panda.net.ntp.TimeStamp Maven / Gradle / Ivy
package panda.net.ntp;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;
/***
* 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.
*
*
* @see java.util.Date
*/
public class TimeStamp implements java.io.Serializable, Comparable {
private static final long serialVersionUID = 8139806907588338737L;
/**
* baseline NTP time if bit-0=0 is 7-Feb-2036 @ 06:28:16 UTC
*/
protected static final long msb0baseTime = 2085978496000L;
/**
* baseline NTP time if bit-0=1 is 1-Jan-1900 @ 01:00:00 UTC
*/
protected static final long msb1baseTime = -2208988800000L;
/**
* Default NTP date string format. E.g. Fri, Sep 12 2003 21:06:23.860. See
* java.text.SimpleDateFormat for code descriptions.
*/
public static final String NTP_DATE_FORMAT = "EEE, MMM dd yyyy HH:mm:ss.SSS";
/**
* 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 final long ntpTime;
private DateFormat simpleFormatter;
private DateFormat utcFormatter;
// 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(); }
*/
/***
* Constructs a newly allocated NTP timestamp object that represents the native 64-bit long
* argument.
*
* @param ntpTime the timestamp
*/
public TimeStamp(long ntpTime) {
this.ntpTime = ntpTime;
}
/***
* Constructs a newly allocated NTP timestamp object that represents the value represented by
* the string in hexdecimal form (e.g. "c1a089bd.fc904f6d").
*
* @param hexStamp the hex timestamp
* @throws NumberFormatException - if the string does not contain a parsable timestamp.
*/
public TimeStamp(String hexStamp) throws NumberFormatException {
ntpTime = decodeNtpHexString(hexStamp);
}
/***
* Constructs a newly allocated NTP timestamp object that represents the Java Date argument.
*
* @param d - the Date to be represented by the Timestamp object.
*/
public TimeStamp(Date d) {
ntpTime = (d == null) ? 0 : toNtpTime(d.getTime());
}
/***
* Returns the value of this Timestamp as a long value.
*
* @return the 64-bit long value represented by this object.
*/
public long ntpValue() {
return ntpTime;
}
/***
* Returns high-order 32-bits representing the seconds of this NTP timestamp.
*
* @return seconds represented by this NTP timestamp.
*/
public long getSeconds() {
return (ntpTime >>> 32) & 0xffffffffL;
}
/***
* Returns low-order 32-bits representing the fractional seconds.
*
* @return fractional seconds represented by this NTP timestamp.
*/
public long getFraction() {
return ntpTime & 0xffffffffL;
}
/***
* Convert NTP timestamp to Java standard time.
*
* @return NTP Timestamp in Java time
*/
public long getTime() {
return getTime(ntpTime);
}
/***
* Convert NTP timestamp to Java Date object.
*
* @return NTP Timestamp in Java Date
*/
public Date getDate() {
long time = getTime(ntpTime);
return new Date(time);
}
/***
* 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 the input time
* @return the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this
* NTP timestamp value.
*/
public static long getTime(long ntpTimeValue) {
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;
}
}
/***
* 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.
*/
public static TimeStamp getNtpTime(long date) {
return new TimeStamp(toNtpTime(date));
}
/***
* 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()
*/
public static TimeStamp getCurrentTime() {
return getNtpTime(System.currentTimeMillis());
}
/***
* Convert NTP timestamp hexstring (e.g. "c1a089bd.fc904f6d") to the NTP 64-bit unsigned
* fixed-point number.
*
* @param hexString the string to convert
* @return NTP 64-bit timestamp value.
* @throws NumberFormatException - if the string does not contain a parsable timestamp.
*/
protected static long decodeNtpHexString(String hexString) throws NumberFormatException {
if (hexString == null) {
throw new NumberFormatException("null");
}
int ind = hexString.indexOf('.');
if (ind == -1) {
if (hexString.length() == 0) {
return 0;
}
return Long.parseLong(hexString, 16) << 32; // no decimal
}
return Long.parseLong(hexString.substring(0, ind), 16) << 32 | Long.parseLong(hexString.substring(ind + 1), 16);
}
/***
* 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.
*/
public static TimeStamp parseNtpString(String s) throws NumberFormatException {
return new TimeStamp(decodeNtpHexString(s));
}
/***
* Converts Java time to 64-bit NTP time representation.
*
* @param t Java time
* @return NTP timestamp representation of Java time value.
*/
protected static long toNtpTime(long t) {
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;
}
/***
* 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:
*
*
* {@code (int)(this.ntpValue()^(this.ntpValue() >>> 32))}
*
*
*
*
* @return a hash code value for this object.
*/
@Override
public int hashCode() {
return (int)(ntpTime ^ (ntpTime >>> 32));
}
/***
* 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.
*/
@Override
public boolean equals(Object obj) {
if (obj instanceof TimeStamp) {
return ntpTime == ((TimeStamp)obj).ntpValue();
}
return false;
}
/***
* 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.
*/
@Override
public String toString() {
return toString(ntpTime);
}
/***
* Left-pad 8-character hex string with 0's
*
* @param buf - StringBuilder which is appended with leading 0's.
* @param l - a long.
*/
private static void appendHexString(StringBuilder buf, long l) {
String s = Long.toHexString(l);
for (int i = s.length(); i < 8; i++) {
buf.append('0');
}
buf.append(s);
}
/***
* 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
*
* @param ntpTime the 64 bit timestamp
* @return NTP timestamp 64-bit long value as hex string with seconds separated by fractional
* seconds.
*/
public static String toString(long ntpTime) {
StringBuilder buf = new StringBuilder();
// 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();
}
/***
* 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.
*/
public String toDateString() {
if (simpleFormatter == null) {
simpleFormatter = new SimpleDateFormat(NTP_DATE_FORMAT, Locale.US);
simpleFormatter.setTimeZone(TimeZone.getDefault());
}
Date ntpDate = getDate();
return simpleFormatter.format(ntpDate);
}
/***
* 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.
*/
public String toUTCString() {
if (utcFormatter == null) {
utcFormatter = new SimpleDateFormat(NTP_DATE_FORMAT + " 'UTC'", Locale.US);
utcFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
}
Date ntpDate = getDate();
return utcFormatter.format(ntpDate);
}
/***
* 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).
*/
// @Override
public int compareTo(TimeStamp anotherTimeStamp) {
long thisVal = this.ntpTime;
long anotherVal = anotherTimeStamp.ntpTime;
return (thisVal < anotherVal ? -1 : (thisVal == anotherVal ? 0 : 1));
}
}
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