SymbolTable.java revision 10941:857efca82258 
1/*
2 * Copyright (c) 2001, 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 */
24
25package sun.jvm.hotspot.memory;
26
27import java.io.*;
28import java.util.*;
29import sun.jvm.hotspot.debugger.*;
30import sun.jvm.hotspot.oops.*;
31import sun.jvm.hotspot.types.*;
32import sun.jvm.hotspot.runtime.*;
33import sun.jvm.hotspot.utilities.*;
34
35public 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. Searches the regular symbol table and the shared symbol
84      table. Null is returned if the given name is not found in both
85      tables. */
86  public Symbol probe(byte[] name) {
87    long hashValue = hashSymbol(name);
88
89    Symbol s = sharedTable.probe(name, hashValue);
90    if (s != null) {
91      return s;
92    }
93
94    for (HashtableEntry e = (HashtableEntry) bucket(hashToIndex(hashValue)); e != null; e = (HashtableEntry) e.next()) {
95      if (e.hash() == hashValue) {
96         Symbol sym = Symbol.create(e.literalValue());
97         if (sym.equals(name)) {
98           return sym;
99         }
100      }
101    }
102
103    return null;
104  }
105
106  public interface SymbolVisitor {
107    public void visit(Symbol sym);
108  }
109
110  public void symbolsDo(SymbolVisitor visitor) {
111    int numBuckets = tableSize();
112    for (int i = 0; i < numBuckets; i++) {
113      for (HashtableEntry e = (HashtableEntry) bucket(i); e != null;
114           e = (HashtableEntry) e.next()) {
115        visitor.visit(Symbol.create(e.literalValue()));
116      }
117    }
118  }
119
120  private static byte[] toModifiedUTF8Bytes(String name) throws IOException {
121    ByteArrayOutputStream baos = new ByteArrayOutputStream();
122    DataOutputStream dos = new DataOutputStream(baos);
123    dos.writeUTF(name);
124    dos.flush();
125    byte[] buf = baos.toByteArray();
126    byte[] res = new byte[buf.length - 2];
127    // skip the length part
128    System.arraycopy(buf, 2, res, 0, res.length);
129    return res;
130  }
131}
132