Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Text / EncoderReplacementFallback.cs / 1 / EncoderReplacementFallback.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // EncoderReplacementFallback.cs // namespace System.Text { using System; [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"); // 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 { get { return strDefault.Length; } } 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)); // 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 (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 = 0; charStart = null; bFallingBack = false; } } }
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