content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF 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
   *
   *    http://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 org.apache.arrow.dataset.jni;
  
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.file.Files;
  import java.nio.file.StandardCopyOption;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Locale;
  import java.util.Set;
  
  /** The JniLoader for Dataset API's native implementation. */
  public final class JniLoader {
  
    private static final JniLoader INSTANCE =
        new JniLoader(Collections.singletonList("arrow_dataset_jni"));
  
    public static JniLoader get() {
      return INSTANCE;
    }
  
    private final Set<String> librariesToLoad;
  
    private JniLoader(List<String> libraryNames) {
      librariesToLoad = new HashSet<>(libraryNames);
    }
  
    private boolean finished() {
      return librariesToLoad.isEmpty();
    }
  
    /** If required JNI libraries are not loaded, then load them. */
    public void ensureLoaded() {
      if (finished()) {
        return;
      }
      loadRemaining();
      ensureS3FinalizedOnShutdown();
    }
  
    private synchronized void loadRemaining() {
      // The method is protected by a mutex via synchronized, if more than one thread race to call
      // loadRemaining, at same time only one will do the actual loading and the others will wait for
      // the mutex to be acquired then check on the remaining list: if there are libraries that were
      // not
      // successfully loaded then the mutex owner will try to load them again.
      if (finished()) {
        return;
      }
      List<String> libs = new ArrayList<>(librariesToLoad);
      for (String lib : libs) {
        load(lib);
        librariesToLoad.remove(lib);
      }
    }
  
    private void load(String name) {
      final String libraryToLoad =
          name + "/" + getNormalizedArch() + "/" + System.mapLibraryName(name);
      try {
        File temp =
            File.createTempFile("jnilib-", ".tmp", new File(System.getProperty("java.io.tmpdir")));
        temp.deleteOnExit();
        try (final InputStream is =
            JniWrapper.class.getClassLoader().getResourceAsStream(libraryToLoad)) {
          if (is == null) {
            throw new FileNotFoundException(libraryToLoad);
          }
          Files.copy(is, temp.toPath(), StandardCopyOption.REPLACE_EXISTING);
          System.load(temp.getAbsolutePath());
        }
      } catch (IOException e) {
        throw new IllegalStateException("error loading native libraries: " + e);
      }
    }
  
    private String getNormalizedArch() {
      String arch = System.getProperty("os.arch").toLowerCase(Locale.US);
      switch (arch) {
        case "amd64":
          arch = "x86_64";
          break;
        case "aarch64":
          arch = "aarch_64";
          break;
        default:
          break;
      }
      return arch;
    }
  
    private void ensureS3FinalizedOnShutdown() {
      Runtime.getRuntime()
          .addShutdownHook(
              new Thread(
                  () -> {
                    JniWrapper.get().ensureS3Finalized();
                  }));
    }
  }
  