Antlr4.Runtime.UnbufferedCharStream.GetText C# (CSharp) Method

        public virtual string GetText(Interval interval)
        {
            if (interval.a < 0 || interval.b < interval.a - 1)
            {
                throw new ArgumentException("invalid interval");
            }
            int bufferStartIndex = BufferStartIndex;
            if (n > 0 && data[n - 1] == char.MaxValue)
            {
                if (interval.a + interval.Length > bufferStartIndex + n)
                {
                    throw new ArgumentException("the interval extends past the end of the stream");
                }
            }
            if (interval.a < bufferStartIndex || interval.b >= bufferStartIndex + n)
            {
                throw new NotSupportedException("interval " + interval + " outside buffer: " + bufferStartIndex + ".." + (bufferStartIndex + n - 1));
            }
            // convert from absolute to local index
            int i = interval.a - bufferStartIndex;
            return new string(data, i, interval.Length);
        }