/*

 * Copyright (c) 1997, 2019, 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

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#ifndef SHARE_CLASSFILE_SYMBOLTABLE_HPP

#define SHARE_CLASSFILE_SYMBOLTABLE_HPP

#include "memory/allocation.hpp"

#include "memory/padded.hpp"

#include "oops/symbol.hpp"

#include "utilities/concurrentHashTable.hpp"

#include "utilities/hashtable.hpp"

class JavaThread;

// 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.

//

// 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; }

};

class CompactHashtableWriter;

class SerializeClosure;

class SymbolTableConfig;

typedef ConcurrentHashTable<Symbol*,

                              SymbolTableConfig, mtSymbol> SymbolTableHash;

class SymbolTableCreateEntry;

class SymbolTable : public CHeapObj<mtSymbol> {

  friend class VMStructs;

  friend class Symbol;

  friend class ClassFileParser;

  friend class SymbolTableConfig;

  friend class SymbolTableCreateEntry;

private:

  static void delete_symbol(Symbol* sym);

  void grow(JavaThread* jt);

  void clean_dead_entries(JavaThread* jt);

  // The symbol table

  static SymbolTable* _the_table;

  static volatile bool _lookup_shared_first;

  static volatile bool _alt_hash;

  // For statistics

  volatile size_t _symbols_removed;

  volatile size_t _symbols_counted;

  SymbolTableHash* _local_table;

  size_t _current_size;

  volatile bool _has_work;

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

  volatile bool _needs_rehashing;

  volatile size_t _items_count;

  volatile bool   _has_items_to_clean;

  double get_load_factor() const;

  void check_concurrent_work();

  static void item_added();

  static void item_removed();

  // For cleaning

  void reset_has_items_to_clean();

  void mark_has_items_to_clean();

  bool has_items_to_clean() const;

  SymbolTable();

  Symbol* do_lookup(const char* name, int len, uintx hash);

  // Adding elements

  static void new_symbols(ClassLoaderData* loader_data,

                          const constantPoolHandle& cp, int names_count,

                          const char** name, int* lengths,

  static Symbol* lookup_shared(const char* name, int len, unsigned int hash);

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

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

  // 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);

  void concurrent_work(JavaThread* jt);

  void print_table_statistics(outputStream* st, const char* table_name);

  void try_rehash_table();

  bool do_rehash();

  inline void update_needs_rehash(bool rehash);

public:

  // The symbol table

  static SymbolTable* the_table() { return _the_table; }

  size_t table_size();

  TableStatistics get_table_statistics();

  enum {

    symbol_alloc_batch_size = 8,

    // Pick initial size based on java -version size measurements

    symbol_alloc_arena_size = 360*K // TODO (revisit)

  };

  static void create_table() {

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

    _the_table = new SymbolTable();

    initialize_symbols(symbol_alloc_arena_size);

  }

  static void do_concurrent_work(JavaThread* jt);

  static bool has_work() { return the_table()->_has_work; }

  static void trigger_cleanup();

  // Probing

  // 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);

  }

  }

  // Create a symbol in the arena for symbols that are not deleted

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

  static void rehash_table();

  static bool needs_rehashing()

    { return SymbolTable::the_table()->_needs_rehashing; }

  // Heap dumper and CDS

  static void symbols_do(SymbolClosure *cl);

  // Sharing

private:

  static void copy_shared_symbol_table(CompactHashtableWriter* ch_table);

public:

  static void write_to_archive() NOT_CDS_RETURN;

  static void serialize_shared_table_header(SerializeClosure* soc) NOT_CDS_RETURN;

  static void metaspace_pointers_do(MetaspaceClosure* it);

  // Jcmd

  static void dump(outputStream* st, bool verbose=false);

  // Debugging

  static void verify();

  // Histogram

  static void print_histogram() PRODUCT_RETURN;

};

#endif // SHARE_CLASSFILE_SYMBOLTABLE_HPP