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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

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  * 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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  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_SHARED_SPACEDECORATOR_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_SHARED_SPACEDECORATOR_HPP

 #include "gc_implementation/shared/mutableSpace.hpp"

 #include "memory/space.hpp"

 #include "utilities/globalDefinitions.hpp"

 class SpaceDecorator: public AllStatic {

  public:

   // Initialization flags.

   static const bool Clear               = true;

   static const bool DontClear           = false;

   static const bool Mangle              = true;

   static const bool DontMangle          = false;

 };

 // Functionality for use with class Space and class MutableSpace.

 //   The approach taken with the mangling is to mangle all

 // the space initially and then to mangle areas that have

 // been allocated since the last collection.  Mangling is

 // done in the context of a generation and in the context

 // of a space.

 //   The space in a generation is mangled when it is first

 // initialized and when the generation grows.  The spaces

 // are not necessarily up-to-date when this mangling occurs

 // and the method mangle_region() is used.

 //   After allocations have been done in a space, the space generally

 // need to be remangled.  Remangling is only done on the

 // recently allocated regions in the space.  Typically, that is

 // the region between the new top and the top just before a

 // garbage collection.

 //   An exception to the usual mangling in a space is done when the

 // space is used for an extraordinary purpose.  Specifically, when

 // to-space is used as scratch space for a mark-sweep-compact

 // collection.

 //   Spaces are mangled after a collection.  If the generation

 // grows after a collection, the added space is mangled as part of

 // the growth of the generation.  No additional mangling is needed when the

 // spaces are resized after an expansion.

 //   The class SpaceMangler keeps a pointer to the top of the allocated

 // area and provides the methods for doing the piece meal mangling.

 // Methods for doing sparces and full checking of the mangling are

 // included.  The full checking is done if DEBUG_MANGLING is defined.

 //   GenSpaceMangler is used with the GenCollectedHeap collectors and

 // MutableSpaceMangler is used with the ParallelScavengeHeap collectors.

 // These subclasses abstract the differences in the types of spaces used

 // by each heap.

 class SpaceMangler: public CHeapObj<mtGC> {

   friend class VMStructs;

   // High water mark for allocations.  Typically, the space above

   // this point have been mangle previously and don't need to be

   // touched again.  Space belows this point has been allocated

   // and remangling is needed between the current top and this

   // high water mark.

   HeapWord* _top_for_allocations;

   HeapWord* top_for_allocations() { return _top_for_allocations; }

  public:

   // Setting _top_for_allocations to NULL at initialization

   // makes it always below top so that mangling done as part

   // of the initialize() call of a space does nothing (as it

   // should since the mangling is done as part of the constructor

   // for the space.

   SpaceMangler() : _top_for_allocations(NULL) {}

   // Methods for top and end that delegate to the specific

   // space type.

   virtual HeapWord* top() const = 0;

   virtual HeapWord* end() const = 0;

   // Return true if q matches the mangled pattern.

   static bool is_mangled(HeapWord* q) PRODUCT_RETURN0;

   // Used to save the an address in a space for later use during mangling.

   void set_top_for_allocations(HeapWord* v);

   // Overwrites the unused portion of this space.

   // Mangle only the region not previously mangled [top, top_previously_mangled)

   void mangle_unused_area();

   // Mangle all the unused region [top, end)

   void mangle_unused_area_complete();

   // Do some sparse checking on the area that should have been mangled.

   void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;

   // Do a complete check of the area that should be mangled.

   void check_mangled_unused_area_complete() PRODUCT_RETURN;

   // Mangle the MemRegion.  This is a non-space specific mangler.  It

   // is used during the initial mangling of a space before the space

   // is fully constructed.  Also is used when a generation is expanded

   // and possibly before the spaces have been reshaped to to the new

   // size of the generation.

   static void mangle_region(MemRegion mr) PRODUCT_RETURN;

 };

 class ContiguousSpace;

 // For use with GenCollectedHeap's

 class GenSpaceMangler: public SpaceMangler {

   ContiguousSpace* _sp;

   ContiguousSpace* sp() { return _sp; }

   HeapWord* top() const { return _sp->top(); }

   HeapWord* end() const { return _sp->end(); }

  public:

   GenSpaceMangler(ContiguousSpace* sp) : SpaceMangler(), _sp(sp) {}

 };

 // For use with ParallelScavengeHeap's.

 class MutableSpaceMangler: public SpaceMangler {

   MutableSpace* _sp;

   MutableSpace* sp() { return _sp; }

   HeapWord* top() const { return _sp->top(); }

   HeapWord* end() const { return _sp->end(); }

  public:

   MutableSpaceMangler(MutableSpace* sp) : SpaceMangler(), _sp(sp) {}

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_SHARED_SPACEDECORATOR_HPP