| /* |
| * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #ifndef SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP |
| #define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP |
| |
| #include "memory/allocation.inline.hpp" |
| #include "oops/symbol.hpp" |
| #include "utilities/hashtable.hpp" |
| |
| // The symbol table holds all Symbol*s and corresponding interned strings. |
| // Symbol*s and literal strings should be canonicalized. |
| // |
| // The interned strings are created lazily. |
| // |
| // It is implemented as an open hash table with a fixed number of buckets. |
| // |
| // %note: |
| // - symbolTableEntrys are allocated in blocks to reduce the space overhead. |
| |
| class BoolObjectClosure; |
| class outputStream; |
| class SerializeClosure; |
| |
| // TempNewSymbol acts as a handle class in a handle/body idiom and is |
| // responsible for proper resource management of the body (which is a Symbol*). |
| // The body is resource managed by a reference counting scheme. |
| // TempNewSymbol can therefore be used to properly hold a newly created or referenced |
| // Symbol* temporarily in scope. |
| // |
| // Routines in SymbolTable will initialize the reference count of a Symbol* before |
| // it becomes "managed" by TempNewSymbol instances. As a handle class, TempNewSymbol |
| // needs to maintain proper reference counting in context of copy semantics. |
| // |
| // In SymbolTable, new_symbol() and lookup() will create a Symbol* if not already in the |
| // symbol table and add to the symbol's reference count. |
| // probe() and lookup_only() will increment the refcount if symbol is found. |
| class TempNewSymbol : public StackObj { |
| Symbol* _temp; |
| |
| public: |
| TempNewSymbol() : _temp(NULL) {} |
| |
| // Conversion from a Symbol* to a TempNewSymbol. |
| // Does not increment the current reference count. |
| TempNewSymbol(Symbol *s) : _temp(s) {} |
| |
| // Copy constructor increments reference count. |
| TempNewSymbol(const TempNewSymbol& rhs) : _temp(rhs._temp) { |
| if (_temp != NULL) { |
| _temp->increment_refcount(); |
| } |
| } |
| |
| // Assignment operator uses a c++ trick called copy and swap idiom. |
| // rhs is passed by value so within the scope of this method it is a copy. |
| // At method exit it contains the former value of _temp, triggering the correct refcount |
| // decrement upon destruction. |
| void operator=(TempNewSymbol rhs) { |
| Symbol* tmp = rhs._temp; |
| rhs._temp = _temp; |
| _temp = tmp; |
| } |
| |
| // Decrement reference counter so it can go away if it's unused |
| ~TempNewSymbol() { |
| if (_temp != NULL) { |
| _temp->decrement_refcount(); |
| } |
| } |
| |
| // Symbol* conversion operators |
| Symbol* operator -> () const { return _temp; } |
| bool operator == (Symbol* o) const { return _temp == o; } |
| operator Symbol*() { return _temp; } |
| }; |
| |
| template <class T, class N> class CompactHashtable; |
| |
| class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> { |
| friend class VMStructs; |
| friend class ClassFileParser; |
| |
| private: |
| // The symbol table |
| static SymbolTable* _the_table; |
| |
| // Set if one bucket is out of balance due to hash algorithm deficiency |
| static bool _needs_rehashing; |
| static bool _lookup_shared_first; |
| |
| // For statistics |
| static int _symbols_removed; |
| static int _symbols_counted; |
| |
| // shared symbol table. |
| static CompactHashtable<Symbol*, char> _shared_table; |
| |
| Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F |
| |
| // Adding elements |
| Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue, |
| bool c_heap, TRAPS); |
| bool basic_add(ClassLoaderData* loader_data, |
| const constantPoolHandle& cp, int names_count, |
| const char** names, int* lengths, int* cp_indices, |
| unsigned int* hashValues, TRAPS); |
| |
| static void new_symbols(ClassLoaderData* loader_data, |
| const constantPoolHandle& cp, int names_count, |
| const char** name, int* lengths, |
| int* cp_indices, unsigned int* hashValues, |
| TRAPS) { |
| add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD); |
| } |
| |
| static Symbol* lookup_shared(const char* name, int len, unsigned int hash); |
| Symbol* lookup_dynamic(int index, const char* name, int len, unsigned int hash); |
| Symbol* lookup(int index, const char* name, int len, unsigned int hash); |
| |
| SymbolTable() |
| : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>)) {} |
| |
| SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries) |
| : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t, |
| number_of_entries) {} |
| |
| // Arena for permanent symbols (null class loader) that are never unloaded |
| static Arena* _arena; |
| static Arena* arena() { return _arena; } // called for statistics |
| |
| static void initialize_symbols(int arena_alloc_size = 0); |
| |
| static volatile int _parallel_claimed_idx; |
| |
| typedef SymbolTable::BucketUnlinkContext BucketUnlinkContext; |
| // Release any dead symbols. Unlinked bucket entries are collected in the given |
| // context to be freed later. |
| // This allows multiple threads to work on the table at once. |
| static void buckets_unlink(int start_idx, int end_idx, BucketUnlinkContext* context); |
| public: |
| enum { |
| symbol_alloc_batch_size = 8, |
| // Pick initial size based on java -version size measurements |
| symbol_alloc_arena_size = 360*K |
| }; |
| |
| // The symbol table |
| static SymbolTable* the_table() { return _the_table; } |
| |
| // Size of one bucket in the string table. Used when checking for rollover. |
| static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); } |
| |
| static void create_table() { |
| assert(_the_table == NULL, "One symbol table allowed."); |
| _the_table = new SymbolTable(); |
| initialize_symbols(symbol_alloc_arena_size); |
| } |
| |
| static unsigned int hash_symbol(const char* s, int len); |
| static unsigned int hash_shared_symbol(const char* s, int len); |
| |
| static Symbol* lookup(const char* name, int len, TRAPS); |
| // lookup only, won't add. Also calculate hash. |
| static Symbol* lookup_only(const char* name, int len, unsigned int& hash); |
| // Only copy to C string to be added if lookup failed. |
| static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS); |
| |
| static void release(Symbol* sym); |
| |
| // Look up the address of the literal in the SymbolTable for this Symbol* |
| static Symbol** lookup_symbol_addr(Symbol* sym); |
| |
| // jchar (UTF16) version of lookups |
| static Symbol* lookup_unicode(const jchar* name, int len, TRAPS); |
| static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash); |
| |
| static void add(ClassLoaderData* loader_data, |
| const constantPoolHandle& cp, int names_count, |
| const char** names, int* lengths, int* cp_indices, |
| unsigned int* hashValues, TRAPS); |
| |
| // Release any dead symbols |
| static void unlink() { |
| int processed = 0; |
| int removed = 0; |
| unlink(&processed, &removed); |
| } |
| static void unlink(int* processed, int* removed); |
| // Release any dead symbols, possibly parallel version |
| static void possibly_parallel_unlink(int* processed, int* removed); |
| |
| // iterate over symbols |
| static void symbols_do(SymbolClosure *cl); |
| static void metaspace_pointers_do(MetaspaceClosure* it); |
| |
| // Symbol creation |
| static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) { |
| assert(utf8_buffer != NULL, "just checking"); |
| return lookup(utf8_buffer, length, THREAD); |
| } |
| static Symbol* new_symbol(const char* name, TRAPS) { |
| return new_symbol(name, (int)strlen(name), THREAD); |
| } |
| static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) { |
| assert(begin <= end && end <= sym->utf8_length(), "just checking"); |
| return lookup(sym, begin, end, THREAD); |
| } |
| |
| // Create a symbol in the arena for symbols that are not deleted |
| static Symbol* new_permanent_symbol(const char* name, TRAPS); |
| |
| // Symbol lookup |
| static Symbol* lookup(int index, const char* name, int len, TRAPS); |
| |
| // Needed for preloading classes in signatures when compiling. |
| // Returns the symbol is already present in symbol table, otherwise |
| // NULL. NO ALLOCATION IS GUARANTEED! |
| static Symbol* probe(const char* name, int len) { |
| unsigned int ignore_hash; |
| return lookup_only(name, len, ignore_hash); |
| } |
| static Symbol* probe_unicode(const jchar* name, int len) { |
| unsigned int ignore_hash; |
| return lookup_only_unicode(name, len, ignore_hash); |
| } |
| |
| // Histogram |
| static void print_histogram() PRODUCT_RETURN; |
| static void print() PRODUCT_RETURN; |
| |
| // Debugging |
| static void verify(); |
| static void dump(outputStream* st, bool verbose=false); |
| static void read(const char* filename, TRAPS); |
| |
| // Sharing |
| static void write_to_archive(); |
| static void serialize(SerializeClosure* soc); |
| static u4 encode_shared(Symbol* sym); |
| static Symbol* decode_shared(u4 offset); |
| |
| // Rehash the symbol table if it gets out of balance |
| static void rehash_table(); |
| static bool needs_rehashing() { return _needs_rehashing; } |
| // Parallel chunked scanning |
| static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; } |
| static int parallel_claimed_index() { return _parallel_claimed_idx; } |
| }; |
| |
| #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP |