/*

 * Copyright 1997-2008 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.

 *

 */

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

class ReferenceProcessor;

// 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 roots (oop*)

class OopClosure : public Closure {

 public:

  ReferenceProcessor* _ref_processor;

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

  OopClosure() : _ref_processor(NULL) { }

  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); }

  // In support of post-processing of weak links of KlassKlass objects;

  // see KlassKlass::oop_oop_iterate().

  virtual const bool should_remember_klasses() const {

    assert(!must_remember_klasses(), "Should have overriden this method.");

    return false;

  }

  virtual void remember_klass(Klass* k) { /* do nothing */ }

  // If "true", invoke on nmethods (when scanning compiled frames).

  virtual const bool do_nmethods() const { return false; }

  // The methods below control how object iterations invoking this closure

  // should be performed:

  // If "true", invoke on header klass field.

  bool do_header() { return true; } // Note that this is non-virtual.

  // 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; }

#ifdef ASSERT

  static bool _must_remember_klasses;

  static bool must_remember_klasses();

  static void set_must_remember_klasses(bool v);

#endif

};

// 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 ObjectClosure {

 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 {

  OopClosure* _cl;

public:

  void do_object(oop obj);

  ObjectToOopClosure(OopClosure* 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;

};

// 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 SerializeOopClosure : public OopClosure {

public:

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

  virtual bool reading() const = 0;

  // Read/write the int pointed to by i.

  virtual void do_int(int* i) = 0;

  // Read/write the size_t pointed to by i.

  virtual void do_size_t(size_t* i) = 0;

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

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

  // Read/write the HeapWord pointer pointed to be p.

  virtual void do_ptr(HeapWord** 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;

};

#ifdef ASSERT

// This class is used to flag phases of a collection that

// can unload classes and which should override the

// should_remember_klasses() and remember_klass() of OopClosure.

// The _must_remember_klasses is set in the contructor and restored

// in the destructor.  _must_remember_klasses is checked in assertions

// in the OopClosure implementations of should_remember_klasses() and

// remember_klass() and the expectation is that the OopClosure

// implementation should not be in use if _must_remember_klasses is set.

// Instances of RememberKlassesChecker can be place in

// marking phases of collections which can do class unloading.

// RememberKlassesChecker can be passed "false" to turn off checking.

// It is used by CMS when CMS yields to a different collector.

class RememberKlassesChecker: StackObj {

 bool _state;

 bool _skip;

 public:

  RememberKlassesChecker(bool checking_on) : _state(false), _skip(false) {

    _skip = !(ClassUnloading && !UseConcMarkSweepGC ||

              CMSClassUnloadingEnabled && UseConcMarkSweepGC);

    if (_skip) {

      return;

    }

    _state = OopClosure::must_remember_klasses();

    OopClosure::set_must_remember_klasses(checking_on);

  }

  ~RememberKlassesChecker() {

    if (_skip) {

      return;

    }

    OopClosure::set_must_remember_klasses(_state);

  }

};

#endif  // ASSERT