ceph/src/arrow/java/c/src/main/java/org/apache/arrow/c/jni/JniLoader.java

   1 /*
   2  * Licensed to the Apache Software Foundation (ASF) under one or more
   3  * contributor license agreements.  See the NOTICE file distributed with
   4  * this work for additional information regarding copyright ownership.
   5  * The ASF licenses this file to You under the Apache License, Version 2.0
   6  * (the "License"); you may not use this file except in compliance with
   7  * the License.  You may obtain a copy of the License at
   8  *
   9  *    http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software
  12  * distributed under the License is distributed on an "AS IS" BASIS,
  13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14  * See the License for the specific language governing permissions and
  15  * limitations under the License.
  16  */
  17
  18 package org.apache.arrow.c.jni;
  19
  20 import java.io.File;
  21 import java.io.FileNotFoundException;
  22 import java.io.IOException;
  23 import java.io.InputStream;
  24 import java.nio.file.Files;
  25 import java.nio.file.StandardCopyOption;
  26 import java.util.ArrayList;
  27 import java.util.Collections;
  28 import java.util.HashSet;
  29 import java.util.List;
  30 import java.util.Set;
  31
  32 /**
  33  * The JniLoader for C Data Interface API's native implementation.
  34  */
  35 public class JniLoader {
  36   private static final JniLoader INSTANCE = new JniLoader(Collections.singletonList("arrow_cdata_jni"));
  37
  38   public static JniLoader get() {
  39     return INSTANCE;
  40   }
  41
  42   private final Set<String> librariesToLoad;
  43
  44   private JniLoader(List<String> libraryNames) {
  45     librariesToLoad = new HashSet<>(libraryNames);
  46   }
  47
  48   private boolean finished() {
  49     return librariesToLoad.isEmpty();
  50   }
  51
  52   /**
  53    * If required JNI libraries are not loaded, then load them.
  54    */
  55   public void ensureLoaded() {
  56     if (finished()) {
  57       return;
  58     }
  59     loadRemaining();
  60   }
  61
  62   private synchronized void loadRemaining() {
  63     // The method is protected by a mutex via synchronized, if more than one thread
  64     // race to call
  65     // loadRemaining, at same time only one will do the actual loading and the
  66     // others will wait for
  67     // the mutex to be acquired then check on the remaining list: if there are
  68     // libraries that were not
  69     // successfully loaded then the mutex owner will try to load them again.
  70     if (finished()) {
  71       return;
  72     }
  73     List<String> libs = new ArrayList<>(librariesToLoad);
  74     for (String lib : libs) {
  75       load(lib);
  76       librariesToLoad.remove(lib);
  77     }
  78   }
  79
  80   private void load(String name) {
  81     final String libraryToLoad = System.mapLibraryName(name);
  82     try {
  83       File temp = File.createTempFile("jnilib-", ".tmp", new File(System.getProperty("java.io.tmpdir")));
  84       try (final InputStream is = JniWrapper.class.getClassLoader().getResourceAsStream(libraryToLoad)) {
  85         if (is == null) {
  86           throw new FileNotFoundException(libraryToLoad);
  87         }
  88         Files.copy(is, temp.toPath(), StandardCopyOption.REPLACE_EXISTING);
  89         System.load(temp.getAbsolutePath());
  90       }
  91     } catch (IOException e) {
  92       throw new IllegalStateException("error loading native libraries: " + e);
  93     }
  94   }
  95 }