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.lzma;
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 lzma compression format.
029 * @ThreadSafe
030 * @since 1.10
031 */
032public class LZMAUtils {
033
034    enum CachedAvailability {
035        DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE
036    }
037
038    private static final FileNameUtil fileNameUtil;
039
040    /**
041     * LZMA Header Magic Bytes begin a LZMA file.
042     */
043    private static final byte[] HEADER_MAGIC = {
044        (byte) 0x5D, 0, 0
045    };
046
047    private static volatile CachedAvailability cachedLZMAAvailability;
048
049    static {
050        final Map<String, String> uncompressSuffix = new HashMap<>();
051        uncompressSuffix.put(".lzma", "");
052        uncompressSuffix.put("-lzma", "");
053        fileNameUtil = new FileNameUtil(uncompressSuffix, ".lzma");
054        cachedLZMAAvailability = CachedAvailability.DONT_CACHE;
055        setCacheLZMAAvailablity(!OsgiUtils.isRunningInOsgiEnvironment());
056    }
057
058    // only exists to support unit tests
059    static CachedAvailability getCachedLZMAAvailability() {
060        return cachedLZMAAvailability;
061    }
062
063    /**
064     * Maps the given file name to the name that the file should have after
065     * compression with lzma.
066     *
067     * @param fileName name of a file
068     * @return name of the corresponding compressed file
069     */
070    public static String getCompressedFilename(final String fileName) {
071        return fileNameUtil.getCompressedFilename(fileName);
072    }
073
074    /**
075     * Maps the given name of a lzma-compressed file to the name that
076     * the file should have after uncompression.  Any file names with
077     * the generic ".lzma" suffix (or any other generic lzma suffix)
078     * is mapped to a name without that suffix. If no lzma suffix is
079     * detected, then the file name is returned unmapped.
080     *
081     * @param fileName name of a file
082     * @return name of the corresponding uncompressed file
083     */
084    public static String getUncompressedFilename(final String fileName) {
085        return fileNameUtil.getUncompressedFilename(fileName);
086    }
087
088    private static boolean internalIsLZMACompressionAvailable() {
089        try {
090            LZMACompressorInputStream.matches(null, 0);
091            return true;
092        } catch (final NoClassDefFoundError error) { // NOSONAR
093            return false;
094        }
095    }
096
097    /**
098     * Detects common lzma suffixes in the given file name.
099     *
100     * @param fileName name of a file
101     * @return {@code true} if the file name has a common lzma suffix,
102     *         {@code false} otherwise
103     */
104    public static boolean isCompressedFilename(final String fileName) {
105        return fileNameUtil.isCompressedFilename(fileName);
106    }
107
108    /**
109     * Are the classes required to support LZMA compression available?
110     * @return true if the classes required to support LZMA
111     * compression are available
112     */
113    public static boolean isLZMACompressionAvailable() {
114        final CachedAvailability cachedResult = cachedLZMAAvailability;
115        if (cachedResult != CachedAvailability.DONT_CACHE) {
116            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
117        }
118        return internalIsLZMACompressionAvailable();
119    }
120
121    /**
122     * Checks if the signature matches what is expected for a .lzma file.
123     *
124     * @param   signature     the bytes to check
125     * @param   length        the number of bytes to check
126     * @return  true if signature matches the .lzma magic bytes, false otherwise
127     */
128    public static boolean matches(final byte[] signature, final int length) {
129        if (length < HEADER_MAGIC.length) {
130            return false;
131        }
132
133        for (int i = 0; i < HEADER_MAGIC.length; ++i) {
134            if (signature[i] != HEADER_MAGIC[i]) {
135                return false;
136            }
137        }
138
139        return true;
140    }
141
142    /**
143     * Whether to cache the result of the LZMA check.
144     *
145     * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p>
146     * @param doCache whether to cache the result
147     */
148    public static void setCacheLZMAAvailablity(final boolean doCache) {
149        if (!doCache) {
150            cachedLZMAAvailability = CachedAvailability.DONT_CACHE;
151        } else if (cachedLZMAAvailability == CachedAvailability.DONT_CACHE) {
152            final boolean hasLzma = internalIsLZMACompressionAvailable();
153            cachedLZMAAvailability = hasLzma ? CachedAvailability.CACHED_AVAILABLE // NOSONAR
154                : CachedAvailability.CACHED_UNAVAILABLE;
155        }
156    }
157
158    /** Private constructor to prevent instantiation of this utility class. */
159    private LZMAUtils() {
160    }
161}