Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/classfile/symbolTable.cpp

src/share/vm/classfile/symbolTable.cpp

changeset 435
a61af66fc99e
child 1040
98cb887364d3
equal deleted inserted replaced
-1:000000000000 435:a61af66fc99e
1 /*
2 * Copyright 1997-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 # include "incls/_precompiled.incl"
26 # include "incls/_symbolTable.cpp.incl"
27
28 // --------------------------------------------------------------------------
29
30 SymbolTable* SymbolTable::_the_table = NULL;
31
32 // Lookup a symbol in a bucket.
33
34 symbolOop SymbolTable::lookup(int index, const char* name,
35 int len, unsigned int hash) {
36 for (HashtableEntry* e = bucket(index); e != NULL; e = e->next()) {
37 if (e->hash() == hash) {
38 symbolOop sym = symbolOop(e->literal());
39 if (sym->equals(name, len)) {
40 return sym;
41 }
42 }
43 }
44 return NULL;
45 }
46
47
48 // We take care not to be blocking while holding the
49 // SymbolTable_lock. Otherwise, the system might deadlock, since the
50 // symboltable is used during compilation (VM_thread) The lock free
51 // synchronization is simplified by the fact that we do not delete
52 // entries in the symbol table during normal execution (only during
53 // safepoints).
54
55 symbolOop SymbolTable::lookup(const char* name, int len, TRAPS) {
56 unsigned int hashValue = hash_symbol(name, len);
57 int index = the_table()->hash_to_index(hashValue);
58
59 symbolOop s = the_table()->lookup(index, name, len, hashValue);
60
61 // Found
62 if (s != NULL) return s;
63
64 // Otherwise, add to symbol to table
65 return the_table()->basic_add(index, (u1*)name, len, hashValue, CHECK_NULL);
66 }
67
68 symbolOop SymbolTable::lookup(symbolHandle sym, int begin, int end, TRAPS) {
69 char* buffer;
70 int index, len;
71 unsigned int hashValue;
72 char* name;
73 {
74 debug_only(No_Safepoint_Verifier nsv;)
75
76 name = (char*)sym->base() + begin;
77 len = end - begin;
78 hashValue = hash_symbol(name, len);
79 index = the_table()->hash_to_index(hashValue);
80 symbolOop s = the_table()->lookup(index, name, len, hashValue);
81
82 // Found
83 if (s != NULL) return s;
84 }
85
86 // Otherwise, add to symbol to table. Copy to a C string first.
87 char stack_buf[128];
88 ResourceMark rm(THREAD);
89 if (len <= 128) {
90 buffer = stack_buf;
91 } else {
92 buffer = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, len);
93 }
94 for (int i=0; i<len; i++) {
95 buffer[i] = name[i];
96 }
97 // Make sure there is no safepoint in the code above since name can't move.
98 // We can't include the code in No_Safepoint_Verifier because of the
99 // ResourceMark.
100
101 return the_table()->basic_add(index, (u1*)buffer, len, hashValue, CHECK_NULL);
102 }
103
104 symbolOop SymbolTable::lookup_only(const char* name, int len,
105 unsigned int& hash) {
106 hash = hash_symbol(name, len);
107 int index = the_table()->hash_to_index(hash);
108
109 return the_table()->lookup(index, name, len, hash);
110 }
111
112 void SymbolTable::add(constantPoolHandle cp, int names_count,
113 const char** names, int* lengths, int* cp_indices,
114 unsigned int* hashValues, TRAPS) {
115 SymbolTable* table = the_table();
116 bool added = table->basic_add(cp, names_count, names, lengths,
117 cp_indices, hashValues, CHECK);
118 if (!added) {
119 // do it the hard way
120 for (int i=0; i<names_count; i++) {
121 int index = table->hash_to_index(hashValues[i]);
122 symbolOop sym = table->basic_add(index, (u1*)names[i], lengths[i],
123 hashValues[i], CHECK);
124 cp->symbol_at_put(cp_indices[i], sym);
125 }
126 }
127 }
128
129 // Needed for preloading classes in signatures when compiling.
130
131 symbolOop SymbolTable::probe(const char* name, int len) {
132 unsigned int hashValue = hash_symbol(name, len);
133 int index = the_table()->hash_to_index(hashValue);
134 return the_table()->lookup(index, name, len, hashValue);
135 }
136
137
138 symbolOop SymbolTable::basic_add(int index, u1 *name, int len,
139 unsigned int hashValue, TRAPS) {
140 assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
141 "proposed name of symbol must be stable");
142
143 // We assume that lookup() has been called already, that it failed,
144 // and symbol was not found. We create the symbol here.
145 symbolKlass* sk = (symbolKlass*) Universe::symbolKlassObj()->klass_part();
146 symbolOop s_oop = sk->allocate_symbol(name, len, CHECK_NULL);
147 symbolHandle sym (THREAD, s_oop);
148
149 // Allocation must be done before grapping the SymbolTable_lock lock
150 MutexLocker ml(SymbolTable_lock, THREAD);
151
152 assert(sym->equals((char*)name, len), "symbol must be properly initialized");
153
154 // Since look-up was done lock-free, we need to check if another
155 // thread beat us in the race to insert the symbol.
156
157 symbolOop test = lookup(index, (char*)name, len, hashValue);
158 if (test != NULL) {
159 // A race occured and another thread introduced the symbol, this one
160 // will be dropped and collected.
161 return test;
162 }
163
164 HashtableEntry* entry = new_entry(hashValue, sym());
165 add_entry(index, entry);
166 return sym();
167 }
168
169 bool SymbolTable::basic_add(constantPoolHandle cp, int names_count,
170 const char** names, int* lengths,
171 int* cp_indices, unsigned int* hashValues,
172 TRAPS) {
173 symbolKlass* sk = (symbolKlass*) Universe::symbolKlassObj()->klass_part();
174 symbolOop sym_oops[symbol_alloc_batch_size];
175 bool allocated = sk->allocate_symbols(names_count, names, lengths,
176 sym_oops, CHECK_false);
177 if (!allocated) {
178 return false;
179 }
180 symbolHandle syms[symbol_alloc_batch_size];
181 int i;
182 for (i=0; i<names_count; i++) {
183 syms[i] = symbolHandle(THREAD, sym_oops[i]);
184 }
185
186 // Allocation must be done before grabbing the SymbolTable_lock lock
187 MutexLocker ml(SymbolTable_lock, THREAD);
188
189 for (i=0; i<names_count; i++) {
190 assert(syms[i]->equals(names[i], lengths[i]), "symbol must be properly initialized");
191 // Since look-up was done lock-free, we need to check if another
192 // thread beat us in the race to insert the symbol.
193 int index = hash_to_index(hashValues[i]);
194 symbolOop test = lookup(index, names[i], lengths[i], hashValues[i]);
195 if (test != NULL) {
196 // A race occured and another thread introduced the symbol, this one
197 // will be dropped and collected. Use test instead.
198 cp->symbol_at_put(cp_indices[i], test);
199 } else {
200 symbolOop sym = syms[i]();
201 HashtableEntry* entry = new_entry(hashValues[i], sym);
202 add_entry(index, entry);
203 cp->symbol_at_put(cp_indices[i], sym);
204 }
205 }
206
207 return true;
208 }
209
210
211 void SymbolTable::verify() {
212 for (int i = 0; i < the_table()->table_size(); ++i) {
213 HashtableEntry* p = the_table()->bucket(i);
214 for ( ; p != NULL; p = p->next()) {
215 symbolOop s = symbolOop(p->literal());
216 guarantee(s != NULL, "symbol is NULL");
217 s->verify();
218 guarantee(s->is_perm(), "symbol not in permspace");
219 unsigned int h = hash_symbol((char*)s->bytes(), s->utf8_length());
220 guarantee(p->hash() == h, "broken hash in symbol table entry");
221 guarantee(the_table()->hash_to_index(h) == i,
222 "wrong index in symbol table");
223 }
224 }
225 }
226
227
228 //---------------------------------------------------------------------------
229 // Non-product code
230
231 #ifndef PRODUCT
232
233 void SymbolTable::print_histogram() {
234 MutexLocker ml(SymbolTable_lock);
235 const int results_length = 100;
236 int results[results_length];
237 int i,j;
238
239 // initialize results to zero
240 for (j = 0; j < results_length; j++) {
241 results[j] = 0;
242 }
243
244 int total = 0;
245 int max_symbols = 0;
246 int out_of_range = 0;
247 for (i = 0; i < the_table()->table_size(); i++) {
248 HashtableEntry* p = the_table()->bucket(i);
249 for ( ; p != NULL; p = p->next()) {
250 int counter = symbolOop(p->literal())->utf8_length();
251 total += counter;
252 if (counter < results_length) {
253 results[counter]++;
254 } else {
255 out_of_range++;
256 }
257 max_symbols = MAX2(max_symbols, counter);
258 }
259 }
260 tty->print_cr("Symbol Table:");
261 tty->print_cr("%8s %5d", "Total ", total);
262 tty->print_cr("%8s %5d", "Maximum", max_symbols);
263 tty->print_cr("%8s %3.2f", "Average",
264 ((float) total / (float) the_table()->table_size()));
265 tty->print_cr("%s", "Histogram:");
266 tty->print_cr(" %s %29s", "Length", "Number chains that length");
267 for (i = 0; i < results_length; i++) {
268 if (results[i] > 0) {
269 tty->print_cr("%6d %10d", i, results[i]);
270 }
271 }
272 int line_length = 70;
273 tty->print_cr("%s %30s", " Length", "Number chains that length");
274 for (i = 0; i < results_length; i++) {
275 if (results[i] > 0) {
276 tty->print("%4d", i);
277 for (j = 0; (j < results[i]) && (j < line_length); j++) {
278 tty->print("%1s", "*");
279 }
280 if (j == line_length) {
281 tty->print("%1s", "+");
282 }
283 tty->cr();
284 }
285 }
286 tty->print_cr(" %s %d: %d\n", "Number chains longer than",
287 results_length, out_of_range);
288 }
289
290 #endif // PRODUCT
291
292 // --------------------------------------------------------------------------
293
294 #ifdef ASSERT
295 class StableMemoryChecker : public StackObj {
296 enum { _bufsize = wordSize*4 };
297
298 address _region;
299 jint _size;
300 u1 _save_buf[_bufsize];
301
302 int sample(u1* save_buf) {
303 if (_size <= _bufsize) {
304 memcpy(save_buf, _region, _size);
305 return _size;
306 } else {
307 // copy head and tail
308 memcpy(&save_buf[0], _region, _bufsize/2);
309 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
310 return (_bufsize/2)*2;
311 }
312 }
313
314 public:
315 StableMemoryChecker(const void* region, jint size) {
316 _region = (address) region;
317 _size = size;
318 sample(_save_buf);
319 }
320
321 bool verify() {
322 u1 check_buf[sizeof(_save_buf)];
323 int check_size = sample(check_buf);
324 return (0 == memcmp(_save_buf, check_buf, check_size));
325 }
326
327 void set_region(const void* region) { _region = (address) region; }
328 };
329 #endif
330
331
332 // --------------------------------------------------------------------------
333
334
335 // Compute the hash value for a java.lang.String object which would
336 // contain the characters passed in. This hash value is used for at
337 // least two purposes.
338 //
339 // (a) As the hash value used by the StringTable for bucket selection
340 // and comparison (stored in the HashtableEntry structures). This
341 // is used in the String.intern() method.
342 //
343 // (b) As the hash value used by the String object itself, in
344 // String.hashCode(). This value is normally calculate in Java code
345 // in the String.hashCode method(), but is precomputed for String
346 // objects in the shared archive file.
347 //
348 // For this reason, THIS ALGORITHM MUST MATCH String.hashCode().
349
350 int StringTable::hash_string(jchar* s, int len) {
351 unsigned h = 0;
352 while (len-- > 0) {
353 h = 31*h + (unsigned) *s;
354 s++;
355 }
356 return h;
357 }
358
359
360 StringTable* StringTable::_the_table = NULL;
361
362 oop StringTable::lookup(int index, jchar* name,
363 int len, unsigned int hash) {
364 for (HashtableEntry* l = bucket(index); l != NULL; l = l->next()) {
365 if (l->hash() == hash) {
366 if (java_lang_String::equals(l->literal(), name, len)) {
367 return l->literal();
368 }
369 }
370 }
371 return NULL;
372 }
373
374
375 oop StringTable::basic_add(int index, Handle string_or_null, jchar* name,
376 int len, unsigned int hashValue, TRAPS) {
377 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
378 assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
379 "proposed name of symbol must be stable");
380
381 Handle string;
382 // try to reuse the string if possible
383 if (!string_or_null.is_null() && string_or_null()->is_perm()) {
384 string = string_or_null;
385 } else {
386 string = java_lang_String::create_tenured_from_unicode(name, len, CHECK_NULL);
387 }
388
389 // Allocation must be done before grapping the SymbolTable_lock lock
390 MutexLocker ml(StringTable_lock, THREAD);
391
392 assert(java_lang_String::equals(string(), name, len),
393 "string must be properly initialized");
394
395 // Since look-up was done lock-free, we need to check if another
396 // thread beat us in the race to insert the symbol.
397
398 oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
399 if (test != NULL) {
400 // Entry already added
401 return test;
402 }
403
404 HashtableEntry* entry = new_entry(hashValue, string());
405 add_entry(index, entry);
406 return string();
407 }
408
409
410 oop StringTable::lookup(symbolOop symbol) {
411 ResourceMark rm;
412 int length;
413 jchar* chars = symbol->as_unicode(length);
414 unsigned int hashValue = hash_string(chars, length);
415 int index = the_table()->hash_to_index(hashValue);
416 return the_table()->lookup(index, chars, length, hashValue);
417 }
418
419
420 oop StringTable::intern(Handle string_or_null, jchar* name,
421 int len, TRAPS) {
422 unsigned int hashValue = hash_string(name, len);
423 int index = the_table()->hash_to_index(hashValue);
424 oop string = the_table()->lookup(index, name, len, hashValue);
425
426 // Found
427 if (string != NULL) return string;
428
429 // Otherwise, add to symbol to table
430 return the_table()->basic_add(index, string_or_null, name, len,
431 hashValue, CHECK_NULL);
432 }
433
434 oop StringTable::intern(symbolOop symbol, TRAPS) {
435 if (symbol == NULL) return NULL;
436 ResourceMark rm(THREAD);
437 int length;
438 jchar* chars = symbol->as_unicode(length);
439 Handle string;
440 oop result = intern(string, chars, length, CHECK_NULL);
441 return result;
442 }
443
444
445 oop StringTable::intern(oop string, TRAPS)
446 {
447 if (string == NULL) return NULL;
448 ResourceMark rm(THREAD);
449 int length;
450 Handle h_string (THREAD, string);
451 jchar* chars = java_lang_String::as_unicode_string(string, length);
452 oop result = intern(h_string, chars, length, CHECK_NULL);
453 return result;
454 }
455
456
457 oop StringTable::intern(const char* utf8_string, TRAPS) {
458 if (utf8_string == NULL) return NULL;
459 ResourceMark rm(THREAD);
460 int length = UTF8::unicode_length(utf8_string);
461 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
462 UTF8::convert_to_unicode(utf8_string, chars, length);
463 Handle string;
464 oop result = intern(string, chars, length, CHECK_NULL);
465 return result;
466 }
467
468 void StringTable::verify() {
469 for (int i = 0; i < the_table()->table_size(); ++i) {
470 HashtableEntry* p = the_table()->bucket(i);
471 for ( ; p != NULL; p = p->next()) {
472 oop s = p->literal();
473 guarantee(s != NULL, "interned string is NULL");
474 guarantee(s->is_perm(), "interned string not in permspace");
475
476 int length;
477 jchar* chars = java_lang_String::as_unicode_string(s, length);
478 unsigned int h = hash_string(chars, length);
479 guarantee(p->hash() == h, "broken hash in string table entry");
480 guarantee(the_table()->hash_to_index(h) == i,
481 "wrong index in string table");
482 }
483 }
484 }

Mercurial Repository: jdk8-mips64-public/hotspot

mercurial