private static final AbstractIntegerDataType getIntegerType(long intTypeIndex,
			DataTypeManager dtm) {
		long dataTypeId =
			((long) DataTypeManagerDB.BUILT_IN << DataTypeManagerDB.DATA_TYPE_KIND_SHIFT) |
				intTypeIndex;
		DataType dataType = dtm.getDataType(dataTypeId);
		if (!(dataType instanceof AbstractIntegerDataType)) {
			return null;
		}
		return (AbstractIntegerDataType) dataType;
	}
Get the integer base type which corresponds to the specified intTypeIndex and the 
specified data type manager.
@param intTypeIndex base data type index used by bit-field
@param dtm data type manager
@return integer data type or null if not found
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/BitFieldDBDataType.java