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Apache Geode provides a database-like consistency model, reliable transaction processing and a shared-nothing architecture to maintain very low latency performance with high concurrency processing

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/*
 * 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;

import java.util.Collections;
import java.util.List;

/**
 * Implementation of MemoryInspector that provides for inspection of meta-data for off-heap memory
 * blocks
 */
public class MemoryInspectorImpl implements MemoryInspector {
  /** The inspection snapshot for MemoryInspector */
  private List memoryBlocks;

  private FreeListManager freeList;

  public MemoryInspectorImpl(FreeListManager freeList) {
    this.freeList = freeList;
  }

  @Override
  public synchronized void clearSnapshot() {
    this.memoryBlocks = null;
  }

  @Override
  public synchronized void createSnapshot() {
    List value = this.memoryBlocks;
    if (value == null) {
      value = getOrderedBlocks();
      this.memoryBlocks = value;
    }
  }

  @Override
  public synchronized List getSnapshot() {
    List value = this.memoryBlocks;
    if (value == null) {
      return Collections.emptyList();
    } else {
      return value;
    }
  }


  @Override
  public MemoryBlock getFirstBlock() {
    final List value = getSnapshot();
    if (value.isEmpty()) {
      return null;
    } else {
      return value.get(0);
    }
  }

  @Override
  public List getAllBlocks() {
    return getOrderedBlocks();
  }

  @Override
  public List getAllocatedBlocks() {
    return this.freeList.getAllocatedBlocks();
  }

  @Override
  public MemoryBlock getBlockAfter(MemoryBlock block) {
    if (block == null) {
      return null;
    }
    List blocks = getSnapshot();
    int nextBlock = blocks.indexOf(block) + 1;
    if (nextBlock > 0 && blocks.size() > nextBlock) {
      return blocks.get(nextBlock);
    } else {
      return null;
    }
  }

  private List getOrderedBlocks() {
    return this.freeList.getOrderedBlocks();
  }

}