ntpv3impl.java

来自「apache推出的net包」· Java 代码 · 共 584 行 · 第 1/2 页

     *
     * @return the reference id string.
     */
    public String getReferenceIdString()
    {
        int version = getVersion();
        int stratum = getStratum();
        if (version == VERSION_3 || version == VERSION_4) {
            if (stratum == 0 || stratum == 1) {
                return idAsString(); // 4-character ASCII string (e.g. GPS, USNO)
            }
            // in NTPv4 servers this is latest transmit timestamp of ref source
            if (version == VERSION_4)
                return idAsHex();
        }

        // Stratum 2 and higher this is a four-octet IPv4 address
        // of the primary reference host.
        if (stratum >= 2) {
            return idAsIPAddress();
        }
        return idAsHex();
    }

    /***
     * Returns Reference id as dotted IP address.
     * @return refId as IP address string.
     */
    private String idAsIPAddress()
    {
        return ui(buf[REFERENCE_ID_INDEX]) + "." +
                ui(buf[REFERENCE_ID_INDEX + 1]) + "." +
                ui(buf[REFERENCE_ID_INDEX + 2]) + "." +
                ui(buf[REFERENCE_ID_INDEX + 3]);
    }

    private String idAsString()
    {
        String id = "";
        for (int i = 0; i <= 3; i++) {
            char c = (char) buf[REFERENCE_ID_INDEX + i];
            if (c == 0) break; // 0-terminated string
            id = id + c;
        }
        return id;
    }

    private String idAsHex()
    {
        return Integer.toHexString(getReferenceId());
    }

    /***
     * Returns the transmit timestamp as defined in RFC-1305.
     *
     * @return the transmit timestamp as defined in RFC-1305.
     * Never returns a null object.
     */
    public TimeStamp getTransmitTimeStamp()
    {
        return getTimestamp(TRANSMIT_TIMESTAMP_INDEX);
    }

    /***
     * Set transmit time with NTP timestamp.
     * If <code>ts</code> is null then zero time is used.
     *
     * @param ts NTP timestamp
     */
    public void setTransmitTime(TimeStamp ts)
    {
        setTimestamp(TRANSMIT_TIMESTAMP_INDEX, ts);
    }

    /***
     * Set originate timestamp given NTP TimeStamp object.
     * If <code>ts</code> is null then zero time is used.
     *
     * @param ts NTP timestamp
     */
    public void setOriginateTimeStamp(TimeStamp ts)
    {
        setTimestamp(ORIGINATE_TIMESTAMP_INDEX, ts);
    }

    /***
     * Returns the originate time as defined in RFC-1305.
     *
     * @return the originate time.
     * Never returns null.
     */
    public TimeStamp getOriginateTimeStamp()
    {
        return getTimestamp(ORIGINATE_TIMESTAMP_INDEX);
    }

    /***
     * Returns the reference time as defined in RFC-1305.
     *
     * @return the reference time as <code>TimeStamp</code> object.
     * Never returns null.
     */
    public TimeStamp getReferenceTimeStamp()
    {
        return getTimestamp(REFERENCE_TIMESTAMP_INDEX);
    }

    /***
     * Set Reference time with NTP timestamp. If <code>ts</code> is null
     * then zero time is used.
     *
     * @param ts NTP timestamp
     */
    public void setReferenceTime(TimeStamp ts)
    {
        setTimestamp(REFERENCE_TIMESTAMP_INDEX, ts);
    }

    /***
     * Returns receive timestamp as defined in RFC-1305.
     *
     * @return the receive time.
     * Never returns null.
     */
    public TimeStamp getReceiveTimeStamp()
    {
        return getTimestamp(RECEIVE_TIMESTAMP_INDEX);
    }

    /***
     * Set receive timestamp given NTP TimeStamp object.
     * If <code>ts</code> is null then zero time is used.
     *
     * @param ts timestamp
     */
    public void setReceiveTimeStamp(TimeStamp ts)
    {
        setTimestamp(RECEIVE_TIMESTAMP_INDEX, ts);
    }

    /***
     * Return type of time packet. The values (e.g. NTP, TIME, ICMP, ...)
     * correspond to the protocol used to obtain the timing information.
     *
     * @return packet type string identifier which in this case is "NTP".
     */
    public String getType()
    {
        return "NTP";
    }

    /***
     * @return 4 bytes as 32-bit int
     */
    private int getInt(int index)
    {
        int i = ui(buf[index]) << 24 |
                ui(buf[index + 1]) << 16 |
                ui(buf[index + 2]) << 8 |
                ui(buf[index + 3]);

        return i;
    }

    /***
     * Get NTP Timestamp at specified starting index.
     *
     * @param index index into data array
     * @return TimeStamp object for 64 bits starting at index
     */
    private TimeStamp getTimestamp(int index)
    {
        return new TimeStamp(getLong(index));
    }

    /***
     * Get Long value represented by bits starting at specified index.
     *
     * @return 8 bytes as 64-bit long
     */
    private long getLong(int index)
    {
        long i = ul(buf[index]) << 56 |
                ul(buf[index + 1]) << 48 |
                ul(buf[index + 2]) << 40 |
                ul(buf[index + 3]) << 32 |
                ul(buf[index + 4]) << 24 |
                ul(buf[index + 5]) << 16 |
                ul(buf[index + 6]) << 8 |
                ul(buf[index + 7]);
        return i;
    }

    /***
     * Sets the NTP timestamp at the given array index.
     *
     * @param index index into the byte array.
     * @param t TimeStamp.
     */
    private void setTimestamp(int index, TimeStamp t)
    {
        long ntpTime = (t == null) ? 0 : t.ntpValue();
        // copy 64-bits from Long value into 8 x 8-bit bytes of array
        // one byte at a time shifting 8-bits for each position.
        for (int i = 7; i >= 0; i--) {
            buf[index + i] = (byte) (ntpTime & 0xFF);
            ntpTime >>>= 8; // shift to next byte
        }
        // buf[index] |= 0x80;  // only set if 1900 baseline....
    }

    /***
     * Returns the datagram packet with the NTP details already filled in.
     *
     * @return a datagram packet.
     */
    public DatagramPacket getDatagramPacket()
    {
        if (dp == null)
            synchronized(this) {
                if (dp == null) {
                    dp = new DatagramPacket(buf, buf.length);
                    dp.setPort(NTP_PORT);
                }
            }
        return dp;
    }

    /***
     * Set the contents of this object from source datagram packet.
     *
     * @param srcDp source DatagramPacket to copy contents from.
     */
    public void setDatagramPacket(DatagramPacket srcDp)
    {
        byte[] incomingBuf = srcDp.getData();
        int len = srcDp.getLength();
        if (len > buf.length)
            len = buf.length;

        System.arraycopy(incomingBuf, 0, buf, 0, len);
    }

    /***
     * Convert byte to unsigned integer.
     * Java only has signed types so we have to do
     * more work to get unsigned ops.
     *
     * @param b
     * @return unsigned int value of byte
     */
    protected final static int ui(byte b)
    {
        int i = b & 0xFF;
        return i;
    }

    /***
     * Convert byte to unsigned long.
     * Java only has signed types so we have to do
     * more work to get unsigned ops
     *
     * @param b
     * @return unsigned long value of byte
     */
    protected final static long ul(byte b)
    {
        long i = b & 0xFF;
        return i;
    }

    /***
     * Returns details of NTP packet as a string.
     *
     * @return details of NTP packet as a string.
     */
    public String toString()
    {
        return "[" +
                "version:" + getVersion() +
                ", mode:" + getMode() +
                ", poll:" + getPoll() +
                ", precision:" + getPrecision() +
                ", delay:" + getRootDelay() +
                ", dispersion(ms):" + getRootDispersionInMillisDouble() +
                ", id:" + getReferenceIdString() +
                ", xmitTime:" + getTransmitTimeStamp().toDateString() +
                " ]";
    }

}