| /* |
| * Copyright 2016-present Open Networking Laboratory |
| * |
| * Licensed 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.onlab.util; |
| |
| import java.util.concurrent.atomic.AtomicLong; |
| import java.util.function.Consumer; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| import static com.google.common.base.Preconditions.checkState; |
| |
| /** |
| * A synchronization utility that defers invocation of a {@link Consumer consumer} |
| * callback until a set number of actions tracked by a {@code long} counter complete. |
| * <p> |
| * Each completion is recorded by invoking the {@link CountDownCompleter#countDown countDown} |
| * method. When the total number of completions is equal to the preset counter value, |
| * this instance is marked as completed and the callback invoked by supplying the object |
| * held by this instance. |
| * |
| * @param <T> object type |
| */ |
| public final class CountDownCompleter<T> { |
| |
| private final T object; |
| private final Consumer<T> onCompleteCallback; |
| private final AtomicLong counter; |
| |
| /** |
| * Constructor. |
| * @param object object |
| * @param count total number of times countDown must be invoked for this completer to complete |
| * @param onCompleteCallback callback to invoke when completer is completed |
| */ |
| public CountDownCompleter(T object, long count, Consumer<T> onCompleteCallback) { |
| checkState(count >= 0, "count must be non-negative"); |
| this.counter = new AtomicLong(count); |
| this.object = checkNotNull(object); |
| this.onCompleteCallback = checkNotNull(onCompleteCallback); |
| if (count == 0) { |
| onCompleteCallback.accept(object); |
| } |
| } |
| |
| /** |
| * Returns the object. |
| * @return object |
| */ |
| public T object() { |
| return object; |
| } |
| |
| /** |
| * Records a single completion. |
| * <p> |
| * If this instance has already completed, this method has no effect |
| */ |
| public void countDown() { |
| if (counter.decrementAndGet() == 0) { |
| onCompleteCallback.accept(object); |
| } |
| } |
| |
| /** |
| * Returns if this instance has completed. |
| * @return {@code true} if completed |
| */ |
| public boolean isComplete() { |
| return counter.get() <= 0; |
| } |
| } |