private long getXorMask(int bufferOffset, int len) {
		long mask = 0;
		for (int i = 0; i < len; i++) {
			mask = (mask << 8) | ((long) xorMaskByte(bufferOffset++, (byte) 0) & 0xff);
		}
		return mask;
	}
Get an XOR obfuscation mask of the specified length in support of the 
short, int and long get/put methods.
@param bufferOffset offset within a single chained buffer, valid values are in the 
range 0 to (dataSpace-1).  The value (bufferOffset+len-1) must be less than dataSpace.
@param len mask length (2, 4, or 8)
@return XOR mask of specified length which corresponds to specified bufferOffset.
Ghidra/Framework/DB/src/main/java/db/ChainedBuffer.java