code: /*
   * 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.datasketches.memory;
  
  /**
   * The MemoryRequestServer is a callback interface to provide a means for direct (off-heap), heap and ByteBuffer
   * backed resources to request more memory.
   *
   * @author Lee Rhodes
   */
  public interface MemoryRequestServer {
  
    /**
     * Request new WritableMemory with the given capacity. The current Writable Memory will be used to
     * determine the byte order of the returned WritableMemory and other checks.
     * @param currentWritableMemory the current writableMemory of the client. It must be non-null.
     * @param capacityBytes The capacity being requested. It must be &ge; 0.
     *
     * @return new WritableMemory with the given capacity.
     */
    WritableMemory request(WritableMemory currentWritableMemory, long capacityBytes);
  
    /**
     * Request close the AutoCloseable resource. This only applies to resources allocated using
     * WritableMemory.allocateDirect(...).
     * This may be ignored depending on the application implementation.
     * @param memToClose the relevant WritbleMemory to be considered for closing. It must be non-null.
     * @param newMemory the newly allocated WritableMemory. It must be non-null.
     * This is returned from the client to facilitate tracking for the convenience of the resource owner.
     */
    void requestClose(final WritableMemory memToClose, WritableMemory newMemory);
  
  }
  