1 /*
   2  * Copyright (c) 2001, 2013, 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 sun.jvm.hotspot.memory;
  26 
  27 import java.io.*;
  28 import java.util.*;
  29 import sun.jvm.hotspot.debugger.*;
  30 import sun.jvm.hotspot.oops.*;
  31 import sun.jvm.hotspot.types.*;
  32 import sun.jvm.hotspot.runtime.*;
  33 import sun.jvm.hotspot.utilities.*;
  34 
  35 public class SymbolTable extends sun.jvm.hotspot.utilities.Hashtable {
  36   static {
  37     VM.registerVMInitializedObserver(new Observer() {
  38         public void update(Observable o, Object data) {
  39           initialize(VM.getVM().getTypeDataBase());
  40         }
  41       });
  42   }
  43 
  44   private static synchronized void initialize(TypeDataBase db) {
  45     Type type = db.lookupType("SymbolTable");
  46     theTableField  = type.getAddressField("_the_table");
  47     sharedTableField = type.getAddressField("_shared_table");
  48   }
  49 
  50   // Fields
  51   private static AddressField theTableField;
  52   private static AddressField sharedTableField;
  53  
  54   private CompactHashTable sharedTable;
  55 
  56   // Accessors
  57   public static SymbolTable getTheTable() {
  58     Address tmp = theTableField.getValue();
  59     SymbolTable table = (SymbolTable) VMObjectFactory.newObject(SymbolTable.class, tmp);
  60     Address shared = sharedTableField.getStaticFieldAddress();
  61     table.sharedTable = (CompactHashTable)VMObjectFactory.newObject(CompactHashTable.class, shared);
  62     return table;
  63   }
  64 
  65   public SymbolTable(Address addr) {
  66     super(addr);
  67   }
  68 
  69   /** Clone of VM's "temporary" probe routine, as the SA currently
  70       does not support mutation so lookup() would have no effect
  71       anyway. Returns null if the given string is not in the symbol
  72       table. */
  73   public Symbol probe(String name) {
  74     try {
  75       return probe(toModifiedUTF8Bytes(name));
  76     } catch (IOException e) {
  77       return null;
  78     }
  79   }
  80 
  81   /** Clone of VM's "temporary" probe routine, as the SA currently
  82       does not support mutation so lookup() would have no effect
  83       anyway. Returns null if the given string is not in the symbol
  84       table. */
  85   public Symbol probe(byte[] name) {
  86     Symbol sym;
  87     long hashValue = hashSymbol(name);
  88     for (HashtableEntry e = (HashtableEntry) bucket(hashToIndex(hashValue)); e != null; e = (HashtableEntry) e.next()) {
  89       if (e.hash() == hashValue) {
  90          sym = Symbol.create(e.literalValue());
  91          if (sym.equals(name)) {
  92            return sym;
  93          }
  94       }
  95     }
  96 
  97     sym = sharedTable.probe(name, hashValue);
  98     return sym;
  99   }
 100 
 101   public interface SymbolVisitor {
 102     public void visit(Symbol sym);
 103   }
 104 
 105   public void symbolsDo(SymbolVisitor visitor) {
 106     int numBuckets = tableSize();
 107     for (int i = 0; i < numBuckets; i++) {
 108       for (HashtableEntry e = (HashtableEntry) bucket(i); e != null;
 109            e = (HashtableEntry) e.next()) {
 110         visitor.visit(Symbol.create(e.literalValue()));
 111       }
 112     }
 113   }
 114 
 115   private static byte[] toModifiedUTF8Bytes(String name) throws IOException {
 116     ByteArrayOutputStream baos = new ByteArrayOutputStream();
 117     DataOutputStream dos = new DataOutputStream(baos);
 118     dos.writeUTF(name);
 119     dos.flush();
 120     byte[] buf = baos.toByteArray();
 121     byte[] res = new byte[buf.length - 2];
 122     // skip the length part
 123     System.arraycopy(buf, 2, res, 0, res.length);
 124     return res;
 125   }
 126 }