    001package org.apache.commons.net.ntp;
    002/*
    003 * Licensed to the Apache Software Foundation (ASF) under one or more
    004 * contributor license agreements.  See the NOTICE file distributed with
    005 * this work for additional information regarding copyright ownership.
    006 * The ASF licenses this file to You under the Apache License, Version 2.0
    007 * (the "License"); you may not use this file except in compliance with
    008 * the License.  You may obtain a copy of the License at
    009 *
    010 *      http://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing, software
    013 * distributed under the License is distributed on an "AS IS" BASIS,
    014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    015 * See the License for the specific language governing permissions and
    016 * limitations under the License.
    017 */
    018
    019
    020
    021import java.text.DateFormat;
    022import java.text.SimpleDateFormat;
    023import java.util.Date;
    024import java.util.Locale;
    025import java.util.TimeZone;
    026
    027/***
    028 * TimeStamp class represents the Network Time Protocol (NTP) timestamp
    029 * as defined in RFC-1305 and SNTP (RFC-2030). It is represented as a
    030 * 64-bit unsigned fixed-point number in seconds relative to 0-hour on 1-January-1900.
    031 * The 32-bit low-order bits are the fractional seconds whose precision is
    032 * about 200 picoseconds. Assumes overflow date when date passes MAX_LONG
    033 * and reverts back to 0 is 2036 and not 1900. Test for most significant
    034 * bit: if MSB=0 then 2036 basis is used otherwise 1900 if MSB=1.
    035 * <p>
    036 * Methods exist to convert NTP timestamps to and from the equivalent Java date
    037 * representation, which is the number of milliseconds since the standard base
    038 * time known as "the epoch", namely January 1, 1970, 00:00:00 GMT.
    039 * </p>
    040 *
    041 * @see java.util.Date
    042 */
    043public class TimeStamp implements java.io.Serializable, Comparable<TimeStamp>
    044{
    045    private static final long serialVersionUID = 8139806907588338737L;
    046
    047    /**
    048     * baseline NTP time if bit-0=0 is 7-Feb-2036 @ 06:28:16 UTC
    049     */
    050    protected static final long msb0baseTime = 2085978496000L;
    051
    052    /**
    053     *  baseline NTP time if bit-0=1 is 1-Jan-1900 @ 01:00:00 UTC
    054     */
    055    protected static final long msb1baseTime = -2208988800000L;
    056
    057    /**
    058     * Default NTP date string format. E.g. Fri, Sep 12 2003 21:06:23.860.
    059     * See <code>java.text.SimpleDateFormat</code> for code descriptions.
    060     */
    061    public static final String NTP_DATE_FORMAT = "EEE, MMM dd yyyy HH:mm:ss.SSS";
    062
    063    /**
    064     * NTP timestamp value: 64-bit unsigned fixed-point number as defined in RFC-1305
    065     * with high-order 32 bits the seconds field and the low-order 32-bits the
    066     * fractional field.
    067     */
    068    private final long ntpTime;
    069
    070    private DateFormat simpleFormatter;
    071    private DateFormat utcFormatter;
    072
    073    // initialization of static time bases
    074    /*
    075    static {
    076        TimeZone utcZone = TimeZone.getTimeZone("UTC");
    077        Calendar calendar = Calendar.getInstance(utcZone);
    078        calendar.set(1900, Calendar.JANUARY, 1, 0, 0, 0);
    079        calendar.set(Calendar.MILLISECOND, 0);
    080        msb1baseTime = calendar.getTime().getTime();
    081        calendar.set(2036, Calendar.FEBRUARY, 7, 6, 28, 16);
    082        calendar.set(Calendar.MILLISECOND, 0);
    083        msb0baseTime = calendar.getTime().getTime();
    084    }
    085    */
    086
    087    /***
    088     * Constructs a newly allocated NTP timestamp object
    089     * that represents the native 64-bit long argument.
    090     * @param ntpTime the timestamp
    091     */
    092    public TimeStamp(long ntpTime)
    093    {
    094        this.ntpTime = ntpTime;
    095    }
    096
    097    /***
    098     * Constructs a newly allocated NTP timestamp object
    099     * that represents the value represented by the string
    100     * in hexdecimal form (e.g. "c1a089bd.fc904f6d").
    101     * @param hexStamp the hex timestamp
    102     *
    103     * @throws NumberFormatException - if the string does not contain a parsable timestamp.
    104     */
    105    public TimeStamp(String hexStamp) throws NumberFormatException
    106    {
    107        ntpTime = decodeNtpHexString(hexStamp);
    108    }
    109
    110    /***
    111     * Constructs a newly allocated NTP timestamp object
    112     * that represents the Java Date argument.
    113     *
    114     * @param d - the Date to be represented by the Timestamp object.
    115     */
    116    public TimeStamp(Date d)
    117    {
    118        ntpTime = (d == null) ? 0 : toNtpTime(d.getTime());
    119    }
    120
    121    /***
    122     * Returns the value of this Timestamp as a long value.
    123     *
    124     * @return the 64-bit long value represented by this object.
    125     */
    126    public long ntpValue()
    127    {
    128        return ntpTime;
    129    }
    130
    131    /***
    132     * Returns high-order 32-bits representing the seconds of this NTP timestamp.
    133     *
    134     * @return seconds represented by this NTP timestamp.
    135     */
    136    public long getSeconds()
    137    {
    138        return (ntpTime >>> 32) & 0xffffffffL;
    139    }
    140
    141    /***
    142     * Returns low-order 32-bits representing the fractional seconds.
    143     *
    144     * @return fractional seconds represented by this NTP timestamp.
    145     */
    146    public long getFraction()
    147    {
    148        return ntpTime & 0xffffffffL;
    149    }
    150
    151    /***
    152     * Convert NTP timestamp to Java standard time.
    153     *
    154     * @return NTP Timestamp in Java time
    155     */
    156    public long getTime()
    157    {
    158        return getTime(ntpTime);
    159    }
    160
    161    /***
    162     * Convert NTP timestamp to Java Date object.
    163     *
    164     * @return NTP Timestamp in Java Date
    165     */
    166    public Date getDate()
    167    {
    168        long time = getTime(ntpTime);
    169        return new Date(time);
    170    }
    171
    172    /***
    173     * Convert 64-bit NTP timestamp to Java standard time.
    174     *
    175     * Note that java time (milliseconds) by definition has less precision
    176     * then NTP time (picoseconds) so converting NTP timestamp to java time and back
    177     * to NTP timestamp loses precision. For example, Tue, Dec 17 2002 09:07:24.810 EST
    178     * is represented by a single Java-based time value of f22cd1fc8a, but its
    179     * NTP equivalent are all values ranging from c1a9ae1c.cf5c28f5 to c1a9ae1c.cf9db22c.
    180     *
    181     * @param ntpTimeValue the input time
    182     * @return the number of milliseconds since January 1, 1970, 00:00:00 GMT
    183     * represented by this NTP timestamp value.
    184     */
    185    public static long getTime(long ntpTimeValue)
    186    {
    187        long seconds = (ntpTimeValue >>> 32) & 0xffffffffL;     // high-order 32-bits
    188        long fraction = ntpTimeValue & 0xffffffffL;             // low-order 32-bits
    189
    190        // Use round-off on fractional part to preserve going to lower precision
    191        fraction = Math.round(1000D * fraction / 0x100000000L);
    192
    193        /*
    194         * If the most significant bit (MSB) on the seconds field is set we use
    195         * a different time base. The following text is a quote from RFC-2030 (SNTP v4):
    196         *
    197         *  If bit 0 is set, the UTC time is in the range 1968-2036 and UTC time
    198         *  is reckoned from 0h 0m 0s UTC on 1 January 1900. If bit 0 is not set,
    199         *  the time is in the range 2036-2104 and UTC time is reckoned from
    200         *  6h 28m 16s UTC on 7 February 2036.
    201         */
    202        long msb = seconds & 0x80000000L;
    203        if (msb == 0) {
    204            // use base: 7-Feb-2036 @ 06:28:16 UTC
    205            return msb0baseTime + (seconds * 1000) + fraction;
    206        } else {
    207            // use base: 1-Jan-1900 @ 01:00:00 UTC
    208            return msb1baseTime + (seconds * 1000) + fraction;
    209        }
    210    }
    211
    212    /***
    213     * Helper method to convert Java time to NTP timestamp object.
    214     * Note that Java time (milliseconds) by definition has less precision
    215     * then NTP time (picoseconds) so converting Ntptime to Javatime and back
    216     * to Ntptime loses precision. For example, Tue, Dec 17 2002 09:07:24.810
    217     * is represented by a single Java-based time value of f22cd1fc8a, but its
    218     * NTP equivalent are all values from c1a9ae1c.cf5c28f5 to c1a9ae1c.cf9db22c.
    219     * @param   date   the milliseconds since January 1, 1970, 00:00:00 GMT.
    220     * @return NTP timestamp object at the specified date.
    221     */
    222    public static TimeStamp getNtpTime(long date)
    223    {
    224        return new TimeStamp(toNtpTime(date));
    225    }
    226
    227    /***
    228     * Constructs a NTP timestamp object and initializes it so that
    229     * it represents the time at which it was allocated, measured to the
    230     * nearest millisecond.
    231     * @return NTP timestamp object set to the current time.
    232     * @see     java.lang.System#currentTimeMillis()
    233     */
    234    public static TimeStamp getCurrentTime()
    235    {
    236        return getNtpTime(System.currentTimeMillis());
    237    }
    238
    239    /***
    240     * Convert NTP timestamp hexstring (e.g. "c1a089bd.fc904f6d") to the NTP
    241     * 64-bit unsigned fixed-point number.
    242     * @param hexString the string to convert
    243     *
    244     * @return NTP 64-bit timestamp value.
    245     * @throws NumberFormatException - if the string does not contain a parsable timestamp.
    246     */
    247    protected static long decodeNtpHexString(String hexString)
    248            throws NumberFormatException
    249    {
    250        if (hexString == null) {
    251            throw new NumberFormatException("null");
    252        }
    253        int ind = hexString.indexOf('.');
    254        if (ind == -1) {
    255            if (hexString.length() == 0) {
    256                return 0;
    257            }
    258            return Long.parseLong(hexString, 16) << 32; // no decimal
    259        }
    260
    261        return Long.parseLong(hexString.substring(0, ind), 16) << 32 |
    262                Long.parseLong(hexString.substring(ind + 1), 16);
    263    }
    264
    265    /***
    266     * Parses the string argument as a NTP hexidecimal timestamp representation string
    267     * (e.g. "c1a089bd.fc904f6d").
    268     *
    269     * @param s - hexstring.
    270     * @return the Timestamp represented by the argument in hexidecimal.
    271     * @throws NumberFormatException - if the string does not contain a parsable timestamp.
    272     */
    273    public static TimeStamp parseNtpString(String s)
    274            throws NumberFormatException
    275    {
    276        return new TimeStamp(decodeNtpHexString(s));
    277    }
    278
    279    /***
    280     * Converts Java time to 64-bit NTP time representation.
    281     *
    282     * @param t Java time
    283     * @return NTP timestamp representation of Java time value.
    284     */
    285    protected static long toNtpTime(long t)
    286    {
    287        boolean useBase1 = t < msb0baseTime;    // time < Feb-2036
    288        long baseTime;
    289        if (useBase1) {
    290            baseTime = t - msb1baseTime; // dates <= Feb-2036
    291        } else {
    292            // if base0 needed for dates >= Feb-2036
    293            baseTime = t - msb0baseTime;
    294        }
    295
    296        long seconds = baseTime / 1000;
    297        long fraction = ((baseTime % 1000) * 0x100000000L) / 1000;
    298
    299        if (useBase1) {
    300            seconds |= 0x80000000L; // set high-order bit if msb1baseTime 1900 used
    301        }
    302
    303        long time = seconds << 32 | fraction;
    304        return time;
    305    }
    306
    307    /***
    308     * Computes a hashcode for this Timestamp. The result is the exclusive
    309     * OR of the two halves of the primitive <code>long</code> value
    310     * represented by this <code>TimeStamp</code> object. That is, the hashcode
    311     * is the value of the expression:
    312     * <blockquote><pre>
    313     * {@code (int)(this.ntpValue()^(this.ntpValue() >>> 32))}
    314     * </pre></blockquote>
    315     *
    316     * @return  a hash code value for this object.
    317     */
    318    @Override
    319    public int hashCode()
    320    {
    321        return (int) (ntpTime ^ (ntpTime >>> 32));
    322    }
    323
    324    /***
    325     * Compares this object against the specified object.
    326     * The result is <code>true</code> if and only if the argument is
    327     * not <code>null</code> and is a <code>Long</code> object that
    328     * contains the same <code>long</code> value as this object.
    329     *
    330     * @param   obj   the object to compare with.
    331     * @return  <code>true</code> if the objects are the same;
    332     *          <code>false</code> otherwise.
    333     */
    334    @Override
    335    public boolean equals(Object obj)
    336    {
    337        if (obj instanceof TimeStamp) {
    338            return ntpTime == ((TimeStamp) obj).ntpValue();
    339        }
    340        return false;
    341    }
    342
    343    /***
    344     * Converts this <code>TimeStamp</code> object to a <code>String</code>.
    345     * The NTP timestamp 64-bit long value is represented as hex string with
    346     * seconds separated by fractional seconds by a decimal point;
    347     * e.g. c1a089bd.fc904f6d == Tue, Dec 10 2002 10:41:49.986
    348     *
    349     * @return NTP timestamp 64-bit long value as hex string with seconds
    350     * separated by fractional seconds.
    351     */
    352    @Override
    353    public String toString()
    354    {
    355        return toString(ntpTime);
    356    }
    357
    358    /***
    359     * Left-pad 8-character hex string with 0's
    360     *
    361     * @param buf - StringBuilder which is appended with leading 0's.
    362     * @param l - a long.
    363     */
    364    private static void appendHexString(StringBuilder buf, long l)
    365    {
    366        String s = Long.toHexString(l);
    367        for (int i = s.length(); i < 8; i++) {
    368            buf.append('0');
    369        }
    370        buf.append(s);
    371    }
    372
    373    /***
    374     * Converts 64-bit NTP timestamp value to a <code>String</code>.
    375     * The NTP timestamp value is represented as hex string with
    376     * seconds separated by fractional seconds by a decimal point;
    377     * e.g. c1a089bd.fc904f6d == Tue, Dec 10 2002 10:41:49.986
    378     * @param ntpTime the 64 bit timestamp
    379     *
    380     * @return NTP timestamp 64-bit long value as hex string with seconds
    381     * separated by fractional seconds.
    382     */
    383    public static String toString(long ntpTime)
    384    {
    385        StringBuilder buf = new StringBuilder();
    386        // high-order second bits (32..63) as hexstring
    387        appendHexString(buf, (ntpTime >>> 32) & 0xffffffffL);
    388
    389        // low-order fractional seconds bits (0..31) as hexstring
    390        buf.append('.');
    391        appendHexString(buf, ntpTime & 0xffffffffL);
    392
    393        return buf.toString();
    394    }
    395
    396    /***
    397     * Converts this <code>TimeStamp</code> object to a <code>String</code>
    398     * of the form:
    399     * <blockquote><pre>
    400     * EEE, MMM dd yyyy HH:mm:ss.SSS</pre></blockquote>
    401     * See java.text.SimpleDataFormat for code descriptions.
    402     *
    403     * @return  a string representation of this date.
    404     */
    405    public String toDateString()
    406    {
    407        if (simpleFormatter == null) {
    408            simpleFormatter = new SimpleDateFormat(NTP_DATE_FORMAT, Locale.US);
    409            simpleFormatter.setTimeZone(TimeZone.getDefault());
    410        }
    411        Date ntpDate = getDate();
    412        return simpleFormatter.format(ntpDate);
    413    }
    414
    415    /***
    416     * Converts this <code>TimeStamp</code> object to a <code>String</code>
    417     * of the form:
    418     * <blockquote><pre>
    419     * EEE, MMM dd yyyy HH:mm:ss.SSS UTC</pre></blockquote>
    420     * See java.text.SimpleDataFormat for code descriptions.
    421     *
    422     * @return  a string representation of this date in UTC.
    423     */
    424    public String toUTCString()
    425    {
    426        if (utcFormatter == null) {
    427            utcFormatter = new SimpleDateFormat(NTP_DATE_FORMAT + " 'UTC'",
    428                    Locale.US);
    429            utcFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
    430        }
    431        Date ntpDate = getDate();
    432        return utcFormatter.format(ntpDate);
    433    }
    434
    435    /***
    436     * Compares two Timestamps numerically.
    437     *
    438     * @param   anotherTimeStamp - the <code>TimeStamp</code> to be compared.
    439     * @return  the value <code>0</code> if the argument TimeStamp is equal to
    440     *          this TimeStamp; a value less than <code>0</code> if this TimeStamp
    441     *          is numerically less than the TimeStamp argument; and a
    442     *          value greater than <code>0</code> if this TimeStamp is
    443     *          numerically greater than the TimeStamp argument
    444     *          (signed comparison).
    445     */
    446    @Override
    447    public int compareTo(TimeStamp anotherTimeStamp)
    448    {
    449        long thisVal = this.ntpTime;
    450        long anotherVal = anotherTimeStamp.ntpTime;
    451        return (thisVal < anotherVal ? -1 : (thisVal == anotherVal ? 0 : 1));
    452    }
    453
    454}