1 /*
   2  * Copyright (c) 2016, 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 jdk.vm.ci.hotspot;
  24 
  25 /**
  26  * Describes a C++ field exposed via {@link HotSpotVMConfigAccess}.
  27  */
  28 public final class VMField {
  29 
  30     /**
  31      * Fully qualified name of the represented field (e.g., "Klass::_name").
  32      */
  33     public final String name;
  34 
  35     /**
  36      * The represented field's type (e.g., "Symbol*"). This may be {@code null}.
  37      */
  38     public final String type;
  39 
  40     /**
  41      * If the represented field is non-static, this is its offset within the containing structure.
  42      */
  43     public final long offset;
  44 
  45     /**
  46      * If the represented field is static, this is its address. Otherwise, this is 0.
  47      */
  48     public final long address;
  49 
  50     /**
  51      * Value of the field represented as a boxed boolean if its C++ type is bool otherwise as a
  52      * boxed long; only valid for non-oop static fields. This value is only captured once, during
  53      * JVMCI initialization. If {@link #type} cannot be meaningfully (e.g., a struct) or safely
  54      * (e.g., an oop) expressed as a boxed object, this is {@code null}.
  55      */
  56     public final Object value;
  57 
  58     /**
  59      * Determines if the represented field is static.
  60      */
  61     public boolean isStatic() {
  62         return address != 0;
  63     }
  64 
  65     /**
  66      * Creates a description of a non-static field.
  67      */
  68     public VMField(String name, String type, long offset) {
  69         this.name = name;
  70         this.type = type;
  71         this.offset = offset;
  72         this.address = 0;
  73         this.value = null;
  74     }
  75 
  76     /**
  77      * Creates a description of a static field.
  78      */
  79     public VMField(String name, String type, long address, Long value) {
  80         this.name = name;
  81         this.type = type;
  82         this.offset = 0;
  83         this.address = address;
  84         this.value = value;
  85     }
  86 
  87     @Override
  88     public String toString() {
  89         String val = value == null ? "null" : String.format("0x%x", value);
  90         return String.format("Field[name=%s, type=%s, offset=%d, address=0x%x, value=%s]", name, type, offset, address, val);
  91     }
  92 }