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TimeStamp.javaAPI DocApache Commons NET 1.4.1 API16915Sat Dec 03 10:05:48 GMT 2005org.apache.commons.net.ntp

TimeStamp

public class TimeStamp extends Object implements Comparable, Serializable
TimeStamp class represents the Network Time Protocol (NTP) timestamp as defined in RFC-1305 and SNTP (RFC-2030). It is represented as a 64-bit unsigned fixed-point number in seconds relative to 0-hour on 1-January-1900. The 32-bit low-order bits are the fractional seconds whose precision is about 200 picoseconds. Assumes overflow date when date passes MAX_LONG and reverts back to 0 is 2036 and not 1900. Test for most significant bit: if MSB=0 then 2036 basis is used otherwise 1900 if MSB=1.

Methods exist to convert NTP timestamps to and from the equivalent Java date representation, which is the number of milliseconds since the standard base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT.

author
Jason Mathews, MITRE Corp
version
$Revision: 165675 $ $Date: 2005-05-02 15:09:55 -0500 (Mon, 02 May 2005) $
see
java.util.Date

Fields Summary
protected static final long
msb0baseTime
baseline NTP time if bit-0=0 -> 7-Feb-2036 @ 06:28:16 UTC
protected static final long
msb1baseTime
baseline NTP time if bit-0=1 -> 1-Jan-1900 @ 01:00:00 UTC
public static final String
NTP_DATE_FORMAT
Default NTP date string format. E.g. Fri, Sep 12 2003 21:06:23.860. See java.text.SimpleDateFormat for code descriptions.
private static SoftReference
simpleFormatter
private static SoftReference
utcFormatter
private long
ntpTime
NTP timestamp value: 64-bit unsigned fixed-point number as defined in RFC-1305 with high-order 32 bits the seconds field and the low-order 32-bits the fractional field.
private static final long
serialVersionUID
Constructors Summary
public TimeStamp(long ntpTime)
Constructs a newly allocated NTP timestamp object that represents the native 64-bit long argument.


    // initialization of static time bases
    /*
    static {
        TimeZone utcZone = TimeZone.getTimeZone("UTC");
        Calendar calendar = Calendar.getInstance(utcZone);
        calendar.set(1900, Calendar.JANUARY, 1, 0, 0, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        msb1baseTime = calendar.getTime().getTime();
        calendar.set(2036, Calendar.FEBRUARY, 7, 6, 28, 16);
        calendar.set(Calendar.MILLISECOND, 0);
        msb0baseTime = calendar.getTime().getTime();
    }
    */

                       
      
    
        this.ntpTime = ntpTime;
    
public TimeStamp(String s)
Constructs a newly allocated NTP timestamp object that represents the value represented by the string in hexdecimal form (e.g. "c1a089bd.fc904f6d").

throws
NumberFormatException - if the string does not contain a parsable timestamp.

        ntpTime = decodeNtpHexString(s);
    
public TimeStamp(Date d)
Constructs a newly allocated NTP timestamp object that represents the Java Date argument.

param
d - the Date to be represented by the Timestamp object.

        ntpTime = (d == null) ? 0 : toNtpTime(d.getTime());
    
Methods Summary
private static voidappendHexString(java.lang.StringBuffer buf, long l)
Left-pad 8-character hex string with 0's

param
buf - StringBuffer which is appended with leading 0's.
param
l - a long.

        String s = Long.toHexString(l);
        for (int i = s.length(); i < 8; i++)
            buf.append('0");
        buf.append(s);
    
public intcompareTo(org.apache.commons.net.ntp.TimeStamp anotherTimeStamp)
Compares two Timestamps numerically.

param
anotherTimeStamp - the TimeStamp to be compared.
return
the value 0 if the argument TimeStamp is equal to this TimeStamp; a value less than 0 if this TimeStamp is numerically less than the TimeStamp argument; and a value greater than 0 if this TimeStamp is numerically greater than the TimeStamp argument (signed comparison).

        long thisVal = this.ntpTime;
        long anotherVal = anotherTimeStamp.ntpTime;
        return (thisVal < anotherVal ? -1 : (thisVal == anotherVal ? 0 : 1));
    
public intcompareTo(java.lang.Object o)
Compares this TimeStamp to another Object. If the Object is a TimeStamp, this function behaves like compareTo(TimeStamp). Otherwise, it throws a ClassCastException (as TimeStamps are comparable only to other TimeStamps).

param
o the Object to be compared.
return
the value 0 if the argument is a TimeStamp numerically equal to this TimeStamp; a value less than 0 if the argument is a TimeStamp numerically greater than this TimeStamp; and a value greater than 0 if the argument is a TimeStamp numerically less than this TimeStamp.
exception
ClassCastException if the argument is not a TimeStamp.
see
java.lang.Comparable

        return compareTo((TimeStamp) o);
    
protected static longdecodeNtpHexString(java.lang.String s)
Convert NTP timestamp hexstring (e.g. "c1a089bd.fc904f6d") to the NTP 64-bit unsigned fixed-point number.

return
NTP 64-bit timestamp value.
throws
NumberFormatException - if the string does not contain a parsable timestamp.

        if (s == null) {
            throw new NumberFormatException("null");
        }
        int ind = s.indexOf('.");
        if (ind == -1) {
            if (s.length() == 0) return 0;
            return Long.parseLong(s, 16) << 32; // no decimal
        }

        return Long.parseLong(s.substring(0, ind), 16) << 32 |
                Long.parseLong(s.substring(ind + 1), 16);
    
public booleanequals(java.lang.Object obj)
Compares this object against the specified object. The result is true if and only if the argument is not null and is a Long object that contains the same long value as this object.

param
obj the object to compare with.
return
true if the objects are the same; false otherwise.

        if (obj instanceof TimeStamp) {
            return ntpTime == ((TimeStamp) obj).ntpValue();
        }
        return false;
    
public static org.apache.commons.net.ntp.TimeStampgetCurrentTime()
Constructs a NTP timestamp object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.

return
NTP timestamp object set to the current time.
see
java.lang.System#currentTimeMillis()

        return getNtpTime(System.currentTimeMillis());
    
public java.util.DategetDate()
Convert NTP timestamp to Java Date object.

return
NTP Timestamp in Java Date

        long time = getTime(ntpTime);
        return new Date(time);
    
public longgetFraction()
Returns low-order 32-bits representing the fractional seconds.

return
fractional seconds represented by this NTP timestamp.

        return ntpTime & 0xffffffffL;
    
public static org.apache.commons.net.ntp.TimeStampgetNtpTime(long date)
Helper method to convert Java time to NTP timestamp object. Note that Java time (milliseconds) by definition has less precision then NTP time (picoseconds) so converting Ntptime to Javatime and back to Ntptime loses precision. For example, Tue, Dec 17 2002 09:07:24.810 is represented by a single Java-based time value of f22cd1fc8a, but its NTP equivalent are all values from c1a9ae1c.cf5c28f5 to c1a9ae1c.cf9db22c.

param
date the milliseconds since January 1, 1970, 00:00:00 GMT.
return
NTP timestamp object at the specified date.

        return new TimeStamp(toNtpTime(date));
    
public longgetSeconds()
Returns high-order 32-bits representing the seconds of this NTP timestamp.

return
seconds represented by this NTP timestamp.

        return (ntpTime >>> 32) & 0xffffffffL;
    
public longgetTime()
Convert NTP timestamp to Java standard time.

return
NTP Timestamp in Java time

        return getTime(ntpTime);
    
public static longgetTime(long ntpTimeValue)
Convert 64-bit NTP timestamp to Java standard time. Note that java time (milliseconds) by definition has less precision then NTP time (picoseconds) so converting NTP timestamp to java time and back to NTP timestamp loses precision. For example, Tue, Dec 17 2002 09:07:24.810 EST is represented by a single Java-based time value of f22cd1fc8a, but its NTP equivalent are all values ranging from c1a9ae1c.cf5c28f5 to c1a9ae1c.cf9db22c.

param
ntpTimeValue
return
the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this NTP timestamp value.

        long seconds = (ntpTimeValue >>> 32) & 0xffffffffL;	// high-order 32-bits
        long fraction = ntpTimeValue & 0xffffffffL;		// low-order 32-bits

        // Use round-off on fractional part to preserve going to lower precision
        fraction = Math.round(1000D * fraction / 0x100000000L);

        /*
         * If the most significant bit (MSB) on the seconds field is set we use
         * a different time base. The following text is a quote from RFC-2030 (SNTP v4):
         *
         *  If bit 0 is set, the UTC time is in the range 1968-2036 and UTC time
         *  is reckoned from 0h 0m 0s UTC on 1 January 1900. If bit 0 is not set,
         *  the time is in the range 2036-2104 and UTC time is reckoned from
         *  6h 28m 16s UTC on 7 February 2036.
         */
        long msb = seconds & 0x80000000L;
        if (msb == 0) {
            // use base: 7-Feb-2036 @ 06:28:16 UTC
            return msb0baseTime + (seconds * 1000) + fraction;
        } else {
            // use base: 1-Jan-1900 @ 01:00:00 UTC
            return msb1baseTime + (seconds * 1000) + fraction;
        }
    
public inthashCode()
Computes a hashcode for this Timestamp. The result is the exclusive OR of the two halves of the primitive long value represented by this TimeStamp object. That is, the hashcode is the value of the expression:
(int)(this.ntpValue()^(this.ntpValue() >>> 32))

return
a hash code value for this object.

        return (int) (ntpTime ^ (ntpTime >>> 32));
    
public longntpValue()
Returns the value of this Timestamp as a long value.

return
the 64-bit long value represented by this object.

        return ntpTime;
    
public static org.apache.commons.net.ntp.TimeStampparseNtpString(java.lang.String s)
Parses the string argument as a NTP hexidecimal timestamp representation string (e.g. "c1a089bd.fc904f6d").

param
s - hexstring.
return
the Timestamp represented by the argument in hexidecimal.
throws
NumberFormatException - if the string does not contain a parsable timestamp.

        return new TimeStamp(decodeNtpHexString(s));
    
public java.lang.StringtoDateString()
Converts this TimeStamp object to a String of the form:
EEE, MMM dd yyyy HH:mm:ss.SSS
See java.text.SimpleDataFormat for code descriptions.

return
a string representation of this date.

        DateFormat formatter = null;
        if (simpleFormatter != null) {
            formatter = (DateFormat) simpleFormatter.get();
        }
        if (formatter == null) {
            // No cache yet, or cached formatter GC'd
            formatter = new SimpleDateFormat(NTP_DATE_FORMAT, Locale.US);
            formatter.setTimeZone(TimeZone.getDefault());
            simpleFormatter = new SoftReference(formatter);
        }
        Date ntpDate = getDate();
        synchronized (formatter) {
            return formatter.format(ntpDate);
        }
    
protected static longtoNtpTime(long t)
Converts Java time to 64-bit NTP time representation.

param
t Java time
return
NTP timestamp representation of Java time value.

        boolean useBase1 = t < msb0baseTime;	// time < Feb-2036
        long baseTime;
        if (useBase1) {
            baseTime = t - msb1baseTime; // dates <= Feb-2036
        } else {
            // if base0 needed for dates >= Feb-2036
            baseTime = t - msb0baseTime;
        }

        long seconds = baseTime / 1000;
        long fraction = ((baseTime % 1000) * 0x100000000L) / 1000;

        if (useBase1) {
            seconds |= 0x80000000L; // set high-order bit if msb1baseTime 1900 used
        }

        long time = seconds << 32 | fraction;
        return time;
    
public java.lang.StringtoString()
Converts this TimeStamp object to a String. The NTP timestamp 64-bit long value is represented as hex string with seconds separated by fractional seconds by a decimal point; e.g. c1a089bd.fc904f6d <=> Tue, Dec 10 2002 10:41:49.986

return
NTP timestamp 64-bit long value as hex string with seconds separated by fractional seconds.

        return toString(ntpTime);
    
public static java.lang.StringtoString(long ntpTime)
Converts 64-bit NTP timestamp value to a String. The NTP timestamp value is represented as hex string with seconds separated by fractional seconds by a decimal point; e.g. c1a089bd.fc904f6d <=> Tue, Dec 10 2002 10:41:49.986

return
NTP timestamp 64-bit long value as hex string with seconds separated by fractional seconds.

        StringBuffer buf = new StringBuffer();
        // high-order second bits (32..63) as hexstring
        appendHexString(buf, (ntpTime >>> 32) & 0xffffffffL);

        // low-order fractional seconds bits (0..31) as hexstring
        buf.append('.");
        appendHexString(buf, ntpTime & 0xffffffffL);

        return buf.toString();
    
public java.lang.StringtoUTCString()
Converts this TimeStamp object to a String of the form:
EEE, MMM dd yyyy HH:mm:ss.SSS UTC
See java.text.SimpleDataFormat for code descriptions.

return
a string representation of this date in UTC.

        DateFormat formatter = null;
        if (utcFormatter != null)
            formatter = (DateFormat) utcFormatter.get();
        if (formatter == null) {
            // No cache yet, or cached formatter GC'd
            formatter = new SimpleDateFormat(NTP_DATE_FORMAT + " 'UTC'",
                    Locale.US);
            formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
            utcFormatter = new SoftReference(formatter);
        }
        Date ntpDate = getDate();
        synchronized (formatter) {
            return formatter.format(ntpDate);
        }