    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 *
    026 * @ThreadSafe
    027 * @since 1.14
    028 */
    029public class BrotliUtils {
    030
    031    enum CachedAvailability {
    032        DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE
    033    }
    034
    035    private static volatile CachedAvailability cachedBrotliAvailability;
    036
    037    static {
    038        cachedBrotliAvailability = CachedAvailability.DONT_CACHE;
    039        setCacheBrotliAvailablity(!OsgiUtils.isRunningInOsgiEnvironment());
    040    }
    041
    042    // only exists to support unit tests
    043    static CachedAvailability getCachedBrotliAvailability() {
    044        return cachedBrotliAvailability;
    045    }
    046
    047    private static boolean internalIsBrotliCompressionAvailable() {
    048        try {
    049            Class.forName("org.brotli.dec.BrotliInputStream");
    050            return true;
    051        } catch (final NoClassDefFoundError | Exception error) { // NOSONAR
    052            return false;
    053        }
    054    }
    055
    056    /**
    057     * Are the classes required to support Brotli compression available?
    058     *
    059     * @return true if the classes required to support Brotli compression are available
    060     */
    061    public static boolean isBrotliCompressionAvailable() {
    062        final CachedAvailability cachedResult = cachedBrotliAvailability;
    063        if (cachedResult != CachedAvailability.DONT_CACHE) {
    064            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
    065        }
    066        return internalIsBrotliCompressionAvailable();
    067    }
    068
    069    /**
    070     * Whether to cache the result of the Brotli for Java check.
    071     *
    072     * <p>
    073     * This defaults to {@code false} in an OSGi environment and {@code true} otherwise.
    074     * </p>
    075     *
    076     * @param doCache whether to cache the result
    077     */
    078    public static void setCacheBrotliAvailablity(final boolean doCache) {
    079        if (!doCache) {
    080            cachedBrotliAvailability = CachedAvailability.DONT_CACHE;
    081        } else if (cachedBrotliAvailability == CachedAvailability.DONT_CACHE) {
    082            final boolean hasBrotli = internalIsBrotliCompressionAvailable();
    083            cachedBrotliAvailability = hasBrotli ? CachedAvailability.CACHED_AVAILABLE : CachedAvailability.CACHED_UNAVAILABLE;
    084        }
    085    }
    086
    087    /** Private constructor to prevent instantiation of this utility class. */
    088    private BrotliUtils() {
    089    }
    090}