/*

 * Copyright 2002-2008 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.

 *

 */

//

// PSPromotionLAB is a parallel scavenge promotion lab. This class acts very

// much like a MutableSpace. We couldn't embed a MutableSpace, though, as

// it has a considerable number of asserts and invariants that are violated.

//

class ObjectStartArray;

class PSPromotionLAB : public CHeapObj {

 protected:

  static size_t filler_header_size;

  enum LabState {

    needs_flush,

    flushed,

    zero_size

  };

  HeapWord* _top;

  HeapWord* _bottom;

  HeapWord* _end;

  LabState _state;

  void set_top(HeapWord* value)    { _top = value; }

  void set_bottom(HeapWord* value) { _bottom = value; }

  void set_end(HeapWord* value)    { _end = value; }

  // The shared initialize code invokes this.

  debug_only(virtual bool lab_is_valid(MemRegion lab) { return false; });

  PSPromotionLAB() : _top(NULL), _bottom(NULL), _end(NULL) { }

 public:

  // Filling and flushing.

  void initialize(MemRegion lab);

  virtual void flush();

  // Accessors

  HeapWord* bottom() const           { return _bottom; }

  HeapWord* end() const              { return _end;    }

  HeapWord* top() const              { return _top;    }

  bool is_flushed()                  { return _state == flushed; }

  bool unallocate_object(oop obj);

  // Returns a subregion containing all objects in this space.

  MemRegion used_region()            { return MemRegion(bottom(), top()); }

  // Boolean querries.

  bool is_empty() const              { return used() == 0; }

  bool not_empty() const             { return used() > 0; }

  bool contains(const void* p) const { return _bottom <= p && p < _end; }

  // Size computations.  Sizes are in bytes.

  size_t capacity() const            { return byte_size(bottom(), end()); }

  size_t used() const                { return byte_size(bottom(), top()); }

  size_t free() const                { return byte_size(top(),    end()); }

};

class PSYoungPromotionLAB : public PSPromotionLAB {

 public:

  PSYoungPromotionLAB() { }

  // Not MT safe

  HeapWord* allocate(size_t size) {

    // Can't assert this, when young fills, we keep the LAB around, but flushed.

    // assert(_state != flushed, "Sanity");

    HeapWord* obj = top();

    HeapWord* new_top = obj + size;

    // The 'new_top>obj' check is needed to detect overflow of obj+size.

    if (new_top > obj && new_top <= end()) {

      set_top(new_top);

      assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),

             "checking alignment");

      return obj;

    }

    return NULL;

  }

  debug_only(virtual bool lab_is_valid(MemRegion lab));

};

class PSOldPromotionLAB : public PSPromotionLAB {

 private:

  ObjectStartArray* _start_array;

 public:

  PSOldPromotionLAB() : _start_array(NULL) { }

  PSOldPromotionLAB(ObjectStartArray* start_array) : _start_array(start_array) { }

  void set_start_array(ObjectStartArray* start_array) { _start_array = start_array; }

  void flush();

  // Not MT safe

  HeapWord* allocate(size_t size) {

    // Cannot test for this now that we're doing promotion failures

    // assert(_state != flushed, "Sanity");

    assert(_start_array != NULL, "Sanity");

    HeapWord* obj = top();

    HeapWord* new_top = obj + size;

    // The 'new_top>obj' check is needed to detect overflow of obj+size.

    if (new_top > obj && new_top <= end()) {

      set_top(new_top);

      assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),

             "checking alignment");

      _start_array->allocate_block(obj);

      return obj;

    }

    return NULL;

  }

  debug_only(virtual bool lab_is_valid(MemRegion lab));

};