org.apache.commons.net.ntp

Class TimeStamp

Implemented Interfaces:
Comparable, java.io.Serializable

public class TimeStamp
extends java.lang.Object
implements java.io.Serializable, Comparable

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.

Version:
$Revision: 165675 $ $Date: 2005-05-02 15:09:55 -0500 (Mon, 02 May 2005) $
Author:
Jason Mathews, MITRE Corp
See Also:
java.util.Date, Serialized Form

Field Summary

static String
NTP_DATE_FORMAT
Default NTP date string format.
protected static long
msb0baseTime
baseline NTP time if bit-0=0 -> 7-Feb-2036 @ 06:28:16 UTC
protected static long
msb1baseTime
baseline NTP time if bit-0=1 -> 1-Jan-1900 @ 01:00:00 UTC

Constructor Summary

TimeStamp(Date d)
Constructs a newly allocated NTP timestamp object that represents the Java Date argument.
TimeStamp(String s)
Constructs a newly allocated NTP timestamp object that represents the value represented by the string in hexdecimal form (e.g.
TimeStamp(long ntpTime)
Constructs a newly allocated NTP timestamp object that represents the native 64-bit long argument.

Method Summary

int
compareTo(Object o)
Compares this TimeStamp to another Object.
int
compareTo(TimeStamp anotherTimeStamp)
Compares two Timestamps numerically.
protected static long
decodeNtpHexString(String s)
Convert NTP timestamp hexstring (e.g.
boolean
equals(Object obj)
Compares this object against the specified object.
static TimeStamp
getCurrentTime()
Constructs a NTP timestamp object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
Date
getDate()
Convert NTP timestamp to Java Date object.
long
getFraction()
Returns low-order 32-bits representing the fractional seconds.
static TimeStamp
getNtpTime(long date)
Helper method to convert Java time to NTP timestamp object.
long
getSeconds()
Returns high-order 32-bits representing the seconds of this NTP timestamp.
long
getTime()
Convert NTP timestamp to Java standard time.
static long
getTime(long ntpTimeValue)
Convert 64-bit NTP timestamp to Java standard time.
int
hashCode()
Computes a hashcode for this Timestamp.
long
ntpValue()
Returns the value of this Timestamp as a long value.
static TimeStamp
parseNtpString(String s)
Parses the string argument as a NTP hexidecimal timestamp representation string (e.g.
String
toDateString()
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.
protected static long
toNtpTime(long t)
Converts Java time to 64-bit NTP time representation.
String
toString()
Converts this TimeStamp object to a String.
static String
toString(long ntpTime)
Converts 64-bit NTP timestamp value to a String.
String
toUTCString()
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.

Field Details

NTP_DATE_FORMAT

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.

msb0baseTime

protected static final long msb0baseTime
baseline NTP time if bit-0=0 -> 7-Feb-2036 @ 06:28:16 UTC
Field Value:
2085978496000L

msb1baseTime

protected static final long msb1baseTime
baseline NTP time if bit-0=1 -> 1-Jan-1900 @ 01:00:00 UTC
Field Value:
-2208988800000L

Constructor Details

TimeStamp

public TimeStamp(Date d)
Constructs a newly allocated NTP timestamp object that represents the Java Date argument.
Parameters:
d - - the Date to be represented by the Timestamp object.

TimeStamp

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

TimeStamp

public TimeStamp(long ntpTime)
Constructs a newly allocated NTP timestamp object that represents the native 64-bit long argument.

Method Details

compareTo

public int compareTo(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).
Parameters:
o - the Object to be compared.
Returns:
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.
See Also:
java.lang.Comparable

compareTo

public int compareTo(TimeStamp anotherTimeStamp)
Compares two Timestamps numerically.
Parameters:
anotherTimeStamp - - the TimeStamp to be compared.
Returns:
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).

decodeNtpHexString

protected static long decodeNtpHexString(String s)
            throws NumberFormatException
Convert NTP timestamp hexstring (e.g. "c1a089bd.fc904f6d") to the NTP 64-bit unsigned fixed-point number.
Returns:
NTP 64-bit timestamp value.

equals

public boolean equals(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.
Parameters:
obj - the object to compare with.
Returns:
true if the objects are the same; false otherwise.

getCurrentTime

public static TimeStamp getCurrentTime()
Constructs a NTP timestamp object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
Returns:
NTP timestamp object set to the current time.
See Also:
java.lang.System.currentTimeMillis()

getDate

public Date getDate()
Convert NTP timestamp to Java Date object.
Returns:
NTP Timestamp in Java Date

getFraction

public long getFraction()
Returns low-order 32-bits representing the fractional seconds.
Returns:
fractional seconds represented by this NTP timestamp.

getNtpTime

public static TimeStamp getNtpTime(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.
Parameters:
date - the milliseconds since January 1, 1970, 00:00:00 GMT.
Returns:
NTP timestamp object at the specified date.

getSeconds

public long getSeconds()
Returns high-order 32-bits representing the seconds of this NTP timestamp.
Returns:
seconds represented by this NTP timestamp.

getTime

public long getTime()
Convert NTP timestamp to Java standard time.
Returns:
NTP Timestamp in Java time

getTime

public static long getTime(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.
Parameters:
ntpTimeValue -
Returns:
the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this NTP timestamp value.

hashCode

public int hashCode()
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))
 
Returns:
a hash code value for this object.

ntpValue

public long ntpValue()
Returns the value of this Timestamp as a long value.
Returns:
the 64-bit long value represented by this object.

parseNtpString

public static TimeStamp parseNtpString(String s)
            throws NumberFormatException
Parses the string argument as a NTP hexidecimal timestamp representation string (e.g. "c1a089bd.fc904f6d").
Parameters:
s - - hexstring.
Returns:
the Timestamp represented by the argument in hexidecimal.

toDateString

public String toDateString()
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.
Returns:
a string representation of this date.

toNtpTime

protected static long toNtpTime(long t)
Converts Java time to 64-bit NTP time representation.
Parameters:
t - Java time
Returns:
NTP timestamp representation of Java time value.

toString

public String toString()
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
Returns:
NTP timestamp 64-bit long value as hex string with seconds separated by fractional seconds.

toString

public static String toString(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
Returns:
NTP timestamp 64-bit long value as hex string with seconds separated by fractional seconds.

toUTCString

public String toUTCString()
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.
Returns:
a string representation of this date in UTC.