1 /*
2 * Copyright (c) 2003, 2017, 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 // Sharing support.
151 void copy_buckets(char** top, char* end);
152 void copy_table(char** top, char* end);
153
154 // Bucket handling
155 int hash_to_index(unsigned int full_hash) const {
156 int h = full_hash % _table_size;
157 assert(h >= 0 && h < _table_size, "Illegal hash value");
158 return h;
159 }
160
161 private:
162 // Instance variables
163 int _table_size;
164 HashtableBucket<F>* _buckets;
165 BasicHashtableEntry<F>* volatile _free_list;
166 char* _first_free_entry;
167 char* _end_block;
168 int _entry_size;
169 volatile int _number_of_entries;
170
171 protected:
172
173 void initialize(int table_size, int entry_size, int number_of_entries);
174
175 // Accessor
176 int entry_size() const { return _entry_size; }
177
178 // The following method is MT-safe and may be used with caution.
179 BasicHashtableEntry<F>* bucket(int i) const;
180
181 // The following method is not MT-safe and must be done under lock.
182 BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); }
183
184 // Attempt to get an entry from the free list
185 BasicHashtableEntry<F>* new_entry_free_list();
186
187 // Table entry management
188 BasicHashtableEntry<F>* new_entry(unsigned int hashValue);
189
190 // Used when moving the entry to another table
191 // Clean up links, but do not add to free_list
192 void unlink_entry(BasicHashtableEntry<F>* entry) {
193 entry->set_next(NULL);
194 --_number_of_entries;
195 }
196
197 // Move over freelist and free block for allocation
198 void copy_freelist(BasicHashtable* src) {
199 _free_list = src->_free_list;
200 src->_free_list = NULL;
201 _first_free_entry = src->_first_free_entry;
202 src->_first_free_entry = NULL;
203 _end_block = src->_end_block;
204 src->_end_block = NULL;
205 }
206
207 // Free the buckets in this hashtable
208 void free_buckets();
209
210 // Helper data structure containing context for the bucket entry unlink process,
211 // storing the unlinked buckets in a linked list.
212 // Also avoids the need to pass around these four members as parameters everywhere.
213 struct BucketUnlinkContext {
214 int _num_processed;
215 int _num_removed;
216 // Head and tail pointers for the linked list of removed entries.
217 BasicHashtableEntry<F>* _removed_head;
218 BasicHashtableEntry<F>* _removed_tail;
219
220 BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) {
221 }
222
223 void free_entry(BasicHashtableEntry<F>* entry);
224 };
225 // Add of bucket entries linked together in the given context to the global free list. This method
226 // is mt-safe wrt. to other calls of this method.
227 void bulk_free_entries(BucketUnlinkContext* context);
228 public:
229 int table_size() { return _table_size; }
230 void set_entry(int index, BasicHashtableEntry<F>* entry);
231
232 void add_entry(int index, BasicHashtableEntry<F>* entry);
233
234 void free_entry(BasicHashtableEntry<F>* entry);
235
236 int number_of_entries() { return _number_of_entries; }
237
238 template <class T> void verify_table(const char* table_name) PRODUCT_RETURN;
239 };
240
241
242 template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> {
243 friend class VMStructs;
244
245 public:
246 Hashtable(int table_size, int entry_size)
247 : BasicHashtable<F>(table_size, entry_size) { }
248
249 Hashtable(int table_size, int entry_size,
250 HashtableBucket<F>* buckets, int number_of_entries)
251 : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { }
252
253 // Debugging
254 void print() PRODUCT_RETURN;
255
256 protected:
257
258 unsigned int compute_hash(Symbol* name) {
259 return (unsigned int) name->identity_hash();
260 }
261
262 int index_for(Symbol* name) {
263 return this->hash_to_index(compute_hash(name));
264 }
265
266 // Table entry management
267 HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj);
268
269 // The following method is MT-safe and may be used with caution.
270 HashtableEntry<T, F>* bucket(int i) const {
271 return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i);
272 }
273
274 // The following method is not MT-safe and must be done under lock.
275 HashtableEntry<T, F>** bucket_addr(int i) {
276 return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i);
277 }
278
279 };
280
281 template <class T, MEMFLAGS F> class RehashableHashtable : public Hashtable<T, F> {
282 friend class VMStructs;
283 protected:
284
285 enum {
286 rehash_count = 100,
287 rehash_multiple = 60
288 };
289
290 // Check that the table is unbalanced
291 bool check_rehash_table(int count);
292
293 public:
294 RehashableHashtable(int table_size, int entry_size)
295 : Hashtable<T, F>(table_size, entry_size) { }
296
297 RehashableHashtable(int table_size, int entry_size,
298 HashtableBucket<F>* buckets, int number_of_entries)
299 : Hashtable<T, F>(table_size, entry_size, buckets, number_of_entries) { }
300
301
302 // Function to move these elements into the new table.
303 void move_to(RehashableHashtable<T, F>* new_table);
304 static bool use_alternate_hashcode();
305 static juint seed();
306
307 static int literal_size(Symbol *symbol);
308 static int literal_size(oop oop);
309
310 // The following two are currently not used, but are needed anyway because some
311 // C++ compilers (MacOS and Solaris) force the instantiation of
312 // Hashtable<ConstantPool*, mtClass>::dump_table() even though we never call this function
313 // in the VM code.
314 static int literal_size(ConstantPool *cp) {Unimplemented(); return 0;}
315 static int literal_size(Klass *k) {Unimplemented(); return 0;}
316
317 void dump_table(outputStream* st, const char *table_name);
318
319 private:
320 static juint _seed;
321 };
322
323 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;
324 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::seed() { return _seed; };
325 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::use_alternate_hashcode() { return _seed != 0; };
326
327 // Versions of hashtable where two handles are used to compute the index.
328
329 template <class T, MEMFLAGS F> class TwoOopHashtable : public Hashtable<T, F> {
330 friend class VMStructs;
331 protected:
332 TwoOopHashtable(int table_size, int entry_size)
333 : Hashtable<T, F>(table_size, entry_size) {}
334
335 TwoOopHashtable(int table_size, int entry_size, HashtableBucket<F>* t,
336 int number_of_entries)
337 : Hashtable<T, F>(table_size, entry_size, t, number_of_entries) {}
338
339 public:
340 unsigned int compute_hash(const Symbol* name, const ClassLoaderData* loader_data) const {
341 unsigned int name_hash = name->identity_hash();
342 // loader is null with CDS
343 assert(loader_data != NULL || UseSharedSpaces || DumpSharedSpaces,
344 "only allowed with shared spaces");
345 unsigned int loader_hash = loader_data == NULL ? 0 : loader_data->identity_hash();
346 return name_hash ^ loader_hash;
347 }
348
349 int index_for(Symbol* name, ClassLoaderData* loader_data) {
350 return this->hash_to_index(compute_hash(name, loader_data));
351 }
352 };
353
354 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP