/*

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 * 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.

 *

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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 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.

  // 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