1 /* |
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2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. |
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8 * |
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9 * This code is distributed in the hope that it will be useful, but WITHOUT |
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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12 * version 2 for more details (a copy is included in the LICENSE file that |
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13 * accompanied this code). |
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14 * |
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15 * You should have received a copy of the GNU General Public License version |
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16 * 2 along with this work; if not, write to the Free Software Foundation, |
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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18 * |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 package sun.jvm.hotspot.memory; |
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26 |
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27 import java.io.*; |
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28 import java.util.*; |
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29 import sun.jvm.hotspot.debugger.*; |
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30 import sun.jvm.hotspot.oops.*; |
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31 import sun.jvm.hotspot.types.*; |
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32 import sun.jvm.hotspot.runtime.*; |
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33 import sun.jvm.hotspot.utilities.*; |
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34 |
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35 public class SymbolTable extends sun.jvm.hotspot.utilities.Hashtable { |
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36 static { |
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37 VM.registerVMInitializedObserver(new Observer() { |
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38 public void update(Observable o, Object data) { |
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39 initialize(VM.getVM().getTypeDataBase()); |
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40 } |
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41 }); |
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42 } |
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43 |
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44 private static synchronized void initialize(TypeDataBase db) { |
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45 Type type = db.lookupType("SymbolTable"); |
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46 theTableField = type.getAddressField("_the_table"); |
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47 sharedTableField = type.getAddressField("_shared_table"); |
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48 type = db.lookupType("RehashableSymbolHashtable"); |
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49 seedField = type.getCIntegerField("_seed"); |
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50 } |
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51 |
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52 // Fields |
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53 private static AddressField theTableField; |
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54 private static AddressField sharedTableField; |
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55 private static CIntegerField seedField; |
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56 |
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57 private CompactHashTable sharedTable; |
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58 |
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59 // Accessors |
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60 public static SymbolTable getTheTable() { |
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61 Address tmp = theTableField.getValue(); |
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62 SymbolTable table = (SymbolTable) VMObjectFactory.newObject(SymbolTable.class, tmp); |
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63 Address shared = sharedTableField.getStaticFieldAddress(); |
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64 table.sharedTable = (CompactHashTable)VMObjectFactory.newObject(CompactHashTable.class, shared); |
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65 return table; |
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66 } |
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67 |
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68 public CompactHashTable getSharedTable() { |
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69 return sharedTable; |
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70 } |
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71 |
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72 public static long getSeed() { |
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73 return (long) seedField.getValue(); |
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74 } |
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75 |
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76 public static boolean useAlternateHashcode() { |
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77 if (getSeed() != 0) { |
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78 return true; |
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79 } |
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80 return false; |
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81 } |
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82 |
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83 public SymbolTable(Address addr) { |
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84 super(addr); |
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85 } |
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86 |
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87 /** Clone of VM's "temporary" probe routine, as the SA currently |
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88 does not support mutation so lookup() would have no effect |
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89 anyway. Returns null if the given string is not in the symbol |
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90 table. */ |
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91 public Symbol probe(String name) { |
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92 try { |
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93 return probe(toModifiedUTF8Bytes(name)); |
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94 } catch (IOException e) { |
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95 return null; |
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96 } |
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97 } |
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98 |
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99 /** Clone of VM's "temporary" probe routine, as the SA currently |
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100 does not support mutation so lookup() would have no effect |
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101 anyway. Searches the regular symbol table and the shared symbol |
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102 table. Null is returned if the given name is not found in both |
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103 tables. */ |
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104 public Symbol probe(byte[] name) { |
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105 long hashValue = hashSymbol(name); |
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106 |
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107 // shared table does not use alternate hashing algorithm, |
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108 // it always uses the same original hash code. |
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109 Symbol s = sharedTable.probe(name, hashValue); |
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110 if (s != null) { |
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111 return s; |
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112 } |
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113 |
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114 if (useAlternateHashcode()) { |
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115 hashValue = AltHashing.murmur3_32(getSeed(), name); |
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116 } |
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117 |
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118 for (HashtableEntry e = (HashtableEntry) bucket(hashToIndex(hashValue)); e != null; e = (HashtableEntry) e.next()) { |
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119 if (e.hash() == hashValue) { |
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120 Symbol sym = Symbol.create(e.literalValue()); |
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121 if (sym.equals(name)) { |
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122 return sym; |
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123 } |
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124 } |
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125 } |
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126 |
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127 return null; |
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128 } |
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129 |
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130 public interface SymbolVisitor { |
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131 public void visit(Symbol sym); |
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132 } |
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133 |
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134 public void symbolsDo(SymbolVisitor visitor) { |
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135 int numBuckets = tableSize(); |
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136 for (int i = 0; i < numBuckets; i++) { |
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137 for (HashtableEntry e = (HashtableEntry) bucket(i); e != null; |
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138 e = (HashtableEntry) e.next()) { |
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139 visitor.visit(Symbol.create(e.literalValue())); |
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140 } |
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141 } |
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142 } |
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143 |
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144 private static byte[] toModifiedUTF8Bytes(String name) throws IOException { |
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145 ByteArrayOutputStream baos = new ByteArrayOutputStream(); |
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146 DataOutputStream dos = new DataOutputStream(baos); |
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147 dos.writeUTF(name); |
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148 dos.flush(); |
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149 byte[] buf = baos.toByteArray(); |
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150 byte[] res = new byte[buf.length - 2]; |
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151 // skip the length part |
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152 System.arraycopy(buf, 2, res, 0, res.length); |
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153 return res; |
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154 } |
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155 } |
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