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.serviceprovider.GraalUnsafeAccess.getUnsafe;
  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         private static final Unsafe UNSAFE = getUnsafe();
  54 
  55         @Override
  56         public long getOffset(Field field) {
  57             return UNSAFE.objectFieldOffset(field);
  58         }
  59     }
  60 
  61     /**
  62      * Describes a field in a class during {@linkplain FieldsScanner scanning}.
  63      */
  64     public static class FieldInfo implements Comparable<FieldInfo> {
  65         public final long offset;
  66         public final String name;
  67         public final Class<?> type;
  68         public final Class<?> declaringClass;
  69 
  70         public FieldInfo(long offset, String name, Class<?> type, Class<?> declaringClass) {
  71             this.offset = offset;
  72             this.name = name;
  73             this.type = type;
  74             this.declaringClass = declaringClass;
  75         }
  76 
  77         /**
  78          * Sorts fields in ascending order by their {@link #offset}s.
  79          */
  80         @Override
  81         public int compareTo(FieldInfo o) {
  82             return offset < o.offset ? -1 : (offset > o.offset ? 1 : 0);
  83         }
  84 
  85         @Override
  86         public String toString() {
  87             return "[" + offset + "]" + name + ":" + type.getSimpleName();
  88         }
  89     }
  90 
  91     private final FieldsScanner.CalcOffset calc;
  92 
  93     /**
  94      * Fields not belonging to a more specific category defined by scanner subclasses are added to
  95      * this list.
  96      */
  97     public final ArrayList<FieldsScanner.FieldInfo> data = new ArrayList<>();
  98 
  99     public FieldsScanner(FieldsScanner.CalcOffset calc) {
 100         this.calc = calc;
 101     }
 102 
 103     /**
 104      * Scans the fields in a class hierarchy.
 105      *
 106      * @param clazz the class at which to start scanning
 107      * @param endClazz scanning stops when this class is encountered (i.e. {@code endClazz} is not
 108      *            scanned)
 109      */
 110     public void scan(Class<?> clazz, Class<?> endClazz, boolean includeTransient) {
 111         Class<?> currentClazz = clazz;
 112         while (currentClazz != endClazz) {
 113             for (Field field : currentClazz.getDeclaredFields()) {
 114                 if (Modifier.isStatic(field.getModifiers())) {
 115                     continue;
 116                 }
 117                 if (!includeTransient && Modifier.isTransient(field.getModifiers())) {
 118                     continue;
 119                 }
 120                 long offset = calc.getOffset(field);
 121                 scanField(field, offset);
 122             }
 123             currentClazz = currentClazz.getSuperclass();
 124         }
 125     }
 126 
 127     protected void scanField(Field field, long offset) {
 128         data.add(new FieldsScanner.FieldInfo(offset, field.getName(), field.getType(), field.getDeclaringClass()));
 129     }
 130 }