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 com.alibaba.metrics;
  
  import static java.lang.Math.min;
  
  /**
   * A {@link Reservoir} implementation backed by a sliding window that stores the last {@code N}
   * measurements.
   */
  public class SlidingWindowReservoir implements Reservoir {
      private final long[] measurements;
      private long count;
  
      /**
       * Creates a new {@link SlidingWindowReservoir} which stores the last {@code size} measurements.
       *
       * @param size the number of measurements to store
       */
      public SlidingWindowReservoir(int size) {
          this.measurements = new long[size];
          this.count = 0;
      }
  
      @Override
      public synchronized int size() {
          return (int) min(count, measurements.length);
      }
  
      @Override
      public synchronized void update(long value) {
          measurements[(int) (count++ % measurements.length)] = value;
      }
  
      @Override
      public Snapshot getSnapshot() {
          final long[] values = new long[size()];
          for (int i = 0; i < values.length; i++) {
              synchronized (this) {
                  values[i] = measurements[i];
              }
          }
          return new UniformSnapshot(values);
      }
  }
  