1 /*
2 * Copyright (c) 1997, 2010, 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_CLASSFILE_SYMBOLTABLE_HPP
26 #define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
27
28 #include "memory/allocation.inline.hpp"
29 #include "oops/symbol.hpp"
30 #include "utilities/hashtable.hpp"
31
32 // The symbol table holds all Symbol*s and corresponding interned strings.
33 // Symbol*s and literal strings should be canonicalized.
34 //
35 // The interned strings are created lazily.
36 //
37 // It is implemented as an open hash table with a fixed number of buckets.
38 //
39 // %note:
40 // - symbolTableEntrys are allocated in blocks to reduce the space overhead.
41
42 class BoolObjectClosure;
43
44
45 // Class to hold a newly created or referenced Symbol* temporarily in scope.
46 // new_symbol() and lookup() will create a Symbol* if not already in the
47 // symbol table and add to the symbol's reference count.
48 // probe() and lookup_only() will increment the refcount if symbol is found.
49 class TempNewSymbol : public StackObj {
50 Symbol* _temp;
51
52 public:
53 TempNewSymbol() : _temp(NULL) {}
54 // Creating or looking up a symbol increments the symbol's reference count
55 TempNewSymbol(Symbol *s) : _temp(s) {}
56
57 // Operator= increments reference count.
58 void operator=(const TempNewSymbol &s) {
59 _temp = s._temp;
60 if (_temp !=NULL) _temp->increment_refcount();
61 }
62
63 // Decrement reference counter so it can go away if it's unique
64 ~TempNewSymbol() { if (_temp != NULL) _temp->decrement_refcount(); }
65
66 // Operators so they can be used like Symbols
67 Symbol* operator -> () const { return _temp; }
68 bool operator == (Symbol* o) const { return _temp == o; }
69 // Sneaky conversion function
70 operator Symbol*() { return _temp; }
71 };
72
73 class SymbolTable : public Hashtable<Symbol*> {
74 friend class VMStructs;
75 friend class ClassFileParser;
76
77 private:
78 // The symbol table
79 static SymbolTable* _the_table;
80
81 // For statistics
82 static int symbols_removed;
83 static int symbols_counted;
84
85 Symbol* allocate_symbol(const u1* name, int len, TRAPS); // Assumes no characters larger than 0x7F
86 bool allocate_symbols(int names_count, const u1** names, int* lengths, Symbol** syms, TRAPS);
87
88 // Adding elements
89 Symbol* basic_add(int index, u1* name, int len,
90 unsigned int hashValue, TRAPS);
91 bool basic_add(constantPoolHandle cp, int names_count,
92 const char** names, int* lengths, int* cp_indices,
93 unsigned int* hashValues, TRAPS);
94
95 static void new_symbols(constantPoolHandle cp, int names_count,
96 const char** name, int* lengths,
97 int* cp_indices, unsigned int* hashValues,
98 TRAPS) {
99 add(cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
100 }
101
102
103 // Table size
104 enum {
105 symbol_table_size = 20011
106 };
107
108 Symbol* lookup(int index, const char* name, int len, unsigned int hash);
109
110 SymbolTable()
111 : Hashtable<Symbol*>(symbol_table_size, sizeof (HashtableEntry<Symbol*>)) {}
112
113 SymbolTable(HashtableBucket* t, int number_of_entries)
114 : Hashtable<Symbol*>(symbol_table_size, sizeof (HashtableEntry<Symbol*>), t,
115 number_of_entries) {}
116
117
118 public:
119 enum {
120 symbol_alloc_batch_size = 8
121 };
122
123 // The symbol table
124 static SymbolTable* the_table() { return _the_table; }
125
126 static void create_table() {
127 assert(_the_table == NULL, "One symbol table allowed.");
128 _the_table = new SymbolTable();
129 }
130
131 static void create_table(HashtableBucket* t, int length,
132 int number_of_entries) {
133 assert(_the_table == NULL, "One symbol table allowed.");
134 assert(length == symbol_table_size * sizeof(HashtableBucket),
135 "bad shared symbol size.");
136 _the_table = new SymbolTable(t, number_of_entries);
137 }
138
139 static Symbol* lookup(const char* name, int len, TRAPS);
140 // lookup only, won't add. Also calculate hash.
141 static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
142 // Only copy to C string to be added if lookup failed.
143 static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
144
145 static void release(Symbol* sym);
146
147 // jchar (utf16) version of lookups
148 static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
149 static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
150
151 static void add(constantPoolHandle cp, int names_count,
152 const char** names, int* lengths, int* cp_indices,
153 unsigned int* hashValues, TRAPS);
154
155 // Release any dead symbols
156 static void unlink();
157
158 // iterate over symbols
159 static void symbols_do(SymbolClosure *cl);
160
161 // Symbol creation
162 static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
163 assert(utf8_buffer != NULL, "just checking");
164 return lookup(utf8_buffer, length, THREAD);
165 }
166 static Symbol* new_symbol(const char* name, TRAPS) {
167 return new_symbol(name, (int)strlen(name), THREAD);
168 }
169 static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
170 assert(begin <= end && end <= sym->utf8_length(), "just checking");
171 return lookup(sym, begin, end, THREAD);
172 }
173
174 // Symbol lookup
175 static Symbol* lookup(int index, const char* name, int len, TRAPS);
176
177 // Needed for preloading classes in signatures when compiling.
178 // Returns the symbol is already present in symbol table, otherwise
179 // NULL. NO ALLOCATION IS GUARANTEED!
180 static Symbol* probe(const char* name, int len) {
181 unsigned int ignore_hash;
182 return lookup_only(name, len, ignore_hash);
183 }
184 static Symbol* probe_unicode(const jchar* name, int len) {
185 unsigned int ignore_hash;
186 return lookup_only_unicode(name, len, ignore_hash);
187 }
188
189 // Histogram
190 static void print_histogram() PRODUCT_RETURN;
191 static void print() PRODUCT_RETURN;
192
193 // Debugging
194 static void verify();
195
196 // Sharing
197 static void copy_buckets(char** top, char*end) {
198 the_table()->Hashtable<Symbol*>::copy_buckets(top, end);
199 }
200 static void copy_table(char** top, char*end) {
201 the_table()->Hashtable<Symbol*>::copy_table(top, end);
202 }
203 static void reverse(void* boundary = NULL) {
204 the_table()->Hashtable<Symbol*>::reverse(boundary);
205 }
206 };
207
208 class StringTable : public Hashtable<oop> {
209 friend class VMStructs;
210
211 private:
212 // The string table
213 static StringTable* _the_table;
214
215 static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
216 oop basic_add(int index, Handle string_or_null, jchar* name, int len,
217 unsigned int hashValue, TRAPS);
218
219 oop lookup(int index, jchar* chars, int length, unsigned int hashValue);
220
221 StringTable() : Hashtable<oop>((int)StringTableSize,
222 sizeof (HashtableEntry<oop>)) {}
223
224 StringTable(HashtableBucket* t, int number_of_entries)
225 : Hashtable<oop>((int)StringTableSize, sizeof (HashtableEntry<oop>), t,
226 number_of_entries) {}
227
228 public:
229 // The string table
230 static StringTable* the_table() { return _the_table; }
231
232 static void create_table() {
233 assert(_the_table == NULL, "One string table allowed.");
234 _the_table = new StringTable();
235 }
236
237 static void create_table(HashtableBucket* t, int length,
238 int number_of_entries) {
239 assert(_the_table == NULL, "One string table allowed.");
240 assert((size_t)length == StringTableSize * sizeof(HashtableBucket),
241 "bad shared string size.");
242 _the_table = new StringTable(t, number_of_entries);
243 }
244
245 static int hash_string(jchar* s, int len);
246
247 // GC support
248 // Delete pointers to otherwise-unreachable objects.
249 static void unlink(BoolObjectClosure* cl);
250
251 // Invoke "f->do_oop" on the locations of all oops in the table.
252 static void oops_do(OopClosure* f);
253
254 // Probing
255 static oop lookup(Symbol* symbol);
256
257 // Interning
258 static oop intern(Symbol* symbol, TRAPS);
259 static oop intern(oop string, TRAPS);
260 static oop intern(const char *utf8_string, TRAPS);
261
262 // Debugging
263 static void verify();
264
265 // Sharing
266 static void copy_buckets(char** top, char*end) {
267 the_table()->Hashtable<oop>::copy_buckets(top, end);
268 }
269 static void copy_table(char** top, char*end) {
270 the_table()->Hashtable<oop>::copy_table(top, end);
271 }
272 static void reverse() {
273 the_table()->Hashtable<oop>::reverse();
274 }
275 };
276
277 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP