private EnumSignedState computeSignedness() {
		int length = record.getByteValue(EnumDBAdapter.ENUM_SIZE_COL);

		if (valueMap.isEmpty()) {
			return NONE;
		}

		long minValue = valueMap.firstKey();
		long maxValue = valueMap.lastKey();

		if (maxValue > getMaxPossibleValue(length, true)) {
			if (minValue < 0) {
				return INVALID;
			}
			return UNSIGNED;
		}

		if (minValue < 0) {
			return SIGNED;
		}

		return NONE;		// we have no negatives and no large unsigned values
	}
Database implementation for the enumerated data type.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/EnumDB.java