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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package jdk.internal.jshell.jdi;
  26 
  27 import java.util.HashMap;
  28 import java.util.Objects;
  29 import com.sun.jdi.ReferenceType;
  30 import java.util.List;
  31 import com.sun.jdi.VirtualMachine;
  32 
  33 /**
  34  * Tracks the state of a class.
  35  */
  36 class ClassTracker {
  37 
  38     private final VirtualMachine vm;
  39     private final HashMap<String, ClassInfo> map;
  40 
  41     ClassTracker(VirtualMachine vm) {
  42         this.vm = vm;
  43         this.map = new HashMap<>();
  44     }
  45 
  46     /**
  47      * Associates a class name, class bytes, and ReferenceType.
  48      */
  49     class ClassInfo {
  50 
  51         // The name of the class -- always set
  52         private final String className;
  53 
  54         // The corresponding compiled class bytes when a load or redefine
  55         // is started.  May not be the loaded bytes.  May be null.
  56         private byte[] bytes;
  57 
  58         // The class bytes successfully loaded/redefined into the remote VM.
  59         private byte[] loadedBytes;
  60 
  61         // The corresponding JDI ReferenceType.  Used by redefineClasses and
  62         // acts as indicator of successful load (null if not loaded).
  63         private ReferenceType rt;
  64 
  65         private ClassInfo(String className) {
  66             this.className = className;
  67         }
  68 
  69         String getClassName() {
  70             return className;
  71         }
  72 
  73         byte[] getLoadedBytes() {
  74             return loadedBytes;
  75         }
  76 
  77         byte[] getBytes() {
  78             return bytes;
  79         }
  80 
  81         private void setBytes(byte[] potentialBytes) {
  82             this.bytes = potentialBytes;
  83         }
  84 
  85         // The class has been successful loaded redefined.  The class bytes
  86         // sent are now actually loaded.
  87         void markLoaded() {
  88             loadedBytes = bytes;
  89         }
  90 
  91         // Ask JDI for the ReferenceType, null if not loaded.
  92         ReferenceType getReferenceTypeOrNull() {
  93             if (rt == null) {
  94                 rt = nameToRef(className);
  95             }
  96             return rt;
  97         }
  98 
  99         private ReferenceType nameToRef(String name) {
 100             List<ReferenceType> rtl = vm.classesByName(name);
 101             if (rtl.size() != 1) {
 102                 return null;
 103             }
 104             return rtl.get(0);
 105         }
 106 
 107         @Override
 108         public boolean equals(Object o) {
 109             return o instanceof ClassInfo
 110                     && ((ClassInfo) o).className.equals(className);
 111         }
 112 
 113         @Override
 114         public int hashCode() {
 115             return Objects.hashCode(this.className);
 116         }
 117     }
 118 
 119     // Map a class name to the current compiled class bytes.
 120     ClassInfo classInfo(String className, byte[] bytes) {
 121         ClassInfo ci = get(className);
 122         ci.setBytes(bytes);
 123         return ci;
 124     }
 125 
 126     // Lookup the ClassInfo by class name, create if it does not exist.
 127     ClassInfo get(String className) {
 128         return map.computeIfAbsent(className, k -> new ClassInfo(k));
 129     }
 130 }