1 /* 2 * Copyright (c) 2001, 2017, 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 type = db.lookupType("RehashableSymbolHashtable"); 49 seedField = type.getCIntegerField("_seed"); 50 } 51 52 // Fields 53 private static AddressField theTableField; 54 private static AddressField sharedTableField; 55 private static CIntegerField seedField; 56 57 private CompactHashTable sharedTable; 58 59 // Accessors 60 public static SymbolTable getTheTable() { 61 Address tmp = theTableField.getValue(); 62 SymbolTable table = (SymbolTable) VMObjectFactory.newObject(SymbolTable.class, tmp); 63 Address shared = sharedTableField.getStaticFieldAddress(); 64 table.sharedTable = (CompactHashTable)VMObjectFactory.newObject(CompactHashTable.class, shared); 65 return table; 66 } 67 68 public static long getSeed() { 69 return (long) seedField.getValue(); 70 } 71 72 public static boolean useAlternateHashcode() { 73 if (getSeed() != 0) { 74 return true; 75 } 76 return false; 77 } 78 79 public SymbolTable(Address addr) { 80 super(addr); 81 } 82 83 /** Clone of VM's "temporary" probe routine, as the SA currently 84 does not support mutation so lookup() would have no effect 85 anyway. Returns null if the given string is not in the symbol 86 table. */ 87 public Symbol probe(String name) { 88 try { 89 return probe(toModifiedUTF8Bytes(name)); 90 } catch (IOException e) { 91 return null; 92 } 93 } 94 95 /** Clone of VM's "temporary" probe routine, as the SA currently 96 does not support mutation so lookup() would have no effect 97 anyway. Searches the regular symbol table and the shared symbol 98 table. Null is returned if the given name is not found in both 99 tables. */ 100 public Symbol probe(byte[] name) { 101 long hashValue = hashSymbol(name); 102 103 // shared table does not use alternate hashing algorithm, 104 // it always uses the same original hash code. 105 Symbol s = sharedTable.probe(name, hashValue); 106 if (s != null) { 107 return s; 108 } 109 110 if (useAlternateHashcode()) { 111 hashValue = AltHashing.murmur3_32(getSeed(), name); 112 } 113 114 for (HashtableEntry e = (HashtableEntry) bucket(hashToIndex(hashValue)); e != null; e = (HashtableEntry) e.next()) { 115 if (e.hash() == hashValue) { 116 Symbol sym = Symbol.create(e.literalValue()); 117 if (sym.equals(name)) { 118 return sym; 119 } 120 } 121 } 122 123 return null; 124 } 125 126 public interface SymbolVisitor { 127 public void visit(Symbol sym); 128 } 129 130 public void symbolsDo(SymbolVisitor visitor) { 131 int numBuckets = tableSize(); 132 for (int i = 0; i < numBuckets; i++) { 133 for (HashtableEntry e = (HashtableEntry) bucket(i); e != null; 134 e = (HashtableEntry) e.next()) { 135 visitor.visit(Symbol.create(e.literalValue())); 136 } 137 } 138 } 139 140 private static byte[] toModifiedUTF8Bytes(String name) throws IOException { 141 ByteArrayOutputStream baos = new ByteArrayOutputStream(); 142 DataOutputStream dos = new DataOutputStream(baos); 143 dos.writeUTF(name); 144 dos.flush(); 145 byte[] buf = baos.toByteArray(); 146 byte[] res = new byte[buf.length - 2]; 147 // skip the length part 148 System.arraycopy(buf, 2, res, 0, res.length); 149 return res; 150 } 151 }