    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.compressors.xz;
    020
    021import java.util.HashMap;
    022import java.util.Map;
    023
    024import org.apache.commons.compress.compressors.FileNameUtil;
    025import org.apache.commons.compress.utils.OsgiUtils;
    026
    027/**
    028 * Utility code for the xz compression format.
    029 * @ThreadSafe
    030 * @since 1.4
    031 */
    032public class XZUtils {
    033
    034    enum CachedAvailability {
    035        DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE
    036    }
    037
    038    private static final FileNameUtil fileNameUtil;
    039
    040    /**
    041     * XZ Header Magic Bytes begin a XZ file.
    042     *
    043     * <p>This is a copy of {@code org.tukaani.xz.XZ.HEADER_MAGIC} in
    044     * XZ for Java version 1.5.</p>
    045     */
    046    private static final byte[] HEADER_MAGIC = {
    047        (byte) 0xFD, '7', 'z', 'X', 'Z', '\0'
    048    };
    049
    050    private static volatile CachedAvailability cachedXZAvailability;
    051
    052    static {
    053        final Map<String, String> uncompressSuffix = new HashMap<>();
    054        uncompressSuffix.put(".txz", ".tar");
    055        uncompressSuffix.put(".xz", "");
    056        uncompressSuffix.put("-xz", "");
    057        fileNameUtil = new FileNameUtil(uncompressSuffix, ".xz");
    058        cachedXZAvailability = CachedAvailability.DONT_CACHE;
    059        setCacheXZAvailablity(!OsgiUtils.isRunningInOsgiEnvironment());
    060    }
    061
    062    // only exists to support unit tests
    063    static CachedAvailability getCachedXZAvailability() {
    064        return cachedXZAvailability;
    065    }
    066
    067    /**
    068     * Maps the given file name to the name that the file should have after
    069     * compression with xz. Common file types with custom suffixes for
    070     * compressed versions are automatically detected and correctly mapped.
    071     * For example the name "package.tar" is mapped to "package.txz". If no
    072     * custom mapping is applicable, then the default ".xz" suffix is appended
    073     * to the file name.
    074     *
    075     * @param fileName name of a file
    076     * @return name of the corresponding compressed file
    077     */
    078    public static String getCompressedFilename(final String fileName) {
    079        return fileNameUtil.getCompressedFilename(fileName);
    080    }
    081
    082    /**
    083     * Maps the given name of a xz-compressed file to the name that the
    084     * file should have after uncompression. Commonly used file type specific
    085     * suffixes like ".txz" are automatically detected and
    086     * correctly mapped. For example the name "package.txz" is mapped to
    087     * "package.tar". And any file names with the generic ".xz" suffix
    088     * (or any other generic xz suffix) is mapped to a name without that
    089     * suffix. If no xz suffix is detected, then the file name is returned
    090     * unmapped.
    091     *
    092     * @param fileName name of a file
    093     * @return name of the corresponding uncompressed file
    094     */
    095    public static String getUncompressedFilename(final String fileName) {
    096        return fileNameUtil.getUncompressedFilename(fileName);
    097    }
    098
    099    private static boolean internalIsXZCompressionAvailable() {
    100        try {
    101            XZCompressorInputStream.matches(null, 0);
    102            return true;
    103        } catch (final NoClassDefFoundError error) { // NOSONAR
    104            return false;
    105        }
    106    }
    107
    108    /**
    109     * Detects common xz suffixes in the given file name.
    110     *
    111     * @param fileName name of a file
    112     * @return {@code true} if the file name has a common xz suffix,
    113     *         {@code false} otherwise
    114     */
    115    public static boolean isCompressedFilename(final String fileName) {
    116        return fileNameUtil.isCompressedFilename(fileName);
    117    }
    118
    119    /**
    120     * Are the classes required to support XZ compression available?
    121     * @since 1.5
    122     * @return true if the classes required to support XZ compression are available
    123     */
    124    public static boolean isXZCompressionAvailable() {
    125        final CachedAvailability cachedResult = cachedXZAvailability;
    126        if (cachedResult != CachedAvailability.DONT_CACHE) {
    127            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
    128        }
    129        return internalIsXZCompressionAvailable();
    130    }
    131
    132    /**
    133     * Checks if the signature matches what is expected for a .xz file.
    134     *
    135     * <p>This is more or less a copy of the version found in {@link
    136     * XZCompressorInputStream} but doesn't depend on the presence of
    137     * XZ for Java.</p>
    138     *
    139     * @param   signature     the bytes to check
    140     * @param   length        the number of bytes to check
    141     * @return  true if signature matches the .xz magic bytes, false otherwise
    142     * @since 1.9
    143     */
    144    public static boolean matches(final byte[] signature, final int length) {
    145        if (length < HEADER_MAGIC.length) {
    146            return false;
    147        }
    148
    149        for (int i = 0; i < HEADER_MAGIC.length; ++i) {
    150            if (signature[i] != HEADER_MAGIC[i]) {
    151                return false;
    152            }
    153        }
    154
    155        return true;
    156    }
    157
    158    /**
    159     * Whether to cache the result of the XZ for Java check.
    160     *
    161     * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p>
    162     * @param doCache whether to cache the result
    163     * @since 1.9
    164     */
    165    public static void setCacheXZAvailablity(final boolean doCache) {
    166        if (!doCache) {
    167            cachedXZAvailability = CachedAvailability.DONT_CACHE;
    168        } else if (cachedXZAvailability == CachedAvailability.DONT_CACHE) {
    169            final boolean hasXz = internalIsXZCompressionAvailable();
    170            cachedXZAvailability = hasXz ? CachedAvailability.CACHED_AVAILABLE // NOSONAR
    171                : CachedAvailability.CACHED_UNAVAILABLE;
    172        }
    173    }
    174
    175    /** Private constructor to prevent instantiation of this utility class. */
    176    private XZUtils() {
    177    }
    178}