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Java example source code file (ZoneInfoFile.java)

This example Java source code file (ZoneInfoFile.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

datainputstream, days_per_cycle, est, hst, ioexception, lastyear, mst, offset_mask, security, string, threading, threads, transition_nshift, use_oldmapping, utc1900, util, zip, zoneinfo, zoneoffsettransitionrule

The ZoneInfoFile.java Java example source code

/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.util.calendar;

import java.io.ByteArrayInputStream;
import java.io.BufferedInputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.StreamCorruptedException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
import java.util.Set;
import java.util.SimpleTimeZone;
import java.util.concurrent.ConcurrentHashMap;
import java.util.zip.CRC32;
import sun.security.action.GetPropertyAction;

/**
 * Loads TZDB time-zone rules for j.u.TimeZone
 * <p>
 * @since 1.8
 */
public final class ZoneInfoFile {

    /**
     * Gets all available IDs supported in the Java run-time.
     *
     * @return a set of time zone IDs.
     */
    public static String[] getZoneIds() {
        int len = regions.length + oldMappings.length;
        if (!USE_OLDMAPPING) {
            len += 3;    // EST/HST/MST not in tzdb.dat
        }
        String[] ids = Arrays.copyOf(regions, len);
        int i = regions.length;
        if (!USE_OLDMAPPING) {
            ids[i++] = "EST";
            ids[i++] = "HST";
            ids[i++] = "MST";
        }
        for (int j = 0; j < oldMappings.length; j++) {
            ids[i++] = oldMappings[j][0];
        }
        return ids;
    }

    /**
     * Gets all available IDs that have the same value as the
     * specified raw GMT offset.
     *
     * @param rawOffset  the GMT offset in milliseconds. This
     *                   value should not include any daylight saving time.
     * @return an array of time zone IDs.
     */
    public static String[] getZoneIds(int rawOffset) {
        List<String> ids = new ArrayList<>();
        for (String id : getZoneIds()) {
            ZoneInfo zi = getZoneInfo(id);
            if (zi.getRawOffset() == rawOffset) {
                ids.add(id);
            }
        }
        // It appears the "zi" implementation returns the
        // sorted list, though the specification does not
        // specify it. Keep the same behavior for better
        // compatibility.
        String[] list = ids.toArray(new String[ids.size()]);
        Arrays.sort(list);
        return list;
    }

    public static ZoneInfo getZoneInfo(String zoneId) {
        if (zoneId == null) {
            return null;
        }
        ZoneInfo zi = getZoneInfo0(zoneId);
        if (zi != null) {
            zi = (ZoneInfo)zi.clone();
            zi.setID(zoneId);
        }
        return zi;
    }

    private static ZoneInfo getZoneInfo0(String zoneId) {
        try {
            ZoneInfo zi = zones.get(zoneId);
            if (zi != null) {
                return zi;
            }
            String zid = zoneId;
            if (aliases.containsKey(zoneId)) {
                zid = aliases.get(zoneId);
            }
            int index = Arrays.binarySearch(regions, zid);
            if (index < 0) {
                return null;
            }
            byte[] bytes = ruleArray[indices[index]];
            DataInputStream dis = new DataInputStream(new ByteArrayInputStream(bytes));
            zi = getZoneInfo(dis, zid);
            zones.put(zoneId, zi);
            return zi;
        } catch (Exception ex) {
            throw new RuntimeException("Invalid binary time-zone data: TZDB:" +
                zoneId + ", version: " + versionId, ex);
        }
    }

    /**
     * Returns a Map from alias time zone IDs to their standard
     * time zone IDs.
     *
     * @return an unmodified alias mapping
     */
    public static Map<String, String> getAliasMap() {
        return Collections.unmodifiableMap(aliases);
    }

    /**
     * Gets the version of this tz data.
     *
     * @return the tzdb version
     */
    public static String getVersion() {
        return versionId;
    }

    /**
     * Gets a ZoneInfo with the given GMT offset. The object
     * has its ID in the format of GMT{+|-}hh:mm.
     *
     * @param originalId  the given custom id (before normalized such as "GMT+9")
     * @param gmtOffset   GMT offset <em>in milliseconds
     * @return a ZoneInfo constructed with the given GMT offset
     */
    public static ZoneInfo getCustomTimeZone(String originalId, int gmtOffset) {
        String id = toCustomID(gmtOffset);
        return new ZoneInfo(id, gmtOffset);
    }

    public static String toCustomID(int gmtOffset) {
        char sign;
        int offset = gmtOffset / 60000;
        if (offset >= 0) {
            sign = '+';
        } else {
            sign = '-';
            offset = -offset;
        }
        int hh = offset / 60;
        int mm = offset % 60;

        char[] buf = new char[] { 'G', 'M', 'T', sign, '0', '0', ':', '0', '0' };
        if (hh >= 10) {
            buf[4] += hh / 10;
        }
        buf[5] += hh % 10;
        if (mm != 0) {
            buf[7] += mm / 10;
            buf[8] += mm % 10;
        }
        return new String(buf);
    }

    ///////////////////////////////////////////////////////////
    private ZoneInfoFile() {
    }

    private static String versionId;
    private final static Map<String, ZoneInfo> zones = new ConcurrentHashMap<>();
    private static Map<String, String> aliases = new HashMap<>();

    private static byte[][] ruleArray;
    private static String[] regions;
    private static int[] indices;

    // Flag for supporting JDK backward compatible IDs, such as "EST".
    private static final boolean USE_OLDMAPPING;

    private static String[][] oldMappings = new String[][] {
        { "ACT", "Australia/Darwin" },
        { "AET", "Australia/Sydney" },
        { "AGT", "America/Argentina/Buenos_Aires" },
        { "ART", "Africa/Cairo" },
        { "AST", "America/Anchorage" },
        { "BET", "America/Sao_Paulo" },
        { "BST", "Asia/Dhaka" },
        { "CAT", "Africa/Harare" },
        { "CNT", "America/St_Johns" },
        { "CST", "America/Chicago" },
        { "CTT", "Asia/Shanghai" },
        { "EAT", "Africa/Addis_Ababa" },
        { "ECT", "Europe/Paris" },
        { "IET", "America/Indiana/Indianapolis" },
        { "IST", "Asia/Kolkata" },
        { "JST", "Asia/Tokyo" },
        { "MIT", "Pacific/Apia" },
        { "NET", "Asia/Yerevan" },
        { "NST", "Pacific/Auckland" },
        { "PLT", "Asia/Karachi" },
        { "PNT", "America/Phoenix" },
        { "PRT", "America/Puerto_Rico" },
        { "PST", "America/Los_Angeles" },
        { "SST", "Pacific/Guadalcanal" },
        { "VST", "Asia/Ho_Chi_Minh" },
    };

    static {
        String oldmapping = AccessController.doPrivileged(
            new GetPropertyAction("sun.timezone.ids.oldmapping", "false")).toLowerCase(Locale.ROOT);
        USE_OLDMAPPING = (oldmapping.equals("yes") || oldmapping.equals("true"));
        AccessController.doPrivileged(new PrivilegedAction<Object>() {
            public Object run() {
                try {
                    String libDir = System.getProperty("java.home") + File.separator + "lib";
                    try (DataInputStream dis = new DataInputStream(
                             new BufferedInputStream(new FileInputStream(
                                 new File(libDir, "tzdb.dat"))))) {
                        load(dis);
                    }
                } catch (Exception x) {
                    throw new Error(x);
                }
                return null;
            }
        });
    }

    private static void addOldMapping() {
        for (String[] alias : oldMappings) {
            aliases.put(alias[0], alias[1]);
        }
        if (USE_OLDMAPPING) {
            aliases.put("EST", "America/New_York");
            aliases.put("MST", "America/Denver");
            aliases.put("HST", "Pacific/Honolulu");
        } else {
            zones.put("EST", new ZoneInfo("EST", -18000000));
            zones.put("MST", new ZoneInfo("MST", -25200000));
            zones.put("HST", new ZoneInfo("HST", -36000000));
        }
    }

    public static boolean useOldMapping() {
       return USE_OLDMAPPING;
    }

    /**
     * Loads the rules from a DateInputStream
     *
     * @param dis  the DateInputStream to load, not null
     * @throws Exception if an error occurs
     */
    private static void load(DataInputStream dis) throws ClassNotFoundException, IOException {
        if (dis.readByte() != 1) {
            throw new StreamCorruptedException("File format not recognised");
        }
        // group
        String groupId = dis.readUTF();
        if ("TZDB".equals(groupId) == false) {
            throw new StreamCorruptedException("File format not recognised");
        }
        // versions, only keep the last one
        int versionCount = dis.readShort();
        for (int i = 0; i < versionCount; i++) {
            versionId = dis.readUTF();

        }
        // regions
        int regionCount = dis.readShort();
        String[] regionArray = new String[regionCount];
        for (int i = 0; i < regionCount; i++) {
            regionArray[i] = dis.readUTF();
        }
        // rules
        int ruleCount = dis.readShort();
        ruleArray = new byte[ruleCount][];
        for (int i = 0; i < ruleCount; i++) {
            byte[] bytes = new byte[dis.readShort()];
            dis.readFully(bytes);
            ruleArray[i] = bytes;
        }
        // link version-region-rules, only keep the last version, if more than one
        for (int i = 0; i < versionCount; i++) {
            regionCount = dis.readShort();
            regions = new String[regionCount];
            indices = new int[regionCount];
            for (int j = 0; j < regionCount; j++) {
                regions[j] = regionArray[dis.readShort()];
                indices[j] = dis.readShort();
            }
        }
        // remove the following ids from the map, they
        // are exclued from the "old" ZoneInfo
        zones.remove("ROC");
        for (int i = 0; i < versionCount; i++) {
            int aliasCount = dis.readShort();
            aliases.clear();
            for (int j = 0; j < aliasCount; j++) {
                String alias = regionArray[dis.readShort()];
                String region = regionArray[dis.readShort()];
                aliases.put(alias, region);
            }
        }
        // old us time-zone names
        addOldMapping();
    }

    /////////////////////////Ser/////////////////////////////////
    public static ZoneInfo getZoneInfo(DataInput in, String zoneId) throws Exception {
        byte type = in.readByte();
        // TBD: assert ZRULES:
        int stdSize = in.readInt();
        long[] stdTrans = new long[stdSize];
        for (int i = 0; i < stdSize; i++) {
            stdTrans[i] = readEpochSec(in);
        }
        int [] stdOffsets = new int[stdSize + 1];
        for (int i = 0; i < stdOffsets.length; i++) {
            stdOffsets[i] = readOffset(in);
        }
        int savSize = in.readInt();
        long[] savTrans = new long[savSize];
        for (int i = 0; i < savSize; i++) {
            savTrans[i] = readEpochSec(in);
        }
        int[] savOffsets = new int[savSize + 1];
        for (int i = 0; i < savOffsets.length; i++) {
            savOffsets[i] = readOffset(in);
        }
        int ruleSize = in.readByte();
        ZoneOffsetTransitionRule[] rules = new ZoneOffsetTransitionRule[ruleSize];
        for (int i = 0; i < ruleSize; i++) {
            rules[i] = new ZoneOffsetTransitionRule(in);
        }
        return getZoneInfo(zoneId, stdTrans, stdOffsets, savTrans, savOffsets, rules);
    }

    public static int readOffset(DataInput in) throws IOException {
        int offsetByte = in.readByte();
        return offsetByte == 127 ? in.readInt() : offsetByte * 900;
    }

    static long readEpochSec(DataInput in) throws IOException {
        int hiByte = in.readByte() & 255;
        if (hiByte == 255) {
            return in.readLong();
        } else {
            int midByte = in.readByte() & 255;
            int loByte = in.readByte() & 255;
            long tot = ((hiByte << 16) + (midByte << 8) + loByte);
            return (tot * 900) - 4575744000L;
        }
    }

    /////////////////////////ZoneRules --> ZoneInfo/////////////////////////////////

    // ZoneInfo starts with UTC1900
    private static final long UTC1900 = -2208988800L;

    // ZoneInfo ends with   UTC2037
    // LocalDateTime.of(2038, 1, 1, 0, 0, 0).toEpochSecond(ZoneOffset.UTC) - 1;
    private static final long UTC2037 = 2145916799L;

    // ZoneInfo has an ending entry for 2037, this need to be offset by
    // a "rawOffset"
    // LocalDateTime.of(2037, 1, 1, 0, 0, 0).toEpochSecond(ZoneOffset.UTC));
    private static final long LDT2037 = 2114380800L;

    //Current time. Used to determine future GMToffset transitions
    private static final long CURRT = System.currentTimeMillis()/1000;

    /* Get a ZoneInfo instance.
     *
     * @param standardTransitions  the standard transitions, not null
     * @param standardOffsets  the standard offsets, not null
     * @param savingsInstantTransitions  the standard transitions, not null
     * @param wallOffsets  the wall offsets, not null
     * @param lastRules  the recurring last rules, size 15 or less, not null
     */
    private static ZoneInfo getZoneInfo(String zoneId,
                                        long[] standardTransitions,
                                        int[] standardOffsets,
                                        long[] savingsInstantTransitions,
                                        int[] wallOffsets,
                                        ZoneOffsetTransitionRule[] lastRules) {
        int rawOffset = 0;
        int dstSavings = 0;
        int checksum = 0;
        int[] params = null;
        boolean willGMTOffsetChange = false;

        // rawOffset, pick the last one
        if (standardTransitions.length > 0) {
            rawOffset = standardOffsets[standardOffsets.length - 1] * 1000;
            willGMTOffsetChange = standardTransitions[standardTransitions.length - 1] > CURRT;
        }
        else
            rawOffset = standardOffsets[0] * 1000;

        // transitions, offsets;
        long[] transitions = null;
        int[]  offsets = null;
        int    nOffsets = 0;
        int    nTrans = 0;

        if (savingsInstantTransitions.length != 0) {
            transitions = new long[250];
            offsets = new int[100];    // TBD: ZoneInfo actually can't handle
                                       // offsets.length > 16 (4-bit index limit)
            // last year in trans table
            // It should not matter to use before or after offset for year
            int lastyear = getYear(savingsInstantTransitions[savingsInstantTransitions.length - 1],
                                   wallOffsets[savingsInstantTransitions.length - 1]);
            int i = 0, k = 1;
            while (i < savingsInstantTransitions.length &&
                   savingsInstantTransitions[i] < UTC1900) {
                i++;     // skip any date before UTC1900
            }
            if (i < savingsInstantTransitions.length) {
                // javazic writes the last GMT offset into index 0!
                if (i < savingsInstantTransitions.length) {
                    offsets[0] = standardOffsets[standardOffsets.length - 1] * 1000;
                    nOffsets = 1;
                }
                // ZoneInfo has a beginning entry for 1900.
                // Only add it if this is not the only one in table
                nOffsets = addTrans(transitions, nTrans++,
                                    offsets, nOffsets,
                                    UTC1900,
                                    wallOffsets[i],
                                    getStandardOffset(standardTransitions, standardOffsets, UTC1900));
            }

            for (; i < savingsInstantTransitions.length; i++) {
                long trans = savingsInstantTransitions[i];
                if (trans > UTC2037) {
                    // no trans beyond LASTYEAR
                    lastyear = LASTYEAR;
                    break;
                }
                while (k < standardTransitions.length) {
                    // some standard offset transitions don't exist in
                    // savingInstantTrans, if the offset "change" doesn't
                    // really change the "effectiveWallOffset". For example
                    // the 1999/2000 pair in Zone Arg/Buenos_Aires, in which
                    // the daylightsaving "happened" but it actually does
                    // not result in the timezone switch. ZoneInfo however
                    // needs them in its transitions table
                    long trans_s = standardTransitions[k];
                    if (trans_s >= UTC1900) {
                        if (trans_s > trans)
                            break;
                        if (trans_s < trans) {
                            if (nOffsets + 2 >= offsets.length) {
                                offsets = Arrays.copyOf(offsets, offsets.length + 100);
                            }
                            if (nTrans + 1 >= transitions.length) {
                                transitions = Arrays.copyOf(transitions, transitions.length + 100);
                            }
                            nOffsets = addTrans(transitions, nTrans++, offsets, nOffsets,
                                                trans_s,
                                                wallOffsets[i],
                                                standardOffsets[k+1]);

                        }
                    }
                    k++;
                }
                if (nOffsets + 2 >= offsets.length) {
                    offsets = Arrays.copyOf(offsets, offsets.length + 100);
                }
                if (nTrans + 1 >= transitions.length) {
                    transitions = Arrays.copyOf(transitions, transitions.length + 100);
                }
                nOffsets = addTrans(transitions, nTrans++, offsets, nOffsets,
                                    trans,
                                    wallOffsets[i + 1],
                                    getStandardOffset(standardTransitions, standardOffsets, trans));

            }
            // append any leftover standard trans
            while (k < standardTransitions.length) {
                long trans = standardTransitions[k];
                if (trans >= UTC1900) {
                    int offset = wallOffsets[i];
                    int offsetIndex = indexOf(offsets, 0, nOffsets, offset);
                    if (offsetIndex == nOffsets)
                        nOffsets++;
                    transitions[nTrans++] = ((trans * 1000) << TRANSITION_NSHIFT) |
                                            (offsetIndex & OFFSET_MASK);
                }
                k++;
            }
            if (lastRules.length > 1) {
                // fill the gap between the last trans until LASTYEAR
                while (lastyear++ < LASTYEAR) {
                    for (ZoneOffsetTransitionRule zotr : lastRules) {
                        long trans = zotr.getTransitionEpochSecond(lastyear);
                        if (nOffsets + 2 >= offsets.length) {
                            offsets = Arrays.copyOf(offsets, offsets.length + 100);
                        }
                        if (nTrans + 1 >= transitions.length) {
                            transitions = Arrays.copyOf(transitions, transitions.length + 100);
                        }
                        nOffsets = addTrans(transitions, nTrans++,
                                            offsets, nOffsets,
                                            trans,
                                            zotr.offsetAfter,
                                            zotr.standardOffset);
                    }
                }
                ZoneOffsetTransitionRule startRule =  lastRules[lastRules.length - 2];
                ZoneOffsetTransitionRule endRule =  lastRules[lastRules.length - 1];
                params = new int[10];
                if (startRule.offsetAfter - startRule.offsetBefore < 0 &&
                    endRule.offsetAfter - endRule.offsetBefore > 0) {
                    ZoneOffsetTransitionRule tmp;
                    tmp = startRule;
                    startRule = endRule;
                    endRule = tmp;
                }
                params[0] = startRule.month - 1;
                int dom = startRule.dom;
                int dow = startRule.dow;
                if (dow == -1) {
                    params[1] = dom;
                    params[2] = 0;
                } else {
                    // ZoneRulesBuilder adjusts < 0 case (-1, for last, don't have
                    // "<=" case yet) to positive value if not February (it appears
                    // we don't have February cutoff in tzdata table yet)
                    // Ideally, if JSR310 can just pass in the nagative and
                    // we can then pass in the dom = -1, dow > 0 into ZoneInfo
                    //
                    // hacking, assume the >=24 is the result of ZRB optimization for
                    // "last", it works for now.
                    if (dom < 0 || dom >= 24) {
                        params[1] = -1;
                        params[2] = toCalendarDOW[dow];
                    } else {
                        params[1] = dom;
                        // To specify a day of week on or after an exact day of month,
                        // set the month to an exact month value, day-of-month to the
                        // day on or after which the rule is applied, and day-of-week
                        // to a negative Calendar.DAY_OF_WEEK DAY_OF_WEEK field value.
                        params[2] = -toCalendarDOW[dow];
                    }
                }
                params[3] = startRule.secondOfDay * 1000;
                params[4] = toSTZTime[startRule.timeDefinition];
                params[5] = endRule.month - 1;
                dom = endRule.dom;
                dow = endRule.dow;
                if (dow == -1) {
                    params[6] = dom;
                    params[7] = 0;
                } else {
                    // hacking: see comment above
                    if (dom < 0 || dom >= 24) {
                        params[6] = -1;
                        params[7] = toCalendarDOW[dow];
                    } else {
                        params[6] = dom;
                        params[7] = -toCalendarDOW[dow];
                    }
                }
                params[8] = endRule.secondOfDay * 1000;
                params[9] = toSTZTime[endRule.timeDefinition];
                dstSavings = (startRule.offsetAfter - startRule.offsetBefore) * 1000;

                // Note: known mismatching -> Asia/Amman
                //                            Asia/Gaza
                //                            Asia/Hebron
                // ZoneInfo :      startDayOfWeek=5     <= Thursday
                //                 startTime=86400000   <= 24 hours
                // This:           startDayOfWeek=6
                //                 startTime=0
                // Below is the workaround, it probably slows down everyone a little
                if (params[2] == 6 && params[3] == 0 &&
                    (zoneId.equals("Asia/Amman") ||
                     zoneId.equals("Asia/Gaza") ||
                     zoneId.equals("Asia/Hebron"))) {
                    params[2] = 5;
                    params[3] = 86400000;
                }
            } else if (nTrans > 0) {  // only do this if there is something in table already
                if (lastyear < LASTYEAR) {
                    // ZoneInfo has an ending entry for 2037
                    //long trans = OffsetDateTime.of(LASTYEAR, 1, 1, 0, 0, 0, 0,
                    //                               ZoneOffset.ofTotalSeconds(rawOffset/1000))
                    //                           .toEpochSecond();
                    long trans = LDT2037 - rawOffset/1000;

                    int offsetIndex = indexOf(offsets, 0, nOffsets, rawOffset/1000);
                    if (offsetIndex == nOffsets)
                        nOffsets++;
                    transitions[nTrans++] = (trans * 1000) << TRANSITION_NSHIFT |
                                       (offsetIndex & OFFSET_MASK);

                } else if (savingsInstantTransitions.length > 2) {
                    // Workaround: create the params based on the last pair for
                    // zones like Israel and Iran which have trans defined
                    // up until 2037, but no "transition rule" defined
                    //
                    // Note: Known mismatching for Israel, Asia/Jerusalem/Tel Aviv
                    // ZoneInfo:        startMode=3
                    //                  startMonth=2
                    //                  startDay=26
                    //                  startDayOfWeek=6
                    //
                    // This:            startMode=1
                    //                  startMonth=2
                    //                  startDay=27
                    //                  startDayOfWeek=0
                    // these two are actually the same for 2037, the SimpleTimeZone
                    // for the last "known" year
                    int m = savingsInstantTransitions.length;
                    long startTrans = savingsInstantTransitions[m - 2];
                    int startOffset = wallOffsets[m - 2 + 1];
                    int startStd = getStandardOffset(standardTransitions, standardOffsets, startTrans);
                    long endTrans =  savingsInstantTransitions[m - 1];
                    int endOffset = wallOffsets[m - 1 + 1];
                    int endStd = getStandardOffset(standardTransitions, standardOffsets, endTrans);
                    if (startOffset > startStd && endOffset == endStd) {
                        // last - 1 trans
                        m = savingsInstantTransitions.length - 2;
                        ZoneOffset before = ZoneOffset.ofTotalSeconds(wallOffsets[m]);
                        ZoneOffset after = ZoneOffset.ofTotalSeconds(wallOffsets[m + 1]);
                        LocalDateTime ldt = LocalDateTime.ofEpochSecond(savingsInstantTransitions[m], 0, before);
                        LocalDateTime startLDT;
                        if (after.getTotalSeconds() > before.getTotalSeconds()) {  // isGap()
                            startLDT = ldt;
                        } else {
                            startLDT = ldt.plusSeconds(wallOffsets[m + 1] - wallOffsets[m]);
                        }
                        // last trans
                        m = savingsInstantTransitions.length - 1;
                        before = ZoneOffset.ofTotalSeconds(wallOffsets[m]);
                        after = ZoneOffset.ofTotalSeconds(wallOffsets[m + 1]);
                        ldt = LocalDateTime.ofEpochSecond(savingsInstantTransitions[m], 0, before);
                        LocalDateTime endLDT;
                        if (after.getTotalSeconds() > before.getTotalSeconds()) {  // isGap()
                            endLDT = ldt.plusSeconds(wallOffsets[m + 1] - wallOffsets[m]);
                        } else {
                            endLDT = ldt;
                        }
                        params = new int[10];
                        params[0] = startLDT.getMonthValue() - 1;
                        params[1] = startLDT.getDayOfMonth();
                        params[2] = 0;
                        params[3] = startLDT.toLocalTime().toSecondOfDay() * 1000;
                        params[4] = SimpleTimeZone.WALL_TIME;
                        params[5] = endLDT.getMonthValue() - 1;
                        params[6] = endLDT.getDayOfMonth();
                        params[7] = 0;
                        params[8] = endLDT.toLocalTime().toSecondOfDay() * 1000;
                        params[9] = SimpleTimeZone.WALL_TIME;
                        dstSavings = (startOffset - startStd) * 1000;
                    }
                }
            }
            if (transitions != null && transitions.length != nTrans) {
                if (nTrans == 0) {
                    transitions = null;
                } else {
                    transitions = Arrays.copyOf(transitions, nTrans);
                }
            }
            if (offsets != null && offsets.length != nOffsets) {
                if (nOffsets == 0) {
                    offsets = null;
                } else {
                    offsets = Arrays.copyOf(offsets, nOffsets);
                }
            }
            if (transitions != null) {
                Checksum sum = new Checksum();
                for (i = 0; i < transitions.length; i++) {
                    long val = transitions[i];
                    int dst = (int)((val >>> DST_NSHIFT) & 0xfL);
                    int saving = (dst == 0) ? 0 : offsets[dst];
                    int index = (int)(val & OFFSET_MASK);
                    int offset = offsets[index];
                    long second = (val >> TRANSITION_NSHIFT);
                    // javazic uses "index of the offset in offsets",
                    // instead of the real offset value itself to
                    // calculate the checksum. Have to keep doing
                    // the same thing, checksum is part of the
                    // ZoneInfo serialization form.
                    sum.update(second + index);
                    sum.update(index);
                    sum.update(dst == 0 ? -1 : dst);
                }
                checksum = (int)sum.getValue();
            }
        }
        return new ZoneInfo(zoneId, rawOffset, dstSavings, checksum, transitions,
                            offsets, params, willGMTOffsetChange);
    }

    private static int getStandardOffset(long[] standardTransitions,
                                         int[] standardOffsets,
                                         long epochSec) {
        // The size of stdOffsets is [0..9], with most are
        // [1..4] entries , simple loop search is faster
        //
        // int index  = Arrays.binarySearch(standardTransitions, epochSec);
        // if (index < 0) {
        //    // switch negative insert position to start of matched range
        //    index = -index - 2;
        // }
        // return standardOffsets[index + 1];
        int index = 0;
        for (; index < standardTransitions.length; index++) {
            if (epochSec < standardTransitions[index]) {
                break;
            }
        }
        return standardOffsets[index];
    }

    static final int SECONDS_PER_DAY = 86400;
    static final int DAYS_PER_CYCLE = 146097;
    static final long DAYS_0000_TO_1970 = (DAYS_PER_CYCLE * 5L) - (30L * 365L + 7L);

    private static int getYear(long epochSecond, int offset) {
        long second = epochSecond + offset;  // overflow caught later
        long epochDay = Math.floorDiv(second, SECONDS_PER_DAY);
        long zeroDay = epochDay + DAYS_0000_TO_1970;
        // find the march-based year
        zeroDay -= 60;  // adjust to 0000-03-01 so leap day is at end of four year cycle
        long adjust = 0;
        if (zeroDay < 0) {
            // adjust negative years to positive for calculation
            long adjustCycles = (zeroDay + 1) / DAYS_PER_CYCLE - 1;
            adjust = adjustCycles * 400;
            zeroDay += -adjustCycles * DAYS_PER_CYCLE;
        }
        long yearEst = (400 * zeroDay + 591) / DAYS_PER_CYCLE;
        long doyEst = zeroDay - (365 * yearEst + yearEst / 4 - yearEst / 100 + yearEst / 400);
        if (doyEst < 0) {
            // fix estimate
            yearEst--;
            doyEst = zeroDay - (365 * yearEst + yearEst / 4 - yearEst / 100 + yearEst / 400);
        }
        yearEst += adjust;  // reset any negative year
        int marchDoy0 = (int) doyEst;
        // convert march-based values back to january-based
        int marchMonth0 = (marchDoy0 * 5 + 2) / 153;
        int month = (marchMonth0 + 2) % 12 + 1;
        int dom = marchDoy0 - (marchMonth0 * 306 + 5) / 10 + 1;
        yearEst += marchMonth0 / 10;
        return (int)yearEst;
    }

    private static final int toCalendarDOW[] = new int[] {
        -1,
        Calendar.MONDAY,
        Calendar.TUESDAY,
        Calendar.WEDNESDAY,
        Calendar.THURSDAY,
        Calendar.FRIDAY,
        Calendar.SATURDAY,
        Calendar.SUNDAY
    };

    private static final int toSTZTime[] = new int[] {
        SimpleTimeZone.UTC_TIME,
        SimpleTimeZone.WALL_TIME,
        SimpleTimeZone.STANDARD_TIME,
    };

    private static final long OFFSET_MASK = 0x0fL;
    private static final long DST_MASK = 0xf0L;
    private static final int  DST_NSHIFT = 4;
    private static final int  TRANSITION_NSHIFT = 12;
    private static final int  LASTYEAR = 2037;

    // from: 0 for offset lookup, 1 for dstsvings lookup
    private static int indexOf(int[] offsets, int from, int nOffsets, int offset) {
        offset *= 1000;
        for (; from < nOffsets; from++) {
            if (offsets[from] == offset)
                return from;
        }
        offsets[from] = offset;
        return from;
    }

    // return updated nOffsets
    private static int addTrans(long transitions[], int nTrans,
                                int offsets[], int nOffsets,
                                long trans, int offset, int stdOffset) {
        int offsetIndex = indexOf(offsets, 0, nOffsets, offset);
        if (offsetIndex == nOffsets)
            nOffsets++;
        int dstIndex = 0;
        if (offset != stdOffset) {
            dstIndex = indexOf(offsets, 1, nOffsets, offset - stdOffset);
            if (dstIndex == nOffsets)
                nOffsets++;
        }
        transitions[nTrans] = ((trans * 1000) << TRANSITION_NSHIFT) |
                              ((dstIndex << DST_NSHIFT) & DST_MASK) |
                              (offsetIndex & OFFSET_MASK);
        return nOffsets;
    }

    // ZoneInfo checksum, copy/pasted from javazic
    private static class Checksum extends CRC32 {
        public void update(int val) {
            byte[] b = new byte[4];
            b[0] = (byte)(val >>> 24);
            b[1] = (byte)(val >>> 16);
            b[2] = (byte)(val >>> 8);
            b[3] = (byte)(val);
            update(b);
        }
        void update(long val) {
            byte[] b = new byte[8];
            b[0] = (byte)(val >>> 56);
            b[1] = (byte)(val >>> 48);
            b[2] = (byte)(val >>> 40);
            b[3] = (byte)(val >>> 32);
            b[4] = (byte)(val >>> 24);
            b[5] = (byte)(val >>> 16);
            b[6] = (byte)(val >>> 8);
            b[7] = (byte)(val);
            update(b);
        }
    }

    // A simple/raw version of j.t.ZoneOffsetTransitionRule
    private static class ZoneOffsetTransitionRule {
        private final int month;
        private final byte dom;
        private final int dow;
        private final int secondOfDay;
        private final boolean timeEndOfDay;
        private final int timeDefinition;
        private final int standardOffset;
        private final int offsetBefore;
        private final int offsetAfter;

        ZoneOffsetTransitionRule(DataInput in) throws IOException {
            int data = in.readInt();
            int dowByte = (data & (7 << 19)) >>> 19;
            int timeByte = (data & (31 << 14)) >>> 14;
            int stdByte = (data & (255 << 4)) >>> 4;
            int beforeByte = (data & (3 << 2)) >>> 2;
            int afterByte = (data & 3);

            this.month = data >>> 28;
            this.dom = (byte)(((data & (63 << 22)) >>> 22) - 32);
            this.dow = dowByte == 0 ? -1 : dowByte;
            this.secondOfDay = timeByte == 31 ? in.readInt() : timeByte * 3600;
            this.timeEndOfDay = timeByte == 24;
            this.timeDefinition = (data & (3 << 12)) >>> 12;

            this.standardOffset = stdByte == 255 ? in.readInt() : (stdByte - 128) * 900;
            this.offsetBefore = beforeByte == 3 ? in.readInt() : standardOffset + beforeByte * 1800;
            this.offsetAfter = afterByte == 3 ? in.readInt() : standardOffset + afterByte * 1800;
        }

        long getTransitionEpochSecond(int year) {
            long epochDay = 0;
            if (dom < 0) {
                epochDay = toEpochDay(year, month, lengthOfMonth(year, month) + 1 + dom);
                if (dow != -1) {
                    epochDay = previousOrSame(epochDay, dow);
                }
            } else {
                epochDay = toEpochDay(year, month, dom);
                if (dow != -1) {
                    epochDay = nextOrSame(epochDay, dow);
                }
            }
            if (timeEndOfDay) {
                epochDay += 1;
            }
            int difference = 0;
            switch (timeDefinition) {
                case 0:    // UTC
                    difference = 0;
                    break;
                case 1:    // WALL
                    difference = -offsetBefore;
                    break;
                case 2:    //STANDARD
                    difference = -standardOffset;
                    break;
            }
            return epochDay * 86400 + secondOfDay + difference;
        }

        static final boolean isLeapYear(int year) {
            return ((year & 3) == 0) && ((year % 100) != 0 || (year % 400) == 0);
        }

        static final int lengthOfMonth(int year, int month) {
            switch (month) {
                case 2:        //FEBRUARY:
                    return isLeapYear(year)? 29 : 28;
                case 4:        //APRIL:
                case 6:        //JUNE:
                case 9:        //SEPTEMBER:
                case 11:       //NOVEMBER:
                    return 30;
                default:
                    return 31;
            }
        }

        static final long toEpochDay(int year, int month, int day) {
            long y = year;
            long m = month;
            long total = 0;
            total += 365 * y;
            if (y >= 0) {
                total += (y + 3) / 4 - (y + 99) / 100 + (y + 399) / 400;
            } else {
                total -= y / -4 - y / -100 + y / -400;
            }
            total += ((367 * m - 362) / 12);
            total += day - 1;
            if (m > 2) {
                total--;
                if (!isLeapYear(year)) {
                    total--;
                }
            }
            return total - DAYS_0000_TO_1970;
        }

        static final long previousOrSame(long epochDay, int dayOfWeek) {
            return adjust(epochDay, dayOfWeek, 1);
        }

        static final long nextOrSame(long epochDay, int dayOfWeek) {
           return adjust(epochDay, dayOfWeek, 0);
        }

        static final long adjust(long epochDay, int dow, int relative) {
            int calDow = (int)Math.floorMod(epochDay + 3, 7L) + 1;
            if (relative < 2 && calDow == dow) {
                return epochDay;
            }
            if ((relative & 1) == 0) {
                int daysDiff = calDow - dow;
                return epochDay + (daysDiff >= 0 ? 7 - daysDiff : -daysDiff);
            } else {
                int daysDiff = dow - calDow;
                return epochDay - (daysDiff >= 0 ? 7 - daysDiff : -daysDiff);
            }
        }
    }
}

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