/*

 * Copyright 2001-2006 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.

 *

 */

class CompactibleFreeListSpace;

// A class for maintaining a free list of FreeChunk's.  The FreeList

// maintains a the structure of the list (head, tail, etc.) plus

// statistics for allocations from the list.  The links between items

// are not part of FreeList.  The statistics are

// used to make decisions about coalescing FreeChunk's when they

// are swept during collection.

//

// See the corresponding .cpp file for a description of the specifics

// for that implementation.

class Mutex;

class FreeList VALUE_OBJ_CLASS_SPEC {

  friend class CompactibleFreeListSpace;

  FreeChunk*    _head;          // List of free chunks

  FreeChunk*    _tail;          // Tail of list of free chunks

  size_t        _size;          // Size in Heap words of each chunks

  ssize_t       _count;         // Number of entries in list

  size_t        _hint;          // next larger size list with a positive surplus

  AllocationStats _allocation_stats;            // statistics for smart allocation

#ifdef ASSERT

  Mutex*        _protecting_lock;

#endif

  // Asserts false if the protecting lock (if any) is not held.

  void assert_proper_lock_protection_work() const PRODUCT_RETURN;

  void assert_proper_lock_protection() const {

#ifdef ASSERT

    if (_protecting_lock != NULL)

      assert_proper_lock_protection_work();

#endif

  }

  // Initialize the allocation statistics.

 protected:

  void init_statistics();

  void set_count(ssize_t v) { _count = v;}

  void decrement_count() {

    _count--;

 public:

  // Constructor

  // Construct a list without any entries.

  FreeList();

  // Construct a list with "fc" as the first (and lone) entry in the list.

  FreeList(FreeChunk* fc);

  // Construct a list which will have a FreeChunk at address "addr" and

  // of size "size" as the first (and lone) entry in the list.

  FreeList(HeapWord* addr, size_t size);

  // Reset the head, tail, hint, and count of a free list.

  void reset(size_t hint);

  // Declare the current free list to be protected by the given lock.

#ifdef ASSERT

  void set_protecting_lock(Mutex* protecting_lock) {

    _protecting_lock = protecting_lock;

  }

#endif

  // Accessors.

  FreeChunk* head() const {

    assert_proper_lock_protection();

    return _head;

  }

  void set_head(FreeChunk* v) {

    assert_proper_lock_protection();

    _head = v;

    assert(!_head || _head->size() == _size, "bad chunk size");

  }

  // Set the head of the list and set the prev field of non-null

  // values to NULL.

  void link_head(FreeChunk* v) {

    assert_proper_lock_protection();

    set_head(v);

    // If this method is not used (just set the head instead),

    // this check can be avoided.

    if (v != NULL) {

      v->linkPrev(NULL);

    }

  }

  FreeChunk* tail() const {

    assert_proper_lock_protection();

    return _tail;

  }

  void set_tail(FreeChunk* v) {

    assert_proper_lock_protection();

    _tail = v;

    assert(!_tail || _tail->size() == _size, "bad chunk size");

  }

  // Set the tail of the list and set the next field of non-null

  // values to NULL.

  void link_tail(FreeChunk* v) {

    assert_proper_lock_protection();

    set_tail(v);

    if (v != NULL) {

      v->clearNext();

    }

  }

  // No locking checks in read-accessors: lock-free reads (only) are benign.

  // Readers are expected to have the lock if they are doing work that

  // requires atomicity guarantees in sections of code.

  size_t size() const {

    return _size;

  }

  void set_size(size_t v) {

    assert_proper_lock_protection();

    _size = v;

  }

  ssize_t count() const {

    return _count;

  }

  size_t hint() const {

    return _hint;

  }

  void set_hint(size_t v) {

    assert_proper_lock_protection();

    assert(v == 0 || _size < v, "Bad hint"); _hint = v;

  }

  // Accessors for statistics

  AllocationStats* allocation_stats() {

    assert_proper_lock_protection();

    return &_allocation_stats;

  }

  ssize_t desired() const {

    return _allocation_stats.desired();

  }

  void compute_desired(float inter_sweep_current,

                       float inter_sweep_estimate) {

    assert_proper_lock_protection();

    _allocation_stats.compute_desired(_count,

                                      inter_sweep_current,

                                      inter_sweep_estimate);

  }

  ssize_t coalDesired() const {

    return _allocation_stats.coalDesired();

  }

  void set_coalDesired(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_coalDesired(v);

  }

  ssize_t surplus() const {

    return _allocation_stats.surplus();

  }

  void set_surplus(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_surplus(v);

  }

  void increment_surplus() {

    assert_proper_lock_protection();

    _allocation_stats.increment_surplus();

  }

  void decrement_surplus() {

    assert_proper_lock_protection();

    _allocation_stats.decrement_surplus();

  }

  ssize_t bfrSurp() const {

    return _allocation_stats.bfrSurp();

  }

  void set_bfrSurp(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_bfrSurp(v);

  }

  ssize_t prevSweep() const {

    return _allocation_stats.prevSweep();

  }

  void set_prevSweep(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_prevSweep(v);

  }

  ssize_t beforeSweep() const {

    return _allocation_stats.beforeSweep();

  }

  void set_beforeSweep(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_beforeSweep(v);

  }

  ssize_t coalBirths() const {

    return _allocation_stats.coalBirths();

  }

  void set_coalBirths(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_coalBirths(v);

  }

  void increment_coalBirths() {

    assert_proper_lock_protection();

    _allocation_stats.increment_coalBirths();

  }

  ssize_t coalDeaths() const {

    return _allocation_stats.coalDeaths();

  }

  void set_coalDeaths(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_coalDeaths(v);

  }

  void increment_coalDeaths() {

    assert_proper_lock_protection();

    _allocation_stats.increment_coalDeaths();

  }

  ssize_t splitBirths() const {

    return _allocation_stats.splitBirths();

  }

  void set_splitBirths(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_splitBirths(v);

  }

  void increment_splitBirths() {

    assert_proper_lock_protection();

    _allocation_stats.increment_splitBirths();

  }

  ssize_t splitDeaths() const {

    return _allocation_stats.splitDeaths();

  }

  void set_splitDeaths(ssize_t v) {

    assert_proper_lock_protection();

    _allocation_stats.set_splitDeaths(v);

  }

  void increment_splitDeaths() {

    assert_proper_lock_protection();

    _allocation_stats.increment_splitDeaths();

  }

  NOT_PRODUCT(

    // For debugging.  The "_returnedBytes" in all the lists are summed

    // and compared with the total number of bytes swept during a

    // collection.

    size_t returnedBytes() const { return _allocation_stats.returnedBytes(); }

    void set_returnedBytes(size_t v) { _allocation_stats.set_returnedBytes(v); }

    void increment_returnedBytes_by(size_t v) {

      _allocation_stats.set_returnedBytes(_allocation_stats.returnedBytes() + v);

    }

  )

  // Unlink head of list and return it.  Returns NULL if

  // the list is empty.

  FreeChunk* getChunkAtHead();

  // Remove the first "n" or "count", whichever is smaller, chunks from the

  // list, setting "fl", which is required to be empty, to point to them.

  void getFirstNChunksFromList(size_t n, FreeList* fl);

  // Unlink this chunk from it's free list

  void removeChunk(FreeChunk* fc);

  // Add this chunk to this free list.

  void returnChunkAtHead(FreeChunk* fc);

  void returnChunkAtTail(FreeChunk* fc);

  // Similar to returnChunk* but also records some diagnostic

  // information.

  void returnChunkAtHead(FreeChunk* fc, bool record_return);

  void returnChunkAtTail(FreeChunk* fc, bool record_return);

  // Prepend "fl" (whose size is required to be the same as that of "this")

  // to the front of "this" list.

  void prepend(FreeList* fl);

  // Verify that the chunk is in the list.

  // found.  Return NULL if "fc" is not found.

  bool verifyChunkInFreeLists(FreeChunk* fc) const;

};