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

        public virtual void Seek(int index)
        {
            if (index == currentCharIndex)
            {
                return;
            }
            if (index > currentCharIndex)
            {
                Sync(index - currentCharIndex);
                index = Math.Min(index, BufferStartIndex + n - 1);
            }
            // index == to bufferStartIndex should set p to 0
            int i = index - BufferStartIndex;
            if (i < 0)
            {
                throw new ArgumentException("cannot seek to negative index " + index);
            }
            else
            {
                if (i >= n)
                {
                    throw new NotSupportedException("seek to index outside buffer: " + index + " not in " + BufferStartIndex + ".." + (BufferStartIndex + n));
                }
            }
            p = i;
            currentCharIndex = index;
            if (p == 0)
            {
                lastChar = lastCharBufferStart;
            }
            else
            {
                lastChar = data[p - 1];
            }
        }