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 /*

  * Copyright (c) 1997, 2013, 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

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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 CLDClosure : public Closure {

  public:

   virtual void do_cld(ClassLoaderData* cld) = 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 : public CLDClosure {

   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 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