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 /*

  * Copyright (c) 1997, 2009, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

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

 class CodeBlob;

 class nmethod;

 class ReferenceProcessor;

 class DataLayout;

 // 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 */ }

   // In support of post-processing of weak references in

   // ProfileData (MethodDataOop) objects; see, for example,

   // VirtualCallData::oop_iterate().

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

   virtual void remember_mdo(DataLayout* v) { /* do nothing */ }

   // 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;

 };

 // 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 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 _saved_state;

  bool _do_check;

  public:

   RememberKlassesChecker(bool checking_on) : _saved_state(false),

     _do_check(true) {

     // The ClassUnloading unloading flag affects the collectors except

     // for CMS.

     // CMS unloads classes if CMSClassUnloadingEnabled is true or

     // if ExplicitGCInvokesConcurrentAndUnloadsClasses is true and

     // the current collection is an explicit collection.  Turning

     // on the checking in general for

     // ExplicitGCInvokesConcurrentAndUnloadsClasses and

     // UseConcMarkSweepGC should not lead to false positives.

     _do_check =

       ClassUnloading && !UseConcMarkSweepGC ||

       CMSClassUnloadingEnabled && UseConcMarkSweepGC ||

       ExplicitGCInvokesConcurrentAndUnloadsClasses && UseConcMarkSweepGC;

     if (_do_check) {

       _saved_state = OopClosure::must_remember_klasses();

       OopClosure::set_must_remember_klasses(checking_on);

     }

   }

   ~RememberKlassesChecker() {

     if (_do_check) {

       OopClosure::set_must_remember_klasses(_saved_state);

     }

   }

 };

 #endif  // ASSERT