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Timestamp: convert epoch milliseconds in the proleptic Gregorian calendar #1165

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137 changes: 83 additions & 54 deletions src/main/java/com/amazon/ion/Timestamp.java
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Original file line number Diff line number Diff line change
@@ -1,18 +1,5 @@
/*
* Copyright 2007-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* or in the "license" file accompanying this file. This file 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.
*/

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
package com.amazon.ion;

import static com.amazon.ion.impl._Private_Utils.safeEquals;
Expand Down Expand Up @@ -90,7 +77,7 @@ public final class Timestamp
/**
* 0001-01-01T00:00:00.0Z in millis.
*/
static final long MINIMUM_TIMESTAMP_IN_MILLIS = -62135769600000L;
static final long MINIMUM_TIMESTAMP_IN_MILLIS = -62135596800000L;

/**
* 0001-01-01T00:00:00.0Z in millis.
Expand Down Expand Up @@ -336,48 +323,80 @@ private static short requireShort(int value, String location) {
}

/**
* This method uses deprecated methods from {@link java.util.Date}
* instead of {@link Calendar} so that this code can be used (more easily)
* on the mobile Java platform (which has Date but does not have Calendar).
* Days from 1970-01-01 to the given proleptic Gregorian date.
*/
private static long epochDayFromCivil(int year, int month, int day)
{
long y = year - (month <= 2 ? 1 : 0);
long era = (y >= 0 ? y : y - 399) / 400;
long yearOfEra = y - era * 400; // [0, 399]
long dayOfYear = (153 * (month + (month > 2 ? -3 : 9)) + 2) / 5 + day - 1; // [0, 365]
long dayOfEra = yearOfEra * 365 + yearOfEra / 4 - yearOfEra / 100 + dayOfYear;
return era * 146097 + dayOfEra - 719468;
}

/**
* Inverse of {@link #epochDayFromCivil(int, int, int)}; fills year, month and day.
*/
private static void civilFromEpochDay(long epochDay, int[] yearMonthDay)
{
long z = epochDay + 719468;
long era = (z >= 0 ? z : z - 146096) / 146097;
long dayOfEra = z - era * 146097; // [0, 146096]
long yearOfEra = (dayOfEra - dayOfEra / 1460 + dayOfEra / 36524 - dayOfEra / 146096) / 365;
long y = yearOfEra + era * 400;
long dayOfYear = dayOfEra - (365 * yearOfEra + yearOfEra / 4 - yearOfEra / 100);
long monthPrime = (5 * dayOfYear + 2) / 153; // [0, 11]
long day = dayOfYear - (153 * monthPrime + 2) / 5 + 1; // [1, 31]
long month = monthPrime + (monthPrime < 10 ? 3 : -9); // [1, 12]
yearMonthDay[0] = (int) (y + (month <= 2 ? 1 : 0));
yearMonthDay[1] = (int) month;
yearMonthDay[2] = (int) day;
}

/**
* Milliseconds from the epoch for the given UTC fields.
*/
private static long utcMillisFromCivil(int year, int month, int day, int hour, int minute, int second)
{
long epochDay = epochDayFromCivil(year, month, day);
return (((epochDay * 24L + hour) * 60L + minute) * 60L + second) * 1000L;
}

/**
* Sets this Timestamp's UTC fields from a millisecond offset from the epoch.
*/
@SuppressWarnings("deprecation")
private void set_fields_from_millis(long millis)
{
if(millis < MINIMUM_TIMESTAMP_IN_MILLIS){
throw new IllegalArgumentException("year is less than 1");
}

Date date = new Date(millis);
long totalSeconds = floorDiv(millis, 1000L);
long epochDay = floorDiv(totalSeconds, 86400L);
int secondOfDay = (int) (totalSeconds - epochDay * 86400L);

// The Date getters return values in the Date's time zone (i.e. the system time zone).
// The components need to be converted to UTC before being validated for exact ranges, because the offset
// conversion can affect which values are considered valid. Simply verify that the values can fit in the
// destination type here. If they do not, they would be out of range no matter the offset.
_minute = requireByte(date.getMinutes(), "Minute");
_second = requireByte(date.getSeconds(), "Second");
_hour = requireByte(date.getHours(), "Hour");
_day = requireByte(date.getDate(), "Day");
_month = requireByte(date.getMonth() + 1, "Month");
int[] yearMonthDay = new int[3];
civilFromEpochDay(epochDay, yearMonthDay);

// Date does not correctly handle year values that represent year 0 or earlier in the system time zone through
// getYear(). This case is detected and forced to zero.
int offset = -date.getTimezoneOffset();
if(offset < 0 && MINIMUM_TIMESTAMP_IN_MILLIS - offset > millis) {
_year = 0;
} else {
_year = requireShort(date.getYear() + 1900, "Year");
}

// Now apply the offset to convert the components to UTC.
apply_offset(offset);
this._year = checkAndCastYear(requireShort(yearMonthDay[0], "Year"));
this._month = checkAndCastMonth(requireByte(yearMonthDay[1], "Month"));
this._day = checkAndCastDay(requireByte(yearMonthDay[2], "Day"), _year, _month);
this._hour = checkAndCastHour(secondOfDay / 3600);
this._minute = checkAndCastMinute((secondOfDay / 60) % 60);
this._second = checkAndCastSecond(secondOfDay % 60);
}

// Now that all components are in UTC, they may be validated for exact ranges.
this._year = checkAndCastYear(_year);
this._month = checkAndCastMonth(_month);
this._day = checkAndCastDay(_day, _year, _month);
this._hour = checkAndCastHour(_hour);
this._minute = checkAndCastMinute(_minute);
this._second = checkAndCastSecond(_second);
/**
* {@code Math.floorDiv} for platforms whose java.lang.Math predates Java 8.
*/
private static long floorDiv(long dividend, long divisor)
{
long quotient = dividend / divisor;
if ((dividend % divisor != 0) && ((dividend ^ divisor) < 0)) {
quotient--;
}
return quotient;
}

/**
Expand Down Expand Up @@ -1565,6 +1584,9 @@ public static Timestamp nowZ()
* <p>
* Because {@link Date} instances are mutable, this method returns a
* new instance from each call.
* <p>
* Uses the proleptic Gregorian calendar, so before 1582-10-15 it differs from a default
* {@link GregorianCalendar}.
*
* @return a new {@code Date} instance, in UTC
*/
Expand All @@ -1581,14 +1603,18 @@ public Date dateValue()
* <p>
* Because {@link Calendar} instances are mutable, this method returns a
* new instance from each call.
* <p>
* The returned {@code Calendar} is proleptic Gregorian, so its fields agree with this
* Timestamp before 1582-10-15.
*
* @return a new {@code Calendar} instance, in its local time.
*

*/
public Calendar calendarValue()
{
Calendar cal = new GregorianCalendar(_Private_Utils.UTC);
GregorianCalendar cal = new GregorianCalendar(_Private_Utils.UTC);
cal.setGregorianChange(new Date(Long.MIN_VALUE));

long millis = getMillis();
Integer offset = _offset;
Expand Down Expand Up @@ -1632,16 +1658,17 @@ public Calendar calendarValue()
* <p>
* This method will return the same result for all Timestamps representing
* the same point in time, regardless of the local offset.
* <p>
* Uses the proleptic Gregorian calendar, so before 1582-10-15 it differs from a default
* {@link GregorianCalendar}.
*
* @return
* number of milliseconds (<em>ignoring</em> any fractional
* milliseconds) from the epoch (1970-01-01T00:00:00.000Z)
*/
@SuppressWarnings("deprecation")
public long getMillis()
{
// month is 0 based for Date
long millis = Date.UTC(this._year - 1900, this._month - 1, this._day, this._hour, this._minute, this._second);
long millis = utcMillisFromCivil(this._year, this._month, this._day, this._hour, this._minute, this._second);
if (this._fraction != null) {
BigDecimal fracAsDecimal = this._fraction.movePointRight(3);
int frac = isIntegralZero(fracAsDecimal) ? 0 : fracAsDecimal.intValue();
Expand All @@ -1658,12 +1685,14 @@ public long getMillis()
* <p>
* This method will return the same result for all Timestamps representing
* the same point in time, regardless of the local offset.
* <p>
* Uses the proleptic Gregorian calendar, so before 1582-10-15 it differs from a default
* {@link GregorianCalendar}.
*
* @return
* number of milliseconds (<em>including</em> any fractional
* milliseconds) from the epoch (1970-01-01T00:00:00.000Z)
*/
@SuppressWarnings("deprecation")
public BigDecimal getDecimalMillis()
{
switch (this._precision) {
Expand All @@ -1673,7 +1702,7 @@ public BigDecimal getDecimalMillis()
case MINUTE:
case SECOND:
case FRACTION:
long millis = Date.UTC(this._year - 1900, this._month - 1, this._day, this._hour, this._minute, this._second);
long millis = utcMillisFromCivil(this._year, this._month, this._day, this._hour, this._minute, this._second);
BigDecimal dec = BigDecimal.valueOf(millis);
if (_fraction != null) {
dec = dec.add(this._fraction.movePointRight(3));
Expand Down
43 changes: 26 additions & 17 deletions src/test/java/com/amazon/ion/TimestampTest.java
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Original file line number Diff line number Diff line change
@@ -1,18 +1,5 @@
/*
* Copyright 2007-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* or in the "license" file accompanying this file. This file 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.
*/

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
package com.amazon.ion;

import static com.amazon.ion.Decimal.NEGATIVE_ZERO;
Expand Down Expand Up @@ -80,7 +67,10 @@ public class TimestampTest

public static Calendar makeUtcCalendar()
{
Calendar cal = Calendar.getInstance(UTC);
GregorianCalendar cal = new GregorianCalendar(UTC);
// Proleptic Gregorian, as Ion timestamps are; the default cutover would make this oracle
// disagree with the values under test before 1582-10-15.
cal.setGregorianChange(new Date(Long.MIN_VALUE));
cal.setTimeInMillis(0); // clear all fields, else they are "now"
return cal;
}
Expand Down Expand Up @@ -362,13 +352,32 @@ public void modifyTimestamp(IonTimestamp value)
* class as other test methods might be based off the correctness of
* assumptions declared here.
*/
@Test
public void testDatesAcrossTheGregorianCutoverAreDistinctInstants()
{
// Under the Julian cutover both of these mapped to the same epoch millisecond, so
// compareTo called them equal while equals did not.
Timestamp before = Timestamp.valueOf("1582-10-05T00:00:00Z");
Timestamp after = Timestamp.valueOf("1582-10-15T00:00:00Z");
assertEquals(10L * 24 * 60 * 60 * 1000, after.getMillis() - before.getMillis());
assertTrue(before.compareTo(after) < 0);
assertEquals("1582-10-05T00:00:00.000Z", Timestamp.forMillis(before.getMillis(), 0).toString());
}

@Test
public void testTimestampConstants()
{
checkFields(1, 1, 1, 0, 0, 0, null, null, DAY, EARLIEST_ION_TIMESTAMP);
assertEquals("0001-01-01", EARLIEST_ION_TIMESTAMP.toZString());
assertEquals("0001-01-01", EARLIEST_ION_TIMESTAMP.toString());
assertEquals(-62135769600000L, EARLIEST_ION_TIMESTAMP.getMillis());
// 0001-01-01T00:00:00Z, proleptic Gregorian, cross-checked against a Calendar with the
// cutover moved out of range.
GregorianCalendar earliest = new GregorianCalendar(UTC);
earliest.setGregorianChange(new Date(Long.MIN_VALUE));
earliest.clear();
earliest.set(1, Calendar.JANUARY, 1, 0, 0, 0);
assertEquals(-62135596800000L, earliest.getTimeInMillis());
assertEquals(-62135596800000L, EARLIEST_ION_TIMESTAMP.getMillis());

checkFields(1970, 1, 1, 0, 0, 0, new BigDecimal("0.000"), 0, FRACTION, UNIX_EPOCH_TIMESTAMP);
assertEquals("1970-01-01T00:00:00.000Z", UNIX_EPOCH_TIMESTAMP.toZString());
Expand Down