Java > Open Source Codes > org > apache > commons > net > ntp > TimeStamp


1 package org.apache.commons.net.ntp;
2 /*
3  * Copyright 2001-2005 The Apache Software Foundation
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17
18
19 import java.util.TimeZone ;
20 import java.util.Date ;
21 import java.util.Locale ;
22 import java.lang.ref.SoftReference ;
23 import java.text.SimpleDateFormat ;
24 import java.text.DateFormat ;
25
26 /***
27  * TimeStamp class represents the Network Time Protocol (NTP) timestamp
28  * as defined in RFC-1305 and SNTP (RFC-2030). It is represented as a
29  * 64-bit unsigned fixed-point number in seconds relative to 0-hour on 1-January-1900.
30  * The 32-bit low-order bits are the fractional seconds whose precision is
31  * about 200 picoseconds. Assumes overflow date when date passes MAX_LONG
32  * and reverts back to 0 is 2036 and not 1900. Test for most significant
33  * bit: if MSB=0 then 2036 basis is used otherwise 1900 if MSB=1.
34  * <p>
35  * Methods exist to convert NTP timestamps to and from the equivalent Java date
36  * representation, which is the number of milliseconds since the standard base
37  * time known as "the epoch", namely January 1, 1970, 00:00:00 GMT.
38  * </p>
39  *
40  * @author Jason Mathews, MITRE Corp
41  * @version $Revision: 165675 $ $Date: 2005-05-02 15:09:55 -0500 (Mon, 02 May 2005) $
42  * @see java.util.Date
43  */
44 public class TimeStamp implements java.io.Serializable , Comparable
45 {
46
47     /**
48      * baseline NTP time if bit-0=0 -> 7-Feb-2036 @ 06:28:16 UTC
49      */
50     protected static final long msb0baseTime = 2085978496000L;
51
52     /**
53      * baseline NTP time if bit-0=1 -> 1-Jan-1900 @ 01:00:00 UTC
54      */
55     protected static final long msb1baseTime = -2208988800000L;
56
57     /**
58      * Default NTP date string format. E.g. Fri, Sep 12 2003 21:06:23.860.
59      * See <code>java.text.SimpleDateFormat</code> for code descriptions.
60      */
61     public final static String NTP_DATE_FORMAT = "EEE, MMM dd yyyy HH:mm:ss.SSS";
62
63     /*
64      * Caches for the DateFormatters used by various toString methods.
65      */
66     private static SoftReference simpleFormatter = null;
67     private static SoftReference utcFormatter = null;
68
69     /**
70      * NTP timestamp value: 64-bit unsigned fixed-point number as defined in RFC-1305
71      * with high-order 32 bits the seconds field and the low-order 32-bits the
72      * fractional field.
73      */
74     private long ntpTime;
75
76     private static final long serialVersionUID = 8139806907588338737L;
77
78     // initialization of static time bases
79 /*
80     static {
81         TimeZone utcZone = TimeZone.getTimeZone("UTC");
82         Calendar calendar = Calendar.getInstance(utcZone);
83         calendar.set(1900, Calendar.JANUARY, 1, 0, 0, 0);
84         calendar.set(Calendar.MILLISECOND, 0);
85         msb1baseTime = calendar.getTime().getTime();
86         calendar.set(2036, Calendar.FEBRUARY, 7, 6, 28, 16);
87         calendar.set(Calendar.MILLISECOND, 0);
88         msb0baseTime = calendar.getTime().getTime();
89     }
90     */
91
92     /***
93      * Constructs a newly allocated NTP timestamp object
94      * that represents the native 64-bit long argument.
95      */
96     public TimeStamp(long ntpTime)
97     {
98         this.ntpTime = ntpTime;
99     }
100
101     /***
102      * Constructs a newly allocated NTP timestamp object
103      * that represents the value represented by the string
104      * in hexdecimal form (e.g. "c1a089bd.fc904f6d").
105      *
106      * @throws NumberFormatException - if the string does not contain a parsable timestamp.
107      */
108     public TimeStamp(String s) throws NumberFormatException
109     {
110         ntpTime = decodeNtpHexString(s);
111     }
112
113     /***
114      * Constructs a newly allocated NTP timestamp object
115      * that represents the Java Date argument.
116      *
117      * @param d - the Date to be represented by the Timestamp object.
118      */
119     public TimeStamp(Date d)
120     {
121         ntpTime = (d == null) ? 0 : toNtpTime(d.getTime());
122     }
123
124     /***
125      * Returns the value of this Timestamp as a long value.
126      *
127      * @return the 64-bit long value represented by this object.
128      */
129     public long ntpValue()
130     {
131         return ntpTime;
132     }
133
134     /***
135      * Returns high-order 32-bits representing the seconds of this NTP timestamp.
136      *
137      * @return seconds represented by this NTP timestamp.
138      */
139     public long getSeconds()
140     {
141         return (ntpTime >>> 32) & 0xffffffffL;
142     }
143
144     /***
145      * Returns low-order 32-bits representing the fractional seconds.
146      *
147      * @return fractional seconds represented by this NTP timestamp.
148      */
149     public long getFraction()
150     {
151         return ntpTime & 0xffffffffL;
152     }
153
154     /***
155      * Convert NTP timestamp to Java standard time.
156      *
157      * @return NTP Timestamp in Java time
158      */
159     public long getTime()
160     {
161         return getTime(ntpTime);
162     }
163
164     /***
165      * Convert NTP timestamp to Java Date object.
166      *
167      * @return NTP Timestamp in Java Date
168      */
169     public Date getDate()
170     {
171         long time = getTime(ntpTime);
172         return new Date (time);
173     }
174
175     /***
176      * Convert 64-bit NTP timestamp to Java standard time.
177      *
178      * Note that java time (milliseconds) by definition has less precision
179      * then NTP time (picoseconds) so converting NTP timestamp to java time and back
180      * to NTP timestamp loses precision. For example, Tue, Dec 17 2002 09:07:24.810 EST
181      * is represented by a single Java-based time value of f22cd1fc8a, but its
182      * NTP equivalent are all values ranging from c1a9ae1c.cf5c28f5 to c1a9ae1c.cf9db22c.
183      *
184      * @param ntpTimeValue
185      * @return the number of milliseconds since January 1, 1970, 00:00:00 GMT
186      * represented by this NTP timestamp value.
187      */
188     public static long getTime(long ntpTimeValue)
189     {
190         long seconds = (ntpTimeValue >>> 32) & 0xffffffffL; // high-order 32-bits
191 long fraction = ntpTimeValue & 0xffffffffL; // low-order 32-bits
192
193         // Use round-off on fractional part to preserve going to lower precision
194 fraction = Math.round(1000D * fraction / 0x100000000L);
195
196         /*
197          * If the most significant bit (MSB) on the seconds field is set we use
198          * a different time base. The following text is a quote from RFC-2030 (SNTP v4):
199          *
200          * If bit 0 is set, the UTC time is in the range 1968-2036 and UTC time
201          * is reckoned from 0h 0m 0s UTC on 1 January 1900. If bit 0 is not set,
202          * the time is in the range 2036-2104 and UTC time is reckoned from
203          * 6h 28m 16s UTC on 7 February 2036.
204          */
205         long msb = seconds & 0x80000000L;
206         if (msb == 0) {
207             // use base: 7-Feb-2036 @ 06:28:16 UTC
208 return msb0baseTime + (seconds * 1000) + fraction;
209         } else {
210             // use base: 1-Jan-1900 @ 01:00:00 UTC
211 return msb1baseTime + (seconds * 1000) + fraction;
212         }
213     }
214
215     /***
216      * Helper method to convert Java time to NTP timestamp object.
217      * Note that Java time (milliseconds) by definition has less precision
218      * then NTP time (picoseconds) so converting Ntptime to Javatime and back
219      * to Ntptime loses precision. For example, Tue, Dec 17 2002 09:07:24.810
220      * is represented by a single Java-based time value of f22cd1fc8a, but its
221      * NTP equivalent are all values from c1a9ae1c.cf5c28f5 to c1a9ae1c.cf9db22c.
222      * @param date the milliseconds since January 1, 1970, 00:00:00 GMT.
223      * @return NTP timestamp object at the specified date.
224      */
225     public static TimeStamp getNtpTime(long date)
226     {
227         return new TimeStamp(toNtpTime(date));
228     }
229
230     /***
231      * Constructs a NTP timestamp object and initializes it so that
232      * it represents the time at which it was allocated, measured to the
233      * nearest millisecond.
234      * @return NTP timestamp object set to the current time.
235      * @see java.lang.System#currentTimeMillis()
236      */
237     public static TimeStamp getCurrentTime()
238     {
239         return getNtpTime(System.currentTimeMillis());
240     }
241
242     /***
243      * Convert NTP timestamp hexstring (e.g. "c1a089bd.fc904f6d") to the NTP
244      * 64-bit unsigned fixed-point number.
245      *
246      * @return NTP 64-bit timestamp value.
247      * @throws NumberFormatException - if the string does not contain a parsable timestamp.
248      */
249     protected static long decodeNtpHexString(String s)
250             throws NumberFormatException
251     {
252         if (s == null) {
253             throw new NumberFormatException ("null");
254         }
255         int ind = s.indexOf('.');
256         if (ind == -1) {
257             if (s.length() == 0) return 0;
258             return Long.parseLong(s, 16) << 32; // no decimal
259 }
260
261         return Long.parseLong(s.substring(0, ind), 16) << 32 |
262                 Long.parseLong(s.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      * (int)(this.ntpValue()^(this.ntpValue() >>> 32))
314      * </pre></blockquote>
315      *
316      * @return a hash code value for this object.
317      */
318     public int hashCode()
319     {
320         return (int) (ntpTime ^ (ntpTime >>> 32));
321     }
322
323     /***
324      * Compares this object against the specified object.
325      * The result is <code>true</code> if and only if the argument is
326      * not <code>null</code> and is a <code>Long</code> object that
327      * contains the same <code>long</code> value as this object.
328      *
329      * @param obj the object to compare with.
330      * @return <code>true</code> if the objects are the same;
331      * <code>false</code> otherwise.
332      */
333     public boolean equals(Object obj)
334     {
335         if (obj instanceof TimeStamp) {
336             return ntpTime == ((TimeStamp) obj).ntpValue();
337         }
338         return false;
339     }
340
341     /***
342      * Converts this <code>TimeStamp</code> object to a <code>String</code>.
343      * The NTP timestamp 64-bit long value is represented as hex string with
344      * seconds separated by fractional seconds by a decimal point;
345      * e.g. c1a089bd.fc904f6d <=> Tue, Dec 10 2002 10:41:49.986
346      *
347      * @return NTP timestamp 64-bit long value as hex string with seconds
348      * separated by fractional seconds.
349      */
350     public String toString()
351     {
352         return toString(ntpTime);
353     }
354
355     /***
356      * Left-pad 8-character hex string with 0's
357      *
358      * @param buf - StringBuffer which is appended with leading 0's.
359      * @param l - a long.
360      */
361     private static void appendHexString(StringBuffer buf, long l)
362     {
363         String s = Long.toHexString(l);
364         for (int i = s.length(); i < 8; i++)
365             buf.append('0');
366         buf.append(s);
367     }
368
369     /***
370      * Converts 64-bit NTP timestamp value to a <code>String</code>.
371      * The NTP timestamp value is represented as hex string with
372      * seconds separated by fractional seconds by a decimal point;
373      * e.g. c1a089bd.fc904f6d <=> Tue, Dec 10 2002 10:41:49.986
374      *
375      * @return NTP timestamp 64-bit long value as hex string with seconds
376      * separated by fractional seconds.
377      */
378     public static String toString(long ntpTime)
379     {
380         StringBuffer buf = new StringBuffer ();
381         // high-order second bits (32..63) as hexstring
382 appendHexString(buf, (ntpTime >>> 32) & 0xffffffffL);
383
384         // low-order fractional seconds bits (0..31) as hexstring
385 buf.append('.');
386         appendHexString(buf, ntpTime & 0xffffffffL);
387
388         return buf.toString();
389     }
390
391     /***
392      * Converts this <code>TimeStamp</code> object to a <code>String</code>
393      * of the form:
394      * <blockquote><pre>
395      * EEE, MMM dd yyyy HH:mm:ss.SSS</pre></blockquote>
396      * See java.text.SimpleDataFormat for code descriptions.
397      *
398      * @return a string representation of this date.
399      */
400     public String toDateString()
401     {
402         DateFormat formatter = null;
403         if (simpleFormatter != null) {
404             formatter = (DateFormat ) simpleFormatter.get();
405         }
406         if (formatter == null) {
407             // No cache yet, or cached formatter GC'd
408 formatter = new SimpleDateFormat (NTP_DATE_FORMAT, Locale.US);
409             formatter.setTimeZone(TimeZone.getDefault());
410             simpleFormatter = new SoftReference (formatter);
411         }
412         Date ntpDate = getDate();
413         synchronized (formatter) {
414             return formatter.format(ntpDate);
415         }
416     }
417
418     /***
419      * Converts this <code>TimeStamp</code> object to a <code>String</code>
420      * of the form:
421      * <blockquote><pre>
422      * EEE, MMM dd yyyy HH:mm:ss.SSS UTC</pre></blockquote>
423      * See java.text.SimpleDataFormat for code descriptions.
424      *
425      * @return a string representation of this date in UTC.
426      */
427     public String toUTCString()
428     {
429         DateFormat formatter = null;
430         if (utcFormatter != null)
431             formatter = (DateFormat ) utcFormatter.get();
432         if (formatter == null) {
433             // No cache yet, or cached formatter GC'd
434 formatter = new SimpleDateFormat (NTP_DATE_FORMAT + " 'UTC'",
435                     Locale.US);
436             formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
437             utcFormatter = new SoftReference (formatter);
438         }
439         Date ntpDate = getDate();
440         synchronized (formatter) {
441             return formatter.format(ntpDate);
442         }
443     }
444
445     /***
446      * Compares two Timestamps numerically.
447      *
448      * @param anotherTimeStamp - the <code>TimeStamp</code> to be compared.
449      * @return the value <code>0</code> if the argument TimeStamp is equal to
450      * this TimeStamp; a value less than <code>0</code> if this TimeStamp
451      * is numerically less than the TimeStamp argument; and a
452      * value greater than <code>0</code> if this TimeStamp is
453      * numerically greater than the TimeStamp argument
454      * (signed comparison).
455      */
456     public int compareTo(TimeStamp anotherTimeStamp)
457     {
458         long thisVal = this.ntpTime;
459         long anotherVal = anotherTimeStamp.ntpTime;
460         return (thisVal < anotherVal ? -1 : (thisVal == anotherVal ? 0 : 1));
461     }
462
463     /***
464      * Compares this TimeStamp to another Object. If the Object is a TimeStamp,
465      * this function behaves like <code>compareTo(TimeStamp)</code>. Otherwise,
466      * it throws a <code>ClassCastException</code> (as TimeStamps are comparable
467      * only to other TimeStamps).
468      *
469      * @param o the <code>Object</code> to be compared.
470      * @return the value <code>0</code> if the argument is a TimeStamp
471      * numerically equal to this TimeStamp; a value less than
472      * <code>0</code> if the argument is a TimeStamp numerically
473      * greater than this TimeStamp; and a value greater than
474      * <code>0</code> if the argument is a TimeStamp numerically
475      * less than this TimeStamp.
476      * @exception ClassCastException if the argument is not a
477      * <code>TimeStamp</code>.
478      * @see java.lang.Comparable
479      */
480     public int compareTo(Object o)
481     {
482         return compareTo((TimeStamp) o);
483     }
484
485 }
486

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