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annotate src/share/vm/utilities/hashtable.hpp @ 2137:ffd725ff6943
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author | johnc |
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date | Thu, 13 Jan 2011 17:19:21 -0800 |
parents | f95d63e2154a |
children | 3582bf76420e |
rev | line source |
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0 | 1 /* |
1972 | 2 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
1552
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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. |
0 | 22 * |
23 */ | |
24 | |
1972 | 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/symbolOop.hpp" | |
31 #include "runtime/handles.hpp" | |
32 | |
0 | 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 class BasicHashtableEntry : public CHeapObj { | |
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* _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* make_ptr(BasicHashtableEntry* p) { | |
73 return (BasicHashtableEntry*)((intptr_t)p & -2); | |
74 } | |
75 | |
76 BasicHashtableEntry* next() const { | |
77 return make_ptr(_next); | |
78 } | |
79 | |
80 void set_next(BasicHashtableEntry* next) { | |
81 _next = next; | |
82 } | |
83 | |
84 BasicHashtableEntry** 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*)((intptr_t)_next | 1); | |
94 } | |
95 }; | |
96 | |
97 | |
98 | |
99 class HashtableEntry : public BasicHashtableEntry { | |
100 friend class VMStructs; | |
101 private: | |
102 oop _literal; // ref to item in table. | |
103 | |
104 public: | |
105 // Literal | |
106 oop literal() const { return _literal; } | |
107 oop* literal_addr() { return &_literal; } | |
108 void set_literal(oop s) { _literal = s; } | |
109 | |
110 HashtableEntry* next() const { | |
111 return (HashtableEntry*)BasicHashtableEntry::next(); | |
112 } | |
113 HashtableEntry** next_addr() { | |
114 return (HashtableEntry**)BasicHashtableEntry::next_addr(); | |
115 } | |
116 }; | |
117 | |
118 | |
119 | |
120 class HashtableBucket : public CHeapObj { | |
121 friend class VMStructs; | |
122 private: | |
123 // Instance variable | |
124 BasicHashtableEntry* _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* get_entry() const; | |
133 void set_entry(BasicHashtableEntry* l); | |
134 | |
135 // The following method is not MT-safe and must be done under lock. | |
136 BasicHashtableEntry** entry_addr() { return &_entry; } | |
137 }; | |
138 | |
139 | |
140 class BasicHashtable : public CHeapObj { | |
141 friend class VMStructs; | |
142 | |
143 public: | |
144 BasicHashtable(int table_size, int entry_size); | |
145 BasicHashtable(int table_size, int entry_size, | |
146 HashtableBucket* buckets, int number_of_entries); | |
147 | |
148 // Sharing support. | |
149 void copy_buckets(char** top, char* end); | |
150 void copy_table(char** top, char* end); | |
151 | |
152 // Bucket handling | |
153 int hash_to_index(unsigned int full_hash) { | |
154 int h = full_hash % _table_size; | |
155 assert(h >= 0 && h < _table_size, "Illegal hash value"); | |
156 return h; | |
157 } | |
158 | |
159 // Reverse the order of elements in each of the buckets. | |
160 void reverse(); | |
161 | |
162 private: | |
163 // Instance variables | |
164 int _table_size; | |
165 HashtableBucket* _buckets; | |
166 BasicHashtableEntry* _free_list; | |
167 char* _first_free_entry; | |
168 char* _end_block; | |
169 int _entry_size; | |
170 int _number_of_entries; | |
171 | |
172 protected: | |
173 | |
174 #ifdef ASSERT | |
175 int _lookup_count; | |
176 int _lookup_length; | |
177 void verify_lookup_length(double load); | |
178 #endif | |
179 | |
180 void initialize(int table_size, int entry_size, int number_of_entries); | |
181 | |
182 // Accessor | |
183 int entry_size() const { return _entry_size; } | |
184 int table_size() { return _table_size; } | |
185 | |
186 // The following method is MT-safe and may be used with caution. | |
187 BasicHashtableEntry* bucket(int i); | |
188 | |
189 // The following method is not MT-safe and must be done under lock. | |
190 BasicHashtableEntry** bucket_addr(int i) { return _buckets[i].entry_addr(); } | |
191 | |
192 // Table entry management | |
193 BasicHashtableEntry* new_entry(unsigned int hashValue); | |
194 | |
195 public: | |
196 void set_entry(int index, BasicHashtableEntry* entry); | |
197 | |
198 void add_entry(int index, BasicHashtableEntry* entry); | |
199 | |
200 void free_entry(BasicHashtableEntry* entry); | |
201 | |
202 int number_of_entries() { return _number_of_entries; } | |
203 | |
204 void verify() PRODUCT_RETURN; | |
205 }; | |
206 | |
207 | |
208 class Hashtable : public BasicHashtable { | |
209 friend class VMStructs; | |
210 | |
211 public: | |
212 Hashtable(int table_size, int entry_size) | |
213 : BasicHashtable(table_size, entry_size) { } | |
214 | |
215 Hashtable(int table_size, int entry_size, | |
216 HashtableBucket* buckets, int number_of_entries) | |
217 : BasicHashtable(table_size, entry_size, buckets, number_of_entries) { } | |
218 | |
219 // Invoke "f->do_oop" on the locations of all oops in the table. | |
220 void oops_do(OopClosure* f); | |
221 | |
222 // Debugging | |
223 void print() PRODUCT_RETURN; | |
224 | |
225 // GC support | |
226 // Delete pointers to otherwise-unreachable objects. | |
227 void unlink(BoolObjectClosure* cl); | |
228 | |
229 // Reverse the order of elements in each of the buckets. Hashtable | |
230 // entries which refer to objects at a lower address than 'boundary' | |
231 // are separated from those which refer to objects at higher | |
232 // addresses, and appear first in the list. | |
233 void reverse(void* boundary = NULL); | |
234 | |
235 protected: | |
236 | |
237 static unsigned int hash_symbol(const char* s, int len); | |
238 | |
239 unsigned int compute_hash(symbolHandle name) { | |
240 return (unsigned int) name->identity_hash(); | |
241 } | |
242 | |
243 int index_for(symbolHandle name) { | |
244 return hash_to_index(compute_hash(name)); | |
245 } | |
246 | |
247 // Table entry management | |
248 HashtableEntry* new_entry(unsigned int hashValue, oop obj); | |
249 | |
250 // The following method is MT-safe and may be used with caution. | |
251 HashtableEntry* bucket(int i) { | |
252 return (HashtableEntry*)BasicHashtable::bucket(i); | |
253 } | |
254 | |
255 // The following method is not MT-safe and must be done under lock. | |
256 HashtableEntry** bucket_addr(int i) { | |
257 return (HashtableEntry**)BasicHashtable::bucket_addr(i); | |
258 } | |
259 }; | |
260 | |
261 | |
262 // Verions of hashtable where two handles are used to compute the index. | |
263 | |
264 class TwoOopHashtable : public Hashtable { | |
265 friend class VMStructs; | |
266 protected: | |
267 TwoOopHashtable(int table_size, int entry_size) | |
268 : Hashtable(table_size, entry_size) {} | |
269 | |
270 TwoOopHashtable(int table_size, int entry_size, HashtableBucket* t, | |
271 int number_of_entries) | |
272 : Hashtable(table_size, entry_size, t, number_of_entries) {} | |
273 | |
274 public: | |
275 unsigned int compute_hash(symbolHandle name, Handle loader) { | |
276 // Be careful with identity_hash(), it can safepoint and if this | |
277 // were one expression, the compiler could choose to unhandle each | |
278 // oop before calling identity_hash() for either of them. If the first | |
279 // causes a GC, the next would fail. | |
280 unsigned int name_hash = name->identity_hash(); | |
281 unsigned int loader_hash = loader.is_null() ? 0 : loader->identity_hash(); | |
282 return name_hash ^ loader_hash; | |
283 } | |
284 | |
285 int index_for(symbolHandle name, Handle loader) { | |
286 return hash_to_index(compute_hash(name, loader)); | |
287 } | |
288 }; | |
1972 | 289 |
290 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP |