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 * 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_MEMORY_ITERATOR_HPP

#define SHARE_VM_MEMORY_ITERATOR_HPP

#include "memory/allocation.hpp"

#include "memory/memRegion.hpp"

#include "runtime/prefetch.hpp"

#include "utilities/top.hpp"

// The following classes are C++ `closures` for iterating over objects, roots and spaces

class CodeBlob;

class nmethod;

class ReferenceProcessor;

class DataLayout;

class KlassClosure;

class ClassLoaderData;

// Closure provides abortability.

class Closure : public StackObj {

 protected:

  bool _abort;

  void set_abort() { _abort = true; }

 public:

  Closure() : _abort(false) {}

  // A subtype can use this mechanism to indicate to some iterator mapping

  // functions that the iteration should cease.

  bool abort() { return _abort; }

  void clear_abort() { _abort = false; }

};

// OopClosure is used for iterating through references to Java objects.

class OopClosure : public Closure {

 public:

  virtual void do_oop(oop* o) = 0;

  virtual void do_oop_v(oop* o) { do_oop(o); }

  virtual void do_oop(narrowOop* o) = 0;

  virtual void do_oop_v(narrowOop* o) { do_oop(o); }

};

// ExtendedOopClosure adds extra code to be run during oop iterations.

// This is needed by the GC and is extracted to a separate type to not

// pollute the OopClosure interface.

class ExtendedOopClosure : public OopClosure {

 public:

  ReferenceProcessor* _ref_processor;

  ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }

  ExtendedOopClosure() : OopClosure(), _ref_processor(NULL) { }

  // If the do_metadata functions return "true",

  // we invoke the following when running oop_iterate():

  //

  // 1) do_klass on the header klass pointer.

  // 2) do_klass on the klass pointer in the mirrors.

  // 3) do_class_loader_data on the class loader data in class loaders.

  //

  // The virtual (without suffix) and the non-virtual (with _nv suffix) need

  // to be updated together, or else the devirtualization will break.

  //

  // Providing default implementations of the _nv functions unfortunately

  // removes the compile-time safeness, but reduces the clutter for the

  // ExtendedOopClosures that don't need to walk the metadata. Currently,

  // only CMS needs these.

  virtual bool do_metadata() { return do_metadata_nv(); }

  bool do_metadata_v()       { return do_metadata(); }

  bool do_metadata_nv()      { return false; }

  virtual void do_klass(Klass* k)   { do_klass_nv(k); }

  void do_klass_v(Klass* k)         { do_klass(k); }

  void do_klass_nv(Klass* k)        { ShouldNotReachHere(); }

  virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }

  // Controls how prefetching is done for invocations of this closure.

  Prefetch::style prefetch_style() { // Note that this is non-virtual.

    return Prefetch::do_none;

  }

  // True iff this closure may be safely applied more than once to an oop

  // location without an intervening "major reset" (like the end of a GC).

  virtual bool idempotent() { return false; }

  virtual bool apply_to_weak_ref_discovered_field() { return false; }

};

// Wrapper closure only used to implement oop_iterate_no_header().

class NoHeaderExtendedOopClosure : public ExtendedOopClosure {

  OopClosure* _wrapped_closure;

 public:

  NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}

  // Warning: this calls the virtual version do_oop in the the wrapped closure.

  void do_oop_nv(oop* p)       { _wrapped_closure->do_oop(p); }

  void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); }

  void do_oop(oop* p)          { assert(false, "Only the _nv versions should be used");

                                 _wrapped_closure->do_oop(p); }

  void do_oop(narrowOop* p)    { assert(false, "Only the _nv versions should be used");

                                 _wrapped_closure->do_oop(p);}

};

class KlassClosure : public Closure {

 public:

  virtual void do_klass(Klass* k) = 0;

};

class KlassToOopClosure : public KlassClosure {

  OopClosure* _oop_closure;

 public:

  KlassToOopClosure(OopClosure* oop_closure) : _oop_closure(oop_closure) {}

  virtual void do_klass(Klass* k);

};

class CLDToOopClosure {

  OopClosure* _oop_closure;

  KlassToOopClosure _klass_closure;

  bool _must_claim_cld;

 public:

  CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :

      _oop_closure(oop_closure),

      _klass_closure(oop_closure),

      _must_claim_cld(must_claim_cld) {}

  void do_cld(ClassLoaderData* cld);

};

// ObjectClosure is used for iterating through an object space

class ObjectClosure : public Closure {

 public:

  // Called for each object.

  virtual void do_object(oop obj) = 0;

};

class BoolObjectClosure : public Closure {

 public:

  virtual bool do_object_b(oop obj) = 0;

};

// Applies an oop closure to all ref fields in objects iterated over in an

// object iteration.

class ObjectToOopClosure: public ObjectClosure {

  ExtendedOopClosure* _cl;

public:

  void do_object(oop obj);

  ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}

};

// A version of ObjectClosure with "memory" (see _previous_address below)

class UpwardsObjectClosure: public BoolObjectClosure {

  HeapWord* _previous_address;

 public:

  UpwardsObjectClosure() : _previous_address(NULL) { }

  void set_previous(HeapWord* addr) { _previous_address = addr; }

  HeapWord* previous()              { return _previous_address; }

  // A return value of "true" can be used by the caller to decide

  // if this object's end should *NOT* be recorded in

  // _previous_address above.

  virtual bool do_object_bm(oop obj, MemRegion mr) = 0;

};

// A version of ObjectClosure that is expected to be robust

// in the face of possibly uninitialized objects.

class ObjectClosureCareful : public ObjectClosure {

 public:

  virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;

  virtual size_t do_object_careful(oop p) = 0;

};

// The following are used in CompactibleFreeListSpace and

// ConcurrentMarkSweepGeneration.

// Blk closure (abstract class)

class BlkClosure : public StackObj {

 public:

  virtual size_t do_blk(HeapWord* addr) = 0;

};

// A version of BlkClosure that is expected to be robust

// in the face of possibly uninitialized objects.

class BlkClosureCareful : public BlkClosure {

 public:

  size_t do_blk(HeapWord* addr) {

    guarantee(false, "call do_blk_careful instead");

    return 0;

  }

  virtual size_t do_blk_careful(HeapWord* addr) = 0;

};

// SpaceClosure is used for iterating over spaces

class Space;

class CompactibleSpace;

class SpaceClosure : public StackObj {

 public:

  // Called for each space

  virtual void do_space(Space* s) = 0;

};

class CompactibleSpaceClosure : public StackObj {

 public:

  // Called for each compactible space

  virtual void do_space(CompactibleSpace* s) = 0;

};

// CodeBlobClosure is used for iterating through code blobs

// in the code cache or on thread stacks

class CodeBlobClosure : public Closure {

 public:

  // Called for each code blob.

  virtual void do_code_blob(CodeBlob* cb) = 0;

};

class MarkingCodeBlobClosure : public CodeBlobClosure {

 public:

  // Called for each code blob, but at most once per unique blob.

  virtual void do_newly_marked_nmethod(nmethod* nm) = 0;

  virtual void do_code_blob(CodeBlob* cb);

    // = { if (!nmethod(cb)->test_set_oops_do_mark())  do_newly_marked_nmethod(cb); }

  class MarkScope : public StackObj {

  protected:

    bool _active;

  public:

    MarkScope(bool activate = true);

      // = { if (active) nmethod::oops_do_marking_prologue(); }

    ~MarkScope();

      // = { if (active) nmethod::oops_do_marking_epilogue(); }

  };

};

// Applies an oop closure to all ref fields in code blobs

// iterated over in an object iteration.

class CodeBlobToOopClosure: public MarkingCodeBlobClosure {

  OopClosure* _cl;

  bool _do_marking;

public:

  virtual void do_newly_marked_nmethod(nmethod* cb);

    // = { cb->oops_do(_cl); }

  virtual void do_code_blob(CodeBlob* cb);

    // = { if (_do_marking)  super::do_code_blob(cb); else cb->oops_do(_cl); }

  CodeBlobToOopClosure(OopClosure* cl, bool do_marking)

    : _cl(cl), _do_marking(do_marking) {}

};

// MonitorClosure is used for iterating over monitors in the monitors cache

class ObjectMonitor;

class MonitorClosure : public StackObj {

 public:

  // called for each monitor in cache

  virtual void do_monitor(ObjectMonitor* m) = 0;

};

// A closure that is applied without any arguments.

class VoidClosure : public StackObj {

 public:

  // I would have liked to declare this a pure virtual, but that breaks

  // in mysterious ways, for unknown reasons.

  virtual void do_void();

};

// YieldClosure is intended for use by iteration loops

// to incrementalize their work, allowing interleaving

// of an interruptable task so as to allow other

// threads to run (which may not otherwise be able to access

// exclusive resources, for instance). Additionally, the

// closure also allows for aborting an ongoing iteration

// by means of checking the return value from the polling

// call.

class YieldClosure : public StackObj {

  public:

   virtual bool should_return() = 0;

};

// Abstract closure for serializing data (read or write).

class SerializeClosure : public Closure {

public:

  // Return bool indicating whether closure implements read or write.

  virtual bool reading() const = 0;

  // Read/write the void pointer pointed to by p.

  virtual void do_ptr(void** p) = 0;

  // Read/write the region specified.

  virtual void do_region(u_char* start, size_t size) = 0;

  // Check/write the tag.  If reading, then compare the tag against

  // the passed in value and fail is they don't match.  This allows

  // for verification that sections of the serialized data are of the

  // correct length.

  virtual void do_tag(int tag) = 0;

};

class SymbolClosure : public StackObj {

 public:

  virtual void do_symbol(Symbol**) = 0;

  // Clear LSB in symbol address; it can be set by CPSlot.

  static Symbol* load_symbol(Symbol** p) {

    return (Symbol*)(intptr_t(*p) & ~1);

  }

  // Store symbol, adjusting new pointer if the original pointer was adjusted

  // (symbol references in constant pool slots have their LSB set to 1).

  static void store_symbol(Symbol** p, Symbol* sym) {

    *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));

  }

};

#endif // SHARE_VM_MEMORY_ITERATOR_HPP