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   /*
    * Copyright 2021 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  
  package io.netty.handler.codec.compression;
  
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  public final class Zstd {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(Zstd.class);
      private static final Throwable cause;
  
      static {
          Throwable t = null;
  
          try {
              Class.forName("com.github.luben.zstd.Zstd", false,
                  PlatformDependent.getClassLoader(Zstd.class));
          } catch (ClassNotFoundException e) {
              t = e;
              logger.debug(
                  "zstd-jni not in the classpath; Zstd support will be unavailable.");
          } catch (Throwable e) {
              t = e;
              logger.debug("Failed to load zstd-jni; Zstd support will be unavailable.", t);
          }
  
          cause = t;
      }
  
      /**
       *
       * @return true when zstd-jni is in the classpath
       * and native library is available on this platform and could be loaded
       */
      public static boolean isAvailable() {
          return cause == null;
      }
  
      /**
       * Throws when zstd support is missing from the classpath or is unavailable on this platform
       * @throws Throwable a ClassNotFoundException if zstd-jni is missing
       * or a ExceptionInInitializerError if zstd native lib can't be loaded
       */
      public static void ensureAvailability() throws Throwable {
          if (cause != null) {
              throw cause;
          }
      }
  
      /**
       * Returns {@link Throwable} of unavailability cause
       */
      public static Throwable cause() {
          return cause;
      }
  
      private Zstd() {
      }
  }