1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 */ 19 package org.apache.commons.compress.compressors.brotli; 20 21 /** 22 * Utility code for the Brotli compression format. 23 * @ThreadSafe 24 * @since 1.14 25 */ 26 public class BrotliUtils { 27 28 enum CachedAvailability { 29 DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE 30 } 31 32 private static volatile CachedAvailability cachedBrotliAvailability; 33 34 static { 35 cachedBrotliAvailability = CachedAvailability.DONT_CACHE; 36 try { 37 Class.forName("org.osgi.framework.BundleEvent"); 38 } catch (final Exception ex) { // NOSONAR 39 setCacheBrotliAvailablity(true); 40 } 41 } 42 43 /** Private constructor to prevent instantiation of this utility class. */ BrotliUtils()44 private BrotliUtils() { 45 } 46 47 48 /** 49 * Are the classes required to support Brotli compression available? 50 * @return true if the classes required to support Brotli compression are available 51 */ isBrotliCompressionAvailable()52 public static boolean isBrotliCompressionAvailable() { 53 final CachedAvailability cachedResult = cachedBrotliAvailability; 54 if (cachedResult != CachedAvailability.DONT_CACHE) { 55 return cachedResult == CachedAvailability.CACHED_AVAILABLE; 56 } 57 return internalIsBrotliCompressionAvailable(); 58 } 59 internalIsBrotliCompressionAvailable()60 private static boolean internalIsBrotliCompressionAvailable() { 61 try { 62 Class.forName("org.brotli.dec.BrotliInputStream"); 63 return true; 64 } catch (NoClassDefFoundError | Exception error) { // NOSONAR 65 return false; 66 } 67 } 68 69 /** 70 * Whether to cache the result of the Brotli for Java check. 71 * 72 * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p> 73 * @param doCache whether to cache the result 74 */ setCacheBrotliAvailablity(final boolean doCache)75 public static void setCacheBrotliAvailablity(final boolean doCache) { 76 if (!doCache) { 77 cachedBrotliAvailability = CachedAvailability.DONT_CACHE; 78 } else if (cachedBrotliAvailability == CachedAvailability.DONT_CACHE) { 79 final boolean hasBrotli = internalIsBrotliCompressionAvailable(); 80 cachedBrotliAvailability = hasBrotli ? CachedAvailability.CACHED_AVAILABLE 81 : CachedAvailability.CACHED_UNAVAILABLE; 82 } 83 } 84 85 // only exists to support unit tests getCachedBrotliAvailability()86 static CachedAvailability getCachedBrotliAvailability() { 87 return cachedBrotliAvailability; 88 } 89 } 90