content: package org.apache.lucene.util;
  
  /**
   * 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.
   */
  
  import java.lang.reflect.*;
  import java.text.DecimalFormat;
  import java.util.*;
  
  /**
   * Estimates the size of a given Object using a given MemoryModel for primitive
   * size information.
   * 
   * Resource Usage: 
   * 
   * Internally uses a Map to temporally hold a reference to every
   * object seen. 
   * 
   * If checkInterned, all Strings checked will be interned, but those
   * that were not already interned will be released for GC when the
   * estimate is complete.
   * 
   * @lucene.internal
   */
  public final class RamUsageEstimator {
  
    public final static int NUM_BYTES_SHORT = 2;
    public final static int NUM_BYTES_INT = 4;
    public final static int NUM_BYTES_LONG = 8;
    public final static int NUM_BYTES_FLOAT = 4;
    public final static int NUM_BYTES_DOUBLE = 8;
    public final static int NUM_BYTES_CHAR = 2;
    public final static int NUM_BYTES_OBJECT_HEADER = 8;
    public final static int NUM_BYTES_OBJECT_REF = Constants.JRE_IS_64BIT ? 8 : 4;
    public final static int NUM_BYTES_ARRAY_HEADER = NUM_BYTES_OBJECT_HEADER + NUM_BYTES_INT + NUM_BYTES_OBJECT_REF;
  
    private MemoryModel memoryModel;
  
    private final Map<Object,Object> seen;
  
    private int refSize;
    private int arraySize;
    private int classSize;
  
    private boolean checkInterned;
  
    /**
     * Constructs this object with an AverageGuessMemoryModel and
     * checkInterned = true.
     */
    public RamUsageEstimator() {
      this(new AverageGuessMemoryModel());
    }
  
    /**
     * @param checkInterned check if Strings are interned and don't add to size
     * if they are. Defaults to true but if you know the objects you are checking
     * won't likely contain many interned Strings, it will be faster to turn off
     * intern checking.
     */
    public RamUsageEstimator(boolean checkInterned) {
      this(new AverageGuessMemoryModel(), checkInterned);
    }
  
    /**
     * @param memoryModel MemoryModel to use for primitive object sizes.
     */
    public RamUsageEstimator(MemoryModel memoryModel) {
      this(memoryModel, true);
    }
  
    /**
     * @param memoryModel MemoryModel to use for primitive object sizes.
     * @param checkInterned check if Strings are interned and don't add to size
     * if they are. Defaults to true but if you know the objects you are checking
     * won't likely contain many interned Strings, it will be faster to turn off
     * intern checking.
     */
    public RamUsageEstimator(MemoryModel memoryModel, boolean checkInterned) {
      this.memoryModel = memoryModel;
      this.checkInterned = checkInterned;
      // Use Map rather than Set so that we can use an IdentityHashMap - not
      // seeing an IdentityHashSet
      seen = new IdentityHashMap<Object,Object>(64);
      this.refSize = memoryModel.getReferenceSize();
      this.arraySize = memoryModel.getArraySize();
      this.classSize = memoryModel.getClassSize();
    }
  
    public long estimateRamUsage(Object obj) {
      long size = size(obj);
      seen.clear();
      return size;
    }
  
    private long size(Object obj) {
      if (obj == null) {
        return 0;
      }
      // interned not part of this object
      if (checkInterned && obj instanceof String
          && obj == ((String) obj).intern()) { // interned string will be eligible
                                               // for GC on
                                               // estimateRamUsage(Object) return
        return 0;
      }
  
      // skip if we have seen before
      if (seen.containsKey(obj)) {
        return 0;
      }
  
      // add to seen
      seen.put(obj, null);
  
      Class<?> clazz = obj.getClass();
      if (clazz.isArray()) {
        return sizeOfArray(obj);
      }
  
      long size = 0;
  
      // walk type hierarchy
      while (clazz != null) {
        Field[] fields = clazz.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
          if (Modifier.isStatic(fields[i].getModifiers())) {
            continue;
          }
  
          if (fields[i].getType().isPrimitive()) {
            size += memoryModel.getPrimitiveSize(fields[i].getType());
          } else {
            size += refSize;
            fields[i].setAccessible(true);
            try {
              Object value = fields[i].get(obj);
              if (value != null) {
                size += size(value);
              }
            } catch (IllegalAccessException ex) {
              // ignore for now?
            }
          }
  
        }
        clazz = clazz.getSuperclass();
      }
      size += classSize;
      return size;
    }
  
    private long sizeOfArray(Object obj) {
      int len = Array.getLength(obj);
      if (len == 0) {
        return 0;
      }
      long size = arraySize;
      Class<?> arrayElementClazz = obj.getClass().getComponentType();
      if (arrayElementClazz.isPrimitive()) {
        size += len * memoryModel.getPrimitiveSize(arrayElementClazz);
      } else {
        for (int i = 0; i < len; i++) {
          size += refSize + size(Array.get(obj, i));
        }
      }
  
      return size;
    }
  
    private static final long ONE_KB = 1024;
    private static final long ONE_MB = ONE_KB * ONE_KB;
    private static final long ONE_GB = ONE_KB * ONE_MB;
  
    /**
     * Return good default units based on byte size.
     */
    public static String humanReadableUnits(long bytes, DecimalFormat df) {
      String newSizeAndUnits;
  
      if (bytes / ONE_GB > 0) {
        newSizeAndUnits = String.valueOf(df.format((float) bytes / ONE_GB))
            + " GB";
      } else if (bytes / ONE_MB > 0) {
        newSizeAndUnits = String.valueOf(df.format((float) bytes / ONE_MB))
            + " MB";
      } else if (bytes / ONE_KB > 0) {
        newSizeAndUnits = String.valueOf(df.format((float) bytes / ONE_KB))
            + " KB";
      } else {
        newSizeAndUnits = String.valueOf(bytes) + " bytes";
      }
  
      return newSizeAndUnits;
    }
  }
  