1 /* 2 * Copyright (c) 2003, 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 #ifndef SHARE_VM_UTILITIES_HASHTABLE_HPP 26 #define SHARE_VM_UTILITIES_HASHTABLE_HPP 27 28 #include "classfile/classLoaderData.hpp" 29 #include "memory/allocation.hpp" 30 #include "oops/oop.hpp" 31 #include "oops/symbol.hpp" 32 #include "runtime/handles.hpp" 33 34 // This is a generic hashtable, designed to be used for the symbol 35 // and string tables. 36 // 37 // It is implemented as an open hash table with a fixed number of buckets. 38 // 39 // %note: 40 // - TableEntrys are allocated in blocks to reduce the space overhead. 41 42 43 44 template <MEMFLAGS F> class BasicHashtableEntry : public CHeapObj<F> { 45 friend class VMStructs; 46 private: 47 unsigned int _hash; // 32-bit hash for item 48 49 // Link to next element in the linked list for this bucket. EXCEPT 50 // bit 0 set indicates that this entry is shared and must not be 51 // unlinked from the table. Bit 0 is set during the dumping of the 52 // archive. Since shared entries are immutable, _next fields in the 53 // shared entries will not change. New entries will always be 54 // unshared and since pointers are align, bit 0 will always remain 0 55 // with no extra effort. 56 BasicHashtableEntry<F>* _next; 57 58 // Windows IA64 compiler requires subclasses to be able to access these 59 protected: 60 // Entry objects should not be created, they should be taken from the 61 // free list with BasicHashtable.new_entry(). 62 BasicHashtableEntry() { ShouldNotReachHere(); } 63 // Entry objects should not be destroyed. They should be placed on 64 // the free list instead with BasicHashtable.free_entry(). 65 ~BasicHashtableEntry() { ShouldNotReachHere(); } 66 67 public: 68 69 unsigned int hash() const { return _hash; } 70 void set_hash(unsigned int hash) { _hash = hash; } 71 unsigned int* hash_addr() { return &_hash; } 72 73 static BasicHashtableEntry<F>* make_ptr(BasicHashtableEntry<F>* p) { 74 return (BasicHashtableEntry*)((intptr_t)p & -2); 75 } 76 77 BasicHashtableEntry<F>* next() const { 78 return make_ptr(_next); 79 } 80 81 void set_next(BasicHashtableEntry<F>* next) { 82 _next = next; 83 } 84 85 BasicHashtableEntry<F>** next_addr() { 86 return &_next; 87 } 88 89 bool is_shared() const { 90 return ((intptr_t)_next & 1) != 0; 91 } 92 93 void set_shared() { 94 _next = (BasicHashtableEntry<F>*)((intptr_t)_next | 1); 95 } 96 }; 97 98 99 100 template <class T, MEMFLAGS F> class HashtableEntry : public BasicHashtableEntry<F> { 101 friend class VMStructs; 102 private: 103 T _literal; // ref to item in table. 104 105 public: 106 // Literal 107 T literal() const { return _literal; } 108 T* literal_addr() { return &_literal; } 109 void set_literal(T s) { _literal = s; } 110 111 HashtableEntry* next() const { 112 return (HashtableEntry*)BasicHashtableEntry<F>::next(); 113 } 114 HashtableEntry** next_addr() { 115 return (HashtableEntry**)BasicHashtableEntry<F>::next_addr(); 116 } 117 }; 118 119 120 121 template <MEMFLAGS F> class HashtableBucket : public CHeapObj<F> { 122 friend class VMStructs; 123 private: 124 // Instance variable 125 BasicHashtableEntry<F>* _entry; 126 127 public: 128 // Accessing 129 void clear() { _entry = NULL; } 130 131 // The following methods use order access methods to avoid race 132 // conditions in multiprocessor systems. 133 BasicHashtableEntry<F>* get_entry() const; 134 void set_entry(BasicHashtableEntry<F>* l); 135 136 // The following method is not MT-safe and must be done under lock. 137 BasicHashtableEntry<F>** entry_addr() { return &_entry; } 138 139 }; 140 141 142 template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> { 143 friend class VMStructs; 144 145 public: 146 BasicHashtable(int table_size, int entry_size); 147 BasicHashtable(int table_size, int entry_size, 148 HashtableBucket<F>* buckets, int number_of_entries); 149 150 // Bucket handling 151 int hash_to_index(unsigned int full_hash) const { 152 int h = full_hash % _table_size; 153 assert(h >= 0 && h < _table_size, "Illegal hash value"); 154 return h; 155 } 156 157 private: 158 // Instance variables 159 int _table_size; 160 HashtableBucket<F>* _buckets; 161 BasicHashtableEntry<F>* volatile _free_list; 162 char* _first_free_entry; 163 char* _end_block; 164 int _entry_size; 165 volatile int _number_of_entries; 166 167 protected: 168 169 void initialize(int table_size, int entry_size, int number_of_entries); 170 171 // Accessor 172 int entry_size() const { return _entry_size; } 173 174 // The following method is MT-safe and may be used with caution. 175 BasicHashtableEntry<F>* bucket(int i) const; 176 177 // The following method is not MT-safe and must be done under lock. 178 BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); } 179 180 // Attempt to get an entry from the free list 181 BasicHashtableEntry<F>* new_entry_free_list(); 182 183 // Table entry management 184 BasicHashtableEntry<F>* new_entry(unsigned int hashValue); 185 186 // Used when moving the entry to another table 187 // Clean up links, but do not add to free_list 188 void unlink_entry(BasicHashtableEntry<F>* entry) { 189 entry->set_next(NULL); 190 --_number_of_entries; 191 } 192 193 // Move over freelist and free block for allocation 194 void copy_freelist(BasicHashtable* src) { 195 _free_list = src->_free_list; 196 src->_free_list = NULL; 197 _first_free_entry = src->_first_free_entry; 198 src->_first_free_entry = NULL; 199 _end_block = src->_end_block; 200 src->_end_block = NULL; 201 } 202 203 // Free the buckets in this hashtable 204 void free_buckets(); 205 206 // Helper data structure containing context for the bucket entry unlink process, 207 // storing the unlinked buckets in a linked list. 208 // Also avoids the need to pass around these four members as parameters everywhere. 209 struct BucketUnlinkContext { 210 int _num_processed; 211 int _num_removed; 212 // Head and tail pointers for the linked list of removed entries. 213 BasicHashtableEntry<F>* _removed_head; 214 BasicHashtableEntry<F>* _removed_tail; 215 216 BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) { 217 } 218 219 void free_entry(BasicHashtableEntry<F>* entry); 220 }; 221 // Add of bucket entries linked together in the given context to the global free list. This method 222 // is mt-safe wrt. to other calls of this method. 223 void bulk_free_entries(BucketUnlinkContext* context); 224 public: 225 int table_size() const { return _table_size; } 226 void set_entry(int index, BasicHashtableEntry<F>* entry); 227 228 void add_entry(int index, BasicHashtableEntry<F>* entry); 229 230 void free_entry(BasicHashtableEntry<F>* entry); 231 232 int number_of_entries() const { return _number_of_entries; } 233 234 bool resize(int new_size); 235 236 template <class T> void verify_table(const char* table_name) PRODUCT_RETURN; 237 }; 238 239 240 template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> { 241 friend class VMStructs; 242 243 public: 244 Hashtable(int table_size, int entry_size) 245 : BasicHashtable<F>(table_size, entry_size) { } 246 247 Hashtable(int table_size, int entry_size, 248 HashtableBucket<F>* buckets, int number_of_entries) 249 : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { } 250 251 // Debugging 252 void print() PRODUCT_RETURN; 253 254 unsigned int compute_hash(const Symbol* name) const { 255 return (unsigned int) name->identity_hash(); 256 } 257 258 int index_for(const Symbol* name) const { 259 return this->hash_to_index(compute_hash(name)); 260 } 261 262 void print_table_statistics(outputStream* st, const char *table_name, T (*literal_load_barrier)(HashtableEntry<T, F>*) = NULL); 263 264 protected: 265 266 // Table entry management 267 HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj); 268 // Don't create and use freelist of HashtableEntry. 269 HashtableEntry<T, F>* allocate_new_entry(unsigned int hashValue, T obj); 270 271 // The following method is MT-safe and may be used with caution. 272 HashtableEntry<T, F>* bucket(int i) const { 273 return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i); 274 } 275 276 // The following method is not MT-safe and must be done under lock. 277 HashtableEntry<T, F>** bucket_addr(int i) { 278 return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i); 279 } 280 }; 281 282 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP