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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   */
20  package org.apache.mina.transport.socket.apr;
21  
22  import org.apache.tomcat.jni.Library;
23  import org.apache.tomcat.jni.Pool;
24  
25  /**
26   * Internal singleton used for initializing correctly the APR native library
27   * and the associated root memory pool.
28   * 
29   * It'll finalize nicely the native resources (libraries and memory pools).
30   * 
31   * Each memory pool used in the APR transport module needs to be children of the
32   * root pool {@link AprLibrary#getRootPool()}.
33   * 
34   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
35   */
36  class AprLibrary {
37  
38      // is APR library was initialized (load of native libraries)
39      private static AprLibrary library = null;
40  
41      /**
42       * get the shared instance of APR library, if none, initialize one
43       * @return the current APR library singleton
44       */
45      static synchronized AprLibrary getInstance() {
46          if (!isInitialized())
47              initialize();
48          return library;
49      }
50  
51      /**
52       * initialize the APR Library by loading the associated native libraries
53       * and creating the associated singleton
54       */
55      private static synchronized void initialize() {
56          if (library == null)
57              library = new AprLibrary();
58      }
59  
60      /**
61       * is the APR library was initialized.
62       * @return true if the Library is initialized, false otherwise
63       */
64      static synchronized boolean isInitialized() {
65          return library != null;
66      }
67  
68      // APR memory pool (package wide mother pool)
69      private final long pool;
70  
71      /**
72       * APR library singleton constructor. Called only when accessing the
73       * singleton the first time.
74       * It's initializing an APR memory pool for the whole package (a.k.a mother or root pool).
75       */
76      private AprLibrary() {
77          try {
78              Library.initialize(null);
79          } catch (Exception e) {
80              throw new RuntimeException("Error loading Apache Portable Runtime (APR).", e);
81          }
82          pool = Pool.create(0);
83      }
84  
85      @Override
86      protected void finalize() throws Throwable {
87          super.finalize();
88          Pool.destroy(pool);
89      }
90  
91      /**
92       * get the package wide root pool, the mother of all the pool created 
93       * in APR transport module.
94       * @return number identifying the root pool 
95       */
96      long getRootPool() {
97          return pool;
98      }
99  }