/*

 * 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_OOPS_KLASS_HPP

#define SHARE_VM_OOPS_KLASS_HPP

#include "gc/shared/specialized_oop_closures.hpp"

#include "memory/iterator.hpp"

#include "memory/memRegion.hpp"

#include "oops/metadata.hpp"

#include "oops/oop.hpp"

#include "trace/traceMacros.hpp"

#include "utilities/accessFlags.hpp"

#include "utilities/macros.hpp"

//

// A Klass provides:

//  1: language level class object (method dictionary etc.)

//  2: provide vm dispatch behavior for the object

// Both functions are combined into one C++ class.

// One reason for the oop/klass dichotomy in the implementation is

// that we don't want a C++ vtbl pointer in every object.  Thus,

// normal oops don't have any virtual functions.  Instead, they

// forward all "virtual" functions to their klass, which does have

// a vtbl and does the C++ dispatch depending on the object's

// actual type.  (See oop.inline.hpp for some of the forwarding code.)

// ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!

// Forward declarations.

template <class T> class Array;

template <class T> class GrowableArray;

class ClassLoaderData;

class fieldDescriptor;

class KlassSizeStats;

class klassVtable;

class ModuleEntry;

class PackageEntry;

class ParCompactionManager;

class PSPromotionManager;

class vtableEntry;

class Klass : public Metadata {

  friend class VMStructs;

  friend class JVMCIVMStructs;

 protected:

  // note: put frequently-used fields together at start of klass structure

  // for better cache behavior (may not make much of a difference but sure won't hurt)

  enum { _primary_super_limit = 8 };

  // The "layout helper" is a combined descriptor of object layout.

  // For klasses which are neither instance nor array, the value is zero.

  //

  // For instances, layout helper is a positive number, the instance size.

  // This size is already passed through align_object_size and scaled to bytes.

  // The low order bit is set if instances of this class cannot be

  // allocated using the fastpath.

  //

  // For arrays, layout helper is a negative number, containing four

  // distinct bytes, as follows:

  //    MSB:[tag, hsz, ebt, log2(esz)]:LSB

  // where:

  //    tag is 0x80 if the elements are oops, 0xC0 if non-oops

  //    hsz is array header size in bytes (i.e., offset of first element)

  //    ebt is the BasicType of the elements

  //    esz is the element size in bytes

  // This packed word is arranged so as to be quickly unpacked by the

  // various fast paths that use the various subfields.

  //

  // The esz bits can be used directly by a SLL instruction, without masking.

  //

  // Note that the array-kind tag looks like 0x00 for instance klasses,

  // since their length in bytes is always less than 24Mb.

  //

  // Final note:  This comes first, immediately after C++ vtable,

  // because it is frequently queried.

  jint        _layout_helper;

  // The fields _super_check_offset, _secondary_super_cache, _secondary_supers

  // and _primary_supers all help make fast subtype checks.  See big discussion

  // in doc/server_compiler/checktype.txt

  //

  // Where to look to observe a supertype (it is &_secondary_super_cache for

  // secondary supers, else is &_primary_supers[depth()].

  juint       _super_check_offset;

  // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,

  // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.

  Symbol*     _name;

  // Cache of last observed secondary supertype

  Klass*      _secondary_super_cache;

  // Array of all secondary supertypes

  Array<Klass*>* _secondary_supers;

  // Ordered list of all primary supertypes

  Klass*      _primary_supers[_primary_super_limit];

  // java/lang/Class instance mirroring this class

  oop       _java_mirror;

  // Superclass

  Klass*      _super;

  // First subclass (NULL if none); _subklass->next_sibling() is next one

  Klass*      _subklass;

  // Sibling link (or NULL); links all subklasses of a klass

  Klass*      _next_sibling;

  // All klasses loaded by a class loader are chained through these links

  Klass*      _next_link;

  // The VM's representation of the ClassLoader used to load this class.

  // Provide access the corresponding instance java.lang.ClassLoader.

  ClassLoaderData* _class_loader_data;

  jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.

  AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.

  TRACE_DEFINE_TRACE_ID_FIELD;

  // Biased locking implementation and statistics

  // (the 64-bit chunk goes first, to avoid some fragmentation)

  jlong    _last_biased_lock_bulk_revocation_time;

  markOop  _prototype_header;   // Used when biased locking is both enabled and disabled for this type

  jint     _biased_lock_revocation_count;

  // vtable length

  int _vtable_len;

  // Remembered sets support for the oops in the klasses.

  jbyte _modified_oops;             // Card Table Equivalent (YC/CMS support)

  jbyte _accumulated_modified_oops; // Mod Union Equivalent (CMS support)

private:

  // This is an index into FileMapHeader::_classpath_entry_table[], to

  // associate this class with the JAR file where it's loaded from during

  // dump time. If a class is not loaded from the shared archive, this field is

  // -1.

  jshort _shared_class_path_index;

  friend class SharedClassUtil;

protected:

  // Constructor

  Klass();

  void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();

 public:

  enum DefaultsLookupMode { find_defaults, skip_defaults };

  enum OverpassLookupMode { find_overpass, skip_overpass };

  enum StaticLookupMode   { find_static,   skip_static };

  enum PrivateLookupMode  { find_private,  skip_private };

  bool is_klass() const volatile { return true; }

  // super

  Klass* super() const               { return _super; }

  void set_super(Klass* k)           { _super = k; }

  // initializes _super link, _primary_supers & _secondary_supers arrays

  void initialize_supers(Klass* k, TRAPS);

  void initialize_supers_impl1(Klass* k);

  void initialize_supers_impl2(Klass* k);

  // klass-specific helper for initializing _secondary_supers

  virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots);

  // java_super is the Java-level super type as specified by Class.getSuperClass.

  virtual Klass* java_super() const  { return NULL; }

  juint    super_check_offset() const  { return _super_check_offset; }

  void set_super_check_offset(juint o) { _super_check_offset = o; }

  Klass* secondary_super_cache() const     { return _secondary_super_cache; }

  void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }

  Array<Klass*>* secondary_supers() const { return _secondary_supers; }

  void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }

  // Return the element of the _super chain of the given depth.

  // If there is no such element, return either NULL or this.

  Klass* primary_super_of_depth(juint i) const {

    assert(i < primary_super_limit(), "oob");

    Klass* super = _primary_supers[i];

    assert(super == NULL || super->super_depth() == i, "correct display");

    return super;

  }

  // Can this klass be a primary super?  False for interfaces and arrays of

  // interfaces.  False also for arrays or classes with long super chains.

  bool can_be_primary_super() const {

    const juint secondary_offset = in_bytes(secondary_super_cache_offset());

    return super_check_offset() != secondary_offset;

  }

  virtual bool can_be_primary_super_slow() const;

  // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].

  juint super_depth() const {

    if (!can_be_primary_super()) {

      return primary_super_limit();

    } else {

      juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);

      assert(d < primary_super_limit(), "oob");

      assert(_primary_supers[d] == this, "proper init");

      return d;

    }

  }

  // store an oop into a field of a Klass

  void klass_oop_store(oop* p, oop v);

  void klass_oop_store(volatile oop* p, oop v);

  // java mirror

  oop java_mirror() const              { return _java_mirror; }

  void set_java_mirror(oop m) { klass_oop_store(&_java_mirror, m); }

  // modifier flags

  jint modifier_flags() const          { return _modifier_flags; }

  void set_modifier_flags(jint flags)  { _modifier_flags = flags; }

  // size helper

  int layout_helper() const            { return _layout_helper; }

  void set_layout_helper(int lh)       { _layout_helper = lh; }

  // Note: for instances layout_helper() may include padding.

  // Use InstanceKlass::contains_field_offset to classify field offsets.

  // sub/superklass links

  Klass* subklass() const              { return _subklass; }

  Klass* next_sibling() const          { return _next_sibling; }

  InstanceKlass* superklass() const;

  void append_to_sibling_list();           // add newly created receiver to superklass' subklass list

  void set_next_link(Klass* k) { _next_link = k; }

  Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.

  // class loader data

  ClassLoaderData* class_loader_data() const               { return _class_loader_data; }

  void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }

  // The Klasses are not placed in the Heap, so the Card Table or

  // the Mod Union Table can't be used to mark when klasses have modified oops.

  // The CT and MUT bits saves this information for the individual Klasses.

  void record_modified_oops()            { _modified_oops = 1; }

  void clear_modified_oops()             { _modified_oops = 0; }

  bool has_modified_oops()               { return _modified_oops == 1; }

  void accumulate_modified_oops()        { if (has_modified_oops()) _accumulated_modified_oops = 1; }

  void clear_accumulated_modified_oops() { _accumulated_modified_oops = 0; }

  bool has_accumulated_modified_oops()   { return _accumulated_modified_oops == 1; }

  int shared_classpath_index() const   {

    return _shared_class_path_index;

  };

  void set_shared_classpath_index(int index) {

    _shared_class_path_index = index;

  };

  // Obtain the module or package for this class

  virtual ModuleEntry* module() const = 0;

  virtual PackageEntry* package() const = 0;

 protected:                                // internal accessors

  void     set_subklass(Klass* s);

  void     set_next_sibling(Klass* s);

 public:

  // Compiler support

  static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }

  static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }

  static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }

  static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }

  static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }

  static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }

  static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }

  static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }

  static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }

  // Unpacking layout_helper:

  enum {

    _lh_neutral_value           = 0,  // neutral non-array non-instance value

    _lh_instance_slow_path_bit  = 0x01,

    _lh_log2_element_size_shift = BitsPerByte*0,

    _lh_log2_element_size_mask  = BitsPerLong-1,

    _lh_element_type_shift      = BitsPerByte*1,

    _lh_element_type_mask       = right_n_bits(BitsPerByte),  // shifted mask

    _lh_header_size_shift       = BitsPerByte*2,

    _lh_header_size_mask        = right_n_bits(BitsPerByte),  // shifted mask

    _lh_array_tag_bits          = 2,

    _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits,

    _lh_array_tag_obj_value     = ~0x01   // 0x80000000 >> 30

  };

  static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30

  static int layout_helper_size_in_bytes(jint lh) {

    assert(lh > (jint)_lh_neutral_value, "must be instance");

    return (int) lh & ~_lh_instance_slow_path_bit;

  }

  static bool layout_helper_needs_slow_path(jint lh) {

    assert(lh > (jint)_lh_neutral_value, "must be instance");

    return (lh & _lh_instance_slow_path_bit) != 0;

  }

  static bool layout_helper_is_instance(jint lh) {

    return (jint)lh > (jint)_lh_neutral_value;

  }

  static bool layout_helper_is_array(jint lh) {

    return (jint)lh < (jint)_lh_neutral_value;

  }

  static bool layout_helper_is_typeArray(jint lh) {

    // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);

    return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);

  }

  static bool layout_helper_is_objArray(jint lh) {

    // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);

    return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);

  }

  static int layout_helper_header_size(jint lh) {

    assert(lh < (jint)_lh_neutral_value, "must be array");

    int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;

    assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");

    return hsize;

  }

  static BasicType layout_helper_element_type(jint lh) {

    assert(lh < (jint)_lh_neutral_value, "must be array");

    int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;

    assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");

    return (BasicType) btvalue;

  }

  // Want a pattern to quickly diff against layout header in register

  // find something less clever!

  static int layout_helper_boolean_diffbit() {

    jint zlh = array_layout_helper(T_BOOLEAN);

    jint blh = array_layout_helper(T_BYTE);

    assert(zlh != blh, "array layout helpers must differ");

    int diffbit = 1;

    while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {

      diffbit <<= 1;

      assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");

    }

    return diffbit;

  }

  static int layout_helper_log2_element_size(jint lh) {

    assert(lh < (jint)_lh_neutral_value, "must be array");

    int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;

    assert(l2esz <= LogBitsPerLong,

           "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);

    return l2esz;

  }

  static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {

    return (tag        << _lh_array_tag_shift)

      |    (hsize      << _lh_header_size_shift)

      |    ((int)etype << _lh_element_type_shift)

      |    (log2_esize << _lh_log2_element_size_shift);

  }

  static jint instance_layout_helper(jint size, bool slow_path_flag) {

    return (size << LogBytesPerWord)

      |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);

  }

  static int layout_helper_to_size_helper(jint lh) {

    assert(lh > (jint)_lh_neutral_value, "must be instance");

    // Note that the following expression discards _lh_instance_slow_path_bit.

    return lh >> LogBytesPerWord;

  }

  // Out-of-line version computes everything based on the etype:

  static jint array_layout_helper(BasicType etype);

  // What is the maximum number of primary superclasses any klass can have?

#ifdef PRODUCT

  static juint primary_super_limit()         { return _primary_super_limit; }

#else

  static juint primary_super_limit() {

    assert(FastSuperclassLimit <= _primary_super_limit, "parameter oob");

    return FastSuperclassLimit;

  }

#endif

  // vtables

  klassVtable vtable() const;

  int vtable_length() const { return _vtable_len; }

  // subclass check

  bool is_subclass_of(const Klass* k) const;

  // subtype check: true if is_subclass_of, or if k is interface and receiver implements it

  bool is_subtype_of(Klass* k) const {

    juint    off = k->super_check_offset();

    Klass* sup = *(Klass**)( (address)this + off );

    const juint secondary_offset = in_bytes(secondary_super_cache_offset());

    if (sup == k) {

      return true;

    } else if (off != secondary_offset) {

      return false;

    } else {

      return search_secondary_supers(k);

    }

  }

  bool search_secondary_supers(Klass* k) const;

  // Find LCA in class hierarchy

  Klass *LCA( Klass *k );

  // Check whether reflection/jni/jvm code is allowed to instantiate this class;

  // if not, throw either an Error or an Exception.

  virtual void check_valid_for_instantiation(bool throwError, TRAPS);

  // array copying

  virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);

  // tells if the class should be initialized

  virtual bool should_be_initialized() const    { return false; }

  // initializes the klass

  virtual void initialize(TRAPS);

  // lookup operation for MethodLookupCache

  friend class MethodLookupCache;

  virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;

  virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature, OverpassLookupMode overpass_mode) const;

 public:

  Method* lookup_method(const Symbol* name, const Symbol* signature) const {

    return uncached_lookup_method(name, signature, find_overpass);

  }

  // array class with specific rank

  Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }

  // array class with this klass as element type

  Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }

  // These will return NULL instead of allocating on the heap:

  // NB: these can block for a mutex, like other functions with TRAPS arg.

  Klass* array_klass_or_null(int rank);

  Klass* array_klass_or_null();

  virtual oop protection_domain() const = 0;

  oop class_loader() const;

  virtual oop klass_holder() const      { return class_loader(); }

 protected:

  virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);

  virtual Klass* array_klass_impl(bool or_null, TRAPS);

  void set_vtable_length(int len) { _vtable_len= len; }

  vtableEntry* start_of_vtable() const;

 public:

  Method* method_at_vtable(int index);

  static ByteSize vtable_start_offset();

  static ByteSize vtable_length_offset() {

    return byte_offset_of(Klass, _vtable_len);

  }

  // CDS support - remove and restore oops from metadata. Oops are not shared.

  virtual void remove_unshareable_info();

  virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);

 protected:

  // computes the subtype relationship

  virtual bool compute_is_subtype_of(Klass* k);

 public:

  // subclass accessor (here for convenience; undefined for non-klass objects)

  virtual bool is_leaf_class() const { fatal("not a class"); return false; }

 public:

  // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP

  // These functions describe behavior for the oop not the KLASS.

  // actual oop size of obj in memory

  virtual int oop_size(oop obj) const = 0;

  // Size of klass in word size.

  virtual int size() const = 0;

#if INCLUDE_SERVICES

  virtual void collect_statistics(KlassSizeStats *sz) const;

#endif

  // Returns the Java name for a class (Resource allocated)

  // For arrays, this returns the name of the element with a leading '['.

  // For classes, this returns the name with the package separators

  //     turned into '.'s.