001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.io;
019    
020    import java.nio.ByteBuffer;
021    
022    import org.apache.hadoop.classification.InterfaceAudience;
023    import org.apache.hadoop.classification.InterfaceStability;
024    
025    @InterfaceAudience.Public
026    @InterfaceStability.Stable
027    public interface ByteBufferPool {
028      /**
029       * Get a new direct ByteBuffer.  The pool can provide this from
030       * removing a buffer from its internal cache, or by allocating a 
031       * new buffer.
032       *
033       * @param direct     Whether the buffer should be direct.
034       * @param length     The minimum length the buffer will have.
035       * @return           A new ByteBuffer.  This ByteBuffer must be direct.
036       *                   Its capacity can be less than what was requested, but
037       *                   must be at least 1 byte.
038       */
039      ByteBuffer getBuffer(boolean direct, int length);
040    
041      /**
042       * Release a buffer back to the pool.
043       * The pool may choose to put this buffer into its cache.
044       *
045       * @param buffer    a direct bytebuffer
046       */
047      void putBuffer(ByteBuffer buffer);
048    }