    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 * http://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.commons.compress.archivers.zip;
    020
    021import java.io.Serializable;
    022import java.nio.file.attribute.FileTime;
    023import java.util.Arrays;
    024import java.util.Date;
    025import java.util.Objects;
    026import java.util.zip.ZipException;
    027
    028import org.apache.commons.compress.utils.TimeUtils;
    029
    030/**
    031 * <p>
    032 * An extra field that stores additional file and directory timestamp data for ZIP entries. Each ZIP entry can include up to three timestamps (modify, access,
    033 * create*). The timestamps are stored as 32 bit signed integers representing seconds since UNIX epoch (Jan 1st, 1970, UTC). This field improves on ZIP's
    034 * default timestamp granularity, since it allows one to store additional timestamps, and, in addition, the timestamps are stored using per-second granularity
    035 * (zip's default behavior can only store timestamps to the nearest <em>even</em> second).
    036 * </p>
    037 * <p>
    038 * Unfortunately, 32 (signed) bits can only store dates up to the year 2037, and so this extra field will eventually be obsolete. Enjoy it while it lasts!
    039 * </p>
    040 * <ul>
    041 * <li><b>modifyTime:</b> most recent time of file/directory modification (or file/dir creation if the entry has not been modified since it was created).</li>
    042 * <li><b>accessTime:</b> most recent time file/directory was opened (e.g., read from disk). Many people disable their operating systems from updating this
    043 * value using the NOATIME mount option to optimize disk behavior, and thus it's not always reliable. In those cases it's always equal to modifyTime.</li>
    044 * <li><b>*createTime:</b> modern Linux file systems (e.g., ext2 and newer) do not appear to store a value like this, and so it's usually omitted altogether in
    045 * the ZIP extra field. Perhaps other Unix systems track this.</li>
    046 * </ul>
    047 * <p>
    048 * We're using the field definition given in Info-Zip's source archive: zip-3.0.tar.gz/proginfo/extrafld.txt
    049 * </p>
    050 *
    051 * <pre>
    052 * Value         Size        Description
    053 * -----         ----        -----------
    054 * 0x5455        Short       tag for this extra block type ("UT")
    055 * TSize         Short       total data size for this block
    056 * Flags         Byte        info bits
    057 * (ModTime)     Long        time of last modification (UTC/GMT)
    058 * (AcTime)      Long        time of last access (UTC/GMT)
    059 * (CrTime)      Long        time of original creation (UTC/GMT)
    060 *
    061 * Central-header version:
    062 *
    063 * Value         Size        Description
    064 * -----         ----        -----------
    065 * 0x5455        Short       tag for this extra block type ("UT")
    066 * TSize         Short       total data size for this block
    067 * Flags         Byte        info bits (refers to local header!)
    068 * (ModTime)     Long        time of last modification (UTC/GMT)
    069 * </pre>
    070 *
    071 * @since 1.5
    072 */
    073public class X5455_ExtendedTimestamp implements ZipExtraField, Cloneable, Serializable {
    074    private static final long serialVersionUID = 1L;
    075
    076    /**
    077     * The header ID for this extra field.
    078     *
    079     * @since 1.23
    080     */
    081    public static final ZipShort HEADER_ID = new ZipShort(0x5455);
    082
    083    /**
    084     * The bit set inside the flags by when the last modification time is present in this extra field.
    085     */
    086    public static final byte MODIFY_TIME_BIT = 1;
    087    /**
    088     * The bit set inside the flags by when the lasr access time is present in this extra field.
    089     */
    090    public static final byte ACCESS_TIME_BIT = 2;
    091    /**
    092     * The bit set inside the flags by when the original creation time is present in this extra field.
    093     */
    094    public static final byte CREATE_TIME_BIT = 4;
    095
    096    /**
    097     * Utility method converts java.util.Date (milliseconds since epoch) into a ZipLong (seconds since epoch).
    098     * <p/>
    099     * Also makes sure the converted ZipLong is not too big to fit in 32 unsigned bits.
    100     *
    101     * @param d java.util.Date to convert to ZipLong
    102     * @return ZipLong
    103     */
    104    private static ZipLong dateToZipLong(final Date d) {
    105        if (d == null) {
    106            return null;
    107        }
    108        return unixTimeToZipLong(d.getTime() / 1000);
    109    }
    110
    111    /**
    112     * Utility method converts {@link FileTime} into a ZipLong (seconds since epoch).
    113     * <p/>
    114     * Also makes sure the converted ZipLong is not too big to fit in 32 unsigned bits.
    115     *
    116     * @param time {@link FileTime} to convert to ZipLong
    117     * @return ZipLong
    118     */
    119    private static ZipLong fileTimeToZipLong(final FileTime time) {
    120        return time == null ? null : unixTimeToZipLong(TimeUtils.toUnixTime(time));
    121    }
    122
    123    private static FileTime unixTimeToFileTime(final ZipLong unixTime) {
    124        return unixTime != null ? TimeUtils.unixTimeToFileTime(unixTime.getIntValue()) : null;
    125    }
    126    // The 3 boolean fields (below) come from this flag's byte. The remaining 5 bits
    127    // are ignored according to the current version of the spec (December 2012).
    128
    129    private static ZipLong unixTimeToZipLong(final long unixTime) {
    130        if (!TimeUtils.isUnixTime(unixTime)) {
    131            throw new IllegalArgumentException("X5455 timestamps must fit in a signed 32 bit integer: " + unixTime);
    132        }
    133        return new ZipLong(unixTime);
    134    }
    135
    136    private static Date zipLongToDate(final ZipLong unixTime) {
    137        return unixTime != null ? new Date(unixTime.getIntValue() * 1000L) : null;
    138    }
    139
    140    private byte flags;
    141    // Note: even if bit1 and bit2 are set, the Central data will still not contain
    142    // access/create fields: only local data ever holds those! This causes
    143    // some of our implementation to look a little odd, with seemingly spurious
    144    // != null and length checks.
    145    private boolean bit0_modifyTimePresent;
    146    private boolean bit1_accessTimePresent;
    147
    148    private boolean bit2_createTimePresent;
    149
    150    private ZipLong modifyTime;
    151
    152    private ZipLong accessTime;
    153
    154    private ZipLong createTime;
    155
    156    /**
    157     * Constructor for X5455_ExtendedTimestamp.
    158     */
    159    public X5455_ExtendedTimestamp() {
    160    }
    161
    162    @Override
    163    public Object clone() throws CloneNotSupportedException {
    164        return super.clone();
    165    }
    166
    167    @Override
    168    public boolean equals(final Object o) {
    169        if (o instanceof X5455_ExtendedTimestamp) {
    170            final X5455_ExtendedTimestamp xf = (X5455_ExtendedTimestamp) o;
    171
    172            // The ZipLong==ZipLong clauses handle the cases where both are null.
    173            // and only last 3 bits of flags matter.
    174            return (flags & 0x07) == (xf.flags & 0x07) && Objects.equals(modifyTime, xf.modifyTime) && Objects.equals(accessTime, xf.accessTime)
    175                    && Objects.equals(createTime, xf.createTime);
    176        }
    177        return false;
    178    }
    179
    180    /**
    181     * Gets the access time as a {@link FileTime} of this ZIP entry, or null if no such timestamp exists in the ZIP entry. The milliseconds are always zeroed
    182     * out, since the underlying data offers only per-second precision.
    183     *
    184     * @return modify time as {@link FileTime} or null.
    185     * @since 1.23
    186     */
    187    public FileTime getAccessFileTime() {
    188        return unixTimeToFileTime(accessTime);
    189    }
    190
    191    /**
    192     * Gets the access time as a java.util.Date of this ZIP entry, or null if no such timestamp exists in the ZIP entry. The milliseconds are always zeroed out,
    193     * since the underlying data offers only per-second precision.
    194     *
    195     * @return access time as java.util.Date or null.
    196     */
    197    public Date getAccessJavaTime() {
    198        return zipLongToDate(accessTime);
    199    }
    200
    201    /**
    202     * Gets the access time (seconds since epoch) of this ZIP entry as a ZipLong object, or null if no such timestamp exists in the ZIP entry.
    203     *
    204     * @return access time (seconds since epoch) or null.
    205     */
    206    public ZipLong getAccessTime() {
    207        return accessTime;
    208    }
    209
    210    /**
    211     * Gets the actual data to put into central directory data - without Header-ID or length specifier.
    212     *
    213     * @return the central directory data
    214     */
    215    @Override
    216    public byte[] getCentralDirectoryData() {
    217        // Truncate out create & access time (last 8 bytes) from
    218        // the copy of the local data we obtained:
    219        return Arrays.copyOf(getLocalFileDataData(), getCentralDirectoryLength().getValue());
    220    }
    221
    222    /**
    223     * Gets the length of the extra field in the local file data - without Header-ID or length specifier.
    224     *
    225     * <p>
    226     * For X5455 the central length is often smaller than the local length, because central cannot contain access or create timestamps.
    227     * </p>
    228     *
    229     * @return a {@code ZipShort} for the length of the data of this extra field
    230     */
    231    @Override
    232    public ZipShort getCentralDirectoryLength() {
    233        return new ZipShort(1 + (bit0_modifyTimePresent ? 4 : 0));
    234    }
    235
    236    /**
    237     * Gets the create time as a {@link FileTime} of this ZIP entry, or null if no such timestamp exists in the ZIP entry. The milliseconds are always zeroed
    238     * out, since the underlying data offers only per-second precision.
    239     *
    240     * @return modify time as {@link FileTime} or null.
    241     * @since 1.23
    242     */
    243    public FileTime getCreateFileTime() {
    244        return unixTimeToFileTime(createTime);
    245    }
    246
    247    /**
    248     * <p>
    249     * Gets the create time as a java.util.Date of this ZIP entry, or null if no such timestamp exists in the ZIP entry. The milliseconds are always zeroed out,
    250     * since the underlying data offers only per-second precision.
    251     * </p>
    252     * <p>
    253     * Note: modern Linux file systems (e.g., ext2) do not appear to store a "create time" value, and so it's usually omitted altogether in the ZIP extra field.
    254     * Perhaps other Unix systems track this.
    255     * </p>
    256     *
    257     * @return create time as java.util.Date or null.
    258     */
    259    public Date getCreateJavaTime() {
    260        return zipLongToDate(createTime);
    261    }
    262
    263    /**
    264     * <p>
    265     * Gets the create time (seconds since epoch) of this ZIP entry as a ZipLong object, or null if no such timestamp exists in the ZIP entry.
    266     * </p>
    267     * <p>
    268     * Note: modern Linux file systems (e.g., ext2) do not appear to store a "create time" value, and so it's usually omitted altogether in the ZIP extra field.
    269     * Perhaps other Unix systems track this.
    270     * </p>
    271     *
    272     * @return create time (seconds since epoch) or null.
    273     */
    274    public ZipLong getCreateTime() {
    275        return createTime;
    276    }
    277
    278    /**
    279     * Gets flags byte. The flags byte tells us which of the three datestamp fields are present in the data:
    280     *
    281     * <pre>
    282     * bit0 - modify time
    283     * bit1 - access time
    284     * bit2 - create time
    285     * </pre>
    286     *
    287     * Only first 3 bits of flags are used according to the latest version of the spec (December 2012).
    288     *
    289     * @return flags byte indicating which of the three datestamp fields are present.
    290     */
    291    public byte getFlags() {
    292        return flags;
    293    }
    294
    295    /**
    296     * Gets the Header-ID.
    297     *
    298     * @return the value for the header id for this extrafield
    299     */
    300    @Override
    301    public ZipShort getHeaderId() {
    302        return HEADER_ID;
    303    }
    304
    305    /**
    306     * Gets the actual data to put into local file data - without Header-ID or length specifier.
    307     *
    308     * @return get the data
    309     */
    310    @Override
    311    public byte[] getLocalFileDataData() {
    312        final byte[] data = new byte[getLocalFileDataLength().getValue()];
    313        int pos = 0;
    314        data[pos++] = 0;
    315        if (bit0_modifyTimePresent) {
    316            data[0] |= MODIFY_TIME_BIT;
    317            System.arraycopy(modifyTime.getBytes(), 0, data, pos, 4);
    318            pos += 4;
    319        }
    320        if (bit1_accessTimePresent && accessTime != null) {
    321            data[0] |= ACCESS_TIME_BIT;
    322            System.arraycopy(accessTime.getBytes(), 0, data, pos, 4);
    323            pos += 4;
    324        }
    325        if (bit2_createTimePresent && createTime != null) {
    326            data[0] |= CREATE_TIME_BIT;
    327            System.arraycopy(createTime.getBytes(), 0, data, pos, 4);
    328            pos += 4; // NOSONAR - assignment as documentation
    329        }
    330        return data;
    331    }
    332
    333    /**
    334     * Gets the length of the extra field in the local file data - without Header-ID or length specifier.
    335     *
    336     * @return a {@code ZipShort} for the length of the data of this extra field
    337     */
    338    @Override
    339    public ZipShort getLocalFileDataLength() {
    340        return new ZipShort(1 + (bit0_modifyTimePresent ? 4 : 0) + (bit1_accessTimePresent && accessTime != null ? 4 : 0)
    341                + (bit2_createTimePresent && createTime != null ? 4 : 0));
    342    }
    343
    344    /**
    345     * Gets the modify time as a {@link FileTime} of this ZIP entry, or null if no such timestamp exists in the ZIP entry. The milliseconds are always zeroed
    346     * out, since the underlying data offers only per-second precision.
    347     *
    348     * @return modify time as {@link FileTime} or null.
    349     * @since 1.23
    350     */
    351    public FileTime getModifyFileTime() {
    352        return unixTimeToFileTime(modifyTime);
    353    }
    354
    355    /**
    356     * Gets the modify time as a java.util.Date of this ZIP entry, or null if no such timestamp exists in the ZIP entry. The milliseconds are always zeroed out,
    357     * since the underlying data offers only per-second precision.
    358     *
    359     * @return modify time as java.util.Date or null.
    360     */
    361    public Date getModifyJavaTime() {
    362        return zipLongToDate(modifyTime);
    363    }
    364
    365    /**
    366     * Gets the modify time (seconds since epoch) of this ZIP entry as a ZipLong object, or null if no such timestamp exists in the ZIP entry.
    367     *
    368     * @return modify time (seconds since epoch) or null.
    369     */
    370    public ZipLong getModifyTime() {
    371        return modifyTime;
    372    }
    373
    374    @Override
    375    public int hashCode() {
    376        int hc = -123 * (flags & 0x07); // only last 3 bits of flags matter
    377        if (modifyTime != null) {
    378            hc ^= modifyTime.hashCode();
    379        }
    380        if (accessTime != null) {
    381            // Since accessTime is often same as modifyTime,
    382            // this prevents them from XOR negating each other.
    383            hc ^= Integer.rotateLeft(accessTime.hashCode(), 11);
    384        }
    385        if (createTime != null) {
    386            hc ^= Integer.rotateLeft(createTime.hashCode(), 22);
    387        }
    388        return hc;
    389    }
    390
    391    /**
    392     * Tests whether bit0 of the flags byte is set or not, which should correspond to the presence or absence of a modify timestamp in this particular ZIP
    393     * entry.
    394     *
    395     * @return true if bit0 of the flags byte is set.
    396     */
    397    public boolean isBit0_modifyTimePresent() {
    398        return bit0_modifyTimePresent;
    399    }
    400
    401    /**
    402     * Tests whether bit1 of the flags byte is set or not, which should correspond to the presence or absence of a "last access" timestamp in this particular
    403     * ZIP entry.
    404     *
    405     * @return true if bit1 of the flags byte is set.
    406     */
    407    public boolean isBit1_accessTimePresent() {
    408        return bit1_accessTimePresent;
    409    }
    410
    411    /**
    412     * Tests whether bit2 of the flags byte is set or not, which should correspond to the presence or absence of a create timestamp in this particular ZIP
    413     * entry.
    414     *
    415     * @return true if bit2 of the flags byte is set.
    416     */
    417    public boolean isBit2_createTimePresent() {
    418        return bit2_createTimePresent;
    419    }
    420
    421    /**
    422     * Doesn't do anything special since this class always uses the same parsing logic for both central directory and local file data.
    423     */
    424    @Override
    425    public void parseFromCentralDirectoryData(final byte[] buffer, final int offset, final int length) throws ZipException {
    426        reset();
    427        parseFromLocalFileData(buffer, offset, length);
    428    }
    429
    430    /**
    431     * Populate data from this array as if it was in local file data.
    432     *
    433     * @param data   an array of bytes
    434     * @param offset the start offset
    435     * @param length the number of bytes in the array from offset
    436     * @throws java.util.zip.ZipException on error
    437     */
    438    @Override
    439    public void parseFromLocalFileData(final byte[] data, int offset, final int length) throws ZipException {
    440        reset();
    441        if (length < 1) {
    442            throw new ZipException("X5455_ExtendedTimestamp too short, only " + length + " bytes");
    443        }
    444        final int len = offset + length;
    445        setFlags(data[offset++]);
    446        if (bit0_modifyTimePresent && offset + 4 <= len) {
    447            modifyTime = new ZipLong(data, offset);
    448            offset += 4;
    449        } else {
    450            bit0_modifyTimePresent = false;
    451        }
    452        if (bit1_accessTimePresent && offset + 4 <= len) {
    453            accessTime = new ZipLong(data, offset);
    454            offset += 4;
    455        } else {
    456            bit1_accessTimePresent = false;
    457        }
    458        if (bit2_createTimePresent && offset + 4 <= len) {
    459            createTime = new ZipLong(data, offset);
    460            offset += 4; // NOSONAR - assignment as documentation
    461        } else {
    462            bit2_createTimePresent = false;
    463        }
    464    }
    465
    466    /**
    467     * Reset state back to newly constructed state. Helps us make sure parse() calls always generate clean results.
    468     */
    469    private void reset() {
    470        setFlags((byte) 0);
    471        this.modifyTime = null;
    472        this.accessTime = null;
    473        this.createTime = null;
    474    }
    475
    476    /**
    477     * <p>
    478     * Sets the acccess time as a {@link FileTime} of this ZIP entry. Supplied value is truncated to per-second precision (milliseconds zeroed-out).
    479     * </p>
    480     * <p>
    481     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    482     * flags is also set.
    483     * </p>
    484     *
    485     * @param time access time as {@link FileTime}
    486     * @since 1.23
    487     */
    488    public void setAccessFileTime(final FileTime time) {
    489        setAccessTime(fileTimeToZipLong(time));
    490    }
    491
    492    /**
    493     * <p>
    494     * Sets the access time as a java.util.Date of this ZIP entry. Supplied value is truncated to per-second precision (milliseconds zeroed-out).
    495     * </p>
    496     * <p>
    497     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    498     * flags is also set.
    499     * </p>
    500     *
    501     * @param d access time as java.util.Date
    502     */
    503    public void setAccessJavaTime(final Date d) {
    504        setAccessTime(dateToZipLong(d));
    505    }
    506
    507    /**
    508     * <p>
    509     * Sets the access time (seconds since epoch) of this ZIP entry using a ZipLong object
    510     * </p>
    511     * <p>
    512     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    513     * flags is also set.
    514     * </p>
    515     *
    516     * @param l ZipLong of the access time (seconds per epoch)
    517     */
    518    public void setAccessTime(final ZipLong l) {
    519        bit1_accessTimePresent = l != null;
    520        flags = (byte) (l != null ? flags | ACCESS_TIME_BIT : flags & ~ACCESS_TIME_BIT);
    521        this.accessTime = l;
    522    }
    523
    524    /**
    525     * <p>
    526     * Sets the create time as a {@link FileTime} of this ZIP entry. Supplied value is truncated to per-second precision (milliseconds zeroed-out).
    527     * </p>
    528     * <p>
    529     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    530     * flags is also set.
    531     * </p>
    532     *
    533     * @param time create time as {@link FileTime}
    534     * @since 1.23
    535     */
    536    public void setCreateFileTime(final FileTime time) {
    537        setCreateTime(fileTimeToZipLong(time));
    538    }
    539
    540    /**
    541     * <p>
    542     * Sets the create time as a java.util.Date of this ZIP entry. Supplied value is truncated to per-second precision (milliseconds zeroed-out).
    543     * </p>
    544     * <p>
    545     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    546     * flags is also set.
    547     * </p>
    548     *
    549     * @param d create time as java.util.Date
    550     */
    551    public void setCreateJavaTime(final Date d) {
    552        setCreateTime(dateToZipLong(d));
    553    }
    554
    555    /**
    556     * <p>
    557     * Sets the create time (seconds since epoch) of this ZIP entry using a ZipLong object
    558     * </p>
    559     * <p>
    560     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    561     * flags is also set.
    562     * </p>
    563     *
    564     * @param l ZipLong of the create time (seconds per epoch)
    565     */
    566    public void setCreateTime(final ZipLong l) {
    567        bit2_createTimePresent = l != null;
    568        flags = (byte) (l != null ? flags | CREATE_TIME_BIT : flags & ~CREATE_TIME_BIT);
    569        this.createTime = l;
    570    }
    571
    572    /**
    573     * Sets flags byte. The flags byte tells us which of the three datestamp fields are present in the data:
    574     *
    575     * <pre>
    576     * bit0 - modify time
    577     * bit1 - access time
    578     * bit2 - create time
    579     * </pre>
    580     *
    581     * Only first 3 bits of flags are used according to the latest version of the spec (December 2012).
    582     *
    583     * @param flags flags byte indicating which of the three datestamp fields are present.
    584     */
    585    public void setFlags(final byte flags) {
    586        this.flags = flags;
    587        this.bit0_modifyTimePresent = (flags & MODIFY_TIME_BIT) == MODIFY_TIME_BIT;
    588        this.bit1_accessTimePresent = (flags & ACCESS_TIME_BIT) == ACCESS_TIME_BIT;
    589        this.bit2_createTimePresent = (flags & CREATE_TIME_BIT) == CREATE_TIME_BIT;
    590    }
    591
    592    /**
    593     * <p>
    594     * Sets the modify time as a {@link FileTime} of this ZIP entry. Supplied value is truncated to per-second precision (milliseconds zeroed-out).
    595     * </p>
    596     * <p>
    597     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    598     * flags is also set.
    599     * </p>
    600     *
    601     * @param time modify time as {@link FileTime}
    602     * @since 1.23
    603     */
    604    public void setModifyFileTime(final FileTime time) {
    605        setModifyTime(fileTimeToZipLong(time));
    606    }
    607
    608    /**
    609     * <p>
    610     * Sets the modify time as a java.util.Date of this ZIP entry. Supplied value is truncated to per-second precision (milliseconds zeroed-out).
    611     * </p>
    612     * <p>
    613     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    614     * flags is also set.
    615     * </p>
    616     *
    617     * @param d modify time as java.util.Date
    618     */
    619    public void setModifyJavaTime(final Date d) {
    620        setModifyTime(dateToZipLong(d));
    621    }
    622
    623    /**
    624     * <p>
    625     * Sets the modify time (seconds since epoch) of this ZIP entry using a ZipLong object.
    626     * </p>
    627     * <p>
    628     * Note: the setters for flags and timestamps are decoupled. Even if the timestamp is not-null, it will only be written out if the corresponding bit in the
    629     * flags is also set.
    630     * </p>
    631     *
    632     * @param l ZipLong of the modify time (seconds per epoch)
    633     */
    634    public void setModifyTime(final ZipLong l) {
    635        bit0_modifyTimePresent = l != null;
    636        flags = (byte) (l != null ? flags | MODIFY_TIME_BIT : flags & ~MODIFY_TIME_BIT);
    637        this.modifyTime = l;
    638    }
    639
    640    /**
    641     * Returns a String representation of this class useful for debugging purposes.
    642     *
    643     * @return A String representation of this class useful for debugging purposes.
    644     */
    645    @Override
    646    public String toString() {
    647        final StringBuilder buf = new StringBuilder();
    648        buf.append("0x5455 Zip Extra Field: Flags=");
    649        buf.append(Integer.toBinaryString(ZipUtil.unsignedIntToSignedByte(flags))).append(" ");
    650        if (bit0_modifyTimePresent && modifyTime != null) {
    651            final Date m = getModifyJavaTime();
    652            buf.append(" Modify:[").append(m).append("] ");
    653        }
    654        if (bit1_accessTimePresent && accessTime != null) {
    655            final Date a = getAccessJavaTime();
    656            buf.append(" Access:[").append(a).append("] ");
    657        }
    658        if (bit2_createTimePresent && createTime != null) {
    659            final Date c = getCreateJavaTime();
    660            buf.append(" Create:[").append(c).append("] ");
    661        }
    662        return buf.toString();
    663    }
    664
    665}