geode-core/src/main/java/org/apache/geode/internal/offheap/MemoryAllocator.java

/*
 * 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.geode.internal.offheap;

/**
 * Basic contract for a heap that manages off heap memory. Any MemoryChunks allocated from a heap
 * are returned to that heap when freed.
 *
 * @since Geode 1.0
 */
public interface MemoryAllocator {
  /**
   * @param size the size in bytes of the chunk of memory to allocate
   * @return the allocated chunk of memory.
   * @throws IllegalStateException if the heap does not have enough memory to grant the request
   */
  StoredObject allocate(int size);

  /**
   * Allocates off heap memory for the given data and returns a StoredObject that is backed by this
   * allocated memory and that contains the data.
   *
   * @param data the bytes of the data to put in the allocated StoredObject
   * @param isSerialized true if data contains a serialized object; false if it is an actual byte
   *        array.
   * @param isCompressed true if data is compressed; false if it is uncompressed.
   * @throws IllegalStateException if the heap does not have enough memory to grant the request
   */
  StoredObject allocateAndInitialize(byte[] data, boolean isSerialized, boolean isCompressed);

  /**
   * Allocates off heap memory for the given data and returns a StoredObject that is backed by this
   * allocated memory and that contains the data and keeps a reference to the original heap data.
   *
   * @param data the bytes of the data to put in the allocated StoredObject
   * @param isSerialized true if data contains a serialized object; false if it is an actual byte
   *        array.
   * @param originalHeapData the original uncompressed heap data
   * @param isCompressed true if data is compressed; false if it is uncompressed.
   * @throws IllegalStateException if the heap does not have enough memory to grant the request
   */
  StoredObject allocateAndInitialize(byte[] data, boolean isSerialized, boolean isCompressed,
      byte[] originalHeapData);

  long getFreeMemory();

  long getUsedMemory();

  long getTotalMemory();

  OffHeapMemoryStats getStats();

  /**
   * This allocator will no longer be used so free up any system memory that belongs to it.
   */
  void close();

  MemoryInspector getMemoryInspector();

  void addMemoryUsageListener(MemoryUsageListener listener);

  void removeMemoryUsageListener(MemoryUsageListener listener);
}