| /* |
| * 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.cassandra.utils.concurrent; |
| |
| import java.util.concurrent.TimeUnit; |
| |
| import org.apache.cassandra.utils.Intercept; |
| import org.apache.cassandra.utils.Shared; |
| |
| import static org.apache.cassandra.utils.Shared.Scope.SIMULATION; |
| |
| @Shared(scope = SIMULATION) |
| public interface Semaphore |
| { |
| /** |
| * @return the number of permits presently in this semaphore |
| */ |
| int permits(); |
| |
| /** |
| * set the number of permits in this semaphore to zero |
| */ |
| int drain(); |
| |
| /** |
| * Increase the number of available permits and signal any waiters that may be served by the release |
| */ |
| void release(int permits); |
| |
| /** |
| * Try to take permits, returning immediately |
| * @return true iff permits acquired |
| */ |
| boolean tryAcquire(int acquire); |
| |
| /** |
| * Try to take permits, waiting up to timeout |
| * @return true iff permits acquired |
| * @throws InterruptedException if interrupted |
| */ |
| boolean tryAcquire(int acquire, long time, TimeUnit unit) throws InterruptedException; |
| |
| /** |
| * Try to take permits, waiting until the deadline |
| * @return true iff permits acquired |
| * @throws InterruptedException if interrupted |
| */ |
| boolean tryAcquireUntil(int acquire, long nanoTimeDeadline) throws InterruptedException; |
| |
| /** |
| * Take permits, waiting indefinitely until available |
| * @throws InterruptedException if interrupted |
| */ |
| void acquire(int acquire) throws InterruptedException; |
| |
| /** |
| * Take permits, waiting indefinitely until available |
| * @throws UncheckedInterruptedException if interrupted |
| */ |
| void acquireThrowUncheckedOnInterrupt(int acquire) throws UncheckedInterruptedException; |
| |
| /** |
| * Factory method used to capture and redirect instantiations for simulation |
| * |
| * Construct an unfair Semaphore initially holding the specified number of permits |
| */ |
| @Intercept |
| public static Semaphore newSemaphore(int permits) |
| { |
| return new Standard(permits, false); |
| } |
| |
| /** |
| * Factory method used to capture and redirect instantiations for simulation |
| * |
| * Construct a fair Semaphore initially holding the specified number of permits |
| */ |
| @Intercept |
| public static Semaphore newFairSemaphore(int permits) |
| { |
| return new Standard(permits, true); |
| } |
| |
| public static class Standard extends java.util.concurrent.Semaphore implements Semaphore |
| { |
| public Standard(int permits) |
| { |
| this(permits, false); |
| } |
| |
| public Standard(int permits, boolean fair) |
| { |
| super(permits, fair); |
| } |
| |
| /** |
| * {@link Semaphore#drain()} |
| */ |
| public int drain() |
| { |
| return drainPermits(); |
| } |
| |
| /** |
| * Number of permits that are available to be acquired. {@link Semaphore#permits()} |
| */ |
| public int permits() |
| { |
| return availablePermits(); |
| } |
| |
| /** |
| * Number of permits that have been acquired in excess of available. {@link Semaphore#permits()} |
| */ |
| public int waiting() |
| { |
| return getQueueLength(); |
| } |
| |
| /** |
| * {@link Semaphore#tryAcquireUntil(int, long)} |
| */ |
| public boolean tryAcquireUntil(int acquire, long nanoTimeDeadline) throws InterruptedException |
| { |
| long wait = nanoTimeDeadline - System.nanoTime(); |
| return tryAcquire(acquire, Math.max(0, wait), TimeUnit.NANOSECONDS); |
| } |
| |
| @Override |
| public void acquireThrowUncheckedOnInterrupt(int acquire) throws UncheckedInterruptedException |
| { |
| try |
| { |
| acquire(acquire); |
| } |
| catch (InterruptedException e) |
| { |
| throw new UncheckedInterruptedException(e); |
| } |
| } |
| } |
| } |