EncoderReplacementFallback.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Text / EncoderReplacementFallback.cs / 1305376 / EncoderReplacementFallback.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// EncoderReplacementFallback.cs
// 
namespace System.Text 
{
    using System; 
    using System.Runtime;
    using System.Diagnostics.Contracts;

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

        public EncoderReplacementFallback(String replacement) 
        { 
            // Must not be null
            if (replacement == null) 
                throw new ArgumentNullException("replacement");
            Contract.EndContractBlock();

            // 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 EncoderFallbackBuffer CreateFallbackBuffer() 
        { 
            return new EncoderReplacementFallbackBuffer(this);
        } 

        // Maximum number of characters that this instance of this fallback could return
        public override int MaxCharCount
        { 
#if !FEATURE_CORECLR
            [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")] 
#endif 
            get
            { 
                return strDefault.Length;
            }
        }
 
#if !FEATURE_CORECLR
        [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")] 
#endif 
        public override bool Equals(Object value)
        { 
            EncoderReplacementFallback that = value as EncoderReplacementFallback;
            if (that != null)
            {
                return (this.strDefault == that.strDefault); 
            }
            return (false); 
        } 

        public override int GetHashCode() 
        {
            return strDefault.GetHashCode();
        }
    } 

 
 
    public sealed class EncoderReplacementFallbackBuffer : EncoderFallbackBuffer
    { 
        // Store our default string
        private String strDefault;
        int fallbackCount = -1;
        int fallbackIndex = -1; 

        // Construction 
        public EncoderReplacementFallbackBuffer(EncoderReplacementFallback fallback) 
        {
            // 2X in case we're a surrogate pair 
            this.strDefault = fallback.DefaultString + fallback.DefaultString;
        }

        // 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.
            if (fallbackCount >= 1) 
            {
                // If we're recursive we may still have something in our buffer that makes this a surrogate
                if (char.IsHighSurrogate(charUnknown) && fallbackCount >= 0 &&
                    char.IsLowSurrogate(strDefault[fallbackIndex+1])) 
                    ThrowLastCharRecursive(Char.ConvertToUtf32(charUnknown, strDefault[fallbackIndex+1]));
 
                // Nope, just one character 
                ThrowLastCharRecursive(unchecked((int)charUnknown));
            } 

            // Go ahead and get our fallback
            // Divide by 2 because we aren't a surrogate pair
            fallbackCount = strDefault.Length/2; 
            fallbackIndex = -1;
 
            return fallbackCount != 0; 
        }
 
        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. 
            if (fallbackCount >= 1)
                ThrowLastCharRecursive(Char.ConvertToUtf32(charUnknownHigh, charUnknownLow)); 

            // Go ahead and get our fallback
            fallbackCount = strDefault.Length;
            fallbackIndex = -1; 

            return fallbackCount != 0; 
        } 

        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 '\0'; 

            // Need to get it out of the buffer.
            // Make sure it didn't wrap from the fast count-- path
            if (fallbackCount == int.MaxValue) 
            {
                fallbackCount = -1; 
                return '\0'; 
            }
 
            // Now make sure its in the expected range
            Contract.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
        [System.Security.SecuritySafeCritical]  // auto-generated 
        public override unsafe void Reset() 
        {
            fallbackCount = -1; 
            fallbackIndex = 0;
            charStart = null;
            bFallingBack = false;
        } 
    }
} 
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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EncoderReplacementFallback.cs source code in C# .NET

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