Newtonsoft.Json.Bson.BsonReader.GetLastFullCharStop C# (CSharp) Method

        private int GetLastFullCharStop(int start)
        {
            int lookbackPos = start;
            int bis = 0;
            while (lookbackPos >= 0)
            {
                bis = BytesInSequence(_byteBuffer[lookbackPos]);
                if (bis == 0)
                {
                    lookbackPos--;
                    continue;
                }
                else if (bis == 1)
                {
                    break;
                }
                else
                {
                    lookbackPos--;
                    break;
                }
            }
            if (bis == start - lookbackPos)
            {
                //Full character.
                return start;
            }
            else
            {
                return lookbackPos;
            }
        }