DecoderExceptionFallbackBuffer.cs

using System.Globalization;

namespace System.Text
{
    public sealed class DecoderExceptionFallbackBuffer : DecoderFallbackBuffer
    {
        public override int Remaining => 0;

        public override bool Fallback(byte[] bytesUnknown, int index)
        {
            Throw(bytesUnknown, index);
            return true;
        }

        public override char GetNextChar()
        {
            return '\0';
        }

        public override bool MovePrevious()
        {
            return false;
        }

        private void Throw(byte[] bytesUnknown, int index)
        {
            StringBuilder stringBuilder = new StringBuilder(bytesUnknown.Length * 3);
            int i;
            for (i = 0; i < bytesUnknown.Length && i < 20; i++)
            {
                stringBuilder.Append("[");
                stringBuilder.Append(bytesUnknown[i].ToString("X2", CultureInfo.InvariantCulture));
                stringBuilder.Append("]");
            }
            if (i == 20)
            {
                stringBuilder.Append(" ...");
            }
            throw new DecoderFallbackException(Environment.GetResourceString("Argument_InvalidCodePageBytesIndex", stringBuilder, index), bytesUnknown, index);
        }
    }
}