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 // 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 //clear(); //FIXME 60 _temp = s._temp; 61 if (_temp !=NULL) _temp->increment_refcount(); 62 } 63 64 // Decrement reference counter so it can go away if it's unique 65 void clear() { if (_temp != NULL) _temp->decrement_refcount(); _temp = NULL; } 66 67 ~TempNewSymbol() { clear(); } 68 69 // Operators so they can be used like Symbols 70 Symbol* operator -> () const { return _temp; } 71 bool operator == (Symbol* o) const { return _temp == o; } 72 // Sneaky conversion function 73 operator Symbol*() { return _temp; } 74 }; 75 76 class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> { 77 friend class VMStructs; 78 friend class ClassFileParser; 79 80 private: 81 // The symbol table 82 static SymbolTable* _the_table; 83 84 // Set if one bucket is out of balance due to hash algorithm deficiency 85 static bool _needs_rehashing; 86 87 // For statistics 88 static int _symbols_removed; 89 static int _symbols_counted; 90 91 Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F 92 93 // Adding elements 94 Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue, 95 bool c_heap, TRAPS); 96 bool basic_add(ClassLoaderData* loader_data, 97 constantPoolHandle cp, int names_count, 98 const char** names, int* lengths, int* cp_indices, 99 unsigned int* hashValues, TRAPS); 100 101 static void new_symbols(ClassLoaderData* loader_data, 102 constantPoolHandle cp, int names_count, 103 const char** name, int* lengths, 104 int* cp_indices, unsigned int* hashValues, 105 TRAPS) { 106 add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD); 107 } 108 109 Symbol* lookup(int index, const char* name, int len, unsigned int hash); 110 111 SymbolTable() 112 : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>)) {} 113 114 SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries) 115 : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t, 116 number_of_entries) {} 117 118 // Arena for permanent symbols (null class loader) that are never unloaded 119 static Arena* _arena; 120 static Arena* arena() { return _arena; } // called for statistics 121 122 static void initialize_symbols(int arena_alloc_size = 0); 123 124 static volatile int _parallel_claimed_idx; 125 126 // Release any dead symbols 127 static void buckets_unlink(int start_idx, int end_idx, int* processed, int* removed, size_t* memory_total); 128 public: 129 enum { 130 symbol_alloc_batch_size = 8, 131 // Pick initial size based on java -version size measurements 132 symbol_alloc_arena_size = 360*K 133 }; 134 135 // The symbol table 136 static SymbolTable* the_table() { return _the_table; } 137 138 // Size of one bucket in the string table. Used when checking for rollover. 139 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); } 140 141 static void create_table() { 142 assert(_the_table == NULL, "One symbol table allowed."); 143 _the_table = new SymbolTable(); 144 initialize_symbols(symbol_alloc_arena_size); 145 } 146 147 static void create_table(HashtableBucket<mtSymbol>* t, int length, 148 int number_of_entries) { 149 assert(_the_table == NULL, "One symbol table allowed."); 150 151 // If CDS archive used a different symbol table size, use that size instead 152 // which is better than giving an error. 153 SymbolTableSize = length/bucket_size(); 154 155 _the_table = new SymbolTable(t, number_of_entries); 156 // if CDS give symbol table a default arena size since most symbols 157 // are already allocated in the shared misc section. 158 initialize_symbols(); 159 } 160 161 static unsigned int hash_symbol(const char* s, int len); 162 163 static Symbol* lookup(const char* name, int len, TRAPS); 164 // lookup only, won't add. Also calculate hash. 165 static Symbol* lookup_only(const char* name, int len, unsigned int& hash); 166 // Only copy to C string to be added if lookup failed. 167 static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS); 168 169 static void release(Symbol* sym); 170 171 // Look up the address of the literal in the SymbolTable for this Symbol* 172 static Symbol** lookup_symbol_addr(Symbol* sym); 173 174 // jchar (utf16) version of lookups 175 static Symbol* lookup_unicode(const jchar* name, int len, TRAPS); 176 static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash); 177 178 static void add(ClassLoaderData* loader_data, 179 constantPoolHandle cp, int names_count, 180 const char** names, int* lengths, int* cp_indices, 181 unsigned int* hashValues, TRAPS); 182 183 // Release any dead symbols 184 static void unlink() { 185 int processed = 0; 186 int removed = 0; 187 unlink(&processed, &removed); 188 } 189 static void unlink(int* processed, int* removed); 190 // Release any dead symbols, possibly parallel version 191 static void possibly_parallel_unlink(int* processed, int* removed); 192 193 // iterate over symbols 194 static void symbols_do(SymbolClosure *cl); 195 196 // Symbol creation 197 static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) { 198 assert(utf8_buffer != NULL, "just checking"); 199 return lookup(utf8_buffer, length, THREAD); 200 } 201 static Symbol* new_symbol(const char* name, TRAPS) { 202 return new_symbol(name, (int)strlen(name), THREAD); 203 } 204 static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) { 205 assert(begin <= end && end <= sym->utf8_length(), "just checking"); 206 return lookup(sym, begin, end, THREAD); 207 } 208 209 // Create a symbol in the arena for symbols that are not deleted 210 static Symbol* new_permanent_symbol(const char* name, TRAPS); 211 212 // Symbol lookup 213 static Symbol* lookup(int index, const char* name, int len, TRAPS); 214 215 // Needed for preloading classes in signatures when compiling. 216 // Returns the symbol is already present in symbol table, otherwise 217 // NULL. NO ALLOCATION IS GUARANTEED! 218 static Symbol* probe(const char* name, int len) { 219 unsigned int ignore_hash; 220 return lookup_only(name, len, ignore_hash); 221 } 222 static Symbol* probe_unicode(const jchar* name, int len) { 223 unsigned int ignore_hash; 224 return lookup_only_unicode(name, len, ignore_hash); 225 } 226 227 // Histogram 228 static void print_histogram() PRODUCT_RETURN; 229 static void print() PRODUCT_RETURN; 230 231 // Debugging 232 static void verify(); 233 static void dump(outputStream* st); 234 235 // Sharing 236 static void copy_buckets(char** top, char*end) { 237 the_table()->Hashtable<Symbol*, mtSymbol>::copy_buckets(top, end); 238 } 239 static void copy_table(char** top, char*end) { 240 the_table()->Hashtable<Symbol*, mtSymbol>::copy_table(top, end); 241 } 242 static void reverse(void* boundary = NULL) { 243 the_table()->Hashtable<Symbol*, mtSymbol>::reverse(boundary); 244 } 245 246 // Rehash the symbol table if it gets out of balance 247 static void rehash_table(); 248 static bool needs_rehashing() { return _needs_rehashing; } 249 // Parallel chunked scanning 250 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; } 251 static int parallel_claimed_index() { return _parallel_claimed_idx; } 252 }; 253 254 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP