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 /*

  * Copyright (c) 1997, 2012, 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

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 #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 to hold a newly created or referenced Symbol* temporarily in scope.

 // 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) {}

   // Creating or looking up a symbol increments the symbol's reference count

   TempNewSymbol(Symbol *s) : _temp(s) {}

   // Operator= increments reference count.

   void operator=(const TempNewSymbol &s) {

     _temp = s._temp;

     if (_temp !=NULL) _temp->increment_refcount();

   }

   // Decrement reference counter so it can go away if it's unique

   ~TempNewSymbol() { if (_temp != NULL) _temp->decrement_refcount(); }

   // Operators so they can be used like Symbols

   Symbol* operator -> () const                   { return _temp; }

   bool    operator == (Symbol* o) const          { return _temp == o; }

   // Sneaky conversion function

   operator Symbol*()                             { return _temp; }

 };

 class SymbolTable : public Hashtable<Symbol*> {

   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 jint _seed;

   // For statistics

   static int symbols_removed;

   static int symbols_counted;

   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(Handle class_loader, constantPoolHandle cp, int names_count,

                  const char** names, int* lengths, int* cp_indices,

                  unsigned int* hashValues, TRAPS);

   static void new_symbols(Handle class_loader, constantPoolHandle cp,

                           int names_count,

                           const char** name, int* lengths,

                           int* cp_indices, unsigned int* hashValues,

                           TRAPS) {

     add(class_loader, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);

   }

   // Table size

   enum {

     symbol_table_size = 20011

   };

   Symbol* lookup(int index, const char* name, int len, unsigned int hash);

   SymbolTable()

     : Hashtable<Symbol*>(symbol_table_size, sizeof (HashtableEntry<Symbol*>)) {}

   SymbolTable(HashtableBucket* t, int number_of_entries)

     : Hashtable<Symbol*>(symbol_table_size, sizeof (HashtableEntry<Symbol*>), 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 bool use_alternate_hashcode()  { return _seed != 0; }

   static jint seed()                    { return _seed; }

   unsigned int new_hash(Symbol* sym);

 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; }

   static void create_table() {

     assert(_the_table == NULL, "One symbol table allowed.");

     _the_table = new SymbolTable();

     initialize_symbols(symbol_alloc_arena_size);

   }

   static void create_table(HashtableBucket* t, int length,

                            int number_of_entries) {

     assert(_the_table == NULL, "One symbol table allowed.");

     assert(length == symbol_table_size * sizeof(HashtableBucket),

            "bad shared symbol size.");

     _the_table = new SymbolTable(t, number_of_entries);

     // if CDS give symbol table a default arena size since most symbols

     // are already allocated in the shared misc section.

     initialize_symbols();

   }

   static unsigned int hash_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(Handle class_loader, constantPoolHandle cp, int names_count,

                   const char** names, int* lengths, int* cp_indices,

                   unsigned int* hashValues, TRAPS);

   // Release any dead symbols

   static void unlink();

   // iterate over symbols

   static void symbols_do(SymbolClosure *cl);

   // 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);

   // Sharing

   static void copy_buckets(char** top, char*end) {

     the_table()->Hashtable<Symbol*>::copy_buckets(top, end);

   }

   static void copy_table(char** top, char*end) {

     the_table()->Hashtable<Symbol*>::copy_table(top, end);

   }

   static void reverse(void* boundary = NULL) {

     the_table()->Hashtable<Symbol*>::reverse(boundary);

   }

   // Rehash the symbol table if it gets out of balance

   static void rehash_table();

   static bool needs_rehashing()         { return _needs_rehashing; }

 };

 class StringTable : public Hashtable<oop> {

   friend class VMStructs;

 private:

   // The string table

   static StringTable* _the_table;

   // Set if one bucket is out of balance due to hash algorithm deficiency

   static bool _needs_rehashing;

   static jint _seed;

   static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);

   oop basic_add(int index, Handle string_or_null, jchar* name, int len,

                 unsigned int hashValue, TRAPS);

   oop lookup(int index, jchar* chars, int length, unsigned int hashValue);

   StringTable() : Hashtable<oop>((int)StringTableSize,

                                  sizeof (HashtableEntry<oop>)) {}

   StringTable(HashtableBucket* t, int number_of_entries)

     : Hashtable<oop>((int)StringTableSize, sizeof (HashtableEntry<oop>), t,

                      number_of_entries) {}

   static bool use_alternate_hashcode()  { return _seed != 0; }

   static jint seed()                    { return _seed; }

   unsigned int new_hash(oop s);

 public:

   // The string table

   static StringTable* the_table() { return _the_table; }

   static void create_table() {

     assert(_the_table == NULL, "One string table allowed.");

     _the_table = new StringTable();

   }

   static void create_table(HashtableBucket* t, int length,

                            int number_of_entries) {

     assert(_the_table == NULL, "One string table allowed.");

     assert((size_t)length == StringTableSize * sizeof(HashtableBucket),

            "bad shared string size.");

     _the_table = new StringTable(t, number_of_entries);

   }

   // GC support

   //   Delete pointers to otherwise-unreachable objects.

   static void unlink(BoolObjectClosure* cl);

   // Invoke "f->do_oop" on the locations of all oops in the table.

   static void oops_do(OopClosure* f);

   // Hashing algorithm, used as the hash value used by the

   //     StringTable for bucket selection and comparison (stored in the

   //     HashtableEntry structures).  This is used in the String.intern() method.

   static unsigned int hash_string(const jchar* s, int len);

   // Internal test.

   static void test_alt_hash() PRODUCT_RETURN;

   // Probing

   static oop lookup(Symbol* symbol);

   // Interning

   static oop intern(Symbol* symbol, TRAPS);

   static oop intern(oop string, TRAPS);

   static oop intern(const char *utf8_string, TRAPS);

   // Debugging

   static void verify();

   static void dump(outputStream* st);

   // Sharing

   static void copy_buckets(char** top, char*end) {

     the_table()->Hashtable<oop>::copy_buckets(top, end);

   }

   static void copy_table(char** top, char*end) {

     the_table()->Hashtable<oop>::copy_table(top, end);

   }

   static void reverse() {

     the_table()->Hashtable<oop>::reverse();

   }

   // Rehash the symbol table if it gets out of balance

   static void rehash_table();

   static bool needs_rehashing() { return _needs_rehashing; }

 };

 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP