    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.brotli;
    020
    021import org.apache.commons.compress.utils.OsgiUtils;
    022
    023/**
    024 * Utility code for the Brotli compression format.
    025 * @ThreadSafe
    026 * @since 1.14
    027 */
    028public class BrotliUtils {
    029
    030    enum CachedAvailability {
    031        DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE
    032    }
    033
    034    private static volatile CachedAvailability cachedBrotliAvailability;
    035
    036    static {
    037        cachedBrotliAvailability = CachedAvailability.DONT_CACHE;
    038        setCacheBrotliAvailablity(!OsgiUtils.isRunningInOsgiEnvironment());
    039    }
    040
    041    /** Private constructor to prevent instantiation of this utility class. */
    042    private BrotliUtils() {
    043    }
    044
    045
    046    /**
    047     * Are the classes required to support Brotli compression available?
    048     * @return true if the classes required to support Brotli compression are available
    049     */
    050    public static boolean isBrotliCompressionAvailable() {
    051        final CachedAvailability cachedResult = cachedBrotliAvailability;
    052        if (cachedResult != CachedAvailability.DONT_CACHE) {
    053            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
    054        }
    055        return internalIsBrotliCompressionAvailable();
    056    }
    057
    058    private static boolean internalIsBrotliCompressionAvailable() {
    059        try {
    060            Class.forName("org.brotli.dec.BrotliInputStream");
    061            return true;
    062        } catch (final NoClassDefFoundError | Exception error) { // NOSONAR
    063            return false;
    064        }
    065    }
    066
    067    /**
    068     * Whether to cache the result of the Brotli for Java check.
    069     *
    070     * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p>
    071     * @param doCache whether to cache the result
    072     */
    073    public static void setCacheBrotliAvailablity(final boolean doCache) {
    074        if (!doCache) {
    075            cachedBrotliAvailability = CachedAvailability.DONT_CACHE;
    076        } else if (cachedBrotliAvailability == CachedAvailability.DONT_CACHE) {
    077            final boolean hasBrotli = internalIsBrotliCompressionAvailable();
    078            cachedBrotliAvailability = hasBrotli ? CachedAvailability.CACHED_AVAILABLE
    079                : CachedAvailability.CACHED_UNAVAILABLE;
    080        }
    081    }
    082
    083    // only exists to support unit tests
    084    static CachedAvailability getCachedBrotliAvailability() {
    085        return cachedBrotliAvailability;
    086    }
    087}