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 "memory/allocation.hpp"
29 #include "oops/oop.hpp"
30 #include "oops/symbol.hpp"
31 #include "runtime/handles.hpp"
32
33 // This is a generic hashtable, designed to be used for the symbol
34 // and string tables.
35 //
36 // It is implemented as an open hash table with a fixed number of buckets.
37 //
38 // %note:
39 // - TableEntrys are allocated in blocks to reduce the space overhead.
40
41
42
43 template <MEMFLAGS F> class BasicHashtableEntry : public CHeapObj<F> {
44 friend class VMStructs;
45 private:
46 unsigned int _hash; // 32-bit hash for item
47
48 // Link to next element in the linked list for this bucket. EXCEPT
49 // bit 0 set indicates that this entry is shared and must not be
50 // unlinked from the table. Bit 0 is set during the dumping of the
51 // archive. Since shared entries are immutable, _next fields in the
52 // shared entries will not change. New entries will always be
53 // unshared and since pointers are align, bit 0 will always remain 0
54 // with no extra effort.
55 BasicHashtableEntry<F>* _next;
56
57 // Windows IA64 compiler requires subclasses to be able to access these
58 protected:
59 // Entry objects should not be created, they should be taken from the
60 // free list with BasicHashtable.new_entry().
61 BasicHashtableEntry() { ShouldNotReachHere(); }
62 // Entry objects should not be destroyed. They should be placed on
63 // the free list instead with BasicHashtable.free_entry().
64 ~BasicHashtableEntry() { ShouldNotReachHere(); }
65
66 public:
67
68 unsigned int hash() const { return _hash; }
69 void set_hash(unsigned int hash) { _hash = hash; }
70 unsigned int* hash_addr() { return &_hash; }
71
72 static BasicHashtableEntry<F>* make_ptr(BasicHashtableEntry<F>* p) {
73 return (BasicHashtableEntry*)((intptr_t)p & -2);
74 }
75
76 BasicHashtableEntry<F>* next() const {
77 return make_ptr(_next);
78 }
79
80 void set_next(BasicHashtableEntry<F>* next) {
81 _next = next;
82 }
83
84 BasicHashtableEntry<F>** next_addr() {
85 return &_next;
86 }
87
88 bool is_shared() const {
89 return ((intptr_t)_next & 1) != 0;
90 }
91
92 void set_shared() {
93 _next = (BasicHashtableEntry<F>*)((intptr_t)_next | 1);
94 }
95 };
96
97
98
99 template <class T, MEMFLAGS F> class HashtableEntry : public BasicHashtableEntry<F> {
100 friend class VMStructs;
101 private:
102 T _literal; // ref to item in table.
103
104 public:
105 // Literal
106 T literal() const { return _literal; }
107 T* literal_addr() { return &_literal; }
108 void set_literal(T s) { _literal = s; }
109
110 HashtableEntry* next() const {
111 return (HashtableEntry*)BasicHashtableEntry<F>::next();
112 }
113 HashtableEntry** next_addr() {
114 return (HashtableEntry**)BasicHashtableEntry<F>::next_addr();
115 }
116 };
117
118
119
120 template <MEMFLAGS F> class HashtableBucket : public CHeapObj<F> {
121 friend class VMStructs;
122 private:
123 // Instance variable
124 BasicHashtableEntry<F>* _entry;
125
126 public:
127 // Accessing
128 void clear() { _entry = NULL; }
129
130 // The following methods use order access methods to avoid race
131 // conditions in multiprocessor systems.
132 BasicHashtableEntry<F>* get_entry() const;
133 void set_entry(BasicHashtableEntry<F>* l);
134
135 // The following method is not MT-safe and must be done under lock.
136 BasicHashtableEntry<F>** entry_addr() { return &_entry; }
137
138 };
139
140
141 template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> {
142 friend class VMStructs;
143
144 public:
145 BasicHashtable(int table_size, int entry_size);
146 BasicHashtable(int table_size, int entry_size,
147 HashtableBucket<F>* buckets, int number_of_entries);
148
149 // Bucket handling
150 int hash_to_index(unsigned int full_hash) const {
151 int h = full_hash % _table_size;
152 assert(h >= 0 && h < _table_size, "Illegal hash value");
153 return h;
154 }
155
156 private:
157 // Instance variables
158 int _table_size;
159 HashtableBucket<F>* _buckets;
160 BasicHashtableEntry<F>* volatile _free_list;
161 char* _first_free_entry;
162 char* _end_block;
163 int _entry_size;
164 volatile int _number_of_entries;
165
166 protected:
167
168 void initialize(int table_size, int entry_size, int number_of_entries);
169
170 // Accessor
171 int entry_size() const { return _entry_size; }
172
173 // The following method is MT-safe and may be used with caution.
174 BasicHashtableEntry<F>* bucket(int i) const;
175
176 // The following method is not MT-safe and must be done under lock.
177 BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); }
178
179 // Attempt to get an entry from the free list
180 BasicHashtableEntry<F>* new_entry_free_list();
181
182 // Table entry management
183 BasicHashtableEntry<F>* new_entry(unsigned int hashValue);
184
185 // Used when moving the entry to another table
186 // Clean up links, but do not add to free_list
187 void unlink_entry(BasicHashtableEntry<F>* entry) {
188 entry->set_next(NULL);
189 --_number_of_entries;
190 }
191
192 // Move over freelist and free block for allocation
193 void copy_freelist(BasicHashtable* src) {
194 _free_list = src->_free_list;
195 src->_free_list = NULL;
196 _first_free_entry = src->_first_free_entry;
197 src->_first_free_entry = NULL;
198 _end_block = src->_end_block;
199 src->_end_block = NULL;
200 }
201
202 // Free the buckets in this hashtable
203 void free_buckets();
204
205 // Helper data structure containing context for the bucket entry unlink process,
206 // storing the unlinked buckets in a linked list.
207 // Also avoids the need to pass around these four members as parameters everywhere.
208 struct BucketUnlinkContext {
209 int _num_processed;
210 int _num_removed;
211 // Head and tail pointers for the linked list of removed entries.
212 BasicHashtableEntry<F>* _removed_head;
213 BasicHashtableEntry<F>* _removed_tail;
214
215 BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) {
216 }
217
218 void free_entry(BasicHashtableEntry<F>* entry);
219 };
220 // Add of bucket entries linked together in the given context to the global free list. This method
221 // is mt-safe wrt. to other calls of this method.
222 void bulk_free_entries(BucketUnlinkContext* context);
223 public:
224 int table_size() const { return _table_size; }
225 void set_entry(int index, BasicHashtableEntry<F>* entry);
226
227 void add_entry(int index, BasicHashtableEntry<F>* entry);
228
229 void free_entry(BasicHashtableEntry<F>* entry);
230
231 int number_of_entries() const { return _number_of_entries; }
232
233 bool resize(int new_size);
234
235 // Grow the number of buckets if the average entries per bucket is over the load_factor
236 bool maybe_grow(int load_factor = 8) {
237 if (number_of_entries() / table_size() > load_factor) {
238 resize(table_size() * 2);
239 return true;
240 } else {
241 return false;
242 }
243 }
244
245 template <class T> void verify_table(const char* table_name) PRODUCT_RETURN;
246 };
247
248
249 template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> {
250 friend class VMStructs;
251
252 public:
253 Hashtable(int table_size, int entry_size)
254 : BasicHashtable<F>(table_size, entry_size) { }
255
256 Hashtable(int table_size, int entry_size,
257 HashtableBucket<F>* buckets, int number_of_entries)
258 : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { }
259
260 // Debugging
261 void print() PRODUCT_RETURN;
262
263 unsigned int compute_hash(const Symbol* name) const {
264 return (unsigned int) name->identity_hash();
265 }
266
267 int index_for(const Symbol* name) const {
268 return this->hash_to_index(compute_hash(name));
269 }
270
271 void print_table_statistics(outputStream* st, const char *table_name, T (*literal_load_barrier)(HashtableEntry<T, F>*) = NULL);
272
273 protected:
274
275 // Table entry management
276 HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj);
277 // Don't create and use freelist of HashtableEntry.
278 HashtableEntry<T, F>* allocate_new_entry(unsigned int hashValue, T obj);
279
280 // The following method is MT-safe and may be used with caution.
281 HashtableEntry<T, F>* bucket(int i) const {
282 return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i);
283 }
284
285 // The following method is not MT-safe and must be done under lock.
286 HashtableEntry<T, F>** bucket_addr(int i) {
287 return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i);
288 }
289 };
290
291 // A subclass of BasicHashtable that allows you to do a simple K -> V mapping
292 // without using tons of boilerplate code.
293 template<
294 typename K, typename V,
295 MEMFLAGS F = mtInternal,
296 unsigned (*HASH) (K const&) = primitive_hash<K>,
297 bool (*EQUALS)(K const&, K const&) = primitive_equals<K>
298 >
299 class KVHashtable : public BasicHashtable<F> {
300 class KVHashtableEntry : public BasicHashtableEntry<F> {
301 public:
302 K _key;
303 V _value;
304 KVHashtableEntry* next() {
305 return (KVHashtableEntry*)BasicHashtableEntry<F>::next();
306 }
307 };
308
309 protected:
310 KVHashtableEntry* bucket(int i) const {
311 return (KVHashtableEntry*)BasicHashtable<F>::bucket(i);
312 }
313
314 KVHashtableEntry* new_entry(unsigned int hashValue, K key, V value) {
315 KVHashtableEntry* entry = (KVHashtableEntry*)BasicHashtable<F>::new_entry(hashValue);
316 entry->_key = key;
317 entry->_value = value;
318 return entry;
319 }
320
321 public:
322 KVHashtable(int table_size) : BasicHashtable<F>(table_size, sizeof(KVHashtableEntry)) {}
323
324 void add(K key, V value) {
325 unsigned int hash = HASH(key);
326 KVHashtableEntry* entry = new_entry(hash, key, value);
327 BasicHashtable<F>::add_entry(BasicHashtable<F>::hash_to_index(hash), entry);
328 }
329
330 V* lookup(K key) {
331 unsigned int hash = HASH(key);
332 int index = BasicHashtable<F>::hash_to_index(hash);
333 for (KVHashtableEntry* e = bucket(index); e != NULL; e = e->next()) {
334 if (e->hash() == hash && e->_key == key) {
335 return &(e->_value);
336 }
337 }
338 return NULL;
339 }
340 };
341
342
343 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP