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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.
namespace System.Text
{
using System;
using System.Diagnostics;
using System.Diagnostics.Contracts;
[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(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(Environment.GetResourceString("Argument_InvalidCharSequenceNoIndex", nameof(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
// 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 '\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 = -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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