DecoderReplacementFallbackBuffer.cs

using System.Security;

namespace System.Text
{
    public sealed class DecoderReplacementFallbackBuffer : DecoderFallbackBuffer
    {
        private 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)
            {
                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;
        }

        [SecuritySafeCritical]
        public unsafe override void Reset()
        {
            fallbackCount = -1;
            fallbackIndex = -1;
            byteStart = null;
        }

        [SecurityCritical]
        internal unsafe override int InternalFallback(byte[] bytes, byte* pBytes)
        {
            return strDefault.Length;
        }
    }
}