DecoderFallbackBufferHelper.cs

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namespace System.Text;
 
internal struct DecoderFallbackBufferHelper
{
    internal unsafe byte* byteStart;
 
    internal unsafe char* charEnd;
 
    private readonly DecoderFallbackBuffer _fallbackBuffer;
 
    public unsafe DecoderFallbackBufferHelper(DecoderFallbackBuffer fallbackBuffer)
    {
        _fallbackBuffer = fallbackBuffer;
        byteStart = null;
        charEnd = null;
    }
 
    internal unsafe void InternalReset()
    {
        byteStart = null;
        _fallbackBuffer.Reset();
    }
 
    internal unsafe void InternalInitialize(byte* _byteStart, char* _charEnd)
    {
        byteStart = _byteStart;
        charEnd = _charEnd;
    }
 
    internal unsafe bool InternalFallback(byte[] bytes, byte* pBytes, ref char* chars)
    {
        if (_fallbackBuffer.Fallback(bytes, (int)(pBytes - byteStart - bytes.Length)))
        {
            char* ptr = chars;
            bool flag = false;
            char nextChar;
            while ((nextChar = _fallbackBuffer.GetNextChar()) != 0)
            {
                if (char.IsSurrogate(nextChar))
                {
                    if (char.IsHighSurrogate(nextChar))
                    {
                        if (flag)
                        {
                            throw new ArgumentException(System.SR.Argument_InvalidCharSequenceNoIndex);
                        }
                        flag = true;
                    }
                    else
                    {
                        if (!flag)
                        {
                            throw new ArgumentException(System.SR.Argument_InvalidCharSequenceNoIndex);
                        }
                        flag = false;
                    }
                }
                if (ptr >= charEnd)
                {
                    return false;
                }
                *(ptr++) = nextChar;
            }
            if (flag)
            {
                throw new ArgumentException(System.SR.Argument_InvalidCharSequenceNoIndex);
            }
            chars = ptr;
        }
        return true;
    }
 
    internal unsafe int InternalFallback(byte[] bytes, byte* pBytes)
    {
        if (_fallbackBuffer.Fallback(bytes, (int)(pBytes - byteStart - bytes.Length)))
        {
            int num = 0;
            bool flag = false;
            char nextChar;
            while ((nextChar = _fallbackBuffer.GetNextChar()) != 0)
            {
                if (char.IsSurrogate(nextChar))
                {
                    if (char.IsHighSurrogate(nextChar))
                    {
                        if (flag)
                        {
                            throw new ArgumentException(System.SR.Argument_InvalidCharSequenceNoIndex);
                        }
                        flag = true;
                    }
                    else
                    {
                        if (!flag)
                        {
                            throw new ArgumentException(System.SR.Argument_InvalidCharSequenceNoIndex);
                        }
                        flag = false;
                    }
                }
                num++;
            }
            if (flag)
            {
                throw new ArgumentException(System.SR.Argument_InvalidCharSequenceNoIndex);
            }
            return num;
        }
        return 0;
    }
}