private int getRecordLength(int index, int offset) {
		if (index == 0) {
			return buffer.length() - offset;
		}
		return getRecordDataOffset(index - 1) - offset;
	}
Get the length of a stored record.  Optimized if record offset 
already known.
@param index index associated with record.
@param offset record offset
Ghidra/Framework/DB/src/main/java/db/FixedKeyVarRecNode.java