DecoderReplacementFallback.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Text / DecoderReplacementFallback.cs / 1 / DecoderReplacementFallback.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// DecoderReplacementFallback.cs
// 
namespace System.Text 
{
    using System; 

    [Serializable]
    public sealed class DecoderReplacementFallback : DecoderFallback
    { 
        // Our variables
        private String strDefault; 
 
        // Construction.  Default replacement fallback uses no best fit and ? replacement string
        public DecoderReplacementFallback() : this("?") 
        {
        }

        public DecoderReplacementFallback(String replacement) 
        {
            if (replacement == null) 
                throw new ArgumentNullException("replacement"); 

            // Make sure it doesn't have bad surrogate pairs 
            bool bFoundHigh=false;
            for (int i = 0; i < replacement.Length; i++)
            {
                // Found a surrogate? 
                if (Char.IsSurrogate(replacement,i))
                { 
                    // High or Low? 
                    if (Char.IsHighSurrogate(replacement, i))
                    { 
                        // if already had a high one, stop
                        if (bFoundHigh)
                            break;  // break & throw at the bFoundHIgh below
                        bFoundHigh = true; 
                    }
                    else 
                    { 
                        // Low, did we have a high?
                        if (!bFoundHigh) 
                        {
                            // Didn't have one, make if fail when we stop
                            bFoundHigh = true;
                            break; 
                        }
 
                        // Clear flag 
                        bFoundHigh = false;
                    } 
                }
                // If last was high we're in trouble (not surrogate so not low surrogate, so break)
                else if (bFoundHigh)
                    break; 
            }
            if (bFoundHigh) 
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex", "replacement")); 

            strDefault = replacement; 
        }

        public String DefaultString
        { 
             get
             { 
                return strDefault; 
             }
        } 

        public override DecoderFallbackBuffer CreateFallbackBuffer()
        {
            return new DecoderReplacementFallbackBuffer(this); 
        }
 
        // Maximum number of characters that this instance of this fallback could return 
        public override int MaxCharCount
        { 
            get
            {
                return strDefault.Length;
            } 
        }
 
        public override bool Equals(Object value) 
        {
            DecoderReplacementFallback that = value as DecoderReplacementFallback; 
            if (that != null)
            {
                return (this.strDefault == that.strDefault);
            } 
            return (false);
        } 
 
        public override int GetHashCode()
        { 
            return strDefault.GetHashCode();
        }
    }
 

 
    public sealed class DecoderReplacementFallbackBuffer : DecoderFallbackBuffer 
    {
        // Store our default string 
        private String strDefault;
        int fallbackCount = -1;
        int fallbackIndex = -1;
 
        // Construction
        public DecoderReplacementFallbackBuffer(DecoderReplacementFallback fallback) 
        { 
            this.strDefault = fallback.DefaultString;
        } 

        // Fallback Methods
        public override bool Fallback(byte[] bytesUnknown, int index)
        { 
            // We expect no previous fallback in our buffer
            BCLDebug.Assert(fallbackCount < 1, "[DecoderReplacementFallbackBuffer.Fallback] Calling fallback without a previously empty buffer"); 
 
            // We can't call recursively but others might (note, we don't test on last char!!!)
            if (fallbackCount >= 1) 
            {
                ThrowLastBytesRecursive(bytesUnknown);
            }
 
            // Go ahead and get our fallback
            if (strDefault.Length == 0) 
                return false; 

            fallbackCount = strDefault.Length; 
            fallbackIndex = -1;

            return true;
        } 

        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. 
            fallbackCount--;
            fallbackIndex++;

            // Do we have anything left? 0 is now last fallback char, negative is nothing left 
            if (fallbackCount < 0)
                return (char)0; 
 
            // Need to get it out of the buffer.
            BCLDebug.Assert(fallbackIndex < strDefault.Length && fallbackIndex >= 0, 
                            "Index exceeds buffer range");
            return strDefault[fallbackIndex];
        }
 
        public override bool MovePrevious()
        { 
            // Back up one, only if we just processed the last character (or earlier) 
            if (fallbackCount >= -1 && fallbackIndex >= 0)
            { 
                fallbackIndex--;
                fallbackCount++;
                return true;
            } 

            // Return false 'cause we couldn't do it. 
            return false; 
        }
 
        // How many characters left to output?
        public override int Remaining
        {
            get 
            {
                // Our count is 0 for 1 character left. 
                return (fallbackCount < 0) ? 0 : fallbackCount; 
            }
        } 

        // Clear the buffer
        public override unsafe void Reset()
        { 
            fallbackCount = -1;
            fallbackIndex = -1; 
            byteStart = null; 
        }
 
        // This version just counts the fallback and doesn't actually copy anything.
        internal unsafe override int InternalFallback(byte[] bytes, byte* pBytes)
        // Right now this has both bytes and bytes[], since we might have extra bytes, hence the
        // array, and we might need the index, hence the byte* 
        {
            // return our replacement string Length 
            return strDefault.Length; 
        }
    } 
}

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