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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Runtime;
using System.Diagnostics;
using System.Diagnostics.Contracts;
namespace System.Text
{
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(nameof(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(SR.Format(SR.Argument_InvalidCharSequenceNoIndex, nameof(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 (strDefault == that.strDefault);
}
return (false);
}
public override int GetHashCode()
{
return strDefault.GetHashCode();
}
}
public sealed class EncoderReplacementFallbackBuffer : EncoderFallbackBuffer
{
// Store our default string
private String strDefault;
private int fallbackCount = -1;
private int fallbackIndex = -1;
// Construction
public EncoderReplacementFallbackBuffer(EncoderReplacementFallback fallback)
{
// 2X in case we're a surrogate pair
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(nameof(charUnknownHigh),
SR.Format(SR.ArgumentOutOfRange_Range, 0xD800, 0xDBFF));
if (!Char.IsLowSurrogate(charUnknownLow))
throw new ArgumentOutOfRangeException(nameof(charUnknownLow),
SR.Format(SR.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
Debug.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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