    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    // only exists to support unit tests
    042    static CachedAvailability getCachedBrotliAvailability() {
    043        return cachedBrotliAvailability;
    044    }
    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     * @return true if the classes required to support Brotli compression are available
    059     */
    060    public static boolean isBrotliCompressionAvailable() {
    061        final CachedAvailability cachedResult = cachedBrotliAvailability;
    062        if (cachedResult != CachedAvailability.DONT_CACHE) {
    063            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
    064        }
    065        return internalIsBrotliCompressionAvailable();
    066    }
    067
    068    /**
    069     * Whether to cache the result of the Brotli for Java check.
    070     *
    071     * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p>
    072     * @param doCache whether to cache the result
    073     */
    074    public static void setCacheBrotliAvailablity(final boolean doCache) {
    075        if (!doCache) {
    076            cachedBrotliAvailability = CachedAvailability.DONT_CACHE;
    077        } else if (cachedBrotliAvailability == CachedAvailability.DONT_CACHE) {
    078            final boolean hasBrotli = internalIsBrotliCompressionAvailable();
    079            cachedBrotliAvailability = hasBrotli ? CachedAvailability.CACHED_AVAILABLE
    080                : CachedAvailability.CACHED_UNAVAILABLE;
    081        }
    082    }
    083
    084    /** Private constructor to prevent instantiation of this utility class. */
    085    private BrotliUtils() {
    086    }
    087}