/*

 * Copyright (c) 1997, 2019, 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_MEMORY_ITERATOR_HPP

#define SHARE_MEMORY_ITERATOR_HPP

#include "memory/allocation.hpp"

#include "memory/memRegion.hpp"

#include "oops/oopsHierarchy.hpp"

class CodeBlob;

class nmethod;

class ReferenceDiscoverer;

class DataLayout;

class KlassClosure;

class ClassLoaderData;

class Symbol;

class Metadata;

// 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;

};

class DoNothingClosure : public OopClosure {

 public:

  virtual void do_oop(oop* p)       {}

  virtual void do_oop(narrowOop* p) {}

};

extern DoNothingClosure do_nothing_cl;

// OopIterateClosure 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 OopIterateClosure : public OopClosure {

 private:

  ReferenceDiscoverer* _ref_discoverer;

 protected:

  OopIterateClosure(ReferenceDiscoverer* rd) : _ref_discoverer(rd) { }

  OopIterateClosure() : _ref_discoverer(NULL) { }

  ~OopIterateClosure() { }

  void set_ref_discoverer_internal(ReferenceDiscoverer* rd) { _ref_discoverer = rd; }

 public:

  ReferenceDiscoverer* ref_discoverer() const { return _ref_discoverer; }

  // Iteration of InstanceRefKlasses differ depending on the closure,

  // the below enum describes the different alternatives.

  enum ReferenceIterationMode {

    DO_DISCOVERY,                // Apply closure and discover references

    DO_DISCOVERED_AND_DISCOVERY, // Apply closure to discovered field and do discovery

    DO_FIELDS,                   // Apply closure to all fields

    DO_FIELDS_EXCEPT_REFERENT    // Apply closure to all fields except the referent field

  };

  // 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.

  virtual bool do_metadata() = 0;

  virtual void do_klass(Klass* k) = 0;

  virtual void do_cld(ClassLoaderData* cld) = 0;

#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

};

// An OopIterateClosure that can be used when there's no need to visit the Metadata.

class BasicOopIterateClosure : public OopIterateClosure {

public:

  BasicOopIterateClosure(ReferenceDiscoverer* rd = NULL) : OopIterateClosure(rd) {}

  virtual bool do_metadata() { return false; }

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

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

};

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 MetadataClosure : public Closure {

 public:

  virtual void do_metadata(Metadata* md) = 0;

};

class CLDToOopClosure : public CLDClosure {

  OopClosure*       _oop_closure;

  int               _cld_claim;

 public:

  CLDToOopClosure(OopClosure* oop_closure,

                  int cld_claim) :

      _oop_closure(oop_closure),

      _cld_claim(cld_claim) {}

  void do_cld(ClassLoaderData* cld);

};

class ClaimMetadataVisitingOopIterateClosure : public OopIterateClosure {

 protected:

  const int _claim;

 public:

  ClaimMetadataVisitingOopIterateClosure(int claim, ReferenceDiscoverer* rd = NULL) :

      OopIterateClosure(rd),

      _claim(claim) { }

  virtual bool do_metadata() { return true; }

  virtual void do_klass(Klass* k);

  virtual 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 MetadataVisitingOopIterateClosure: public ClaimMetadataVisitingOopIterateClosure {

 public:

  MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = NULL);

};

// 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 {

  OopIterateClosure* _cl;

public:

  void do_object(oop obj);

  ObjectToOopClosure(OopIterateClosure* 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);

};

class NMethodClosure : public Closure {

 public:

  virtual void do_nmethod(nmethod* n) = 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;

 // Yield on a fine-grain level. The check in case of not yielding should be very fast.

 virtual bool should_return_fine_grain() { return false; }

};

// 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 bool pointed to by p.

  virtual void do_bool(bool* 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;

  // Read/write the oop

  virtual void do_oop(oop* o) = 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));

  }

};

// Dispatches to the non-virtual functions if OopClosureType has

// a concrete implementation, otherwise a virtual call is taken.

class Devirtualizer {

 public:

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

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

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

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

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

};

class OopIteratorClosureDispatch {

 public:

  template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass);

  template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr);

  template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass);

};

#endif // SHARE_MEMORY_ITERATOR_HPP