       1 /*
       2  * Copyright (c) 1997, 2013, 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 class outputStream;
      44
      45
      46 // Class to hold a newly created or referenced Symbol* temporarily in scope.
      47 // new_symbol() and lookup() will create a Symbol* if not already in the
      48 // symbol table and add to the symbol's reference count.
      49 // probe() and lookup_only() will increment the refcount if symbol is found.
      50 class TempNewSymbol : public StackObj {
      51   Symbol* _temp;
      52
      53  public:
      54   TempNewSymbol() : _temp(NULL) {}
      55   // Creating or looking up a symbol increments the symbol's reference count
      56   TempNewSymbol(Symbol *s) : _temp(s) {}
      57
      58   // Operator= increments reference count.
      59   void operator=(const TempNewSymbol &s) {
      60     //clear();  //FIXME
      61     _temp = s._temp;
      62     if (_temp !=NULL) _temp->increment_refcount();
      63   }
      64
      65   // Decrement reference counter so it can go away if it's unique
      66   void clear() { if (_temp != NULL)  _temp->decrement_refcount();  _temp = NULL; }
      67
      68   ~TempNewSymbol() { clear(); }
      69
      70   // Operators so they can be used like Symbols
      71   Symbol* operator -> () const                   { return _temp; }
      72   bool    operator == (Symbol* o) const          { return _temp == o; }
      73   // Sneaky conversion function
      74   operator Symbol*()                             { return _temp; }
      75 };
      76
      77 class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> {
      78   friend class VMStructs;
      79   friend class ClassFileParser;
      80
      81 private:
      82   // The symbol table
      83   static SymbolTable* _the_table;
      84
      85   // Set if one bucket is out of balance due to hash algorithm deficiency
      86   static bool _needs_rehashing;
      87
      88   // For statistics
      89   static int _symbols_removed;
      90   static int _symbols_counted;
      91
      92   Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
      93
      94   // Adding elements
      95   Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue,
      96                     bool c_heap, TRAPS);
      97   bool basic_add(ClassLoaderData* loader_data,
      98                  constantPoolHandle cp, int names_count,
      99                  const char** names, int* lengths, int* cp_indices,
     100                  unsigned int* hashValues, TRAPS);
     101
     102   static void new_symbols(ClassLoaderData* loader_data,
     103                           constantPoolHandle cp, int names_count,
     104                           const char** name, int* lengths,
     105                           int* cp_indices, unsigned int* hashValues,
     106                           TRAPS) {
     107     add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
     108   }
     109
     110   Symbol* lookup(int index, const char* name, int len, unsigned int hash);
     111
     112   SymbolTable()
     113     : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>))
     114     {
     115 #ifdef PRINT_HASHTABLES_CREATION
     116       fprintf(stderr, "SymbolTable1 %p with size %d\n", this, (int)SymbolTableSize);
     117 #endif
     118     }
     119
     120   SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
     121     : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t,
     122                 number_of_entries)
     123   {
     124 #ifdef PRINT_HASHTABLES_CREATION
     125     fprintf(stderr, "SymbolTable2 %p with size %d\n", this, (int)SymbolTableSize);
     126 #endif
     127   }
     128
     129   // Arena for permanent symbols (null class loader) that are never unloaded
     130   static Arena*  _arena;
     131   static Arena* arena() { return _arena; }  // called for statistics
     132
     133   static void initialize_symbols(int arena_alloc_size = 0);
     134
     135   static volatile int _parallel_claimed_idx;
     136
     137   // Release any dead symbols
     138   static void buckets_unlink(int start_idx, int end_idx, int* processed, int* removed, size_t* memory_total);
     139 public:
     140   enum {
     141     symbol_alloc_batch_size = 8,
     142     // Pick initial size based on java -version size measurements
     143     symbol_alloc_arena_size = 360*K
     144   };
     145
     146   // The symbol table
     147   static SymbolTable* the_table() { return _the_table; }
     148
     149   // Size of one bucket in the string table.  Used when checking for rollover.
     150   static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
     151
     152   static void create_table() {
     153     assert(_the_table == NULL, "One symbol table allowed.");
     154     _the_table = new SymbolTable();
     155     initialize_symbols(symbol_alloc_arena_size);
     156   }
     157
     158   static void create_table(HashtableBucket<mtSymbol>* t, int length,
     159                            int number_of_entries) {
     160     assert(_the_table == NULL, "One symbol table allowed.");
     161
     162     // If CDS archive used a different symbol table size, use that size instead
     163     // which is better than giving an error.
     164     SymbolTableSize = length/bucket_size();
     165
     166     _the_table = new SymbolTable(t, number_of_entries);
     167     // if CDS give symbol table a default arena size since most symbols
     168     // are already allocated in the shared misc section.
     169     initialize_symbols();
     170   }
     171
     172   static unsigned int hash_symbol(const char* s, int len);
     173
     174   static Symbol* lookup(const char* name, int len, TRAPS);
     175   // lookup only, won't add. Also calculate hash.
     176   static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
     177   // Only copy to C string to be added if lookup failed.
     178   static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
     179
     180   static void release(Symbol* sym);
     181
     182   // Look up the address of the literal in the SymbolTable for this Symbol*
     183   static Symbol** lookup_symbol_addr(Symbol* sym);
     184
     185   // jchar (utf16) version of lookups
     186   static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
     187   static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
     188
     189   static void add(ClassLoaderData* loader_data,
     190                   constantPoolHandle cp, int names_count,
     191                   const char** names, int* lengths, int* cp_indices,
     192                   unsigned int* hashValues, TRAPS);
     193
     194   // Release any dead symbols
     195   static void unlink() {
     196     int processed = 0;
     197     int removed = 0;
     198     unlink(&processed, &removed);
     199   }
     200   static void unlink(int* processed, int* removed);
     201   // Release any dead symbols, possibly parallel version
     202   static void possibly_parallel_unlink(int* processed, int* removed);
     203
     204   // iterate over symbols
     205   static void symbols_do(SymbolClosure *cl);
     206
     207   // Symbol creation
     208   static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
     209     assert(utf8_buffer != NULL, "just checking");
     210     return lookup(utf8_buffer, length, THREAD);
     211   }
     212   static Symbol*       new_symbol(const char* name, TRAPS) {
     213     return new_symbol(name, (int)strlen(name), THREAD);
     214   }
     215   static Symbol*       new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
     216     assert(begin <= end && end <= sym->utf8_length(), "just checking");
     217     return lookup(sym, begin, end, THREAD);
     218   }
     219
     220   // Create a symbol in the arena for symbols that are not deleted
     221   static Symbol* new_permanent_symbol(const char* name, TRAPS);
     222
     223   // Symbol lookup
     224   static Symbol* lookup(int index, const char* name, int len, TRAPS);
     225
     226   // Needed for preloading classes in signatures when compiling.
     227   // Returns the symbol is already present in symbol table, otherwise
     228   // NULL.  NO ALLOCATION IS GUARANTEED!
     229   static Symbol* probe(const char* name, int len) {
     230     unsigned int ignore_hash;
     231     return lookup_only(name, len, ignore_hash);
     232   }
     233   static Symbol* probe_unicode(const jchar* name, int len) {
     234     unsigned int ignore_hash;
     235     return lookup_only_unicode(name, len, ignore_hash);
     236   }
     237
     238   // Histogram
     239   static void print_histogram()     PRODUCT_RETURN;
     240   static void print()     PRODUCT_RETURN;
     241
     242   // Debugging
     243   static void verify();
     244
     245   // Sharing
     246   static void copy_buckets(char** top, char*end) {
     247     the_table()->Hashtable<Symbol*, mtSymbol>::copy_buckets(top, end);
     248   }
     249   static void copy_table(char** top, char*end) {
     250     the_table()->Hashtable<Symbol*, mtSymbol>::copy_table(top, end);
     251   }
     252   static void reverse(void* boundary = NULL) {
     253     the_table()->Hashtable<Symbol*, mtSymbol>::reverse(boundary);
     254   }
     255
     256   // Rehash the symbol table if it gets out of balance
     257   static void rehash_table();
     258   static bool needs_rehashing()         { return _needs_rehashing; }
     259   // Parallel chunked scanning
     260   static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
     261   static int parallel_claimed_index()        { return _parallel_claimed_idx; }
     262 };
     263
     264 class StringTable : public RehashableHashtable<oop, mtSymbol> {
     265   friend class VMStructs;
     266
     267 private:
     268   // The string table
     269   static StringTable* _the_table;
     270
     271   // Set if one bucket is out of balance due to hash algorithm deficiency
     272   static bool _needs_rehashing;
     273
     274   // Claimed high water mark for parallel chunked scanning
     275   static volatile int _parallel_claimed_idx;
     276
     277   static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
     278   oop basic_add(int index, Handle string_or_null, jchar* name, int len,
     279                 unsigned int hashValue, TRAPS);
     280
     281   oop lookup(int index, jchar* chars, int length, unsigned int hashValue);
     282
     283   // Apply the give oop closure to the entries to the buckets
     284   // in the range [start_idx, end_idx).
     285   static void buckets_oops_do(OopClosure* f, int start_idx, int end_idx);
     286   // Unlink or apply the give oop closure to the entries to the buckets
     287   // in the range [start_idx, end_idx).
     288   static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed);
     289
     290   StringTable() : RehashableHashtable<oop, mtSymbol>((int)StringTableSize,
     291                               sizeof (HashtableEntry<oop, mtSymbol>))
     292   {
     293 #ifdef PRINT_HASHTABLES_CREATION
     294     fprintf(stderr, "StringTable1 %p with size %d\n", this, (int)StringTableSize);
     295 #endif
     296   }
     297
     298   StringTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
     299     : RehashableHashtable<oop, mtSymbol>((int)StringTableSize, sizeof (HashtableEntry<oop, mtSymbol>), t,
     300                      number_of_entries)
     301   {
     302 #ifdef PRINT_HASHTABLES_CREATION
     303   fprintf(stderr, "StringTable2 %p with size %d\n", this, (int)StringTableSize);
     304 #endif
     305   }
     306
     307 public:
     308   // The string table
     309   static StringTable* the_table() { return _the_table; }
     310
     311   // Size of one bucket in the string table.  Used when checking for rollover.
     312   static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
     313
     314   static void create_table() {
     315     assert(_the_table == NULL, "One string table allowed.");
     316     _the_table = new StringTable();
     317   }
     318
     319   // GC support
     320   //   Delete pointers to otherwise-unreachable objects.
     321   static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f) {
     322     int processed = 0;
     323     int removed = 0;
     324     unlink_or_oops_do(cl, f, &processed, &removed);
     325   }
     326   static void unlink(BoolObjectClosure* cl) {
     327     int processed = 0;
     328     int removed = 0;
     329     unlink_or_oops_do(cl, NULL, &processed, &removed);
     330   }
     331   static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
     332   static void unlink(BoolObjectClosure* cl, int* processed, int* removed) {
     333     unlink_or_oops_do(cl, NULL, processed, removed);
     334   }
     335   // Serially invoke "f->do_oop" on the locations of all oops in the table.
     336   static void oops_do(OopClosure* f);
     337
     338   // Possibly parallel versions of the above
     339   static void possibly_parallel_unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
     340   static void possibly_parallel_unlink(BoolObjectClosure* cl, int* processed, int* removed) {
     341     possibly_parallel_unlink_or_oops_do(cl, NULL, processed, removed);
     342   }
     343   static void possibly_parallel_oops_do(OopClosure* f);
     344
     345   // Hashing algorithm, used as the hash value used by the
     346   //     StringTable for bucket selection and comparison (stored in the
     347   //     HashtableEntry structures).  This is used in the String.intern() method.
     348   static unsigned int hash_string(const jchar* s, int len);
     349
     350   // Internal test.
     351   static void test_alt_hash() PRODUCT_RETURN;
     352
     353   // Probing
     354   static oop lookup(Symbol* symbol);
     355   static oop lookup(jchar* chars, int length);
     356
     357   // Interning
     358   static oop intern(Symbol* symbol, TRAPS);
     359   static oop intern(oop string, TRAPS);
     360   static oop intern(const char *utf8_string, TRAPS);
     361
     362   // Debugging
     363   static void verify();
     364
     365   enum VerifyMesgModes {
     366     _verify_quietly    = 0,
     367     _verify_with_mesgs = 1
     368   };
     369
     370   enum VerifyRetTypes {
     371     _verify_pass          = 0,
     372     _verify_fail_continue = 1,
     373     _verify_fail_done     = 2
     374   };
     375
     376   static VerifyRetTypes compare_entries(int bkt1, int e_cnt1,
     377                                         HashtableEntry<oop, mtSymbol>* e_ptr1,
     378                                         int bkt2, int e_cnt2,
     379                                         HashtableEntry<oop, mtSymbol>* e_ptr2);
     380   static VerifyRetTypes verify_entry(int bkt, int e_cnt,
     381                                      HashtableEntry<oop, mtSymbol>* e_ptr,
     382                                      VerifyMesgModes mesg_mode);
     383   static int verify_and_compare_entries();
     384
     385   // Sharing
     386   static void copy_buckets(char** top, char*end) {
     387     the_table()->Hashtable<oop, mtSymbol>::copy_buckets(top, end);
     388   }
     389   static void copy_table(char** top, char*end) {
     390     the_table()->Hashtable<oop, mtSymbol>::copy_table(top, end);
     391   }
     392   static void reverse() {
     393     the_table()->Hashtable<oop, mtSymbol>::reverse();
     394   }
     395
     396   // Rehash the symbol table if it gets out of balance
     397   static void rehash_table();
     398   static bool needs_rehashing() { return _needs_rehashing; }
     399
     400   // Parallel chunked scanning
     401   static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
     402   static int parallel_claimed_index() { return _parallel_claimed_idx; }
     403 };
     404 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP