/*
    * Copyright (c) 2012 the original author or authors.
    *
    * 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.eclipse.jetty.spdy;
  
  import java.nio.ByteBuffer;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.ConcurrentMap;
  
  public class StandardByteBufferPool implements ByteBufferPool
  {
      private final ConcurrentMap<Integer, Queue<ByteBuffer>> directBuffers = new ConcurrentHashMap<>();
      private final ConcurrentMap<Integer, Queue<ByteBuffer>> heapBuffers = new ConcurrentHashMap<>();
      private final int factor;
  
      public StandardByteBufferPool()
      {
          this(1024);
      }
  
      public StandardByteBufferPool(int factor)
      {
          this.factor = factor;
      }
  
      public ByteBuffer acquire(int size, boolean direct)
      {
          int bucket = bucketFor(size);
          ConcurrentMap<Integer, Queue<ByteBuffer>> buffers = buffersFor(direct);
  
          ByteBuffer result = null;
          Queue<ByteBuffer> byteBuffers = buffers.get(bucket);
          if (byteBuffers != null)
              result = byteBuffers.poll();
  
          if (result == null)
          {
              int capacity = bucket * factor;
              result = direct ? ByteBuffer.allocateDirect(capacity) : ByteBuffer.allocate(capacity);
          }
  
          result.clear();
          result.limit(size);
  
          return result;
      }
  
      public void release(ByteBuffer buffer)
      {
          int bucket = bucketFor(buffer.capacity());
          ConcurrentMap<Integer, Queue<ByteBuffer>> buffers = buffersFor(buffer.isDirect());
  
          // Avoid to create a new queue every time, just to be discarded immediately
          Queue<ByteBuffer> byteBuffers = buffers.get(bucket);
          if (byteBuffers == null)
          {
              byteBuffers = new ConcurrentLinkedQueue<>();
              Queue<ByteBuffer> existing = buffers.putIfAbsent(bucket, byteBuffers);
              if (existing != null)
                  byteBuffers = existing;
          }
  
          buffer.clear();
          byteBuffers.offer(buffer);
      }
  
      public void clear()
      {
          directBuffers.clear();
          heapBuffers.clear();
      }
  
      private int bucketFor(int size)
      {
          int bucket = size / factor;
          if (size % factor > 0)
              ++bucket;
          return bucket;
      }
  
      private ConcurrentMap<Integer, Queue<ByteBuffer>> buffersFor(boolean direct)
      {
          return direct ? directBuffers : heapBuffers;
      }
 }