/*

 * Copyright (c) 1997, 2017, 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

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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 "oops/oopsHierarchy.hpp"

class CodeBlob;

class nmethod;

class ReferenceProcessor;

class DataLayout;

class KlassClosure;

class ClassLoaderData;

class Symbol;

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

class Closure : public StackObj { };

// 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(narrowOop* o) = 0;

};

// 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 {

 private:

  ReferenceProcessor* _ref_processor;

 protected:

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

  ExtendedOopClosure() : _ref_processor(NULL) { }

  ~ExtendedOopClosure() { }

  void set_ref_processor_internal(ReferenceProcessor* rp) { _ref_processor = rp; }

 public:

  ReferenceProcessor* ref_processor() const { return _ref_processor; }

  // Iteration of InstanceRefKlasses differ depending on the closure,

  // the below enum describes the different alternatives.

  enum ReferenceIterationMode {

  };

  // The default iteration mode is to do discovery.

  virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }

  // 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_cld   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 and G1 need these.

  bool do_metadata_nv()      { return false; }

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

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

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

  void do_cld_nv(ClassLoaderData* cld)      { ShouldNotReachHere(); }

  virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }

  // 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; }

#ifdef ASSERT

  // Default verification of each visited oop field.

  template <typename T> void verify(T* p);

  // Can be used by subclasses to turn off the default verification of oop fields.

  virtual bool should_verify_oops() { return true; }

#endif

};

// 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 {

  friend class MetadataAwareOopClosure;

  friend class MetadataAwareOopsInGenClosure;

  OopClosure* _oop_closure;

  // Used when _oop_closure couldn't be set in an initialization list.

  void initialize(OopClosure* oop_closure) {

    assert(_oop_closure == NULL, "Should only be called once");

    _oop_closure = oop_closure;

  }

 public:

  KlassToOopClosure(OopClosure* oop_closure = NULL) : _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);

};

class CLDToKlassAndOopClosure : public CLDClosure {

  friend class G1CollectedHeap;

 protected:

  OopClosure*   _oop_closure;

  KlassClosure* _klass_closure;

  bool          _must_claim_cld;

 public:

  CLDToKlassAndOopClosure(KlassClosure* klass_closure,

                          OopClosure* oop_closure,

                          bool must_claim_cld) :

                              _oop_closure(oop_closure),

                              _klass_closure(klass_closure),

                              _must_claim_cld(must_claim_cld) {}

  void do_cld(ClassLoaderData* cld);

};

// The base class for all concurrent marking closures,

// that participates in class unloading.

// It's used to proxy through the metadata to the oops defined in them.

class MetadataAwareOopClosure: public ExtendedOopClosure {

  KlassToOopClosure _klass_closure;

 public:

  MetadataAwareOopClosure() : ExtendedOopClosure() {

    _klass_closure.initialize(this);

  }

  MetadataAwareOopClosure(ReferenceProcessor* rp) : ExtendedOopClosure(rp) {

    _klass_closure.initialize(this);

  }

  bool do_metadata_nv()      { return true; }

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

  void do_klass_nv(Klass* k);

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

  void do_cld_nv(ClassLoaderData* cld);

  virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(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;

};

class AlwaysTrueClosure: public BoolObjectClosure {

 public:

  bool do_object_b(oop p) { return true; }

};

class AlwaysFalseClosure : public BoolObjectClosure {

 public:

  bool do_object_b(oop p) { return false; }

};

// 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;

};

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

// iterated over in an object iteration.

class CodeBlobToOopClosure : public CodeBlobClosure {

  OopClosure* _cl;

  bool _fix_relocations;

 protected:

  void do_nmethod(nmethod* nm);

 public:

  // If fix_relocations(), then cl must copy objects to their new location immediately to avoid

  // patching nmethods with the old locations.

  CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}

  virtual void do_code_blob(CodeBlob* cb);

  bool fix_relocations() const { return _fix_relocations; }

  const static bool FixRelocations = true;

};

class MarkingCodeBlobClosure : public CodeBlobToOopClosure {

 public:

  MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}

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

  virtual void do_code_blob(CodeBlob* cb);

};

// 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 32-bit unsigned integer pointed to by p.

  virtual void do_u4(u4* 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;

  bool writing() {

    return !reading();

  }

};

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));

  }

};

// The two class template specializations are used to dispatch calls

// to the ExtendedOopClosure functions. If use_non_virtual_call is true,

// the non-virtual versions are called (E.g. do_oop_nv), otherwise the

// virtual versions are called (E.g. do_oop).

template <bool use_non_virtual_call>

class Devirtualizer {};

// Dispatches to the non-virtual functions.

template <> class Devirtualizer<true> {

 public:

  template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);

  template <class OopClosureType>             static void do_klass(OopClosureType* closure, Klass* k);

  template <class OopClosureType>             static void do_cld(OopClosureType* closure, ClassLoaderData* cld);

  template <class OopClosureType>             static bool do_metadata(OopClosureType* closure);

};

// Dispatches to the virtual functions.

template <> class Devirtualizer<false> {

 public:

  template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);

  template <class OopClosureType>             static void do_klass(OopClosureType* closure, Klass* k);

  template <class OopClosureType>             static void do_cld(OopClosureType* closure, ClassLoaderData* cld);

  template <class OopClosureType>             static bool do_metadata(OopClosureType* closure);

};

#endif // SHARE_VM_MEMORY_ITERATOR_HPP