static long readNextIndex(BinaryReader reader, boolean is32bit) throws IOException {
		if (is32bit) {
			return reader.readNextInt() & Conv.INT_MASK;
		}
		return reader.readNextLong();
	}
Reads the next index value. If is32bit is true, then 4 bytes
will be read to form index. Otherwise, 8 bytes will be read to form index.
Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/objc2/ObjectiveC2_Utilities.java