public int getNumInitialFixedBits(int marked) {
		if (dits == null) {
			return 0;
		}
		if ((marked <= 0) || (marked > dits.length)) {
			return 0;//perhaps return -1 instead?
		}
		int popcnt = 0;
		for (int i = 0; i < marked; ++i) {
			popcnt += popcount[0xff & dits[i]];
		}
		return popcnt;
	}
Get the number of bits that are fixed, not ditted (don't care)

@param marked number of bytes in the pattern to check

@return number of initial fixed bits
Ghidra/Features/Base/src/main/java/ghidra/util/bytesearch/DittedBitSequence.java