1 /*
2 * Copyright (c) 1997, 2019, 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.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 "gc/shared/oopStorage.inline.hpp"
33 #include "logging/log.hpp"
34 #include "logging/logStream.hpp"
35 #include "memory/allocation.inline.hpp"
36 #include "memory/filemap.hpp"
37 #include "memory/heapShared.inline.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.hpp"
40 #include "oops/access.inline.hpp"
41 #include "oops/compressedOops.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "oops/typeArrayOop.inline.hpp"
44 #include "oops/weakHandle.inline.hpp"
45 #include "runtime/atomic.hpp"
46 #include "runtime/handles.inline.hpp"
47 #include "runtime/mutexLocker.hpp"
48 #include "runtime/safepointVerifiers.hpp"
49 #include "runtime/timerTrace.hpp"
50 #include "runtime/interfaceSupport.inline.hpp"
51 #include "services/diagnosticCommand.hpp"
52 #include "utilities/concurrentHashTable.inline.hpp"
53 #include "utilities/concurrentHashTableTasks.inline.hpp"
54 #include "utilities/macros.hpp"
55 #include "utilities/utf8.hpp"
56
57 // We prefer short chains of avg 2
58 const double PREF_AVG_LIST_LEN = 2.0;
59 // 2^24 is max size
60 const size_t END_SIZE = 24;
61 // If a chain gets to 100 something might be wrong
62 const size_t REHASH_LEN = 100;
63 // If we have as many dead items as 50% of the number of bucket
64 const double CLEAN_DEAD_HIGH_WATER_MARK = 0.5;
65
66 #if INCLUDE_CDS_JAVA_HEAP
67 inline oop read_string_from_compact_hashtable(address base_address, u4 offset) {
68 assert(sizeof(narrowOop) == sizeof(offset), "must be");
69 narrowOop v = (narrowOop)offset;
70 return HeapShared::decode_from_archive(v);
71 }
72
73 static CompactHashtable<
74 const jchar*, oop,
75 read_string_from_compact_hashtable,
76 java_lang_String::equals
77 > _shared_table;
78 #endif
79
80 // --------------------------------------------------------------------------
81
82 typedef ConcurrentHashTable<StringTableConfig, mtSymbol> StringTableHash;
83 static StringTableHash* _local_table = NULL;
84
85 volatile bool StringTable::_has_work = false;
86 volatile bool StringTable::_needs_rehashing = false;
87
88 volatile size_t StringTable::_uncleaned_items_count = 0;
89 OopStorage* StringTable::_weak_handles = NULL;
90
91 static size_t _current_size = 0;
92 static volatile size_t _items_count = 0;
93
94 volatile bool _alt_hash = false;
95 static juint murmur_seed = 0;
96
97 uintx hash_string(const jchar* s, int len, bool useAlt) {
98 return useAlt ?
99 AltHashing::murmur3_32(murmur_seed, s, len) :
100 java_lang_String::hash_code(s, len);
101 }
102
103 class StringTableConfig : public StackObj {
104 private:
105 public:
106 typedef WeakHandle<vm_string_table_data> Value;
107
108 static uintx get_hash(Value const& value, bool* is_dead) {
109 EXCEPTION_MARK;
110 oop val_oop = value.peek();
111 if (val_oop == NULL) {
112 *is_dead = true;
113 return 0;
114 }
115 *is_dead = false;
116 ResourceMark rm(THREAD);
117 // All String oops are hashed as unicode
118 int length;
119 jchar* chars = java_lang_String::as_unicode_string(val_oop, length, THREAD);
120 if (chars != NULL) {
121 return hash_string(chars, length, _alt_hash);
122 }
123 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "get hash from oop");
124 return 0;
125 }
126 // We use default allocation/deallocation but counted
127 static void* allocate_node(size_t size, Value const& value) {
128 StringTable::item_added();
129 return AllocateHeap(size, mtSymbol);
130 }
131 static void free_node(void* memory, Value const& value) {
132 value.release();
133 FreeHeap(memory);
134 StringTable::item_removed();
135 }
136 };
137
138 class StringTableLookupJchar : StackObj {
139 private:
140 Thread* _thread;
141 uintx _hash;
142 int _len;
143 const jchar* _str;
144 Handle _found;
145
146 public:
147 StringTableLookupJchar(Thread* thread, uintx hash, const jchar* key, int len)
148 : _thread(thread), _hash(hash), _len(len), _str(key) {
149 }
150 uintx get_hash() const {
151 return _hash;
152 }
153 bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) {
154 oop val_oop = value->peek();
155 if (val_oop == NULL) {
156 // dead oop, mark this hash dead for cleaning
157 *is_dead = true;
158 return false;
159 }
160 bool equals = java_lang_String::equals(val_oop, _str, _len);
161 if (!equals) {
162 return false;
163 }
164 // Need to resolve weak handle and Handleize through possible safepoint.
165 _found = Handle(_thread, value->resolve());
166 return true;
167 }
168 };
169
170 class StringTableLookupOop : public StackObj {
171 private:
172 Thread* _thread;
173 uintx _hash;
174 Handle _find;
175 Handle _found; // Might be a different oop with the same value that's already
176 // in the table, which is the point.
177 public:
178 StringTableLookupOop(Thread* thread, uintx hash, Handle handle)
179 : _thread(thread), _hash(hash), _find(handle) { }
180
181 uintx get_hash() const {
182 return _hash;
183 }
184
185 bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) {
186 oop val_oop = value->peek();
187 if (val_oop == NULL) {
188 // dead oop, mark this hash dead for cleaning
189 *is_dead = true;
190 return false;
191 }
192 bool equals = java_lang_String::equals(_find(), val_oop);
193 if (!equals) {
194 return false;
195 }
196 // Need to resolve weak handle and Handleize through possible safepoint.
197 _found = Handle(_thread, value->resolve());
198 return true;
199 }
200 };
201
202 static size_t ceil_log2(size_t val) {
203 size_t ret;
204 for (ret = 1; ((size_t)1 << ret) < val; ++ret);
205 return ret;
206 }
207
208 void StringTable::create_table() {
209 _weak_handles = new OopStorage("StringTable weak",
210 StringTableWeakAlloc_lock,
211 StringTableWeakActive_lock);
212 size_t start_size_log_2 = ceil_log2(StringTableSize);
213 _current_size = ((size_t)1) << start_size_log_2;
214 log_trace(stringtable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
215 _current_size, start_size_log_2);
216 _local_table = new StringTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
217 }
218
219 size_t StringTable::item_added() {
220 return Atomic::add((size_t)1, &_items_count);
221 }
222
223 size_t StringTable::add_items_to_clean(size_t ndead) {
224 size_t total = Atomic::add((size_t)ndead, &_uncleaned_items_count);
225 log_trace(stringtable)(
226 "Uncleaned items:" SIZE_FORMAT " added: " SIZE_FORMAT " total:" SIZE_FORMAT,
227 _uncleaned_items_count, ndead, total);
228 return total;
229 }
230
231 void StringTable::item_removed() {
232 Atomic::add((size_t)-1, &_items_count);
233 }
234
235 double StringTable::get_load_factor() {
236 return (double)_items_count/_current_size;
237 }
238
239 double StringTable::get_dead_factor() {
240 return (double)_uncleaned_items_count/_current_size;
241 }
242
243 size_t StringTable::table_size() {
244 return ((size_t)1) << _local_table->get_size_log2(Thread::current());
245 }
246
247 void StringTable::trigger_concurrent_work() {
248 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
249 _has_work = true;
250 Service_lock->notify_all();
251 }
252
253 // Probing
254 oop StringTable::lookup(Symbol* symbol) {
255 ResourceMark rm;
256 int length;
257 jchar* chars = symbol->as_unicode(length);
258 return lookup(chars, length);
259 }
260
261 oop StringTable::lookup(const jchar* name, int len) {
262 unsigned int hash = java_lang_String::hash_code(name, len);
263 oop string = lookup_shared(name, len, hash);
264 if (string != NULL) {
265 return string;
266 }
267 if (_alt_hash) {
268 hash = hash_string(name, len, true);
269 }
270 return do_lookup(name, len, hash);
271 }
272
273 class StringTableGet : public StackObj {
274 Thread* _thread;
275 Handle _return;
276 public:
277 StringTableGet(Thread* thread) : _thread(thread) {}
278 void operator()(WeakHandle<vm_string_table_data>* val) {
279 oop result = val->resolve();
280 assert(result != NULL, "Result should be reachable");
281 _return = Handle(_thread, result);
282 }
283 oop get_res_oop() {
284 return _return();
285 }
286 };
287
288 oop StringTable::do_lookup(const jchar* name, int len, uintx hash) {
289 Thread* thread = Thread::current();
290 StringTableLookupJchar lookup(thread, hash, name, len);
291 StringTableGet stg(thread);
292 bool rehash_warning;
293 _local_table->get(thread, lookup, stg, &rehash_warning);
294 update_needs_rehash(rehash_warning);
295 return stg.get_res_oop();
296 }
297
298 // Interning
299 oop StringTable::intern(Symbol* symbol, TRAPS) {
300 if (symbol == NULL) return NULL;
301 ResourceMark rm(THREAD);
302 int length;
303 jchar* chars = symbol->as_unicode(length);
304 Handle string;
305 oop result = intern(string, chars, length, CHECK_NULL);
306 return result;
307 }
308
309 oop StringTable::intern(oop string, TRAPS) {
310 if (string == NULL) return NULL;
311 ResourceMark rm(THREAD);
312 int length;
313 Handle h_string (THREAD, string);
314 jchar* chars = java_lang_String::as_unicode_string(string, length,
315 CHECK_NULL);
316 oop result = intern(h_string, chars, length, CHECK_NULL);
317 return result;
318 }
319
320 oop StringTable::intern(const char* utf8_string, TRAPS) {
321 if (utf8_string == NULL) return NULL;
322 ResourceMark rm(THREAD);
323 int length = UTF8::unicode_length(utf8_string);
324 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
325 UTF8::convert_to_unicode(utf8_string, chars, length);
326 Handle string;
327 oop result = intern(string, chars, length, CHECK_NULL);
328 return result;
329 }
330
331 oop StringTable::intern(Handle string_or_null_h, const jchar* name, int len, TRAPS) {
332 // shared table always uses java_lang_String::hash_code
333 unsigned int hash = java_lang_String::hash_code(name, len);
334 oop found_string = lookup_shared(name, len, hash);
335 if (found_string != NULL) {
336 return found_string;
337 }
338 if (_alt_hash) {
339 hash = hash_string(name, len, true);
340 }
341 found_string = do_lookup(name, len, hash);
342 if (found_string != NULL) {
343 return found_string;
344 }
345 return do_intern(string_or_null_h, name, len, hash, THREAD);
346 }
347
348 oop StringTable::do_intern(Handle string_or_null_h, const jchar* name,
349 int len, uintx hash, TRAPS) {
350 HandleMark hm(THREAD); // cleanup strings created
351 Handle string_h;
352
353 if (!string_or_null_h.is_null()) {
354 string_h = string_or_null_h;
355 } else {
356 string_h = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
357 }
358
359 // Deduplicate the string before it is interned. Note that we should never
360 // deduplicate a string after it has been interned. Doing so will counteract
361 // compiler optimizations done on e.g. interned string literals.
362 Universe::heap()->deduplicate_string(string_h());
363
364 assert(java_lang_String::equals(string_h(), name, len),
365 "string must be properly initialized");
366 assert(len == java_lang_String::length(string_h()), "Must be same length");
367
368 StringTableLookupOop lookup(THREAD, hash, string_h);
369 StringTableGet stg(THREAD);
370
371 bool rehash_warning;
372 do {
373 // Callers have already looked up the String using the jchar* name, so just go to add.
374 WeakHandle<vm_string_table_data> wh = WeakHandle<vm_string_table_data>::create(string_h);
375 // The hash table takes ownership of the WeakHandle, even if it's not inserted.
376 if (_local_table->insert(THREAD, lookup, wh, &rehash_warning)) {
377 update_needs_rehash(rehash_warning);
378 return wh.resolve();
379 }
380 // In case another thread did a concurrent add, return value already in the table.
381 // This could fail if the String got gc'ed concurrently, so loop back until success.
382 if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) {
383 update_needs_rehash(rehash_warning);
384 return stg.get_res_oop();
385 }
386 } while(true);
387 }
388
389 void StringTable::oops_do(OopClosure* f) {
390 assert(f != NULL, "No closure");
391 _weak_handles->oops_do(f);
392 }
393
394 // Concurrent work
395 void StringTable::grow(JavaThread* jt) {
396 StringTableHash::GrowTask gt(_local_table);
397 if (!gt.prepare(jt)) {
398 return;
399 }
400 log_trace(stringtable)("Started to grow");
401 {
402 TraceTime timer("Grow", TRACETIME_LOG(Debug, stringtable, perf));
403 while (gt.do_task(jt)) {
404 gt.pause(jt);
405 {
406 ThreadBlockInVM tbivm(jt);
407 }
408 gt.cont(jt);
409 }
410 }
411 gt.done(jt);
412 _current_size = table_size();
413 log_debug(stringtable)("Grown to size:" SIZE_FORMAT, _current_size);
414 }
415
416 struct StringTableDoDelete : StackObj {
417 void operator()(WeakHandle<vm_string_table_data>* val) {
418 /* do nothing */
419 }
420 };
421
422 struct StringTableDeleteCheck : StackObj {
423 long _count;
424 long _item;
425 StringTableDeleteCheck() : _count(0), _item(0) {}
426 bool operator()(WeakHandle<vm_string_table_data>* val) {
427 ++_item;
428 oop tmp = val->peek();
429 if (tmp == NULL) {
430 ++_count;
431 return true;
432 } else {
433 return false;
434 }
435 }
436 };
437
438 void StringTable::clean_dead_entries(JavaThread* jt) {
439 StringTableHash::BulkDeleteTask bdt(_local_table);
440 if (!bdt.prepare(jt)) {
441 return;
442 }
443
444 StringTableDeleteCheck stdc;
445 StringTableDoDelete stdd;
446 {
447 TraceTime timer("Clean", TRACETIME_LOG(Debug, stringtable, perf));
448 while(bdt.do_task(jt, stdc, stdd)) {
449 bdt.pause(jt);
450 {
451 ThreadBlockInVM tbivm(jt);
452 }
453 bdt.cont(jt);
454 }
455 bdt.done(jt);
456 }
457 log_debug(stringtable)("Cleaned %ld of %ld", stdc._count, stdc._item);
458 }
459
460 void StringTable::check_concurrent_work() {
461 if (_has_work) {
462 return;
463 }
464
465 double load_factor = StringTable::get_load_factor();
466 double dead_factor = StringTable::get_dead_factor();
467 // We should clean/resize if we have more dead than alive,
468 // more items than preferred load factor or
469 // more dead items than water mark.
470 if ((dead_factor > load_factor) ||
471 (load_factor > PREF_AVG_LIST_LEN) ||
472 (dead_factor > CLEAN_DEAD_HIGH_WATER_MARK)) {
473 log_debug(stringtable)("Concurrent work triggered, live factor: %g dead factor: %g",
474 load_factor, dead_factor);
475 trigger_concurrent_work();
476 }
477 }
478
479 void StringTable::do_concurrent_work(JavaThread* jt) {
480 _has_work = false;
481 double load_factor = get_load_factor();
482 log_debug(stringtable, perf)("Concurrent work, live factor: %g", load_factor);
483 // We prefer growing, since that also removes dead items
484 if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
485 grow(jt);
486 } else {
487 clean_dead_entries(jt);
488 }
489 }
490
491 // Rehash
492 bool StringTable::do_rehash() {
493 if (!_local_table->is_safepoint_safe()) {
494 return false;
495 }
496
497 // We use current size, not max size.
498 size_t new_size = _local_table->get_size_log2(Thread::current());
499 StringTableHash* new_table = new StringTableHash(new_size, END_SIZE, REHASH_LEN);
500 // Use alt hash from now on
501 _alt_hash = true;
502 if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {
503 _alt_hash = false;
504 delete new_table;
505 return false;
506 }
507
508 // free old table
509 delete _local_table;
510 _local_table = new_table;
511
512 return true;
513 }
514
515 void StringTable::rehash_table() {
516 static bool rehashed = false;
517 log_debug(stringtable)("Table imbalanced, rehashing called.");
518
519 // Grow instead of rehash.
520 if (get_load_factor() > PREF_AVG_LIST_LEN &&
521 !_local_table->is_max_size_reached()) {
522 log_debug(stringtable)("Choosing growing over rehashing.");
523 trigger_concurrent_work();
524 _needs_rehashing = false;
525 return;
526 }
527 // Already rehashed.
528 if (rehashed) {
529 log_warning(stringtable)("Rehashing already done, still long lists.");
530 trigger_concurrent_work();
531 _needs_rehashing = false;
532 return;
533 }
534
535 murmur_seed = AltHashing::compute_seed();
536 {
537 if (do_rehash()) {
538 rehashed = true;
539 } else {
540 log_info(stringtable)("Resizes in progress rehashing skipped.");
541 }
542 }
543 _needs_rehashing = false;
544 }
545
546 // Statistics
547 static int literal_size(oop obj) {
548 // NOTE: this would over-count if (pre-JDK8)
549 // java_lang_Class::has_offset_field() is true and the String.value array is
550 // shared by several Strings. However, starting from JDK8, the String.value
551 // array is not shared anymore.
552 if (obj == NULL) {
553 return 0;
554 } else if (obj->klass() == SystemDictionary::String_klass()) {
555 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize;
556 } else {
557 return obj->size();
558 }
559 }
560
561 struct SizeFunc : StackObj {
562 size_t operator()(WeakHandle<vm_string_table_data>* val) {
563 oop s = val->peek();
564 if (s == NULL) {
565 // Dead
566 return 0;
567 }
568 return literal_size(s);
569 };
570 };
571
572 TableStatistics StringTable::get_table_statistics() {
573 static TableStatistics ts;
574 SizeFunc sz;
575 ts = _local_table->statistics_get(Thread::current(), sz, ts);
576 return ts;
577 }
578
579 void StringTable::print_table_statistics(outputStream* st,
580 const char* table_name) {
581 SizeFunc sz;
582 _local_table->statistics_to(Thread::current(), sz, st, table_name);
583 }
584
585 // Verification
586 class VerifyStrings : StackObj {
587 public:
588 bool operator()(WeakHandle<vm_string_table_data>* val) {
589 oop s = val->peek();
590 if (s != NULL) {
591 assert(java_lang_String::length(s) >= 0, "Length on string must work.");
592 }
593 return true;
594 };
595 };
596
597 // This verification is part of Universe::verify() and needs to be quick.
598 void StringTable::verify() {
599 Thread* thr = Thread::current();
600 VerifyStrings vs;
601 if (!_local_table->try_scan(thr, vs)) {
602 log_info(stringtable)("verify unavailable at this moment");
603 }
604 }
605
606 // Verification and comp
607 class VerifyCompStrings : StackObj {
608 GrowableArray<oop>* _oops;
609 public:
610 size_t _errors;
611 VerifyCompStrings(GrowableArray<oop>* oops) : _oops(oops), _errors(0) {}
612 bool operator()(WeakHandle<vm_string_table_data>* val) {
613 oop s = val->resolve();
614 if (s == NULL) {
615 return true;
616 }
617 int len = _oops->length();
618 for (int i = 0; i < len; i++) {
619 bool eq = java_lang_String::equals(s, _oops->at(i));
620 assert(!eq, "Duplicate strings");
621 if (eq) {
622 _errors++;
623 }
624 }
625 _oops->push(s);
626 return true;
627 };
628 };
629
630 size_t StringTable::verify_and_compare_entries() {
631 Thread* thr = Thread::current();
632 GrowableArray<oop>* oops =
633 new (ResourceObj::C_HEAP, mtInternal)
634 GrowableArray<oop>((int)_current_size, true);
635
636 VerifyCompStrings vcs(oops);
637 if (!_local_table->try_scan(thr, vcs)) {
638 log_info(stringtable)("verify unavailable at this moment");
639 }
640 delete oops;
641 return vcs._errors;
642 }
643
644 // Dumping
645 class PrintString : StackObj {
646 Thread* _thr;
647 outputStream* _st;
648 public:
649 PrintString(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
650 bool operator()(WeakHandle<vm_string_table_data>* val) {
651 oop s = val->peek();
652 if (s == NULL) {
653 return true;
654 }
655 typeArrayOop value = java_lang_String::value_no_keepalive(s);
656 int length = java_lang_String::length(s);
657 bool is_latin1 = java_lang_String::is_latin1(s);
658
659 if (length <= 0) {
660 _st->print("%d: ", length);
661 } else {
662 ResourceMark rm(_thr);
663 int utf8_length = length;
664 char* utf8_string;
665
666 if (!is_latin1) {
667 jchar* chars = value->char_at_addr(0);
668 utf8_string = UNICODE::as_utf8(chars, utf8_length);
669 } else {
670 jbyte* bytes = value->byte_at_addr(0);
671 utf8_string = UNICODE::as_utf8(bytes, utf8_length);
672 }
673
674 _st->print("%d: ", utf8_length);
675 HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
676 }
677 _st->cr();
678 return true;
679 };
680 };
681
682 void StringTable::dump(outputStream* st, bool verbose) {
683 if (!verbose) {
684 print_table_statistics(st, "StringTable");
685 } else {
686 Thread* thr = Thread::current();
687 ResourceMark rm(thr);
688 st->print_cr("VERSION: 1.1");
689 PrintString ps(thr, st);
690 if (!_local_table->try_scan(thr, ps)) {
691 st->print_cr("dump unavailable at this moment");
692 }
693 }
694 }
695
696 // Utility for dumping strings
697 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
698 DCmdWithParser(output, heap),
699 _verbose("-verbose", "Dump the content of each string in the table",
700 "BOOLEAN", false, "false") {
701 _dcmdparser.add_dcmd_option(&_verbose);
702 }
703
704 void StringtableDCmd::execute(DCmdSource source, TRAPS) {
705 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings,
706 _verbose.value());
707 VMThread::execute(&dumper);
708 }
709
710 int StringtableDCmd::num_arguments() {
711 ResourceMark rm;
712 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false);
713 if (dcmd != NULL) {
714 DCmdMark mark(dcmd);
715 return dcmd->_dcmdparser.num_arguments();
716 } else {
717 return 0;
718 }
719 }
720
721 // Sharing
722 #if INCLUDE_CDS_JAVA_HEAP
723 oop StringTable::lookup_shared(const jchar* name, int len, unsigned int hash) {
724 assert(hash == java_lang_String::hash_code(name, len),
725 "hash must be computed using java_lang_String::hash_code");
726 return _shared_table.lookup(name, hash, len);
727 }
728
729 oop StringTable::create_archived_string(oop s, Thread* THREAD) {
730 assert(DumpSharedSpaces, "this function is only used with -Xshare:dump");
731
732 if (HeapShared::is_archived_object(s)) {
733 return s;
734 }
735
736 oop new_s = NULL;
737 typeArrayOop v = java_lang_String::value_no_keepalive(s);
738 typeArrayOop new_v = (typeArrayOop)HeapShared::archive_heap_object(v, THREAD);
739 if (new_v == NULL) {
740 return NULL;
741 }
742 new_s = HeapShared::archive_heap_object(s, THREAD);
743 if (new_s == NULL) {
744 return NULL;
745 }
746
747 // adjust the pointer to the 'value' field in the new String oop
748 java_lang_String::set_value_raw(new_s, new_v);
749 return new_s;
750 }
751
752 struct CopyToArchive : StackObj {
753 CompactHashtableWriter* _writer;
754 CopyToArchive(CompactHashtableWriter* writer) : _writer(writer) {}
755 bool operator()(WeakHandle<vm_string_table_data>* val) {
756 oop s = val->peek();
757 if (s == NULL) {
758 return true;
759 }
760 unsigned int hash = java_lang_String::hash_code(s);
761 oop new_s = StringTable::create_archived_string(s, Thread::current());
762 if (new_s == NULL) {
763 return true;
764 }
765
766 val->replace(new_s);
767 // add to the compact table
768 _writer->add(hash, CompressedOops::encode(new_s));
769 return true;
770 }
771 };
772
773 void StringTable::copy_shared_string_table(CompactHashtableWriter* writer) {
774 assert(HeapShared::is_heap_object_archiving_allowed(), "must be");
775
776 CopyToArchive copy(writer);
777 _local_table->do_safepoint_scan(copy);
778 }
779
780 void StringTable::write_to_archive() {
781 assert(HeapShared::is_heap_object_archiving_allowed(), "must be");
782
783 _shared_table.reset();
784 CompactHashtableWriter writer(_items_count, &MetaspaceShared::stats()->string);
785
786 // Copy the interned strings into the "string space" within the java heap
787 copy_shared_string_table(&writer);
788 writer.dump(&_shared_table, "string");
789 }
790
791 void StringTable::serialize_shared_table_header(SerializeClosure* soc) {
792 _shared_table.serialize_header(soc);
793
794 if (soc->writing()) {
795 // Sanity. Make sure we don't use the shared table at dump time
796 _shared_table.reset();
797 } else if (!HeapShared::closed_archive_heap_region_mapped()) {
798 _shared_table.reset();
799 }
800 }
801
802 class SharedStringIterator {
803 OopClosure* _oop_closure;
804 public:
805 SharedStringIterator(OopClosure* f) : _oop_closure(f) {}
806 void do_value(oop string) {
807 _oop_closure->do_oop(&string);
808 }
809 };
810
811 void StringTable::shared_oops_do(OopClosure* f) {
812 SharedStringIterator iter(f);
813 _shared_table.iterate(&iter);
814 }
815 #endif //INCLUDE_CDS_JAVA_HEAP