content: /*
   * 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.beam.runners.dataflow.worker.streaming;
  
  import java.util.concurrent.Semaphore;
  import java.util.function.Function;
  
  public final class WeightedSemaphore<V> {
    private final int maxWeight;
    private final Semaphore limit;
    private final Function<V, Integer> weigher;
  
    private WeightedSemaphore(int maxWeight, Semaphore limit, Function<V, Integer> weigher) {
      this.maxWeight = maxWeight;
      this.limit = limit;
      this.weigher = weigher;
    }
  
    public static <V> WeightedSemaphore<V> create(int maxWeight, Function<V, Integer> weigherFn) {
      return new WeightedSemaphore<>(maxWeight, new Semaphore(maxWeight, true), weigherFn);
    }
  
    public void acquireUninterruptibly(V value) {
      limit.acquireUninterruptibly(computePermits(value));
    }
  
    public void release(V value) {
      limit.release(computePermits(value));
    }
  
    private int computePermits(V value) {
      return Math.min(weigher.apply(value), maxWeight);
    }
  
    public int currentWeight() {
      return maxWeight - limit.availablePermits();
    }
  }
  