/*

 * Copyright 2001-2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

// Sparse remembered set for a heap region (the "owning" region).  Maps

// indices of other regions to short sequences of cards in the other region

// that might contain pointers into the owner region.

// These tables only expand while they are accessed in parallel --

// deletions may be done in single-threaded code.  This allows us to allow

// unsynchronized reads/iterations, as long as expansions caused by

// insertions only enqueue old versions for deletions, but do not delete

// old versions synchronously.

class SparsePRTEntry: public CHeapObj {

public:

  enum SomePublicConstants {

    CardsPerEntry = (short)4,

    NullEntry = (short)-1,

    DeletedEntry = (short)-2

  };

private:

  short _region_ind;

  short _next_index;

  short _cards[CardsPerEntry];

public:

  // Set the region_ind to the given value, and delete all cards.

  inline void init(short region_ind);

  short r_ind() const { return _region_ind; }

  bool valid_entry() const { return r_ind() >= 0; }

  void set_r_ind(short rind) { _region_ind = rind; }

  short next_index() const { return _next_index; }

  short* next_index_addr() { return &_next_index; }

  void set_next_index(short ni) { _next_index = ni; }

  // Returns "true" iff the entry contains the given card index.

  inline bool contains_card(short card_index) const;

  // Returns the number of non-NULL card entries.

  inline int num_valid_cards() const;

  // Requires that the entry not contain the given card index.  If there is

  // space available, add the given card index to the entry and return

  // "true"; otherwise, return "false" to indicate that the entry is full.

  enum AddCardResult {

    overflow,

    found,

    added

  };

  inline AddCardResult add_card(short card_index);

  // Copy the current entry's cards into "cards".

  inline void copy_cards(short* cards) const;

  // Copy the current entry's cards into the "_card" array of "e."

  inline void copy_cards(SparsePRTEntry* e) const;

  inline short card(int i) const { return _cards[i]; }

};

class RSHashTable : public CHeapObj {

  friend class RSHashTableIter;

  enum SomePrivateConstants {

    NullEntry = -1

  };

  size_t _capacity;

  size_t _capacity_mask;

  size_t _occupied_entries;

  size_t _occupied_cards;

  SparsePRTEntry* _entries;

  short* _buckets;

  short  _free_region;

  short  _free_list;

  static RSHashTable* _head_deleted_list;

  RSHashTable* _next_deleted;

  RSHashTable* next_deleted() { return _next_deleted; }

  void set_next_deleted(RSHashTable* rsht) { _next_deleted = rsht; }

  bool _deleted;

  void set_deleted(bool b) { _deleted = b; }

  // Requires that the caller hold a lock preventing parallel modifying

  // operations, and that the the table be less than completely full.  If

  // an entry for "region_ind" is already in the table, finds it and

  // returns its address; otherwise returns "NULL."

  SparsePRTEntry* entry_for_region_ind(short region_ind) const;

  // Requires that the caller hold a lock preventing parallel modifying

  // operations, and that the the table be less than completely full.  If

  // an entry for "region_ind" is already in the table, finds it and

  // returns its address; otherwise allocates, initializes, inserts and

  // returns a new entry for "region_ind".

  SparsePRTEntry* entry_for_region_ind_create(short region_ind);

  // Returns the index of the next free entry in "_entries".

  short alloc_entry();

  // Declares the entry "fi" to be free.  (It must have already been

  // deleted from any bucket lists.

  void free_entry(short fi);

public:

  RSHashTable(size_t capacity);

  ~RSHashTable();

  // Attempts to ensure that the given card_index in the given region is in

  // the sparse table.  If successful (because the card was already

  // present, or because it was successfullly added) returns "true".

  // Otherwise, returns "false" to indicate that the addition would

  // overflow the entry for the region.  The caller must transfer these

  // entries to a larger-capacity representation.

  bool add_card(short region_id, short card_index);

  bool get_cards(short region_id, short* cards);

  bool delete_entry(short region_id);

  bool contains_card(short region_id, short card_index) const;

  void add_entry(SparsePRTEntry* e);

  void clear();

  size_t capacity() const      { return _capacity;       }

  size_t capacity_mask() const { return _capacity_mask;  }

  size_t occupied_entries() const { return _occupied_entries; }

  size_t occupied_cards() const   { return _occupied_cards;   }

  size_t mem_size() const;

  bool deleted() { return _deleted; }

  SparsePRTEntry* entry(int i) const { return &_entries[i]; }

  void print();

  static void add_to_deleted_list(RSHashTable* rsht);

  static RSHashTable* get_from_deleted_list();

};

  // ValueObj because will be embedded in HRRS iterator.

class RSHashTableIter VALUE_OBJ_CLASS_SPEC {

    short _tbl_ind;

    short _bl_ind;

    short _card_ind;

    RSHashTable* _rsht;

    size_t _heap_bot_card_ind;

    enum SomePrivateConstants {

      CardsPerRegion = HeapRegion::GrainBytes >> CardTableModRefBS::card_shift

    };

    // If the bucket list pointed to by _bl_ind contains a card, sets

    // _bl_ind to the index of that entry, and returns the card.

    // Otherwise, returns SparseEntry::NullEnty.

    short find_first_card_in_list();

    // Computes the proper card index for the card whose offset in the

    // current region (as indicated by _bl_ind) is "ci".

    // This is subject to errors when there is iteration concurrent with

    // modification, but these errors should be benign.

    size_t compute_card_ind(short ci);

  public:

    RSHashTableIter(size_t heap_bot_card_ind) :

      _tbl_ind(RSHashTable::NullEntry),

      _bl_ind(RSHashTable::NullEntry),

      _card_ind((SparsePRTEntry::CardsPerEntry-1)),

      _rsht(NULL),

      _heap_bot_card_ind(heap_bot_card_ind)

    {}

    void init(RSHashTable* rsht) {

      _rsht = rsht;

      _tbl_ind = -1; // So that first increment gets to 0.

      _bl_ind = RSHashTable::NullEntry;

      _card_ind = (SparsePRTEntry::CardsPerEntry-1);

    }

    bool has_next(size_t& card_index);

  };

// Concurrent accesss to a SparsePRT must be serialized by some external

// mutex.

class SparsePRTIter;

class SparsePRT VALUE_OBJ_CLASS_SPEC {

  //  Iterations are done on the _cur hash table, since they only need to

  //  see entries visible at the start of a collection pause.

  //  All other operations are done using the _next hash table.

  RSHashTable* _cur;

  RSHashTable* _next;

  HeapRegion* _hr;

  enum SomeAdditionalPrivateConstants {

    InitialCapacity = 16

  };

  void expand();

  bool _expanded;

  bool expanded() { return _expanded; }

  void set_expanded(bool b) { _expanded = b; }

  SparsePRT* _next_expanded;

  SparsePRT* next_expanded() { return _next_expanded; }

  void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; }

  static SparsePRT* _head_expanded_list;

public:

  SparsePRT(HeapRegion* hr);

  ~SparsePRT();

  size_t occupied() const { return _next->occupied_cards(); }

  size_t mem_size() const;

  // Attempts to ensure that the given card_index in the given region is in

  // the sparse table.  If successful (because the card was already

  // present, or because it was successfullly added) returns "true".

  // Otherwise, returns "false" to indicate that the addition would

  // overflow the entry for the region.  The caller must transfer these

  // entries to a larger-capacity representation.

  bool add_card(short region_id, short card_index);

  // If the table hold an entry for "region_ind",  Copies its

  // cards into "cards", which must be an array of length at least

  // "CardsPerEntry", and returns "true"; otherwise, returns "false".

  bool get_cards(short region_ind, short* cards);

  // If there is an entry for "region_ind", removes it and return "true";

  // otherwise returns "false."

  bool delete_entry(short region_ind);

  // Clear the table, and reinitialize to initial capacity.

  void clear();

  // Ensure that "_cur" and "_next" point to the same table.

  void cleanup();

  // Clean up all tables on the expanded list.  Called single threaded.

  static void cleanup_all();

  RSHashTable* cur() const { return _cur; }

  void init_iterator(SparsePRTIter* sprt_iter);

  static void add_to_expanded_list(SparsePRT* sprt);

  static SparsePRT* get_from_expanded_list();

  bool contains_card(short region_id, short card_index) const {

    return _next->contains_card(region_id, card_index);

  }

#if 0

  void verify_is_cleared();

  void print();

#endif

};

class SparsePRTIter: public /* RSHashTable:: */RSHashTableIter {

public:

  SparsePRTIter(size_t heap_bot_card_ind) :

    /* RSHashTable:: */RSHashTableIter(heap_bot_card_ind)

  {}

  void init(const SparsePRT* sprt) {

    RSHashTableIter::init(sprt->cur());

  }

  bool has_next(size_t& card_index) {

    return RSHashTableIter::has_next(card_index);

  }

};