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/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed 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.
*/
/*
* Elements of the WallTime class are a port of Bionic's localtime.c to Java. That code had the
* following header:
*
* This file is in the public domain, so clarified as of
* 1996-06-05 by Arthur David Olson.
*/
package libcore.util;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;
import libcore.io.BufferIterator;
/**
* Our concrete TimeZone implementation, backed by zoneinfo data.
*
* <p>This reads time zone information from a binary file stored on the platform. The binary file
* is essentially a single file containing compacted versions of all the tzfile (see
* {@code man 5 tzfile} for details of the source) and an index by long name, e.g. Europe/London.
*
* <p>The compacted form is created by {@code external/icu/tools/ZoneCompactor.java} and is used
* by both this and Bionic. {@link ZoneInfoDB} is responsible for mapping the binary file, and
* reading the index and creating a {@link BufferIterator} that provides access to an entry for a
* specific file. This class is responsible for reading the data from that {@link BufferIterator}
* and storing it a representation to support the {@link TimeZone} and {@link GregorianCalendar}
* implementations. See {@link ZoneInfo#readTimeZone(String, BufferIterator, long)}.
*
* <p>The main difference between {@code tzfile} and the compacted form is that the
* {@code struct ttinfo} only uses a single byte for {@code tt_isdst} and {@code tt_abbrind}.
*
* <p>This class does not use all the information from the {@code tzfile}; it uses:
* {@code tzh_timecnt} and the associated transition times and type information. For each type
* (described by {@code struct ttinfo}) it uses {@code tt_gmtoff} and {@code tt_isdst}. Note, that
* the definition of {@code struct ttinfo} uses {@code long}, and {@code int} but they do not have
* the same meaning as Java. The prose following the definition makes it clear that the {@code long}
* is 4 bytes and the {@code int} fields are 1 byte.
*
* <p>As the data uses 32 bits to store the time in seconds the time range is limited to roughly
* 69 years either side of the epoch (1st Jan 1970 00:00:00) that means that it cannot handle any
* dates before 1900 and after 2038. There is an extended version of the table that uses 64 bits
* to store the data but that information is not used by this.
*
* @hide - used to implement TimeZone
*/
public final class ZoneInfo extends TimeZone {
private static final long MILLISECONDS_PER_DAY = 24 * 60 * 60 * 1000;
private static final long MILLISECONDS_PER_400_YEARS =
MILLISECONDS_PER_DAY * (400 * 365 + 100 - 3);
private static final long UNIX_OFFSET = 62167219200000L;
private static final int[] NORMAL = new int[] {
0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
};
private static final int[] LEAP = new int[] {
0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335,
};
// Proclaim serialization compatibility with pre-OpenJDK AOSP
static final long serialVersionUID = -4598738130123921552L;
private int mRawOffset;
private final int mEarliestRawOffset;
/**
* Implements {@link #useDaylightTime()}
*
* <p>True if the transition active at the time this instance was created, or future
* transitions support DST. It is possible that caching this value at construction time and
* using it for the lifetime of the instance does not match the contract of the
* {@link TimeZone#useDaylightTime()} method but it appears to be what the RI does and that
* method is not particularly useful when it comes to historical or future times as it does not
* allow the time to be specified.
*
* <p>When this is false then {@link #mDstSavings} will be 0.
*
* @see #mDstSavings
*/
private final boolean mUseDst;
/**
* Implements {@link #getDSTSavings()}
*
* <p>This should be final but is not because it may need to be fixed up by
* {@link #readObject(ObjectInputStream)} to correct an inconsistency in the previous version
* of the code whereby this was set to a non-zero value even though DST was not actually used.
*
* @see #mUseDst
*/
private int mDstSavings;
/**
* The times (in seconds) at which the offsets changes for any reason, whether that is a change
* in the offset from UTC or a change in the DST.
*
* <p>These times are pre-calculated externally from a set of rules (both historical and
* future) and stored in a file from which {@link ZoneInfo#readTimeZone(String, BufferIterator,
* long)} reads the data. That is quite different to {@link java.util.SimpleTimeZone}, which has
* essentially human readable rules (e.g. DST starts at 01:00 on the first Sunday in March and
* ends at 01:00 on the last Sunday in October) that can be used to determine the DST transition
* times across a number of years
*
* <p>In terms of {@link ZoneInfo tzfile} structure this array is of length {@code tzh_timecnt}
* and contains the times in seconds converted to long to make them safer to use.
*
* <p>They are stored in order from earliest (lowest) time to latest (highest). A transition is
* identified by its index within this array. A transition {@code T} is active at a specific
* time {@code X} if {@code T} is the highest transition whose time is less than or equal to
* {@code X}.
*
* @see #mTypes
*/
private final long[] mTransitions;
/**
* The type of the transition, where type is a pair consisting of the offset and whether the
* offset includes DST or not.
*
* <p>Each transition in {@link #mTransitions} has an associated type in this array at the same
* index. The type is an index into the arrays {@link #mOffsets} and {@link #mIsDsts} that each
* contain one part of the pair.
*
* <p>In the {@link ZoneInfo tzfile} structure the type array only contains unique instances of
* the {@code struct ttinfo} to save space and each type may be referenced by multiple
* transitions. However, the type pairs stored in this class are not guaranteed unique because
* they do not include the {@code tt_abbrind}, which is the abbreviated identifier to use for
* the time zone after the transition.
*
* @see #mTransitions
* @see #mOffsets
* @see #mIsDsts
*/
private final byte[] mTypes;
/**
* The offset parts of the transition types, in seconds.
*
* <p>These are actually a delta to the {@link #mRawOffset}. So, if the offset is say +7200
* seconds and {@link #mRawOffset} is say +3600 then this will have a value of +3600.
*
* <p>The offset in milliseconds can be computed using:
* {@code mRawOffset + mOffsets[type] * 1000}
*
* @see #mTypes
* @see #mIsDsts
*/
private final int[] mOffsets;
/**
* Specifies whether an associated offset includes DST or not.
*
* <p>Each entry in here is 1 if the offset at the same index in {@link #mOffsets} includes DST
* and 0 otherwise.
*
* @see #mTypes
* @see #mOffsets
*/
private final byte[] mIsDsts;
public static ZoneInfo readTimeZone(String id, BufferIterator it, long currentTimeMillis)
throws IOException {
// Variable names beginning tzh_ correspond to those in "tzfile.h".
// Check tzh_magic.
int tzh_magic = it.readInt();
if (tzh_magic != 0x545a6966) { // "TZif"
throw new IOException("Timezone id=" + id + " has an invalid header=" + tzh_magic);
}
// Skip the uninteresting part of the header.
it.skip(28);
// Read the sizes of the arrays we're about to read.
int tzh_timecnt = it.readInt();
// Arbitrary ceiling to prevent allocating memory for corrupt data.
// 2 per year with 2^32 seconds would give ~272 transitions.
final int MAX_TRANSITIONS = 2000;
if (tzh_timecnt < 0 || tzh_timecnt > MAX_TRANSITIONS) {
throw new IOException(
"Timezone id=" + id + " has an invalid number of transitions=" + tzh_timecnt);
}
int tzh_typecnt = it.readInt();
final int MAX_TYPES = 256;
if (tzh_typecnt < 1) {
throw new IOException("ZoneInfo requires at least one type "
+ "to be provided for each timezone but could not find one for '" + id + "'");
} else if (tzh_typecnt > MAX_TYPES) {
throw new IOException(
"Timezone with id " + id + " has too many types=" + tzh_typecnt);
}
it.skip(4); // Skip tzh_charcnt.
// Transitions are signed 32 bit integers, but we store them as signed 64 bit
// integers since it's easier to compare them against 64 bit inputs (see getOffset
// and isDaylightTime) with much less risk of an overflow in our calculations.
//
// The alternative of checking the input against the first and last transition in
// the array is far more awkward and error prone.
int[] transitions32 = new int[tzh_timecnt];
it.readIntArray(transitions32, 0, transitions32.length);
long[] transitions64 = new long[tzh_timecnt];
for (int i = 0; i < tzh_timecnt; ++i) {
transitions64[i] = transitions32[i];
if (i > 0 && transitions64[i] <= transitions64[i - 1]) {
throw new IOException(
id + " transition at " + i + " is not sorted correctly, is "
+ transitions64[i] + ", previous is " + transitions64[i - 1]);
}
}
byte[] type = new byte[tzh_timecnt];
it.readByteArray(type, 0, type.length);
for (int i = 0; i < type.length; i++) {
int typeIndex = type[i] & 0xff;
if (typeIndex >= tzh_typecnt) {
throw new IOException(
id + " type at " + i + " is not < " + tzh_typecnt + ", is " + typeIndex);
}
}
int[] gmtOffsets = new int[tzh_typecnt];
byte[] isDsts = new byte[tzh_typecnt];
for (int i = 0; i < tzh_typecnt; ++i) {
gmtOffsets[i] = it.readInt();
byte isDst = it.readByte();
if (isDst != 0 && isDst != 1) {
throw new IOException(id + " dst at " + i + " is not 0 or 1, is " + isDst);
}
isDsts[i] = isDst;
// We skip the abbreviation index. This would let us provide historically-accurate
// time zone abbreviations (such as "AHST", "YST", and "AKST" for standard time in
// America/Anchorage in 1982, 1983, and 1984 respectively). ICU only knows the current
// names, though, so even if we did use this data to provide the correct abbreviations
// for en_US, we wouldn't be able to provide correct abbreviations for other locales,
// nor would we be able to provide correct long forms (such as "Yukon Standard Time")
// for any locale. (The RI doesn't do any better than us here either.)
it.skip(1);
}
return new ZoneInfo(id, transitions64, type, gmtOffsets, isDsts, currentTimeMillis);
}
private ZoneInfo(String name, long[] transitions, byte[] types, int[] gmtOffsets, byte[] isDsts,
long currentTimeMillis) {
if (gmtOffsets.length == 0) {
throw new IllegalArgumentException("ZoneInfo requires at least one offset "
+ "to be provided for each timezone but could not find one for '" + name + "'");
}
mTransitions = transitions;
mTypes = types;
mIsDsts = isDsts;
setID(name);
// Find the latest daylight and standard offsets (if any).
int lastStd = -1;
int lastDst = -1;
for (int i = mTransitions.length - 1; (lastStd == -1 || lastDst == -1) && i >= 0; --i) {
int type = mTypes[i] & 0xff;
if (lastStd == -1 && mIsDsts[type] == 0) {
lastStd = i;
}
if (lastDst == -1 && mIsDsts[type] != 0) {
lastDst = i;
}
}
// Use the latest non-daylight offset (if any) as the raw offset.
if (mTransitions.length == 0) {
// If there are no transitions then use the first GMT offset.
mRawOffset = gmtOffsets[0];
} else {
if (lastStd == -1) {
throw new IllegalStateException( "ZoneInfo requires at least one non-DST "
+ "transition to be provided for each timezone that has at least one "
+ "transition but could not find one for '" + name + "'");
}
mRawOffset = gmtOffsets[mTypes[lastStd] & 0xff];
}
if (lastDst != -1) {
// Check to see if the last DST transition is in the future or the past. If it is in
// the past then we treat it as if it doesn't exist, at least for the purposes of
// setting mDstSavings and mUseDst.
long lastDSTTransitionTime = mTransitions[lastDst];
// Convert the current time in millis into seconds. Unlike other places that convert
// time in milliseconds into seconds in order to compare with transition time this
// rounds up rather than down. It does that because this is interested in what
// transitions apply in future
long currentUnixTimeSeconds = roundUpMillisToSeconds(currentTimeMillis);
// Is this zone observing DST currently or in the future?
// We don't care if they've historically used it: most places have at least once.
// See http://code.google.com/p/android/issues/detail?id=877.
// This test means that for somewhere like Morocco, which tried DST in 2009 but has
// no future plans (and thus no future schedule info) will report "true" from
// useDaylightTime at the start of 2009 but "false" at the end. This seems appropriate.
if (lastDSTTransitionTime < currentUnixTimeSeconds) {
// The last DST transition is before now so treat it as if it doesn't exist.
lastDst = -1;
}
}
if (lastDst == -1) {
// There were no DST transitions or at least no future DST transitions so DST is not
// used.
mDstSavings = 0;
mUseDst = false;
} else {
// Use the latest transition's pair of offsets to compute the DST savings.
// This isn't generally useful, but it's exposed by TimeZone.getDSTSavings.
int lastGmtOffset = gmtOffsets[mTypes[lastStd] & 0xff];
int lastDstOffset = gmtOffsets[mTypes[lastDst] & 0xff];
mDstSavings = Math.abs(lastGmtOffset - lastDstOffset) * 1000;
mUseDst = true;
}
// Cache the oldest known raw offset, in case we're asked about times that predate our
// transition data.
int firstStd = -1;
for (int i = 0; i < mTransitions.length; ++i) {
if (mIsDsts[mTypes[i] & 0xff] == 0) {
firstStd = i;
break;
}
}
int earliestRawOffset = (firstStd != -1) ? gmtOffsets[mTypes[firstStd] & 0xff] : mRawOffset;
// Rather than keep offsets from UTC, we use offsets from local time, so the raw offset
// can be changed and automatically affect all the offsets.
mOffsets = gmtOffsets;
for (int i = 0; i < mOffsets.length; i++) {
mOffsets[i] -= mRawOffset;
}
// tzdata uses seconds, but Java uses milliseconds.
mRawOffset *= 1000;
mEarliestRawOffset = earliestRawOffset * 1000;
}
/**
* Ensure that when deserializing an instance that {@link #mDstSavings} is always 0 when
* {@link #mUseDst} is false.
*/
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
if (!mUseDst && mDstSavings != 0) {
mDstSavings = 0;
}
}
@Override
public int getOffset(int era, int year, int month, int day, int dayOfWeek, int millis) {
// XXX This assumes Gregorian always; Calendar switches from
// Julian to Gregorian in 1582. What calendar system are the
// arguments supposed to come from?
long calc = (year / 400) * MILLISECONDS_PER_400_YEARS;
year %= 400;
calc += year * (365 * MILLISECONDS_PER_DAY);
calc += ((year + 3) / 4) * MILLISECONDS_PER_DAY;
if (year > 0) {
calc -= ((year - 1) / 100) * MILLISECONDS_PER_DAY;
}
boolean isLeap = (year == 0 || (year % 4 == 0 && year % 100 != 0));
int[] mlen = isLeap ? LEAP : NORMAL;
calc += mlen[month] * MILLISECONDS_PER_DAY;
calc += (day - 1) * MILLISECONDS_PER_DAY;
calc += millis;
calc -= mRawOffset;
calc -= UNIX_OFFSET;
return getOffset(calc);
}
/**
* Find the transition in the {@code timezone} in effect at {@code seconds}.
*
* <p>Returns an index in the range -1..timeZone.mTransitions.length - 1. -1 is used to
* indicate the time is before the first transition. Other values are an index into
* timeZone.mTransitions.
*/
public int findTransitionIndex(long seconds) {
int transition = Arrays.binarySearch(mTransitions, seconds);
if (transition < 0) {
transition = ~transition - 1;
if (transition < 0) {
return -1;
}
}
return transition;
}
/**
* Finds the index within the {@link #mOffsets}/{@link #mIsDsts} arrays for the specified time
* in seconds, since 1st Jan 1970 00:00:00.
* @param seconds the time in seconds.
* @return -1 if the time is before the first transition, or [0..{@code mOffsets}-1] for the
* active offset.
*/
int findOffsetIndexForTimeInSeconds(long seconds) {
int transition = findTransitionIndex(seconds);
if (transition < 0) {
return -1;
}
return mTypes[transition] & 0xff;
}
/**
* Finds the index within the {@link #mOffsets}/{@link #mIsDsts} arrays for the specified time
* in milliseconds, since 1st Jan 1970 00:00:00.000.
* @param millis the time in milliseconds.
* @return -1 if the time is before the first transition, or [0..{@code mOffsets}-1] for the
* active offset.
*/
int findOffsetIndexForTimeInMilliseconds(long millis) {
// This rounds the time in milliseconds down to the time in seconds.
//
// It can't just divide a timestamp in millis by 1000 to obtain a transition time in
// seconds because / (div) in Java rounds towards zero. Times before 1970 are negative and
// if they have a millisecond component then div would result in obtaining a time that is
// one second after what we need.
//
// e.g. dividing -12,001 milliseconds by 1000 would result in -12 seconds. If there was a
// transition at -12 seconds then that would be incorrectly treated as being active
// for a time of -12,001 milliseconds even though that time is before the transition
// should occur.
return findOffsetIndexForTimeInSeconds(roundDownMillisToSeconds(millis));
}
/**
* Converts time in milliseconds into a time in seconds, rounding down to the closest time
* in seconds before the time in milliseconds.
*
* <p>It's not sufficient to simply divide by 1000 because that rounds towards 0 and so while
* for positive numbers it produces a time in seconds that precedes the time in milliseconds
* for negative numbers it can produce a time in seconds that follows the time in milliseconds.
*
* <p>This basically does the same as {@code (long) Math.floor(millis / 1000.0)} but should be
* faster.
*
* @param millis the time in milliseconds, may be negative.
* @return the time in seconds.
*/
static long roundDownMillisToSeconds(long millis) {
if (millis < 0) {
// If the time is less than zero then subtract 999 and then divide by 1000 rounding
// towards 0 as usual, e.g.
// -12345 -> -13344 / 1000 = -13
// -12000 -> -12999 / 1000 = -12
// -12001 -> -13000 / 1000 = -13
return (millis - 999) / 1000;
} else {
return millis / 1000;
}
}
/**
* Converts time in milliseconds into a time in seconds, rounding up to the closest time
* in seconds before the time in milliseconds.
*
* <p>It's not sufficient to simply divide by 1000 because that rounds towards 0 and so while
* for negative numbers it produces a time in seconds that follows the time in milliseconds
* for positive numbers it can produce a time in seconds that precedes the time in milliseconds.
*
* <p>This basically does the same as {@code (long) Math.ceil(millis / 1000.0)} but should be
* faster.
*
* @param millis the time in milliseconds, may be negative.
* @return the time in seconds.
*/
static long roundUpMillisToSeconds(long millis) {
if (millis > 0) {
// If the time is greater than zero then add 999 and then divide by 1000 rounding
// towards 0 as usual, e.g.
// 12345 -> 13344 / 1000 = 13
// 12000 -> 12999 / 1000 = 12
// 12001 -> 13000 / 1000 = 13
return (millis + 999) / 1000;
} else {
return millis / 1000;
}
}
/**
* Get the raw and DST offsets for the specified time in milliseconds since
* 1st Jan 1970 00:00:00.000 UTC.
*
* <p>The raw offset, i.e. that part of the total offset which is not due to DST, is stored at
* index 0 of the {@code offsets} array and the DST offset, i.e. that part of the offset which
* is due to DST is stored at index 1.
*
* @param utcTimeInMillis the UTC time in milliseconds.
* @param offsets the array whose length must be greater than or equal to 2.
* @return the total offset which is the sum of the raw and DST offsets.
*/
public int getOffsetsByUtcTime(long utcTimeInMillis, int[] offsets) {
int transitionIndex = findTransitionIndex(roundDownMillisToSeconds(utcTimeInMillis));
int totalOffset;
int rawOffset;
int dstOffset;
if (transitionIndex == -1) {
// See getOffset(long) and inDaylightTime(Date) for an explanation as to why these
// values are used for times before the first transition.
rawOffset = mEarliestRawOffset;
dstOffset = 0;
totalOffset = rawOffset;
} else {
int type = mTypes[transitionIndex] & 0xff;
// Get the total offset used for the transition.
totalOffset = mRawOffset + mOffsets[type] * 1000;
if (mIsDsts[type] == 0) {
// Offset does not include DST so DST is 0 and the raw offset is the total offset.
rawOffset = totalOffset;
dstOffset = 0;
} else {
// Offset does include DST, we need to find the preceding transition that did not
// include the DST offset so that we can calculate the DST offset.
rawOffset = -1;
for (transitionIndex -= 1; transitionIndex >= 0; --transitionIndex) {
type = mTypes[transitionIndex] & 0xff;
if (mIsDsts[type] == 0) {
rawOffset = mRawOffset + mOffsets[type] * 1000;
break;
}
}
// If no previous transition was found then use the earliest raw offset.
if (rawOffset == -1) {
rawOffset = mEarliestRawOffset;
}
// The DST offset is the difference between the total and the raw offset.
dstOffset = totalOffset - rawOffset;
}
}
offsets[0] = rawOffset;
offsets[1] = dstOffset;
return totalOffset;
}
@Override
public int getOffset(long when) {
int offsetIndex = findOffsetIndexForTimeInMilliseconds(when);
if (offsetIndex == -1) {
// Assume that all times before our first transition correspond to the
// oldest-known non-daylight offset. The obvious alternative would be to
// use the current raw offset, but that seems like a greater leap of faith.
return mEarliestRawOffset;
}
return mRawOffset + mOffsets[offsetIndex] * 1000;
}
@Override public boolean inDaylightTime(Date time) {
long when = time.getTime();
int offsetIndex = findOffsetIndexForTimeInMilliseconds(when);
if (offsetIndex == -1) {
// Assume that all times before our first transition are non-daylight.
// Transition data tends to start with a transition to daylight, so just
// copying the first transition would assume the opposite.
// http://code.google.com/p/android/issues/detail?id=14395
return false;
}
return mIsDsts[offsetIndex] == 1;
}
@Override public int getRawOffset() {
return mRawOffset;
}
@Override public void setRawOffset(int off) {
mRawOffset = off;
}
@Override public int getDSTSavings() {
return mDstSavings;
}
@Override public boolean useDaylightTime() {
return mUseDst;
}
@Override public boolean hasSameRules(TimeZone timeZone) {
if (!(timeZone instanceof ZoneInfo)) {
return false;
}
ZoneInfo other = (ZoneInfo) timeZone;
if (mUseDst != other.mUseDst) {
return false;
}
if (!mUseDst) {
return mRawOffset == other.mRawOffset;
}
return mRawOffset == other.mRawOffset
// Arrays.equals returns true if both arrays are null
&& Arrays.equals(mOffsets, other.mOffsets)
&& Arrays.equals(mIsDsts, other.mIsDsts)
&& Arrays.equals(mTypes, other.mTypes)
&& Arrays.equals(mTransitions, other.mTransitions);
}
@Override public boolean equals(Object obj) {
if (!(obj instanceof ZoneInfo)) {
return false;
}
ZoneInfo other = (ZoneInfo) obj;
return getID().equals(other.getID()) && hasSameRules(other);
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + getID().hashCode();
result = prime * result + Arrays.hashCode(mOffsets);
result = prime * result + Arrays.hashCode(mIsDsts);
result = prime * result + mRawOffset;
result = prime * result + Arrays.hashCode(mTransitions);
result = prime * result + Arrays.hashCode(mTypes);
result = prime * result + (mUseDst ? 1231 : 1237);
return result;
}
@Override
public String toString() {
return getClass().getName() + "[id=\"" + getID() + "\"" +
",mRawOffset=" + mRawOffset +
",mEarliestRawOffset=" + mEarliestRawOffset +
",mUseDst=" + mUseDst +
",mDstSavings=" + mDstSavings +
",transitions=" + mTransitions.length +
"]";
}
@Override
public Object clone() {
// Overridden for documentation. The default clone() behavior is exactly what we want.
// Though mutable, the arrays of offset data are treated as immutable. Only ID and
// mRawOffset are mutable in this class, and those are an immutable object and a primitive
// respectively.
return super.clone();
}
/**
* A class that represents a "wall time". This class is modeled on the C tm struct and
* is used to support android.text.format.Time behavior. Unlike the tm struct the year is
* represented as the full year, not the years since 1900.
*
* <p>This class contains a rewrite of various native functions that android.text.format.Time
* once relied on such as mktime_tz and localtime_tz. This replacement does not support leap
* seconds but does try to preserve behavior around ambiguous date/times found in the BSD
* version of mktime that was previously used.
*
* <p>The original native code used a 32-bit value for time_t on 32-bit Android, which
* was the only variant of Android available at the time. To preserve old behavior this code
* deliberately uses {@code int} rather than {@code long} for most things and performs
* calculations in seconds. This creates deliberate truncation issues for date / times before
* 1901 and after 2038. This is intentional but might be fixed in future if all the knock-ons
* can be resolved: Application code may have come to rely on the range so previously values
* like zero for year could indicate an invalid date but if we move to long the year zero would
* be valid.
*
* <p>All offsets are considered to be safe for addition / subtraction / multiplication without
* worrying about overflow. All absolute time arithmetic is checked for overflow / underflow.
*/
public static class WallTime {
// We use a GregorianCalendar (set to UTC) to handle all the date/time normalization logic
// and to convert from a broken-down date/time to a millis value.
// Unfortunately, it cannot represent an initial state with a zero day and would
// automatically normalize it, so we must copy values into and out of it as needed.
private final GregorianCalendar calendar;
private int year;
private int month;
private int monthDay;
private int hour;
private int minute;
private int second;
private int weekDay;
private int yearDay;
private int isDst;
private int gmtOffsetSeconds;
public WallTime() {
this.calendar = new GregorianCalendar(0, 0, 0, 0, 0, 0);
calendar.setTimeZone(TimeZone.getTimeZone("UTC"));
}
/**
* Sets the wall time to a point in time using the time zone information provided. This
* is a replacement for the old native localtime_tz() function.
*
* <p>When going from an instant to a wall time it is always unambiguous because there
* is only one offset rule acting at any given instant. We do not consider leap seconds.
*/
public void localtime(int timeSeconds, ZoneInfo zoneInfo) {
try {
int offsetSeconds = zoneInfo.mRawOffset / 1000;
// Find out the timezone DST state and adjustment.
byte isDst;
if (zoneInfo.mTransitions.length == 0) {
isDst = 0;
} else {
// offsetIndex can be in the range -1..zoneInfo.mOffsets.length - 1
int offsetIndex = zoneInfo.findOffsetIndexForTimeInSeconds(timeSeconds);
if (offsetIndex == -1) {
// -1 means timeSeconds is "before the first recorded transition". The first
// recorded transition is treated as a transition from non-DST and the raw
// offset.
isDst = 0;
} else {
offsetSeconds += zoneInfo.mOffsets[offsetIndex];
isDst = zoneInfo.mIsDsts[offsetIndex];
}
}
// Perform arithmetic that might underflow before setting fields.
int wallTimeSeconds = checkedAdd(timeSeconds, offsetSeconds);
// Set fields.
calendar.setTimeInMillis(wallTimeSeconds * 1000L);
copyFieldsFromCalendar();
this.isDst = isDst;
this.gmtOffsetSeconds = offsetSeconds;
} catch (CheckedArithmeticException e) {
// Just stop, leaving fields untouched.
}
}
/**
* Returns the time in seconds since beginning of the Unix epoch for the wall time using the
* time zone information provided. This is a replacement for an old native mktime_tz() C
* function.
*
* <p>When going from a wall time to an instant the answer can be ambiguous. A wall
* time can map to zero, one or two instants given sane date/time transitions. Sane
* in this case means that transitions occur less frequently than the offset
* differences between them (which could cause all sorts of craziness like the
* skipping out of transitions).
*
* <p>For example, this is not fully supported:
* <ul>
* <li>t1 { time = 1, offset = 0 }
* <li>t2 { time = 2, offset = -1 }
* <li>t3 { time = 3, offset = -2 }
* </ul>
* A wall time in this case might map to t1, t2 or t3.
*
* <p>We do not handle leap seconds.
* <p>We assume that no timezone offset transition has an absolute offset > 24 hours.
* <p>We do not assume that adjacent transitions modify the DST state; adjustments can
* occur for other reasons such as when a zone changes its raw offset.
*/
public int mktime(ZoneInfo zoneInfo) {
// Normalize isDst to -1, 0 or 1 to simplify isDst equality checks below.
this.isDst = this.isDst > 0 ? this.isDst = 1 : this.isDst < 0 ? this.isDst = -1 : 0;
copyFieldsToCalendar();
final long longWallTimeSeconds = calendar.getTimeInMillis() / 1000;
if (Integer.MIN_VALUE > longWallTimeSeconds
|| longWallTimeSeconds > Integer.MAX_VALUE) {
// For compatibility with the old native 32-bit implementation we must treat
// this as an error. Note: -1 could be confused with a real time.
return -1;
}
try {
final int wallTimeSeconds = (int) longWallTimeSeconds;
final int rawOffsetSeconds = zoneInfo.mRawOffset / 1000;
final int rawTimeSeconds = checkedSubtract(wallTimeSeconds, rawOffsetSeconds);
if (zoneInfo.mTransitions.length == 0) {
// There is no transition information. There is just a raw offset for all time.
if (this.isDst > 0) {
// Caller has asserted DST, but there is no DST information available.
return -1;
}
copyFieldsFromCalendar();
this.isDst = 0;
this.gmtOffsetSeconds = rawOffsetSeconds;
return rawTimeSeconds;
}
// We cannot know for sure what instant the wall time will map to. Unfortunately, in
// order to know for sure we need the timezone information, but to get the timezone
// information we need an instant. To resolve this we use the raw offset to find an
// OffsetInterval; this will get us the OffsetInterval we need or very close.
// The initialTransition can be between -1 and (zoneInfo.mTransitions - 1). -1
// indicates the rawTime is before the first transition and is handled gracefully by
// createOffsetInterval().
final int initialTransitionIndex = zoneInfo.findTransitionIndex(rawTimeSeconds);
if (isDst < 0) {
// This is treated as a special case to get it out of the way:
// When a caller has set isDst == -1 it means we can return the first match for
// the wall time we find. If the caller has specified a wall time that cannot
// exist this always returns -1.
Integer result = doWallTimeSearch(zoneInfo, initialTransitionIndex,
wallTimeSeconds, true /* mustMatchDst */);
return result == null ? -1 : result;
}
// If the wall time asserts a DST (isDst == 0 or 1) the search is performed twice:
// 1) The first attempts to find a DST offset that matches isDst exactly.
// 2) If it fails, isDst is assumed to be incorrect and adjustments are made to see
// if a valid wall time can be created. The result can be somewhat arbitrary.
Integer result = doWallTimeSearch(zoneInfo, initialTransitionIndex, wallTimeSeconds,
true /* mustMatchDst */);
if (result == null) {
result = doWallTimeSearch(zoneInfo, initialTransitionIndex, wallTimeSeconds,
false /* mustMatchDst */);
}
if (result == null) {
result = -1;
}
return result;
} catch (CheckedArithmeticException e) {
return -1;
}
}
/**
* Attempt to apply DST adjustments to {@code oldWallTimeSeconds} to create a wall time in
* {@code targetInterval}.
*
* <p>This is used when a caller has made an assertion about standard time / DST that cannot
* be matched to any offset interval that exists. We must therefore assume that the isDst
* assertion is incorrect and the invalid wall time is the result of some modification the
* caller made to a valid wall time that pushed them outside of the offset interval they
* were in. We must correct for any DST change that should have been applied when they did
* so.
*
* <p>Unfortunately, we have no information about what adjustment they made and so cannot
* know which offset interval they were previously in. For example, they may have added a
* second or a year to a valid time to arrive at what they have.
*
* <p>We try all offset types that are not the same as the isDst the caller asserted. For
* each possible offset we work out the offset difference between that and
* {@code targetInterval}, apply it, and see if we are still in {@code targetInterval}. If
* we are, then we have found an adjustment.
*/
private Integer tryOffsetAdjustments(ZoneInfo zoneInfo, int oldWallTimeSeconds,
OffsetInterval targetInterval, int transitionIndex, int isDstToFind)
throws CheckedArithmeticException {
int[] offsetsToTry = getOffsetsOfType(zoneInfo, transitionIndex, isDstToFind);
for (int j = 0; j < offsetsToTry.length; j++) {
int rawOffsetSeconds = zoneInfo.mRawOffset / 1000;
int jOffsetSeconds = rawOffsetSeconds + offsetsToTry[j];
int targetIntervalOffsetSeconds = targetInterval.getTotalOffsetSeconds();
int adjustmentSeconds = targetIntervalOffsetSeconds - jOffsetSeconds;
int adjustedWallTimeSeconds = checkedAdd(oldWallTimeSeconds, adjustmentSeconds);
if (targetInterval.containsWallTime(adjustedWallTimeSeconds)) {
// Perform any arithmetic that might overflow.
int returnValue = checkedSubtract(adjustedWallTimeSeconds,
targetIntervalOffsetSeconds);
// Modify field state and return the result.
calendar.setTimeInMillis(adjustedWallTimeSeconds * 1000L);
copyFieldsFromCalendar();
this.isDst = targetInterval.getIsDst();
this.gmtOffsetSeconds = targetIntervalOffsetSeconds;
return returnValue;
}
}
return null;
}
/**
* Return an array of offsets that have the requested {@code isDst} value.
* The {@code startIndex} is used as a starting point so transitions nearest
* to that index are returned first.
*/
private static int[] getOffsetsOfType(ZoneInfo zoneInfo, int startIndex, int isDst) {
// +1 to account for the synthetic transition we invent before the first recorded one.
int[] offsets = new int[zoneInfo.mOffsets.length + 1];
boolean[] seen = new boolean[zoneInfo.mOffsets.length];
int numFound = 0;
int delta = 0;
boolean clampTop = false;
boolean clampBottom = false;
do {
// delta = { 1, -1, 2, -2, 3, -3...}
delta *= -1;
if (delta >= 0) {
delta++;
}
int transitionIndex = startIndex + delta;
if (delta < 0 && transitionIndex < -1) {
clampBottom = true;
continue;
} else if (delta > 0 && transitionIndex >= zoneInfo.mTypes.length) {
clampTop = true;
continue;
}
if (transitionIndex == -1) {
if (isDst == 0) {
// Synthesize a non-DST transition before the first transition we have
// data for.
offsets[numFound++] = 0; // offset of 0 from raw offset
}
continue;
}
int type = zoneInfo.mTypes[transitionIndex] & 0xff;
if (!seen[type]) {
if (zoneInfo.mIsDsts[type] == isDst) {
offsets[numFound++] = zoneInfo.mOffsets[type];
}
seen[type] = true;
}
} while (!(clampTop && clampBottom));
int[] toReturn = new int[numFound];
System.arraycopy(offsets, 0, toReturn, 0, numFound);
return toReturn;
}
/**
* Find a time <em>in seconds</em> the same or close to {@code wallTimeSeconds} that
* satisfies {@code mustMatchDst}. The search begins around the timezone offset transition
* with {@code initialTransitionIndex}.
*
* <p>If {@code mustMatchDst} is {@code true} the method can only return times that
* use timezone offsets that satisfy the {@code this.isDst} requirements.
* If {@code this.isDst == -1} it means that any offset can be used.
*
* <p>If {@code mustMatchDst} is {@code false} any offset that covers the
* currently set time is acceptable. That is: if {@code this.isDst} == -1, any offset
* transition can be used, if it is 0 or 1 the offset used must match {@code this.isDst}.
*
* <p>Note: This method both uses and can modify field state. It returns the matching time
* in seconds if a match has been found and modifies fields, or it returns {@code null} and
* leaves the field state unmodified.
*/
private Integer doWallTimeSearch(ZoneInfo zoneInfo, int initialTransitionIndex,
int wallTimeSeconds, boolean mustMatchDst) throws CheckedArithmeticException {
// The loop below starts at the initialTransitionIndex and radiates out from that point
// up to 24 hours in either direction by applying transitionIndexDelta to inspect
// adjacent transitions (0, -1, +1, -2, +2). 24 hours is used because we assume that no
// total offset from UTC is ever > 24 hours. clampTop and clampBottom are used to
// indicate whether the search has either searched > 24 hours or exhausted the
// transition data in that direction. The search stops when a match is found or if
// clampTop and clampBottom are both true.
// The match logic employed is determined by the mustMatchDst parameter.
final int MAX_SEARCH_SECONDS = 24 * 60 * 60;
boolean clampTop = false, clampBottom = false;
int loop = 0;
do {
// transitionIndexDelta = { 0, -1, 1, -2, 2,..}
int transitionIndexDelta = (loop + 1) / 2;
if (loop % 2 == 1) {
transitionIndexDelta *= -1;
}
loop++;
// Only do any work in this iteration if we need to.
if (transitionIndexDelta > 0 && clampTop
|| transitionIndexDelta < 0 && clampBottom) {
continue;
}
// Obtain the OffsetInterval to use.
int currentTransitionIndex = initialTransitionIndex + transitionIndexDelta;
OffsetInterval offsetInterval =
OffsetInterval.create(zoneInfo, currentTransitionIndex);
if (offsetInterval == null) {
// No transition exists with the index we tried: Stop searching in the
// current direction.
clampTop |= (transitionIndexDelta > 0);
clampBottom |= (transitionIndexDelta < 0);
continue;
}
// Match the wallTimeSeconds against the OffsetInterval.
if (mustMatchDst) {
// Work out if the interval contains the wall time the caller specified and
// matches their isDst value.
if (offsetInterval.containsWallTime(wallTimeSeconds)) {
if (this.isDst == -1 || offsetInterval.getIsDst() == this.isDst) {
// This always returns the first OffsetInterval it finds that matches
// the wall time and isDst requirements. If this.isDst == -1 this means
// the result might be a DST or a non-DST answer for wall times that can
// exist in two OffsetIntervals.
int totalOffsetSeconds = offsetInterval.getTotalOffsetSeconds();
int returnValue = checkedSubtract(wallTimeSeconds,
totalOffsetSeconds);
copyFieldsFromCalendar();
this.isDst = offsetInterval.getIsDst();
this.gmtOffsetSeconds = totalOffsetSeconds;
return returnValue;
}
}
} else {
// To retain similar behavior to the old native implementation: if the caller is
// asserting the same isDst value as the OffsetInterval we are looking at we do
// not try to find an adjustment from another OffsetInterval of the same isDst
// type. If you remove this you get different results in situations like a
// DST -> DST transition or STD -> STD transition that results in an interval of
// "skipped" wall time. For example: if 01:30 (DST) is invalid and between two
// DST intervals, and the caller has passed isDst == 1, this results in a -1
// being returned.
if (isDst != offsetInterval.getIsDst()) {
final int isDstToFind = isDst;
Integer returnValue = tryOffsetAdjustments(zoneInfo, wallTimeSeconds,
offsetInterval, currentTransitionIndex, isDstToFind);
if (returnValue != null) {
return returnValue;
}
}
}
// See if we can avoid another loop in the current direction.
if (transitionIndexDelta > 0) {
// If we are searching forward and the OffsetInterval we have ends
// > MAX_SEARCH_SECONDS after the wall time, we don't need to look any further
// forward.
boolean endSearch = offsetInterval.getEndWallTimeSeconds() - wallTimeSeconds
> MAX_SEARCH_SECONDS;
if (endSearch) {
clampTop = true;
}
} else if (transitionIndexDelta < 0) {
boolean endSearch = wallTimeSeconds - offsetInterval.getStartWallTimeSeconds()
>= MAX_SEARCH_SECONDS;
if (endSearch) {
// If we are searching backward and the OffsetInterval starts
// > MAX_SEARCH_SECONDS before the wall time, we don't need to look any
// further backwards.
clampBottom = true;
}
}
} while (!(clampTop && clampBottom));
return null;
}
public void setYear(int year) {
this.year = year;
}
public void setMonth(int month) {
this.month = month;
}
public void setMonthDay(int monthDay) {
this.monthDay = monthDay;
}
public void setHour(int hour) {
this.hour = hour;
}
public void setMinute(int minute) {
this.minute = minute;
}
public void setSecond(int second) {
this.second = second;
}
public void setWeekDay(int weekDay) {
this.weekDay = weekDay;
}
public void setYearDay(int yearDay) {
this.yearDay = yearDay;
}
public void setIsDst(int isDst) {
this.isDst = isDst;
}
public void setGmtOffset(int gmtoff) {
this.gmtOffsetSeconds = gmtoff;
}
public int getYear() {
return year;
}
public int getMonth() {
return month;
}
public int getMonthDay() {
return monthDay;
}
public int getHour() {
return hour;
}
public int getMinute() {
return minute;
}
public int getSecond() {
return second;
}
public int getWeekDay() {
return weekDay;
}
public int getYearDay() {
return yearDay;
}
public int getGmtOffset() {
return gmtOffsetSeconds;
}
public int getIsDst() {
return isDst;
}
private void copyFieldsToCalendar() {
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, month);
calendar.set(Calendar.DAY_OF_MONTH, monthDay);
calendar.set(Calendar.HOUR_OF_DAY, hour);
calendar.set(Calendar.MINUTE, minute);
calendar.set(Calendar.SECOND, second);
calendar.set(Calendar.MILLISECOND, 0);
}
private void copyFieldsFromCalendar() {
year = calendar.get(Calendar.YEAR);
month = calendar.get(Calendar.MONTH);
monthDay = calendar.get(Calendar.DAY_OF_MONTH);
hour = calendar.get(Calendar.HOUR_OF_DAY);
minute = calendar.get(Calendar.MINUTE);
second = calendar.get(Calendar.SECOND);
// Calendar uses Sunday == 1. Android Time uses Sunday = 0.
weekDay = calendar.get(Calendar.DAY_OF_WEEK) - 1;
// Calendar enumerates from 1, Android Time enumerates from 0.
yearDay = calendar.get(Calendar.DAY_OF_YEAR) - 1;
}
}
/**
* A wall-time representation of a timezone offset interval.
*
* <p>Wall-time means "as it would appear locally in the timezone in which it applies".
* For example in 2007:
* PST was a -8:00 offset that ran until Mar 11, 2:00 AM.
* PDT was a -7:00 offset and ran from Mar 11, 3:00 AM to Nov 4, 2:00 AM.
* PST was a -8:00 offset and ran from Nov 4, 1:00 AM.
* Crucially this means that there was a "gap" after PST when PDT started, and an overlap when
* PDT ended and PST began.
*
* <p>For convenience all wall-time values are represented as the number of seconds since the
* beginning of the Unix epoch <em>in UTC</em>. To convert from a wall-time to the actual time
* in the offset it is necessary to <em>subtract</em> the {@code totalOffsetSeconds}.
* For example: If the offset in PST is -07:00 hours, then:
* timeInPstSeconds = wallTimeUtcSeconds - offsetSeconds
* i.e. 13:00 UTC - (-07:00) = 20:00 UTC = 13:00 PST
*/
static class OffsetInterval {
private final int startWallTimeSeconds;
private final int endWallTimeSeconds;
private final int isDst;
private final int totalOffsetSeconds;
/**
* Creates an {@link OffsetInterval}.
*
* <p>If {@code transitionIndex} is -1, the transition is synthesized to be a non-DST offset
* that runs from the beginning of time until the first transition in {@code timeZone} and
* has an offset of {@code timezone.mRawOffset}. If {@code transitionIndex} is the last
* transition that transition is considered to run until the end of representable time.
* Otherwise, the information is extracted from {@code timeZone.mTransitions},
* {@code timeZone.mOffsets} an {@code timeZone.mIsDsts}.
*/
public static OffsetInterval create(ZoneInfo timeZone, int transitionIndex)
throws CheckedArithmeticException {
if (transitionIndex < -1 || transitionIndex >= timeZone.mTransitions.length) {
return null;
}
int rawOffsetSeconds = timeZone.mRawOffset / 1000;
if (transitionIndex == -1) {
int endWallTimeSeconds = checkedAdd(timeZone.mTransitions[0], rawOffsetSeconds);
return new OffsetInterval(Integer.MIN_VALUE, endWallTimeSeconds, 0 /* isDst */,
rawOffsetSeconds);
}
int type = timeZone.mTypes[transitionIndex] & 0xff;
int totalOffsetSeconds = timeZone.mOffsets[type] + rawOffsetSeconds;
int endWallTimeSeconds;
if (transitionIndex == timeZone.mTransitions.length - 1) {
// If this is the last transition, make up the end time.
endWallTimeSeconds = Integer.MAX_VALUE;
} else {
endWallTimeSeconds = checkedAdd(timeZone.mTransitions[transitionIndex + 1],
totalOffsetSeconds);
}
int isDst = timeZone.mIsDsts[type];
int startWallTimeSeconds =
checkedAdd(timeZone.mTransitions[transitionIndex], totalOffsetSeconds);
return new OffsetInterval(
startWallTimeSeconds, endWallTimeSeconds, isDst, totalOffsetSeconds);
}
private OffsetInterval(int startWallTimeSeconds, int endWallTimeSeconds, int isDst,
int totalOffsetSeconds) {
this.startWallTimeSeconds = startWallTimeSeconds;
this.endWallTimeSeconds = endWallTimeSeconds;
this.isDst = isDst;
this.totalOffsetSeconds = totalOffsetSeconds;
}
public boolean containsWallTime(long wallTimeSeconds) {
return wallTimeSeconds >= startWallTimeSeconds && wallTimeSeconds < endWallTimeSeconds;
}
public int getIsDst() {
return isDst;
}
public int getTotalOffsetSeconds() {
return totalOffsetSeconds;
}
public long getEndWallTimeSeconds() {
return endWallTimeSeconds;
}
public long getStartWallTimeSeconds() {
return startWallTimeSeconds;
}
}
/**
* An exception used to indicate an arithmetic overflow or underflow.
*/
private static class CheckedArithmeticException extends Exception {
}
/**
* Calculate (a + b).
*
* @throws CheckedArithmeticException if overflow or underflow occurs
*/
private static int checkedAdd(long a, int b) throws CheckedArithmeticException {
// Adapted from Guava IntMath.checkedAdd();
long result = a + b;
if (result != (int) result) {
throw new CheckedArithmeticException();
}
return (int) result;
}
/**
* Calculate (a - b).
*
* @throws CheckedArithmeticException if overflow or underflow occurs
*/
private static int checkedSubtract(int a, int b) throws CheckedArithmeticException {
// Adapted from Guava IntMath.checkedSubtract();
long result = (long) a - b;
if (result != (int) result) {
throw new CheckedArithmeticException();
}
return (int) result;
}
}