* @return the SID object
     * @throws IOException if an I/O error occurs
     * @throws PACDecodingException if the SID data is invalid
     */
    public SID readSid() throws IOException, PACDecodingException {
        final int sidSize = readInt();
        final byte[] bytes = new byte[8 + sidSize * 4];
        readFully(bytes);
        return new SID(bytes, 0);
    }

        // RID = 0x12345678 (305419896 in decimal, little-endian)
        byte[] data = new byte[] { 0x78, 0x56, 0x34, 0x12 };
        PacDataInputStream pdis = createInputStream(data);
        SID sid = pdis.readId();
        // The readId method creates a SID with authority 5 and the RID value
        // Expected format: S-1-5-305419896
        String sidString = sid.toString();
        assertNotNull(sidString);