1 /*
2 * Copyright (c) 1997, 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 #include "precompiled.hpp"
26 #include "classfile/altHashing.hpp"
27 #include "classfile/compactHashtable.inline.hpp"
28 #include "classfile/javaClasses.inline.hpp"
29 #include "classfile/stringTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "gc/shared/collectedHeap.hpp"
32 #include "logging/log.hpp"
33 #include "memory/allocation.inline.hpp"
34 #include "memory/filemap.hpp"
35 #include "memory/metaspaceShared.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "memory/universe.hpp"
38 #include "oops/access.inline.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "oops/typeArrayOop.inline.hpp"
41 #include "runtime/atomic.hpp"
42 #include "runtime/handles.inline.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/safepointVerifiers.hpp"
45 #include "services/diagnosticCommand.hpp"
46 #include "utilities/hashtable.inline.hpp"
47 #include "utilities/macros.hpp"
48
49 // the number of buckets a thread claims
50 const int ClaimChunkSize = 32;
51
52 #ifdef ASSERT
53 class StableMemoryChecker : public StackObj {
54 enum { _bufsize = wordSize*4 };
55
56 address _region;
57 jint _size;
58 u1 _save_buf[_bufsize];
59
60 int sample(u1* save_buf) {
61 if (_size <= _bufsize) {
62 memcpy(save_buf, _region, _size);
63 return _size;
64 } else {
65 // copy head and tail
66 memcpy(&save_buf[0], _region, _bufsize/2);
67 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
68 return (_bufsize/2)*2;
69 }
70 }
71
72 public:
73 StableMemoryChecker(const void* region, jint size) {
74 _region = (address) region;
75 _size = size;
76 sample(_save_buf);
77 }
78
79 bool verify() {
80 u1 check_buf[sizeof(_save_buf)];
81 int check_size = sample(check_buf);
82 return (0 == memcmp(_save_buf, check_buf, check_size));
83 }
84
85 void set_region(const void* region) { _region = (address) region; }
86 };
87 #endif
88
89
90 // --------------------------------------------------------------------------
91 StringTable* StringTable::_the_table = NULL;
92 bool StringTable::_shared_string_mapped = false;
93 bool StringTable::_needs_rehashing = false;
94
95 volatile int StringTable::_parallel_claimed_idx = 0;
96
97 CompactHashtable<oop, char> StringTable::_shared_table;
98
99 // Pick hashing algorithm
100 unsigned int StringTable::hash_string(const jchar* s, int len) {
101 return use_alternate_hashcode() ? alt_hash_string(s, len) :
102 java_lang_String::hash_code(s, len);
103 }
104
105 unsigned int StringTable::alt_hash_string(const jchar* s, int len) {
106 return AltHashing::murmur3_32(seed(), s, len);
107 }
108
109 unsigned int StringTable::hash_string(oop string) {
110 EXCEPTION_MARK;
111 if (string == NULL) {
112 return hash_string((jchar*)NULL, 0);
113 }
114 ResourceMark rm(THREAD);
115 // All String oops are hashed as unicode
116 int length;
117 jchar* chars = java_lang_String::as_unicode_string(string, length, THREAD);
118 if (chars != NULL) {
119 return hash_string(chars, length);
120 } else {
121 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification");
122 return 0;
123 }
124 }
125
126 oop StringTable::string_object(HashtableEntry<oop, mtSymbol>* entry) {
127 return RootAccess<ON_PHANTOM_OOP_REF>::oop_load(entry->literal_addr());
128 }
129
130 oop StringTable::string_object_no_keepalive(HashtableEntry<oop, mtSymbol>* entry) {
131 // The AS_NO_KEEPALIVE peeks at the oop without keeping it alive.
132 // This is *very dangerous* in general but is okay in this specific
133 // case. The subsequent oop_load keeps the oop alive if it it matched
134 // the jchar* string.
135 return RootAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(entry->literal_addr());
136 }
137
138 void StringTable::set_string_object(HashtableEntry<oop, mtSymbol>* entry, oop string) {
139 RootAccess<ON_PHANTOM_OOP_REF>::oop_store(entry->literal_addr(), string);
140 }
141
142 oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) {
143 assert(hash == java_lang_String::hash_code(name, len),
144 "hash must be computed using java_lang_String::hash_code");
145 return _shared_table.lookup((const char*)name, hash, len);
146 }
147
148 oop StringTable::lookup_in_main_table(int index, jchar* name,
149 int len, unsigned int hash) {
150 int count = 0;
151 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
152 count++;
153 if (l->hash() == hash) {
154 if (java_lang_String::equals(string_object_no_keepalive(l), name, len)) {
155 // We must perform a new load with string_object() that keeps the string
156 // alive as we must expose the oop as strongly reachable when exiting
157 // this context, in case the oop gets published.
158 return string_object(l);
159 }
160 }
161 }
162 // If the bucket size is too deep check if this hash code is insufficient.
163 if (count >= rehash_count && !needs_rehashing()) {
164 _needs_rehashing = check_rehash_table(count);
165 }
166 return NULL;
167 }
168
169
170 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
171 int len, unsigned int hashValue_arg, TRAPS) {
172
173 assert(java_lang_String::equals(string(), name, len),
174 "string must be properly initialized");
175 // Cannot hit a safepoint in this function because the "this" pointer can move.
176 NoSafepointVerifier nsv;
177
178 // Check if the symbol table has been rehashed, if so, need to recalculate
179 // the hash value and index before second lookup.
180 unsigned int hashValue;
181 int index;
182 if (use_alternate_hashcode()) {
183 hashValue = alt_hash_string(name, len);
184 index = hash_to_index(hashValue);
185 } else {
186 hashValue = hashValue_arg;
187 index = index_arg;
188 }
189
190 // Since look-up was done lock-free, we need to check if another
191 // thread beat us in the race to insert the symbol.
192
193 // No need to lookup the shared table from here since the caller (intern()) already did
194 oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int)
195 if (test != NULL) {
196 // Entry already added
197 return test;
198 }
199
200 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
201 add_entry(index, entry);
202 return string();
203 }
204
205
206 oop StringTable::lookup(Symbol* symbol) {
207 ResourceMark rm;
208 int length;
209 jchar* chars = symbol->as_unicode(length);
210 return lookup(chars, length);
211 }
212
213 oop StringTable::lookup(jchar* name, int len) {
214 // shared table always uses java_lang_String::hash_code
215 unsigned int hash = java_lang_String::hash_code(name, len);
216 oop string = lookup_shared(name, len, hash);
217 if (string != NULL) {
218 return string;
219 }
220 if (use_alternate_hashcode()) {
221 hash = alt_hash_string(name, len);
222 }
223 int index = the_table()->hash_to_index(hash);
224 string = the_table()->lookup_in_main_table(index, name, len, hash);
225
226 return string;
227 }
228
229 oop StringTable::intern(Handle string_or_null, jchar* name,
230 int len, TRAPS) {
231 // shared table always uses java_lang_String::hash_code
232 unsigned int hashValue = java_lang_String::hash_code(name, len);
233 oop found_string = lookup_shared(name, len, hashValue);
234 if (found_string != NULL) {
235 return found_string;
236 }
237 if (use_alternate_hashcode()) {
238 hashValue = alt_hash_string(name, len);
239 }
240 int index = the_table()->hash_to_index(hashValue);
241 found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);
242
243 // Found
244 if (found_string != NULL) {
245 return found_string;
246 }
247
248 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
249 assert(!Universe::heap()->is_in_reserved(name),
250 "proposed name of symbol must be stable");
251
252 HandleMark hm(THREAD); // cleanup strings created
253 Handle string;
254 // try to reuse the string if possible
255 if (!string_or_null.is_null()) {
256 string = string_or_null;
257 } else {
258 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
259 }
260
261 // Deduplicate the string before it is interned. Note that we should never
262 // deduplicate a string after it has been interned. Doing so will counteract
263 // compiler optimizations done on e.g. interned string literals.
264 Universe::heap()->deduplicate_string(string());
265
266 // Grab the StringTable_lock before getting the_table() because it could
267 // change at safepoint.
268 oop added_or_found;
269 {
270 MutexLocker ml(StringTable_lock, THREAD);
271 // Otherwise, add to symbol to table
272 added_or_found = the_table()->basic_add(index, string, name, len,
273 hashValue, CHECK_NULL);
274 }
275
276 return added_or_found;
277 }
278
279 oop StringTable::intern(Symbol* symbol, TRAPS) {
280 if (symbol == NULL) return NULL;
281 ResourceMark rm(THREAD);
282 int length;
283 jchar* chars = symbol->as_unicode(length);
284 Handle string;
285 oop result = intern(string, chars, length, CHECK_NULL);
286 return result;
287 }
288
289
290 oop StringTable::intern(oop string, TRAPS)
291 {
292 if (string == NULL) return NULL;
293 ResourceMark rm(THREAD);
294 int length;
295 Handle h_string (THREAD, string);
296 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
297 oop result = intern(h_string, chars, length, CHECK_NULL);
298 return result;
299 }
300
301
302 oop StringTable::intern(const char* utf8_string, TRAPS) {
303 if (utf8_string == NULL) return NULL;
304 ResourceMark rm(THREAD);
305 int length = UTF8::unicode_length(utf8_string);
306 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
307 UTF8::convert_to_unicode(utf8_string, chars, length);
308 Handle string;
309 oop result = intern(string, chars, length, CHECK_NULL);
310 return result;
311 }
312
313 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
314 BucketUnlinkContext context;
315 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), &context);
316 _the_table->bulk_free_entries(&context);
317 *processed = context._num_processed;
318 *removed = context._num_removed;
319 }
320
321 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
322 // Readers of the table are unlocked, so we should only be removing
323 // entries at a safepoint.
324 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
325 const int limit = the_table()->table_size();
326
327 BucketUnlinkContext context;
328 for (;;) {
329 // Grab next set of buckets to scan
330 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
331 if (start_idx >= limit) {
332 // End of table
333 break;
334 }
335
336 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
337 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, &context);
338 }
339 _the_table->bulk_free_entries(&context);
340 *processed = context._num_processed;
341 *removed = context._num_removed;
342 }
343
344 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
345 const int limit = the_table()->table_size();
346
347 assert(0 <= start_idx && start_idx <= limit,
348 "start_idx (%d) is out of bounds", start_idx);
349 assert(0 <= end_idx && end_idx <= limit,
350 "end_idx (%d) is out of bounds", end_idx);
351 assert(start_idx <= end_idx,
352 "Index ordering: start_idx=%d, end_idx=%d",
353 start_idx, end_idx);
354
355 for (int i = start_idx; i < end_idx; i += 1) {
356 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
357 while (entry != NULL) {
358 assert(!entry->is_shared(), "CDS not used for the StringTable");
359
360 f->do_oop((oop*)entry->literal_addr());
361
362 entry = entry->next();
363 }
364 }
365 }
366
367 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context) {
368 const int limit = the_table()->table_size();
369
370 assert(0 <= start_idx && start_idx <= limit,
371 "start_idx (%d) is out of bounds", start_idx);
372 assert(0 <= end_idx && end_idx <= limit,
373 "end_idx (%d) is out of bounds", end_idx);
374 assert(start_idx <= end_idx,
375 "Index ordering: start_idx=%d, end_idx=%d",
376 start_idx, end_idx);
377
378 for (int i = start_idx; i < end_idx; ++i) {
379 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
380 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
381 while (entry != NULL) {
382 assert(!entry->is_shared(), "CDS not used for the StringTable");
383
384 if (is_alive->do_object_b(string_object_no_keepalive(entry))) {
385 if (f != NULL) {
386 f->do_oop(entry->literal_addr());
387 }
388 p = entry->next_addr();
389 } else {
390 *p = entry->next();
391 context->free_entry(entry);
392 }
393 context->_num_processed++;
394 entry = *p;
395 }
396 }
397 }
398
399 void StringTable::oops_do(OopClosure* f) {
400 buckets_oops_do(f, 0, the_table()->table_size());
401 }
402
403 void StringTable::possibly_parallel_oops_do(OopClosure* f) {
404 const int limit = the_table()->table_size();
405
406 for (;;) {
407 // Grab next set of buckets to scan
408 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
409 if (start_idx >= limit) {
410 // End of table
411 break;
412 }
413
414 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
415 buckets_oops_do(f, start_idx, end_idx);
416 }
417 }
418
419 // This verification is part of Universe::verify() and needs to be quick.
420 // See StringTable::verify_and_compare() below for exhaustive verification.
421 void StringTable::verify() {
422 for (int i = 0; i < the_table()->table_size(); ++i) {
423 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
424 for ( ; p != NULL; p = p->next()) {
425 oop s = string_object_no_keepalive(p);
426 guarantee(s != NULL, "interned string is NULL");
427 unsigned int h = hash_string(s);
428 guarantee(p->hash() == h, "broken hash in string table entry");
429 guarantee(the_table()->hash_to_index(h) == i,
430 "wrong index in string table");
431 }
432 }
433 }
434
435 void StringTable::dump(outputStream* st, bool verbose) {
436 if (!verbose) {
437 the_table()->print_table_statistics(st, "StringTable", string_object_no_keepalive);
438 } else {
439 Thread* THREAD = Thread::current();
440 st->print_cr("VERSION: 1.1");
441 for (int i = 0; i < the_table()->table_size(); ++i) {
442 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
443 for ( ; p != NULL; p = p->next()) {
444 oop s = string_object_no_keepalive(p);
445 typeArrayOop value = java_lang_String::value_no_keepalive(s);
446 int length = java_lang_String::length(s);
447 bool is_latin1 = java_lang_String::is_latin1(s);
448
449 if (length <= 0) {
450 st->print("%d: ", length);
451 } else {
452 ResourceMark rm(THREAD);
453 int utf8_length = length;
454 char* utf8_string;
455
456 if (!is_latin1) {
457 jchar* chars = value->char_at_addr(0);
458 utf8_string = UNICODE::as_utf8(chars, utf8_length);
459 } else {
460 jbyte* bytes = value->byte_at_addr(0);
461 utf8_string = UNICODE::as_utf8(bytes, utf8_length);
462 }
463
464 st->print("%d: ", utf8_length);
465 HashtableTextDump::put_utf8(st, utf8_string, utf8_length);
466 }
467 st->cr();
468 }
469 }
470 }
471 }
472
473 StringTable::VerifyRetTypes StringTable::compare_entries(
474 int bkt1, int e_cnt1,
475 HashtableEntry<oop, mtSymbol>* e_ptr1,
476 int bkt2, int e_cnt2,
477 HashtableEntry<oop, mtSymbol>* e_ptr2) {
478 // These entries are sanity checked by verify_and_compare_entries()
479 // before this function is called.
480 oop str1 = string_object_no_keepalive(e_ptr1);
481 oop str2 = string_object_no_keepalive(e_ptr2);
482
483 if (str1 == str2) {
484 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
485 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
486 p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2);
487 return _verify_fail_continue;
488 }
489
490 if (java_lang_String::equals(str1, str2)) {
491 tty->print_cr("ERROR: identical String values in entry @ "
492 "bucket[%d][%d] and entry @ bucket[%d][%d]",
493 bkt1, e_cnt1, bkt2, e_cnt2);
494 return _verify_fail_continue;
495 }
496
497 return _verify_pass;
498 }
499
500 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
501 HashtableEntry<oop, mtSymbol>* e_ptr,
502 StringTable::VerifyMesgModes mesg_mode) {
503
504 VerifyRetTypes ret = _verify_pass; // be optimistic
505
506 oop str = string_object_no_keepalive(e_ptr);
507 if (str == NULL) {
508 if (mesg_mode == _verify_with_mesgs) {
509 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
510 e_cnt);
511 }
512 // NULL oop means no more verifications are possible
513 return _verify_fail_done;
514 }
515
516 if (str->klass() != SystemDictionary::String_klass()) {
517 if (mesg_mode == _verify_with_mesgs) {
518 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
519 bkt, e_cnt);
520 }
521 // not a String means no more verifications are possible
522 return _verify_fail_done;
523 }
524
525 unsigned int h = hash_string(str);
526 if (e_ptr->hash() != h) {
527 if (mesg_mode == _verify_with_mesgs) {
528 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
529 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
530 }
531 ret = _verify_fail_continue;
532 }
533
534 if (the_table()->hash_to_index(h) != bkt) {
535 if (mesg_mode == _verify_with_mesgs) {
536 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
537 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
538 the_table()->hash_to_index(h));
539 }
540 ret = _verify_fail_continue;
541 }
542
543 return ret;
544 }
545
546 // See StringTable::verify() above for the quick verification that is
547 // part of Universe::verify(). This verification is exhaustive and
548 // reports on every issue that is found. StringTable::verify() only
549 // reports on the first issue that is found.
550 //
551 // StringTable::verify_entry() checks:
552 // - oop value != NULL (same as verify())
553 // - oop value is a String
554 // - hash(String) == hash in entry (same as verify())
555 // - index for hash == index of entry (same as verify())
556 //
557 // StringTable::compare_entries() checks:
558 // - oops are unique across all entries
559 // - String values are unique across all entries
560 //
561 int StringTable::verify_and_compare_entries() {
562 assert(StringTable_lock->is_locked(), "sanity check");
563
564 int fail_cnt = 0;
565
566 // first, verify all the entries individually:
567 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
568 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
569 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
570 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
571 if (ret != _verify_pass) {
572 fail_cnt++;
573 }
574 }
575 }
576
577 // Optimization: if the above check did not find any failures, then
578 // the comparison loop below does not need to call verify_entry()
579 // before calling compare_entries(). If there were failures, then we
580 // have to call verify_entry() to see if the entry can be passed to
581 // compare_entries() safely. When we call verify_entry() in the loop
582 // below, we do so quietly to void duplicate messages and we don't
583 // increment fail_cnt because the failures have already been counted.
584 bool need_entry_verify = (fail_cnt != 0);
585
586 // second, verify all entries relative to each other:
587 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
588 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
589 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
590 if (need_entry_verify) {
591 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
592 _verify_quietly);
593 if (ret == _verify_fail_done) {
594 // cannot use the current entry to compare against other entries
595 continue;
596 }
597 }
598
599 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
600 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
601 int e_cnt2;
602 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
603 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
604 // skip the entries up to and including the one that
605 // we're comparing against
606 continue;
607 }
608
609 if (need_entry_verify) {
610 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
611 _verify_quietly);
612 if (ret == _verify_fail_done) {
613 // cannot compare against this entry
614 continue;
615 }
616 }
617
618 // compare two entries, report and count any failures:
619 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
620 != _verify_pass) {
621 fail_cnt++;
622 }
623 }
624 }
625 }
626 }
627 return fail_cnt;
628 }
629
630 // Create a new table and using alternate hash code, populate the new table
631 // with the existing strings. Set flag to use the alternate hash code afterwards.
632 void StringTable::rehash_table() {
633 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
634 // This should never happen with -Xshare:dump but it might in testing mode.
635 if (DumpSharedSpaces) return;
636 StringTable* new_table = new StringTable();
637
638 // Rehash the table
639 the_table()->move_to(new_table);
640
641 // Delete the table and buckets (entries are reused in new table).
642 delete _the_table;
643 // Don't check if we need rehashing until the table gets unbalanced again.
644 // Then rehash with a new global seed.
645 _needs_rehashing = false;
646 _the_table = new_table;
647 }
648
649 // Utility for dumping strings
650 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
651 DCmdWithParser(output, heap),
652 _verbose("-verbose", "Dump the content of each string in the table",
653 "BOOLEAN", false, "false") {
654 _dcmdparser.add_dcmd_option(&_verbose);
655 }
656
657 void StringtableDCmd::execute(DCmdSource source, TRAPS) {
658 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings,
659 _verbose.value());
660 VMThread::execute(&dumper);
661 }
662
663 int StringtableDCmd::num_arguments() {
664 ResourceMark rm;
665 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false);
666 if (dcmd != NULL) {
667 DCmdMark mark(dcmd);
668 return dcmd->_dcmdparser.num_arguments();
669 } else {
670 return 0;
671 }
672 }
673
674 #if INCLUDE_CDS_JAVA_HEAP
675 // Sharing
676 oop StringTable::create_archived_string(oop s, Thread* THREAD) {
677 assert(DumpSharedSpaces, "this function is only used with -Xshare:dump");
678
679 oop new_s = NULL;
680 typeArrayOop v = java_lang_String::value_no_keepalive(s);
681 typeArrayOop new_v = (typeArrayOop)MetaspaceShared::archive_heap_object(v, THREAD);
682 if (new_v == NULL) {
683 return NULL;
684 }
685 new_s = MetaspaceShared::archive_heap_object(s, THREAD);
686 if (new_s == NULL) {
687 return NULL;
688 }
689
690 // adjust the pointer to the 'value' field in the new String oop
691 java_lang_String::set_value_raw(new_s, new_v);
692 return new_s;
693 }
694
695 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space,
696 CompactStringTableWriter* writer) {
697 assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
698
699 Thread* THREAD = Thread::current();
700 for (int i = 0; i < the_table()->table_size(); ++i) {
701 HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i);
702 for ( ; bucket != NULL; bucket = bucket->next()) {
703 oop s = string_object_no_keepalive(bucket);
704 unsigned int hash = java_lang_String::hash_code(s);
705 if (hash == 0) {
706 continue;
707 }
708
709 java_lang_String::set_hash(s, hash);
710 oop new_s = create_archived_string(s, THREAD);
711 if (new_s == NULL) {
712 continue;
713 }
714
715 // set the archived string in bucket
716 set_string_object(bucket, new_s);
717
718 // add to the compact table
719 writer->add(hash, new_s);
720 }
721 }
722
723 return true;
724 }
725
726 void StringTable::write_to_archive(GrowableArray<MemRegion> *string_space) {
727 assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
728
729 _shared_table.reset();
730 int num_buckets = the_table()->number_of_entries() /
731 SharedSymbolTableBucketSize;
732 // calculation of num_buckets can result in zero buckets, we need at least one
733 CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1,
734 &MetaspaceShared::stats()->string);
735
736 // Copy the interned strings into the "string space" within the java heap
737 if (copy_shared_string(string_space, &writer)) {
738 writer.dump(&_shared_table);
739 }
740 }
741
742 void StringTable::serialize(SerializeClosure* soc) {
743 _shared_table.set_type(CompactHashtable<oop, char>::_string_table);
744 _shared_table.serialize(soc);
745
746 if (soc->writing()) {
747 _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time
748 } else if (!_shared_string_mapped) {
749 _shared_table.reset();
750 }
751 }
752
753 void StringTable::shared_oops_do(OopClosure* f) {
754 _shared_table.oops_do(f);
755 }
756 #endif //INCLUDE_CDS_JAVA_HEAP