1 /*
   2  * Copyright (c) 2014, 2018, 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 
  24 
  25 package org.graalvm.compiler.core.common;
  26 
  27 import static org.graalvm.compiler.core.common.UnsafeAccess.UNSAFE;
  28 
  29 import java.lang.reflect.Field;
  30 import java.lang.reflect.Modifier;
  31 import java.util.ArrayList;
  32 
  33 import sun.misc.Unsafe;
  34 
  35 /**
  36  * Scans the fields in a class hierarchy.
  37  */
  38 public class FieldsScanner {
  39 
  40     /**
  41      * Determines the offset (in bytes) of a field.
  42      */
  43     public interface CalcOffset {
  44 
  45         long getOffset(Field field);
  46     }
  47 
  48     /**
  49      * Determines the offset (in bytes) of a field using {@link Unsafe#objectFieldOffset(Field)}.
  50      */
  51     public static class DefaultCalcOffset implements CalcOffset {
  52 
  53         @Override
  54         public long getOffset(Field field) {
  55             return UNSAFE.objectFieldOffset(field);
  56         }
  57     }
  58 
  59     /**
  60      * Describes a field in a class during {@linkplain FieldsScanner scanning}.
  61      */
  62     public static class FieldInfo implements Comparable<FieldInfo> {
  63         public final long offset;
  64         public final String name;
  65         public final Class<?> type;
  66         public final Class<?> declaringClass;
  67 
  68         public FieldInfo(long offset, String name, Class<?> type, Class<?> declaringClass) {
  69             this.offset = offset;
  70             this.name = name;
  71             this.type = type;
  72             this.declaringClass = declaringClass;
  73         }
  74 
  75         /**
  76          * Sorts fields in ascending order by their {@link #offset}s.
  77          */
  78         @Override
  79         public int compareTo(FieldInfo o) {
  80             return offset < o.offset ? -1 : (offset > o.offset ? 1 : 0);
  81         }
  82 
  83         @Override
  84         public String toString() {
  85             return "[" + offset + "]" + name + ":" + type.getSimpleName();
  86         }
  87     }
  88 
  89     private final FieldsScanner.CalcOffset calc;
  90 
  91     /**
  92      * Fields not belonging to a more specific category defined by scanner subclasses are added to
  93      * this list.
  94      */
  95     public final ArrayList<FieldsScanner.FieldInfo> data = new ArrayList<>();
  96 
  97     public FieldsScanner(FieldsScanner.CalcOffset calc) {
  98         this.calc = calc;
  99     }
 100 
 101     /**
 102      * Scans the fields in a class hierarchy.
 103      *
 104      * @param clazz the class at which to start scanning
 105      * @param endClazz scanning stops when this class is encountered (i.e. {@code endClazz} is not
 106      *            scanned)
 107      */
 108     public void scan(Class<?> clazz, Class<?> endClazz, boolean includeTransient) {
 109         Class<?> currentClazz = clazz;
 110         while (currentClazz != endClazz) {
 111             for (Field field : currentClazz.getDeclaredFields()) {
 112                 if (Modifier.isStatic(field.getModifiers())) {
 113                     continue;
 114                 }
 115                 if (!includeTransient && Modifier.isTransient(field.getModifiers())) {
 116                     continue;
 117                 }
 118                 long offset = calc.getOffset(field);
 119                 scanField(field, offset);
 120             }
 121             currentClazz = currentClazz.getSuperclass();
 122         }
 123     }
 124 
 125     protected void scanField(Field field, long offset) {
 126         data.add(new FieldsScanner.FieldInfo(offset, field.getName(), field.getType(), field.getDeclaringClass()));
 127     }
 128 }