/**
    * Copyright The Apache Software Foundation
    *
    * 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.hadoop.hbase.util;
  
  import java.lang.reflect.Field;
  import java.lang.reflect.Modifier;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentSkipListMap;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  /**
   * Class for determining the "size" of a class, an attempt to calculate the
   * actual bytes that an object of this class will occupy in memory
   *
   * The core of this class is taken from the Derby project
   */
  @InterfaceAudience.Private
  public class ClassSize {
    static final Log LOG = LogFactory.getLog(ClassSize.class);
  
    private static int nrOfRefsPerObj = 2;
  
    /** Array overhead */
    public static final int ARRAY;
  
    /** Overhead for ArrayList(0) */
    public static final int ARRAYLIST;
  
    /** Overhead for ByteBuffer */
    public static final int BYTE_BUFFER;
  
    /** Overhead for an Integer */
    public static final int INTEGER;
  
    /** Overhead for entry in map */
    public static final int MAP_ENTRY;
  
    /** Object overhead is minimum 2 * reference size (8 bytes on 64-bit) */
    public static final int OBJECT;
  
    /** Reference size is 8 bytes on 64-bit, 4 bytes on 32-bit */
    public static final int REFERENCE;
  
    /** String overhead */
    public static final int STRING;
  
    /** Overhead for TreeMap */
    public static final int TREEMAP;
  
    /** Overhead for ConcurrentHashMap */
    public static final int CONCURRENT_HASHMAP;
  
    /** Overhead for ConcurrentHashMap.Entry */
    public static final int CONCURRENT_HASHMAP_ENTRY;
  
    /** Overhead for ConcurrentHashMap.Segment */
    public static final int CONCURRENT_HASHMAP_SEGMENT;
  
    /** Overhead for ConcurrentSkipListMap */
    public static final int CONCURRENT_SKIPLISTMAP;
  
    /** Overhead for ConcurrentSkipListMap Entry */
    public static final int CONCURRENT_SKIPLISTMAP_ENTRY;
  
    /** Overhead for ReentrantReadWriteLock */
    public static final int REENTRANT_LOCK;
  
    /** Overhead for AtomicLong */
    public static final int ATOMIC_LONG;
  
    /** Overhead for AtomicInteger */
    public static final int ATOMIC_INTEGER;
  
    /** Overhead for AtomicBoolean */
    public static final int ATOMIC_BOOLEAN;
  
    /** Overhead for CopyOnWriteArraySet */
    public static final int COPYONWRITE_ARRAYSET;
 
   /** Overhead for CopyOnWriteArrayList */
   public static final int COPYONWRITE_ARRAYLIST;
 
   /** Overhead for timerange */
   public static final int TIMERANGE;
 
   /** Overhead for TimeRangeTracker */
   public static final int TIMERANGE_TRACKER;
 
   /** Overhead for CellSkipListSet */
   public static final int CELL_SKIPLIST_SET;
 
   /* Are we running on jdk7? */
   private static final boolean JDK7;
   static {
     final String version = System.getProperty("java.version");
     // Verify String looks like this: 1.6.0_29
     if (!version.matches("\\d\\.\\d\\..*")) {
       throw new RuntimeException("Unexpected version format: " + version);
     }
     // Convert char to int
     int major = (int)(version.charAt(0) - '0');
     int minor = (int)(version.charAt(2) - '0');
     JDK7 = major == 1 && minor == 7;
   }
 
   /**
    * Method for reading the arc settings and setting overheads according
    * to 32-bit or 64-bit architecture.
    */
   static {
     //Default value is set to 8, covering the case when arcModel is unknown
     if (is32BitJVM()) {
       REFERENCE = 4;
     } else {
       REFERENCE = 8;
     }
 
     OBJECT = 2 * REFERENCE;
 
     ARRAY = align(3 * REFERENCE);
 
     ARRAYLIST = align(OBJECT + align(REFERENCE) + align(ARRAY) +
         (2 * Bytes.SIZEOF_INT));
 
     //noinspection PointlessArithmeticExpression
     BYTE_BUFFER = align(OBJECT + align(REFERENCE) + align(ARRAY) +
         (5 * Bytes.SIZEOF_INT) +
         (3 * Bytes.SIZEOF_BOOLEAN) + Bytes.SIZEOF_LONG);
 
     INTEGER = align(OBJECT + Bytes.SIZEOF_INT);
 
     MAP_ENTRY = align(OBJECT + 5 * REFERENCE + Bytes.SIZEOF_BOOLEAN);
 
     TREEMAP = align(OBJECT + (2 * Bytes.SIZEOF_INT) + align(7 * REFERENCE));
 
     // STRING is different size in jdk6 and jdk7. Just use what we estimate as size rather than
     // have a conditional on whether jdk7.
     STRING = (int) estimateBase(String.class, false);
 
     // CONCURRENT_HASHMAP is different size in jdk6 and jdk7; it looks like its different between
     // 23.6-b03 and 23.0-b21. Just use what we estimate as size rather than have a conditional on
     // whether jdk7.
     CONCURRENT_HASHMAP = (int) estimateBase(ConcurrentHashMap.class, false);
 
     CONCURRENT_HASHMAP_ENTRY = align(REFERENCE + OBJECT + (3 * REFERENCE) +
         (2 * Bytes.SIZEOF_INT));
 
     CONCURRENT_HASHMAP_SEGMENT = align(REFERENCE + OBJECT +
         (3 * Bytes.SIZEOF_INT) + Bytes.SIZEOF_FLOAT + ARRAY);
 
     // The size changes from jdk7 to jdk8, estimate the size rather than use a conditional
     CONCURRENT_SKIPLISTMAP = (int) estimateBase(ConcurrentSkipListMap.class, false);
 
     CONCURRENT_SKIPLISTMAP_ENTRY = align(
         align(OBJECT + (3 * REFERENCE)) + /* one node per entry */
         align((OBJECT + (3 * REFERENCE))/2)); /* one index per two entries */
 
     REENTRANT_LOCK = align(OBJECT + (3 * REFERENCE));
 
     ATOMIC_LONG = align(OBJECT + Bytes.SIZEOF_LONG);
 
     ATOMIC_INTEGER = align(OBJECT + Bytes.SIZEOF_INT);
 
     ATOMIC_BOOLEAN = align(OBJECT + Bytes.SIZEOF_BOOLEAN);
 
     COPYONWRITE_ARRAYSET = align(OBJECT + REFERENCE);
 
     COPYONWRITE_ARRAYLIST = align(OBJECT + (2 * REFERENCE) + ARRAY);
 
     TIMERANGE = align(ClassSize.OBJECT + Bytes.SIZEOF_LONG * 2 + Bytes.SIZEOF_BOOLEAN);
 
     TIMERANGE_TRACKER = align(ClassSize.OBJECT + Bytes.SIZEOF_LONG * 2);
 
     CELL_SKIPLIST_SET = align(OBJECT + REFERENCE);
   }
 
   /**
    * The estimate of the size of a class instance depends on whether the JVM
    * uses 32 or 64 bit addresses, that is it depends on the size of an object
    * reference. It is a linear function of the size of a reference, e.g.
    * 24 + 5*r where r is the size of a reference (usually 4 or 8 bytes).
    *
    * This method returns the coefficients of the linear function, e.g. {24, 5}
    * in the above example.
    *
    * @param cl A class whose instance size is to be estimated
    * @param debug debug flag
    * @return an array of 3 integers. The first integer is the size of the
    * primitives, the second the number of arrays and the third the number of
    * references.
    */
   @SuppressWarnings("unchecked")
   private static int [] getSizeCoefficients(Class cl, boolean debug) {
     int primitives = 0;
     int arrays = 0;
     //The number of references that a new object takes
     int references = nrOfRefsPerObj;
     int index = 0;
 
     for ( ; null != cl; cl = cl.getSuperclass()) {
       Field[] field = cl.getDeclaredFields();
       if (null != field) {
         for (Field aField : field) {
           if (Modifier.isStatic(aField.getModifiers())) continue;
           Class fieldClass = aField.getType();
           if (fieldClass.isArray()) {
             arrays++;
             references++;
           } else if (!fieldClass.isPrimitive()) {
             references++;
           } else {// Is simple primitive
             String name = fieldClass.getName();
 
             if (name.equals("int") || name.equals("I"))
               primitives += Bytes.SIZEOF_INT;
             else if (name.equals("long") || name.equals("J"))
               primitives += Bytes.SIZEOF_LONG;
             else if (name.equals("boolean") || name.equals("Z"))
               primitives += Bytes.SIZEOF_BOOLEAN;
             else if (name.equals("short") || name.equals("S"))
               primitives += Bytes.SIZEOF_SHORT;
             else if (name.equals("byte") || name.equals("B"))
               primitives += Bytes.SIZEOF_BYTE;
             else if (name.equals("char") || name.equals("C"))
               primitives += Bytes.SIZEOF_CHAR;
             else if (name.equals("float") || name.equals("F"))
               primitives += Bytes.SIZEOF_FLOAT;
             else if (name.equals("double") || name.equals("D"))
               primitives += Bytes.SIZEOF_DOUBLE;
           }
           if (debug) {
             if (LOG.isDebugEnabled()) {
               LOG.debug("" + index + " " + aField.getName() + " " + aField.getType());
             }
           }
           index++;
         }
       }
     }
     return new int [] {primitives, arrays, references};
   }
 
   /**
    * Estimate the static space taken up by a class instance given the
    * coefficients returned by getSizeCoefficients.
    *
    * @param coeff the coefficients
    *
    * @param debug debug flag
    * @return the size estimate, in bytes
    */
   private static long estimateBaseFromCoefficients(int [] coeff, boolean debug) {
     long prealign_size = coeff[0] + align(coeff[1] * ARRAY) + coeff[2] * REFERENCE;
 
     // Round up to a multiple of 8
     long size = align(prealign_size);
     if(debug) {
       if (LOG.isDebugEnabled()) {
         LOG.debug("Primitives=" + coeff[0] + ", arrays=" + coeff[1] +
             ", references(includes " + nrOfRefsPerObj +
             " for object overhead)=" + coeff[2] + ", refSize " + REFERENCE +
             ", size=" + size + ", prealign_size=" + prealign_size);
       }
     }
     return size;
   }
 
   /**
    * Estimate the static space taken up by the fields of a class. This includes
    * the space taken up by by references (the pointer) but not by the referenced
    * object. So the estimated size of an array field does not depend on the size
    * of the array. Similarly the size of an object (reference) field does not
    * depend on the object.
    *
    * @param cl class
    * @param debug debug flag
    * @return the size estimate in bytes.
    */
   @SuppressWarnings("unchecked")
   public static long estimateBase(Class cl, boolean debug) {
     return estimateBaseFromCoefficients( getSizeCoefficients(cl, debug), debug);
   }
 
   /**
    * Aligns a number to 8.
    * @param num number to align to 8
    * @return smallest number >= input that is a multiple of 8
    */
   public static int align(int num) {
     return (int)(align((long)num));
   }
 
   /**
    * Aligns a number to 8.
    * @param num number to align to 8
    * @return smallest number >= input that is a multiple of 8
    */
   public static long align(long num) {
     //The 7 comes from that the alignSize is 8 which is the number of bytes
     //stored and sent together
     return  ((num + 7) >> 3) << 3;
   }
 
   /**
    * Determines if we are running in a 32-bit JVM. Some unit tests need to
    * know this too.
    */
   public static boolean is32BitJVM() {
     return System.getProperty("sun.arch.data.model").equals("32");
   }
 
 }