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Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
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/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.commons.compress.archivers.zip;

import java.io.IOException;
import java.util.Calendar;
import java.util.Date;
import java.util.zip.CRC32;
import java.util.zip.ZipEntry;

/**
 * Utility class for handling DOS and Java time conversions.
 * @Immutable
 */
public abstract class ZipUtil {
    /**
     * Smallest date/time ZIP can handle.
     */
    private static final byte[] DOS_TIME_MIN = ZipLong.getBytes(0x00002100L);

    /**
     * Convert a Date object to a DOS date/time field.
     * @param time the Date to convert
     * @return the date as a ZipLong
     */
    public static ZipLong toDosTime(Date time) {
        return new ZipLong(toDosTime(time.getTime()));
    }

    /**
     * Convert a Date object to a DOS date/time field.
     *
     * Stolen from InfoZip's fileio.c
     * @param t number of milliseconds since the epoch
     * @return the date as a byte array
     */
    public static byte[] toDosTime(long t) {
        Calendar c = Calendar.getInstance();
        c.setTimeInMillis(t);

        int year = c.get(Calendar.YEAR);
        if (year < 1980) {
            return copy(DOS_TIME_MIN); // stop callers from changing the array
        }
        int month = c.get(Calendar.MONTH) + 1;
        long value =  ((year - 1980) << 25)
            |         (month << 21)
            |         (c.get(Calendar.DAY_OF_MONTH) << 16)
            |         (c.get(Calendar.HOUR_OF_DAY) << 11)
            |         (c.get(Calendar.MINUTE) << 5)
            |         (c.get(Calendar.SECOND) >> 1);
        return ZipLong.getBytes(value);
    }

    /**
     * Assumes a negative integer really is a positive integer that
     * has wrapped around and re-creates the original value.
     *
     * This methods is no longer used as of Apache Commons Compress
     * 1.3
     *
     * @param i the value to treat as unsigned int.
     * @return the unsigned int as a long.
     */
    public static long adjustToLong(int i) {
        if (i < 0) {
            return 2 * ((long) Integer.MAX_VALUE) + 2 + i;
        } else {
            return i;
        }
    }

    /**
     * Convert a DOS date/time field to a Date object.
     *
     * @param zipDosTime contains the stored DOS time.
     * @return a Date instance corresponding to the given time.
     */
    public static Date fromDosTime(ZipLong zipDosTime) {
        long dosTime = zipDosTime.getValue();
        return new Date(dosToJavaTime(dosTime));
    }

    /**
     * Converts DOS time to Java time (number of milliseconds since
     * epoch).
     */
    public static long dosToJavaTime(long dosTime) {
        Calendar cal = Calendar.getInstance();
        // CheckStyle:MagicNumberCheck OFF - no point
        cal.set(Calendar.YEAR, (int) ((dosTime >> 25) & 0x7f) + 1980);
        cal.set(Calendar.MONTH, (int) ((dosTime >> 21) & 0x0f) - 1);
        cal.set(Calendar.DATE, (int) (dosTime >> 16) & 0x1f);
        cal.set(Calendar.HOUR_OF_DAY, (int) (dosTime >> 11) & 0x1f);
        cal.set(Calendar.MINUTE, (int) (dosTime >> 5) & 0x3f);
        cal.set(Calendar.SECOND, (int) (dosTime << 1) & 0x3e);
        // CheckStyle:MagicNumberCheck ON
        return cal.getTime().getTime();
    }

    /**
     * If the entry has Unicode*ExtraFields and the CRCs of the
     * names/comments match those of the extra fields, transfer the
     * known Unicode values from the extra field.
     */
    static void setNameAndCommentFromExtraFields(ZipArchiveEntry ze,
                                                 byte[] originalNameBytes,
                                                 byte[] commentBytes) {
        UnicodePathExtraField name = (UnicodePathExtraField)
            ze.getExtraField(UnicodePathExtraField.UPATH_ID);
        String originalName = ze.getName();
        String newName = getUnicodeStringIfOriginalMatches(name,
                                                           originalNameBytes);
        if (newName != null && !originalName.equals(newName)) {
            ze.setName(newName);
        }

        if (commentBytes != null && commentBytes.length > 0) {
            UnicodeCommentExtraField cmt = (UnicodeCommentExtraField)
                ze.getExtraField(UnicodeCommentExtraField.UCOM_ID);
            String newComment =
                getUnicodeStringIfOriginalMatches(cmt, commentBytes);
            if (newComment != null) {
                ze.setComment(newComment);
            }
        }
    }

    /**
     * If the stored CRC matches the one of the given name, return the
     * Unicode name of the given field.
     *
     * If the field is null or the CRCs don't match, return null
     * instead.
     */
    private static 
        String getUnicodeStringIfOriginalMatches(AbstractUnicodeExtraField f,
                                                 byte[] orig) {
        if (f != null) {
            CRC32 crc32 = new CRC32();
            crc32.update(orig);
            long origCRC32 = crc32.getValue();

            if (origCRC32 == f.getNameCRC32()) {
                try {
                    return ZipEncodingHelper
                        .UTF8_ZIP_ENCODING.decode(f.getUnicodeName());
                } catch (IOException ex) {
                    // UTF-8 unsupported?  should be impossible the
                    // Unicode*ExtraField must contain some bad bytes

                    // TODO log this anywhere?
                    return null;
                }
            }
        }
        return null;
    }

    /**
     * Create a copy of the given array - or return null if the
     * argument is null.
     */
    static byte[] copy(byte[] from) {
        if (from != null) {
            byte[] to = new byte[from.length];
            System.arraycopy(from, 0, to, 0, to.length);
            return to;
        }
        return null;
    }

    /**
     * Whether this library is able to read or write the given entry.
     */
    static boolean canHandleEntryData(ZipArchiveEntry entry) {
        return supportsEncryptionOf(entry) && supportsMethodOf(entry);
    }

    /**
     * Whether this library supports the encryption used by the given
     * entry.
     *
     * @return true if the entry isn't encrypted at all
     */
    private static boolean supportsEncryptionOf(ZipArchiveEntry entry) {
        return !entry.getGeneralPurposeBit().usesEncryption();
    }

    /**
     * Whether this library supports the compression method used by
     * the given entry.
     *
     * @return true if the compression method is STORED or DEFLATED
     */
    private static boolean supportsMethodOf(ZipArchiveEntry entry) {
        return entry.getMethod() == ZipEntry.STORED
            || entry.getMethod() == ZipEntry.DEFLATED;
    }

    /**
     * Checks whether the entry requires features not (yet) supported
     * by the library and throws an exception if it does.
     */
    static void checkRequestedFeatures(ZipArchiveEntry ze)
        throws UnsupportedZipFeatureException {
        if (!supportsEncryptionOf(ze)) {
            throw
                new UnsupportedZipFeatureException(UnsupportedZipFeatureException
                                                   .Feature.ENCRYPTION, ze);
        }
        if (!supportsMethodOf(ze)) {
            throw
                new UnsupportedZipFeatureException(UnsupportedZipFeatureException
                                                   .Feature.METHOD, ze);
        }
    }
}