TimeStamp.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.net.ntp;
import java.io.Serializable;
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.
* <p>
* 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.
* </p>
*
* @see java.util.Date
*/
public class TimeStamp implements Serializable, Comparable<TimeStamp> {
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 <code>java.text.SimpleDateFormat</code> for code descriptions.
*/
public static final String NTP_DATE_FORMAT = "EEE, MMM dd yyyy HH:mm:ss.SSS";
/**
* 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(final StringBuilder buf, final long l) {
final String s = Long.toHexString(l);
for (int i = s.length(); i < 8; i++) {
buf.append('0');
}
buf.append(s);
}
/**
* 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(final String hexString) throws NumberFormatException {
if (hexString == null) {
throw new NumberFormatException("null");
}
final int ind = hexString.indexOf('.');
if (ind == -1) {
if (hexString.isEmpty()) {
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);
}
/**
* 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 System#currentTimeMillis()
*/
public static TimeStamp getCurrentTime() {
return getNtpTime(System.currentTimeMillis());
}
// 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(); }
*/
/**
* Helper method to convert Java time to NTP timestamp object. Note that Java time (milliseconds) by definition has less precision than 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 dateMillis the milliseconds since January 1, 1970, 00:00:00 GMT.
* @return NTP timestamp object at the specified date.
*/
public static TimeStamp getNtpTime(final long dateMillis) {
return new TimeStamp(toNtpTime(dateMillis));
}
/**
* Converts 64-bit NTP timestamp to Java standard time.
*
* Note that java time (milliseconds) by definition has less precision than 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(final long ntpTimeValue) {
final 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.
*/
final long msb = seconds & 0x80000000L;
if (msb == 0) {
// use base: 7-Feb-2036 @ 06:28:16 UTC
return msb0baseTime + seconds * 1000 + fraction;
}
// use base: 1-Jan-1900 @ 01:00:00 UTC
return msb1baseTime + seconds * 1000 + fraction;
}
/**
* 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(final String s) throws NumberFormatException {
return new TimeStamp(decodeNtpHexString(s));
}
/**
* Converts Java time to 64-bit NTP time representation.
*
* @param millis Java time
* @return NTP timestamp representation of Java time value.
*/
protected static long toNtpTime(final long millis) {
final boolean useBase1 = millis < msb0baseTime; // time < Feb-2036
final long baseTimeMillis;
if (useBase1) {
baseTimeMillis = millis - msb1baseTime; // dates <= Feb-2036
} else {
// if base0 needed for dates >= Feb-2036
baseTimeMillis = millis - msb0baseTime;
}
long seconds = baseTimeMillis / 1000;
final long fraction = baseTimeMillis % 1000 * 0x100000000L / 1000;
if (useBase1) {
seconds |= 0x80000000L; // set high-order bit if msb1baseTime 1900 used
}
return seconds << 32 | fraction;
}
/**
* Converts 64-bit NTP timestamp value to a <code>String</code>. 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(final long ntpTime) {
final 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();
}
/**
* 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;
/**
* 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(final Date d) {
ntpTime = d == null ? 0 : toNtpTime(d.getTime());
}
/**
* Constructs a newly allocated NTP timestamp object that represents the native 64-bit long argument.
*
* @param ntpTime the timestamp
*/
public TimeStamp(final 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(final String hexStamp) throws NumberFormatException {
ntpTime = decodeNtpHexString(hexStamp);
}
/**
* Compares two Timestamps numerically.
*
* @param anotherTimeStamp - the <code>TimeStamp</code> to be compared.
* @return the value <code>0</code> if the argument TimeStamp is equal to this TimeStamp; a value less than <code>0</code> if this TimeStamp is numerically
* less than the TimeStamp argument; and a value greater than <code>0</code> if this TimeStamp is numerically greater than the TimeStamp argument
* (signed comparison).
*/
@Override
public int compareTo(final TimeStamp anotherTimeStamp) {
final long thisVal = this.ntpTime;
final long anotherVal = anotherTimeStamp.ntpTime;
return Long.compare(thisVal, anotherVal);
}
/**
* Compares this object against the specified object. The result is {@code true} if and only if the argument is not <code>null</code> and is a
* <code>Long</code> object that contains the same <code>long</code> value as this object.
*
* @param obj the object to compare with.
* @return {@code true} if the objects are the same; {@code false} otherwise.
*/
@Override
public boolean equals(final Object obj) {
if (obj instanceof TimeStamp) {
return ntpTime == ((TimeStamp) obj).ntpValue();
}
return false;
}
/**
* Converts NTP timestamp to Java Date object.
*
* @return NTP Timestamp in Java Date
*/
public Date getDate() {
return new Date(getTime(ntpTime));
}
/**
* Returns low-order 32-bits representing the fractional seconds.
*
* @return fractional seconds represented by this NTP timestamp.
*/
public long getFraction() {
return ntpTime & 0xffffffffL;
}
/**
* 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;
}
/**
* Converts NTP timestamp to Java standard time.
*
* @return the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this NTP timestamp value.
*/
public long getTime() {
return getTime(ntpTime);
}
/**
* Computes a hash code for this Timestamp. The result is the exclusive OR of the two halves of the primitive <code>long</code> value represented by this
* <code>TimeStamp</code> object. That is, the hash code is the value of the expression: <blockquote>
*
* <pre>
* {@code
* (int) (this.ntpValue() ^ (this.ntpValue() >>> 32))
* }
* </pre>
*
* </blockquote>
*
* @return a hash code value for this object.
*/
@Override
public int hashCode() {
return (int) (ntpTime ^ ntpTime >>> 32);
}
/**
* 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;
}
private void readObject(final java.io.ObjectInputStream in) {
throw new UnsupportedOperationException("Serialization is not supported");
}
/**
* Converts this <code>TimeStamp</code> object to a <code>String</code> of the form: <blockquote>
*
* <pre>
* EEE, MMM dd yyyy HH:mm:ss.SSS
* </pre>
*
* </blockquote> 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());
}
final Date ntpDate = getDate();
return simpleFormatter.format(ntpDate);
}
/**
* Converts this <code>TimeStamp</code> object to a <code>String</code>. 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);
}
/*
* Serialization is unnecessary for this class. Reject attempts to do so until such time as the Serializable attribute can be dropped.
*/
/**
* Converts this <code>TimeStamp</code> object to a <code>String</code> of the form: <blockquote>
*
* <pre>
* EEE, MMM dd yyyy HH:mm:ss.SSS UTC
* </pre>
*
* </blockquote> 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"));
}
final Date ntpDate = getDate();
return utcFormatter.format(ntpDate);
}
private void writeObject(final java.io.ObjectOutputStream out) {
throw new UnsupportedOperationException("Serialization is not supported");
}
}