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