1 /*
   2  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package org.graalvm.compiler.core.common;
  24 
  25 import static org.graalvm.compiler.core.common.UnsafeAccess.UNSAFE;
  26 
  27 import java.lang.reflect.Field;
  28 import java.lang.reflect.Modifier;
  29 import java.util.ArrayList;
  30 
  31 import sun.misc.Unsafe;
  32 
  33 /**
  34  * Scans the fields in a class hierarchy.
  35  */
  36 public class FieldsScanner {
  37 
  38     /**
  39      * Determines the offset (in bytes) of a field.
  40      */
  41     public interface CalcOffset {
  42 
  43         long getOffset(Field field);
  44     }
  45 
  46     /**
  47      * Determines the offset (in bytes) of a field using {@link Unsafe#objectFieldOffset(Field)}.
  48      */
  49     public static class DefaultCalcOffset implements CalcOffset {
  50 
  51         @Override
  52         public long getOffset(Field field) {
  53             return UNSAFE.objectFieldOffset(field);
  54         }
  55     }
  56 
  57     /**
  58      * Describes a field in a class during {@linkplain FieldsScanner scanning}.
  59      */
  60     public static class FieldInfo implements Comparable<FieldInfo> {
  61         public final long offset;
  62         public final String name;
  63         public final Class<?> type;
  64         public final Class<?> declaringClass;
  65 
  66         public FieldInfo(long offset, String name, Class<?> type, Class<?> declaringClass) {
  67             this.offset = offset;
  68             this.name = name;
  69             this.type = type;
  70             this.declaringClass = declaringClass;
  71         }
  72 
  73         /**
  74          * Sorts fields in ascending order by their {@link #offset}s.
  75          */
  76         @Override
  77         public int compareTo(FieldInfo o) {
  78             return offset < o.offset ? -1 : (offset > o.offset ? 1 : 0);
  79         }
  80 
  81         @Override
  82         public String toString() {
  83             return "[" + offset + "]" + name + ":" + type.getSimpleName();
  84         }
  85     }
  86 
  87     private final FieldsScanner.CalcOffset calc;
  88 
  89     /**
  90      * Fields not belonging to a more specific category defined by scanner subclasses are added to
  91      * this list.
  92      */
  93     public final ArrayList<FieldsScanner.FieldInfo> data = new ArrayList<>();
  94 
  95     public FieldsScanner(FieldsScanner.CalcOffset calc) {
  96         this.calc = calc;
  97     }
  98 
  99     /**
 100      * Scans the fields in a class hierarchy.
 101      *
 102      * @param clazz the class at which to start scanning
 103      * @param endClazz scanning stops when this class is encountered (i.e. {@code endClazz} is not
 104      *            scanned)
 105      */
 106     public void scan(Class<?> clazz, Class<?> endClazz, boolean includeTransient) {
 107         Class<?> currentClazz = clazz;
 108         while (currentClazz != endClazz) {
 109             for (Field field : currentClazz.getDeclaredFields()) {
 110                 if (Modifier.isStatic(field.getModifiers())) {
 111                     continue;
 112                 }
 113                 if (!includeTransient && Modifier.isTransient(field.getModifiers())) {
 114                     continue;
 115                 }
 116                 long offset = calc.getOffset(field);
 117                 scanField(field, offset);
 118             }
 119             currentClazz = currentClazz.getSuperclass();
 120         }
 121     }
 122 
 123     protected void scanField(Field field, long offset) {
 124         data.add(new FieldsScanner.FieldInfo(offset, field.getName(), field.getType(), field.getDeclaringClass()));
 125     }
 126 }