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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  package org.eclipse.aether.named.providers;
20  
21  import javax.inject.Named;
22  import javax.inject.Singleton;
23  
24  import java.util.concurrent.Semaphore;
25  import java.util.concurrent.TimeUnit;
26  
27  import org.eclipse.aether.named.NamedLockKey;
28  import org.eclipse.aether.named.support.AdaptedSemaphoreNamedLock;
29  import org.eclipse.aether.named.support.NamedLockFactorySupport;
30  
31  /**
32   * A JVM-local named lock factory that uses named {@link Semaphore}s.
33   */
34  @Singleton
35  @Named(LocalSemaphoreNamedLockFactory.NAME)
36  public class LocalSemaphoreNamedLockFactory extends NamedLockFactorySupport {
37      public static final String NAME = "semaphore-local";
38  
39      @Override
40      protected AdaptedSemaphoreNamedLock createLock(final NamedLockKey key) {
41          Semaphore semaphore = new Semaphore(Integer.MAX_VALUE);
42          return new AdaptedSemaphoreNamedLock(key, this, new JVMSemaphore(semaphore));
43      }
44  
45      /**
46       * Adapted JVM {@link java.util.concurrent.Semaphore}.
47       */
48      private static final class JVMSemaphore implements AdaptedSemaphoreNamedLock.AdaptedSemaphore {
49          private final Semaphore semaphore;
50  
51          private JVMSemaphore(final Semaphore semaphore) {
52              this.semaphore = semaphore;
53          }
54  
55          @Override
56          public boolean tryAcquire(final int perms, final long time, final TimeUnit unit) throws InterruptedException {
57              return semaphore.tryAcquire(perms, time, unit);
58          }
59  
60          @Override
61          public void release(final int perms) {
62              semaphore.release(perms);
63          }
64      }
65  }