 
            } 
        }
 
        // Get each of our generic fallbacks.

        public static EncoderFallback ReplacementFallback
        { 
            get
            { 
                if (replacementFallback == null) 
                    lock(InternalSyncObject)
                        if (replacementFallback == null) 
                            replacementFallback = new EncoderReplacementFallback();

                return replacementFallback;
            } 
        }
 
 
        public static EncoderFallback ExceptionFallback
        { 
            get
            {
                if (exceptionFallback == null)
                    lock(InternalSyncObject) 
                        if (exceptionFallback == null)
                            exceptionFallback = new EncoderExceptionFallback(); 
 
                return exceptionFallback;
            } 
        }

        // Fallback
        // 
        // Return the appropriate unicode string alternative to the character that need to fall back.
        // Most implimentations will be: 
        //      return new MyCustomEncoderFallbackBuffer(this); 

        public abstract EncoderFallbackBuffer CreateFallbackBuffer(); 

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

        public abstract int MaxCharCount { get; } 
    }
 
 
    public abstract class EncoderFallbackBuffer
    { 
        // Most implementations will probably need an implemenation-specific constructor

        // Public methods that cannot be overriden that let us do our fallback thing
        // These wrap the internal methods so that we can check for people doing stuff that is incorrect 

        public abstract bool Fallback(char charUnknown, int index); 
 
        public abstract bool Fallback(char charUnknownHigh, char charUnknownLow, 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; }

        // Not sure if this should be public or not. 
        // 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 char*   charStart;
        internal    unsafe char*   charEnd; 
        internal    EncoderNLS     encoder; 
        internal    bool           setEncoder;
        internal    bool           bUsedEncoder; 
        internal    bool           bFallingBack = false;
        internal    int            iRecursionCount = 0;
        private const int          iMaxRecursion = 250;
 
        // Internal Reset
        // For example, what if someone fails a conversion and wants to reset one of our fallback buffers? 
        [System.Security.SecurityCritical]  // auto-generated 
        internal unsafe void InternalReset()
        { 
            charStart = null;
            bFallingBack = false;
            iRecursionCount = 0;
            Reset(); 
        }
 
        // Set the above values 
        // This can't be part of the constructor because EncoderFallbacks would have to know how to impliment these.
        [System.Security.SecurityCritical]  // auto-generated 
        internal unsafe void InternalInitialize(char* charStart, char* charEnd, EncoderNLS encoder, bool setEncoder)
        {
            this.charStart = charStart;
            this.charEnd = charEnd; 
            this.encoder = encoder;
            this.setEncoder = setEncoder; 
            this.bUsedEncoder = false; 
            this.bFallingBack = false;
            this.iRecursionCount = 0; 
        }

        internal char InternalGetNextChar()
        { 
            char ch = GetNextChar();
            bFallingBack = (ch != 0); 
            if (ch == 0) iRecursionCount = 0; 
            return ch;
        } 

        // Fallback the current character using the remaining buffer and encoder if necessary
        // This can only be called by our encodings (other have to use the public fallback methods), so
        // we can use our EncoderNLS here too. 
        // setEncoder is true if we're calling from a GetBytes method, false if we're calling from a GetByteCount
        // 
        // Note that this could also change the contents of this.encoder, which is the same 
        // object that the caller is using, so the caller could mess up the encoder for us
        // if they aren't careful. 
        [System.Security.SecurityCritical]  // auto-generated
        internal unsafe virtual bool InternalFallback(char ch, ref char* chars)
        {
            // Shouldn't have null charStart 
            Contract.Assert(charStart != null,
                "[EncoderFallback.InternalFallbackBuffer]Fallback buffer is not initialized"); 
 
            // Get our index, remember chars was preincremented to point at next char, so have to -1
            int index = (int)(chars - charStart) - 1; 

            // See if it was a high surrogate
            if (Char.IsHighSurrogate(ch))
            { 
                // See if there's a low surrogate to go with it
                if (chars >= this.charEnd) 
                { 
                    // Nothing left in input buffer
                    // No input, return 0 if mustflush is false 
                    if (this.encoder != null && !this.encoder.MustFlush)
                    {
                        // Done, nothing to fallback
                        if (this.setEncoder) 
                        {
                            bUsedEncoder = true; 
                            this.encoder.charLeftOver = ch; 
                        }
                        bFallingBack = false; 
                        return false;
                    }
                }
                else 
                {
                    // Might have a low surrogate 
                    char cNext = *chars; 
                    if (Char.IsLowSurrogate(cNext))
                    { 
                        // If already falling back then fail
                        if (bFallingBack && iRecursionCount++ > iMaxRecursion)
                            ThrowLastCharRecursive(Char.ConvertToUtf32(ch, cNext));
 
                        // Next is a surrogate, add it as surrogate pair, and increment chars
                        chars++; 
                        bFallingBack = Fallback(ch, cNext, index); 
                        return bFallingBack;
                    } 

                    // Next isn't a low surrogate, just fallback the high surrogate
                }
            } 

            // If already falling back then fail 
            if (bFallingBack && iRecursionCount++ > iMaxRecursion) 
                ThrowLastCharRecursive((int)ch);
 
            // Fall back our char
            bFallingBack = Fallback(ch, index);

            return bFallingBack; 
        }
 
        // private helper methods 
        internal void ThrowLastCharRecursive(int charRecursive)
        { 
            // Throw it, using our complete character
            throw new ArgumentException(
                Environment.GetResourceString("Argument_RecursiveFallback",
                    charRecursive), "chars"); 
        }
 
    } 
}

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

                        

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