1 /* 2 * Copyright (c) 2001, 2018, 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 CompactHashTable getSharedTable() { 69 return sharedTable; 70 } 71 72 public static long getSeed() { 73 return (long) seedField.getValue(); 74 } 75 76 public static boolean useAlternateHashcode() { 77 if (getSeed() != 0) { 78 return true; 79 } 80 return false; 81 } 82 83 public SymbolTable(Address addr) { 84 super(addr); 85 } 86 87 /** Clone of VM's "temporary" probe routine, as the SA currently 88 does not support mutation so lookup() would have no effect 89 anyway. Returns null if the given string is not in the symbol 90 table. */ 91 public Symbol probe(String name) { 92 try { 93 return probe(toModifiedUTF8Bytes(name)); 94 } catch (IOException e) { 95 return null; 96 } 97 } 98 99 /** Clone of VM's "temporary" probe routine, as the SA currently 100 does not support mutation so lookup() would have no effect 101 anyway. Searches the regular symbol table and the shared symbol 102 table. Null is returned if the given name is not found in both 103 tables. */ 104 public Symbol probe(byte[] name) { 105 long hashValue = hashSymbol(name); 106 107 // shared table does not use alternate hashing algorithm, 108 // it always uses the same original hash code. 109 Symbol s = sharedTable.probe(name, hashValue); 110 if (s != null) { 111 return s; 112 } 113 114 if (useAlternateHashcode()) { 115 hashValue = AltHashing.murmur3_32(getSeed(), name); 116 } 117 118 for (HashtableEntry e = (HashtableEntry) bucket(hashToIndex(hashValue)); e != null; e = (HashtableEntry) e.next()) { 119 if (e.hash() == hashValue) { 120 Symbol sym = Symbol.create(e.literalValue()); 121 if (sym.equals(name)) { 122 return sym; 123 } 124 } 125 } 126 127 return null; 128 } 129 130 public interface SymbolVisitor { 131 public void visit(Symbol sym); 132 } 133 134 public void symbolsDo(SymbolVisitor visitor) { 135 int numBuckets = tableSize(); 136 for (int i = 0; i < numBuckets; i++) { 137 for (HashtableEntry e = (HashtableEntry) bucket(i); e != null; 138 e = (HashtableEntry) e.next()) { 139 visitor.visit(Symbol.create(e.literalValue())); 140 } 141 } 142 } 143 144 private static byte[] toModifiedUTF8Bytes(String name) throws IOException { 145 ByteArrayOutputStream baos = new ByteArrayOutputStream(); 146 DataOutputStream dos = new DataOutputStream(baos); 147 dos.writeUTF(name); 148 dos.flush(); 149 byte[] buf = baos.toByteArray(); 150 byte[] res = new byte[buf.length - 2]; 151 // skip the length part 152 System.arraycopy(buf, 2, res, 0, res.length); 153 return res; 154 } 155 }