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;
023import org.apache.commons.compress.compressors.FileNameUtil;
024import org.apache.commons.compress.utils.OsgiUtils;
025
026/**
027 * Utility code for the lzma compression format.
028 * @ThreadSafe
029 * @since 1.10
030 */
031public class LZMAUtils {
032
033    private static final FileNameUtil fileNameUtil;
034
035    /**
036     * LZMA Header Magic Bytes begin a LZMA file.
037     */
038    private static final byte[] HEADER_MAGIC = {
039        (byte) 0x5D, 0, 0
040    };
041
042    enum CachedAvailability {
043        DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE
044    }
045
046    private static volatile CachedAvailability cachedLZMAAvailability;
047
048    static {
049        final Map<String, String> uncompressSuffix = new HashMap<>();
050        uncompressSuffix.put(".lzma", "");
051        uncompressSuffix.put("-lzma", "");
052        fileNameUtil = new FileNameUtil(uncompressSuffix, ".lzma");
053        cachedLZMAAvailability = CachedAvailability.DONT_CACHE;
054        setCacheLZMAAvailablity(!OsgiUtils.isRunningInOsgiEnvironment());
055    }
056
057    /** Private constructor to prevent instantiation of this utility class. */
058    private LZMAUtils() {
059    }
060
061    /**
062     * Checks if the signature matches what is expected for a .lzma file.
063     *
064     * @param   signature     the bytes to check
065     * @param   length        the number of bytes to check
066     * @return  true if signature matches the .lzma magic bytes, false otherwise
067     */
068    public static boolean matches(final byte[] signature, final int length) {
069        if (length < HEADER_MAGIC.length) {
070            return false;
071        }
072
073        for (int i = 0; i < HEADER_MAGIC.length; ++i) {
074            if (signature[i] != HEADER_MAGIC[i]) {
075                return false;
076            }
077        }
078
079        return true;
080    }
081
082    /**
083     * Are the classes required to support LZMA compression available?
084     * @return true if the classes required to support LZMA
085     * compression are available
086     */
087    public static boolean isLZMACompressionAvailable() {
088        final CachedAvailability cachedResult = cachedLZMAAvailability;
089        if (cachedResult != CachedAvailability.DONT_CACHE) {
090            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
091        }
092        return internalIsLZMACompressionAvailable();
093    }
094
095    private static boolean internalIsLZMACompressionAvailable() {
096        try {
097            LZMACompressorInputStream.matches(null, 0);
098            return true;
099        } catch (final NoClassDefFoundError error) { // NOSONAR
100            return false;
101        }
102    }
103
104    /**
105     * Detects common lzma suffixes in the given file name.
106     *
107     * @param fileName name of a file
108     * @return {@code true} if the file name has a common lzma suffix,
109     *         {@code false} otherwise
110     */
111    public static boolean isCompressedFilename(final String fileName) {
112        return fileNameUtil.isCompressedFilename(fileName);
113    }
114
115    /**
116     * Maps the given name of a lzma-compressed file to the name that
117     * the file should have after uncompression.  Any file names with
118     * the generic ".lzma" suffix (or any other generic lzma suffix)
119     * is mapped to a name without that suffix. If no lzma suffix is
120     * detected, then the file name is returned unmapped.
121     *
122     * @param fileName name of a file
123     * @return name of the corresponding uncompressed file
124     */
125    public static String getUncompressedFilename(final String fileName) {
126        return fileNameUtil.getUncompressedFilename(fileName);
127    }
128
129    /**
130     * Maps the given file name to the name that the file should have after
131     * compression with lzma.
132     *
133     * @param fileName name of a file
134     * @return name of the corresponding compressed file
135     */
136    public static String getCompressedFilename(final String fileName) {
137        return fileNameUtil.getCompressedFilename(fileName);
138    }
139
140    /**
141     * Whether to cache the result of the LZMA check.
142     *
143     * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p>
144     * @param doCache whether to cache the result
145     */
146    public static void setCacheLZMAAvailablity(final boolean doCache) {
147        if (!doCache) {
148            cachedLZMAAvailability = CachedAvailability.DONT_CACHE;
149        } else if (cachedLZMAAvailability == CachedAvailability.DONT_CACHE) {
150            final boolean hasLzma = internalIsLZMACompressionAvailable();
151            cachedLZMAAvailability = hasLzma ? CachedAvailability.CACHED_AVAILABLE // NOSONAR
152                : CachedAvailability.CACHED_UNAVAILABLE;
153        }
154    }
155
156    // only exists to support unit tests
157    static CachedAvailability getCachedLZMAAvailability() {
158        return cachedLZMAAvailability;
159    }
160}