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.cassandra.io.util;
  
  import javax.annotation.concurrent.NotThreadSafe;
  
  import com.google.common.primitives.Ints;
  import com.google.common.util.concurrent.RateLimiter;
  
  /**
   * Rebufferer wrapper that applies rate limiting.
   * <p>
   * Instantiated once per RandomAccessReader, thread-unsafe.
   * The instances reuse themselves as the BufferHolder to avoid having to return a new object for each rebuffer call.
   * Only one BufferHolder can be active at a time. Calling {@link #rebuffer(long)} before the previously obtained
   * buffer holder is released will throw {@link AssertionError}.
   */
  @NotThreadSafe
  public class LimitingRebufferer extends WrappingRebufferer
  {
      final private RateLimiter limiter;
      final private int limitQuant;
  
      public LimitingRebufferer(Rebufferer wrapped, RateLimiter limiter, int limitQuant)
      {
          super(wrapped);
          this.limiter = limiter;
          this.limitQuant = limitQuant;
      }
  
      @Override
      public BufferHolder rebuffer(long position)
      {
          super.rebuffer(position);
          int posInBuffer = Ints.checkedCast(position - offset);
          int remaining = buffer.limit() - posInBuffer;
          if (remaining == 0)
              return this;
  
          if (remaining > limitQuant)
          {
              buffer.limit(posInBuffer + limitQuant); // certainly below current limit
              remaining = limitQuant;
          }
          limiter.acquire(remaining);
          return this;
      }
  
      @Override
      public String toString()
      {
          return "LimitingRebufferer[" + limiter + "]:" + wrapped;
      }
  }