DecoderReplacementFallbackBuffer.cs

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namespace System.Text;
 
public sealed class DecoderReplacementFallbackBuffer : DecoderFallbackBuffer
{
    private readonly string _strDefault;
 
    private int _fallbackCount = -1;
 
    private int _fallbackIndex = -1;
 
    public override int Remaining
    {
        get
        {
            if (_fallbackCount >= 0)
            {
                return _fallbackCount;
            }
            return 0;
        }
    }
 
    public DecoderReplacementFallbackBuffer(DecoderReplacementFallback fallback)
    {
        _strDefault = fallback.DefaultString;
    }
 
    public override bool Fallback(byte[] bytesUnknown, int index)
    {
        if (_fallbackCount >= 1)
        {
            DecoderFallbackBuffer.ThrowLastBytesRecursive(bytesUnknown);
        }
        if (_strDefault.Length == 0)
        {
            return false;
        }
        _fallbackCount = _strDefault.Length;
        _fallbackIndex = -1;
        return true;
    }
 
    public override char GetNextChar()
    {
        _fallbackCount--;
        _fallbackIndex++;
        if (_fallbackCount < 0)
        {
            return '\0';
        }
        if (_fallbackCount == int.MaxValue)
        {
            _fallbackCount = -1;
            return '\0';
        }
        return _strDefault[_fallbackIndex];
    }
 
    public override bool MovePrevious()
    {
        if (_fallbackCount >= -1 && _fallbackIndex >= 0)
        {
            _fallbackIndex--;
            _fallbackCount++;
            return true;
        }
        return false;
    }
 
    public unsafe override void Reset()
    {
        _fallbackCount = -1;
        _fallbackIndex = -1;
        byteStart = null;
    }
 
    internal unsafe override int InternalFallback(byte[] bytes, byte* pBytes)
    {
        return _strDefault.Length;
    }
}