Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Text / EncoderFallback.cs / 1 / EncoderFallback.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== using System; using System.Threading; namespace System.Text { [Serializable] public abstract class EncoderFallback { internal bool bIsMicrosoftBestFitFallback = false; 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 implimentations will probably need an implimenation-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's 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 = null; 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? 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. 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. internal unsafe virtual bool InternalFallback(char ch, ref char* chars) { // Shouldn't have null charStart BCLDebug.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"); } } }
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