annotate src/share/vm/utilities/hashtable.hpp @ 1972:f95d63e2154a

6989984: Use standard include model for Hospot Summary: Replaced MakeDeps and the includeDB files with more standardized solutions. Reviewed-by: coleenp, kvn, kamg
author stefank
date Tue, 23 Nov 2010 13:22:55 -0800
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children 3582bf76420e
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1 /*
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2 * Copyright (c) 2003, 2010, 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 #ifndef SHARE_VM_UTILITIES_HASHTABLE_HPP
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26 #define SHARE_VM_UTILITIES_HASHTABLE_HPP
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27
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28 #include "memory/allocation.hpp"
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29 #include "oops/oop.hpp"
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30 #include "oops/symbolOop.hpp"
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31 #include "runtime/handles.hpp"
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32
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33 // This is a generic hashtable, designed to be used for the symbol
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34 // and string tables.
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35 //
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36 // It is implemented as an open hash table with a fixed number of buckets.
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37 //
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38 // %note:
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39 // - TableEntrys are allocated in blocks to reduce the space overhead.
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40
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41
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42
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43 class BasicHashtableEntry : public CHeapObj {
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44 friend class VMStructs;
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45 private:
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46 unsigned int _hash; // 32-bit hash for item
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47
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48 // Link to next element in the linked list for this bucket. EXCEPT
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49 // bit 0 set indicates that this entry is shared and must not be
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50 // unlinked from the table. Bit 0 is set during the dumping of the
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51 // archive. Since shared entries are immutable, _next fields in the
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52 // shared entries will not change. New entries will always be
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53 // unshared and since pointers are align, bit 0 will always remain 0
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54 // with no extra effort.
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55 BasicHashtableEntry* _next;
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56
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57 // Windows IA64 compiler requires subclasses to be able to access these
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58 protected:
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59 // Entry objects should not be created, they should be taken from the
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60 // free list with BasicHashtable.new_entry().
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61 BasicHashtableEntry() { ShouldNotReachHere(); }
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62 // Entry objects should not be destroyed. They should be placed on
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63 // the free list instead with BasicHashtable.free_entry().
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64 ~BasicHashtableEntry() { ShouldNotReachHere(); }
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65
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66 public:
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67
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68 unsigned int hash() const { return _hash; }
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69 void set_hash(unsigned int hash) { _hash = hash; }
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70 unsigned int* hash_addr() { return &_hash; }
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71
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72 static BasicHashtableEntry* make_ptr(BasicHashtableEntry* p) {
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73 return (BasicHashtableEntry*)((intptr_t)p & -2);
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74 }
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75
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76 BasicHashtableEntry* next() const {
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77 return make_ptr(_next);
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78 }
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79
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80 void set_next(BasicHashtableEntry* next) {
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81 _next = next;
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82 }
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83
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84 BasicHashtableEntry** next_addr() {
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85 return &_next;
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86 }
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87
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88 bool is_shared() const {
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89 return ((intptr_t)_next & 1) != 0;
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90 }
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91
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92 void set_shared() {
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93 _next = (BasicHashtableEntry*)((intptr_t)_next | 1);
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94 }
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95 };
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96
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97
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98
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99 class HashtableEntry : public BasicHashtableEntry {
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100 friend class VMStructs;
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101 private:
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102 oop _literal; // ref to item in table.
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103
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104 public:
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105 // Literal
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106 oop literal() const { return _literal; }
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107 oop* literal_addr() { return &_literal; }
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108 void set_literal(oop s) { _literal = s; }
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109
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110 HashtableEntry* next() const {
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111 return (HashtableEntry*)BasicHashtableEntry::next();
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112 }
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113 HashtableEntry** next_addr() {
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114 return (HashtableEntry**)BasicHashtableEntry::next_addr();
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115 }
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116 };
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117
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118
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119
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120 class HashtableBucket : public CHeapObj {
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121 friend class VMStructs;
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122 private:
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123 // Instance variable
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124 BasicHashtableEntry* _entry;
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125
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126 public:
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127 // Accessing
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128 void clear() { _entry = NULL; }
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129
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130 // The following methods use order access methods to avoid race
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131 // conditions in multiprocessor systems.
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132 BasicHashtableEntry* get_entry() const;
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133 void set_entry(BasicHashtableEntry* l);
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134
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135 // The following method is not MT-safe and must be done under lock.
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136 BasicHashtableEntry** entry_addr() { return &_entry; }
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137 };
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138
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139
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140 class BasicHashtable : public CHeapObj {
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141 friend class VMStructs;
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142
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143 public:
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144 BasicHashtable(int table_size, int entry_size);
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145 BasicHashtable(int table_size, int entry_size,
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146 HashtableBucket* buckets, int number_of_entries);
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147
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148 // Sharing support.
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149 void copy_buckets(char** top, char* end);
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150 void copy_table(char** top, char* end);
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151
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152 // Bucket handling
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153 int hash_to_index(unsigned int full_hash) {
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154 int h = full_hash % _table_size;
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155 assert(h >= 0 && h < _table_size, "Illegal hash value");
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156 return h;
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157 }
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158
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159 // Reverse the order of elements in each of the buckets.
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160 void reverse();
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161
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162 private:
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163 // Instance variables
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164 int _table_size;
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165 HashtableBucket* _buckets;
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166 BasicHashtableEntry* _free_list;
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167 char* _first_free_entry;
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168 char* _end_block;
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169 int _entry_size;
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170 int _number_of_entries;
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171
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172 protected:
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173
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174 #ifdef ASSERT
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175 int _lookup_count;
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176 int _lookup_length;
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177 void verify_lookup_length(double load);
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178 #endif
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179
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180 void initialize(int table_size, int entry_size, int number_of_entries);
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181
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182 // Accessor
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183 int entry_size() const { return _entry_size; }
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184 int table_size() { return _table_size; }
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185
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186 // The following method is MT-safe and may be used with caution.
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187 BasicHashtableEntry* bucket(int i);
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188
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189 // The following method is not MT-safe and must be done under lock.
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190 BasicHashtableEntry** bucket_addr(int i) { return _buckets[i].entry_addr(); }
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191
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192 // Table entry management
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193 BasicHashtableEntry* new_entry(unsigned int hashValue);
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194
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195 public:
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196 void set_entry(int index, BasicHashtableEntry* entry);
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197
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198 void add_entry(int index, BasicHashtableEntry* entry);
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199
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200 void free_entry(BasicHashtableEntry* entry);
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201
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202 int number_of_entries() { return _number_of_entries; }
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203
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204 void verify() PRODUCT_RETURN;
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205 };
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206
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207
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208 class Hashtable : public BasicHashtable {
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209 friend class VMStructs;
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210
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211 public:
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212 Hashtable(int table_size, int entry_size)
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213 : BasicHashtable(table_size, entry_size) { }
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214
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215 Hashtable(int table_size, int entry_size,
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216 HashtableBucket* buckets, int number_of_entries)
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217 : BasicHashtable(table_size, entry_size, buckets, number_of_entries) { }
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218
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219 // Invoke "f->do_oop" on the locations of all oops in the table.
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220 void oops_do(OopClosure* f);
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221
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222 // Debugging
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223 void print() PRODUCT_RETURN;
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224
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225 // GC support
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226 // Delete pointers to otherwise-unreachable objects.
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227 void unlink(BoolObjectClosure* cl);
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228
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229 // Reverse the order of elements in each of the buckets. Hashtable
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230 // entries which refer to objects at a lower address than 'boundary'
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231 // are separated from those which refer to objects at higher
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232 // addresses, and appear first in the list.
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233 void reverse(void* boundary = NULL);
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234
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235 protected:
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236
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237 static unsigned int hash_symbol(const char* s, int len);
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238
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239 unsigned int compute_hash(symbolHandle name) {
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240 return (unsigned int) name->identity_hash();
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241 }
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242
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243 int index_for(symbolHandle name) {
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244 return hash_to_index(compute_hash(name));
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245 }
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246
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247 // Table entry management
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248 HashtableEntry* new_entry(unsigned int hashValue, oop obj);
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249
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250 // The following method is MT-safe and may be used with caution.
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251 HashtableEntry* bucket(int i) {
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252 return (HashtableEntry*)BasicHashtable::bucket(i);
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253 }
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254
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255 // The following method is not MT-safe and must be done under lock.
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256 HashtableEntry** bucket_addr(int i) {
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257 return (HashtableEntry**)BasicHashtable::bucket_addr(i);
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258 }
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259 };
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260
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261
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262 // Verions of hashtable where two handles are used to compute the index.
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263
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264 class TwoOopHashtable : public Hashtable {
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265 friend class VMStructs;
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266 protected:
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267 TwoOopHashtable(int table_size, int entry_size)
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268 : Hashtable(table_size, entry_size) {}
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269
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270 TwoOopHashtable(int table_size, int entry_size, HashtableBucket* t,
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271 int number_of_entries)
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272 : Hashtable(table_size, entry_size, t, number_of_entries) {}
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273
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274 public:
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275 unsigned int compute_hash(symbolHandle name, Handle loader) {
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276 // Be careful with identity_hash(), it can safepoint and if this
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277 // were one expression, the compiler could choose to unhandle each
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278 // oop before calling identity_hash() for either of them. If the first
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279 // causes a GC, the next would fail.
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280 unsigned int name_hash = name->identity_hash();
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281 unsigned int loader_hash = loader.is_null() ? 0 : loader->identity_hash();
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282 return name_hash ^ loader_hash;
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283 }
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284
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285 int index_for(symbolHandle name, Handle loader) {
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286 return hash_to_index(compute_hash(name, loader));
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287 }
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288 };
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289
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290 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP