001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.named.providers;
020
021import javax.inject.Named;
022import javax.inject.Singleton;
023
024import java.util.concurrent.Semaphore;
025import java.util.concurrent.TimeUnit;
026
027import org.eclipse.aether.named.NamedLockKey;
028import org.eclipse.aether.named.support.AdaptedSemaphoreNamedLock;
029import org.eclipse.aether.named.support.NamedLockFactorySupport;
030
031/**
032 * A JVM-local named lock factory that uses named {@link Semaphore}s.
033 */
034@Singleton
035@Named(LocalSemaphoreNamedLockFactory.NAME)
036public class LocalSemaphoreNamedLockFactory extends NamedLockFactorySupport {
037    public static final String NAME = "semaphore-local";
038
039    @Override
040    protected AdaptedSemaphoreNamedLock createLock(final NamedLockKey key) {
041        Semaphore semaphore = new Semaphore(Integer.MAX_VALUE);
042        return new AdaptedSemaphoreNamedLock(key, this, new JVMSemaphore(semaphore));
043    }
044
045    /**
046     * Adapted JVM {@link java.util.concurrent.Semaphore}.
047     */
048    private static final class JVMSemaphore implements AdaptedSemaphoreNamedLock.AdaptedSemaphore {
049        private final Semaphore semaphore;
050
051        private JVMSemaphore(final Semaphore semaphore) {
052            this.semaphore = semaphore;
053        }
054
055        @Override
056        public boolean tryAcquire(final int perms, final long time, final TimeUnit unit) throws InterruptedException {
057            return semaphore.tryAcquire(perms, time, unit);
058        }
059
060        @Override
061        public void release(final int perms) {
062            semaphore.release(perms);
063        }
064    }
065}