/*

 * Copyright 1997-2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

// A Klass is the part of the klassOop that 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. The toplevel class "Klass"

// implements purpose 1 whereas all subclasses provide extra virtual functions

// for purpose 2.

// 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_"!

//  Klass layout:

//    [header        ] klassOop

//    [klass pointer ] klassOop

//    [C++ vtbl ptr  ] (contained in Klass_vtbl)

//    [layout_helper ]

//    [super_check_offset   ] for fast subtype checks

//    [secondary_super_cache] for fast subtype checks

//    [secondary_supers     ] array of 2ndary supertypes

//    [primary_supers 0]

//    [primary_supers 1]

//    [primary_supers 2]

//    ...

//    [primary_supers 7]

//    [java_mirror   ]

//    [super         ]

//    [name          ]

//    [first subklass]

//    [next_sibling  ] link to chain additional subklasses

//    [modifier_flags]

//    [access_flags  ]

//    [verify_count  ] - not in product

//    [alloc_count   ]

//    [last_biased_lock_bulk_revocation_time] (64 bits)

//    [prototype_header]

//    [biased_lock_revocation_count]

// Forward declarations.

class klassVtable;

class KlassHandle;

class OrderAccess;

// Holder (or cage) for the C++ vtable of each kind of Klass.

// We want to tightly constrain the location of the C++ vtable in the overall layout.

class Klass_vtbl {

 protected:

  // The following virtual exists only to force creation of a C++ vtable,

  // so that this class truly is the location of the vtable of all Klasses.

  virtual void unused_initial_virtual() { }

 public:

  // The following virtual makes Klass_vtbl play a second role as a

  // factory protocol for subclasses of Klass ("sub-Klasses").

  // Here's how it works....

  //

  // This VM uses metaobjects as factories for their instances.

  //

  // In order to initialize the C++ vtable of a new instance, its

  // metaobject is forced to use the C++ placed new operator to

  // allocate the instance.  In a typical C++-based system, each

  // sub-class would have its own factory routine which

  // directly uses the placed new operator on the desired class,

  // and then calls the appropriate chain of C++ constructors.

  //

  // However, this system uses shared code to performs the first

  // allocation and initialization steps for all sub-Klasses.

  // (See base_create_klass() and base_create_array_klass().)

  // This does not factor neatly into a hierarchy of C++ constructors.

  // Each caller of these shared "base_create" routines knows

  // exactly which sub-Klass it is creating, but the shared routine

  // does not, even though it must perform the actual allocation.

  //

  // Therefore, the caller of the shared "base_create" must wrap

  // the specific placed new call in a virtual function which

  // performs the actual allocation and vtable set-up.  That

  // virtual function is here, Klass_vtbl::allocate_permanent.

  //

  // The arguments to Universe::allocate_permanent() are passed

  // straight through the placed new operator, which in turn

  // obtains them directly from this virtual call.

  //

  // This virtual is called on a temporary "example instance" of the

  // sub-Klass being instantiated, a C++ auto variable.  The "real"

  // instance created by this virtual is on the VM heap, where it is

  // equipped with a klassOopDesc header.

  //

  // It is merely an accident of implementation that we use "example

  // instances", but that is why the virtual function which implements

  // each sub-Klass factory happens to be defined by the same sub-Klass

  // for which it creates instances.

  //

  // The vtbl_value() call (see below) is used to strip away the

  // accidental Klass-ness from an "example instance" and present it as

  // a factory.  Think of each factory object as a mere container of the

  // C++ vtable for the desired sub-Klass.  Since C++ does not allow

  // direct references to vtables, the factory must also be delegated

  // the task of allocating the instance, but the essential point is

  // that the factory knows how to initialize the C++ vtable with the

  // right pointer value.  All other common initializations are handled

  // by the shared "base_create" subroutines.

  //

  virtual void* allocate_permanent(KlassHandle& klass, int size, TRAPS) const = 0;

  void post_new_init_klass(KlassHandle& klass, klassOop obj, int size) const;

  // Every subclass on which vtbl_value is called must include this macro.

  // Delay the installation of the klassKlass pointer until after the

  // the vtable for a new klass has been installed (after the call to new()).

#define DEFINE_ALLOCATE_PERMANENT(thisKlass)                                  \

  void* allocate_permanent(KlassHandle& klass_klass, int size, TRAPS) const { \

    void* result = new(klass_klass, size, THREAD) thisKlass();                \

    if (HAS_PENDING_EXCEPTION) return NULL;                                   \

    klassOop new_klass = ((Klass*) result)->as_klassOop();                    \

    OrderAccess::storestore();                                                \

    post_new_init_klass(klass_klass, new_klass, size);                        \

    return result;                                                            \

  }

  bool null_vtbl() { return *(intptr_t*)this == 0; }

 protected:

  void* operator new(size_t ignored, KlassHandle& klass, int size, TRAPS);

};

class Klass : public Klass_vtbl {

  friend class VMStructs;

 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 Klass_vtbl,

  // 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;

 public:

  oop* oop_block_beg() const { return adr_secondary_super_cache(); }

  oop* oop_block_end() const { return adr_next_sibling() + 1; }

 protected:

  //

  // The oop block.  All oop fields must be declared here and only oop fields

  // may be declared here.  In addition, the first and last fields in this block

  // must remain first and last, unless oop_block_beg() and/or oop_block_end()

  // are updated.  Grouping the oop fields in a single block simplifies oop

  // iteration.

  //

  // Cache of last observed secondary supertype

  klassOop    _secondary_super_cache;

  // Array of all secondary supertypes

  objArrayOop _secondary_supers;

  // Ordered list of all primary supertypes

  klassOop    _primary_supers[_primary_super_limit];

  // java/lang/Class instance mirroring this class

  oop       _java_mirror;

  // Superclass

  klassOop  _super;

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

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

  symbolOop _name;

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

  klassOop _subklass;

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

  klassOop _next_sibling;

  //

  // End of the oop block.

  //

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

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

#ifndef PRODUCT

  int           _verify_count;  // to avoid redundant verifies

#endif

  juint    _alloc_count;        // allocation profiling support - update klass_size_in_bytes() if moved/deleted

  // 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;

 public:

  // returns the enclosing klassOop

  klassOop as_klassOop() const {

    // see klassOop.hpp for layout.

    return (klassOop) (((char*) this) - sizeof(klassOopDesc));

  }

 public:

  // Allocation

  const Klass_vtbl& vtbl_value() const { return *this; }  // used only on "example instances"

  static KlassHandle base_create_klass(KlassHandle& klass, int size, const Klass_vtbl& vtbl, TRAPS);

  static klassOop base_create_klass_oop(KlassHandle& klass, int size, const Klass_vtbl& vtbl, TRAPS);

  // super

  klassOop super() const               { return _super; }

  void set_super(klassOop k)           { oop_store_without_check((oop*) &_super, (oop) k); }

  // initializes _super link, _primary_supers & _secondary_supers arrays

  void initialize_supers(klassOop k, TRAPS);

  void initialize_supers_impl1(klassOop k);

  void initialize_supers_impl2(klassOop k);

  // klass-specific helper for initializing _secondary_supers

  virtual objArrayOop compute_secondary_supers(int num_extra_slots, TRAPS);

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

  virtual klassOop 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; }

  klassOop secondary_super_cache() const     { return _secondary_super_cache; }

  void set_secondary_super_cache(klassOop k) { oop_store_without_check((oop*) &_secondary_super_cache, (oop) k); }

  objArrayOop secondary_supers() const { return _secondary_supers; }

  void set_secondary_supers(objArrayOop k) { oop_store_without_check((oop*) &_secondary_supers, (oop) k); }

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

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

  klassOop primary_super_of_depth(juint i) const {

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

    klassOop super = _primary_supers[i];

    assert(super == NULL || super->klass_part()->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 = secondary_super_cache_offset_in_bytes() + sizeof(oopDesc);

    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() - (primary_supers_offset_in_bytes() + sizeof(oopDesc))) / sizeof(klassOop);

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

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

      return d;

    }

  }

  // java mirror

  oop java_mirror() const              { return _java_mirror; }

  void set_java_mirror(oop m)          { oop_store((oop*) &_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

  instanceKlass* superklass() const;

  Klass* subklass() const;

  Klass* next_sibling() const;

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

  void remove_from_sibling_list();         // remove receiver from sibling list

 protected:                                // internal accessors

  klassOop subklass_oop() const            { return _subklass; }

  klassOop next_sibling_oop() const        { return _next_sibling; }

  void     set_subklass(klassOop s);

  void     set_next_sibling(klassOop s);

  oop* adr_super()           const { return (oop*)&_super;             }

  oop* adr_primary_supers()  const { return (oop*)&_primary_supers[0]; }

  oop* adr_secondary_super_cache() const { return (oop*)&_secondary_super_cache; }

  oop* adr_secondary_supers()const { return (oop*)&_secondary_supers;  }

  oop* adr_java_mirror()     const { return (oop*)&_java_mirror;       }

  oop* adr_name()            const { return (oop*)&_name;              }

  oop* adr_subklass()        const { return (oop*)&_subklass;          }

  oop* adr_next_sibling()    const { return (oop*)&_next_sibling;      }

 public:

  // Allocation profiling support

  juint alloc_count() const          { return _alloc_count; }

  void set_alloc_count(juint n)      { _alloc_count = n; }

  virtual juint alloc_size() const = 0;

  virtual void set_alloc_size(juint n) = 0;

  // Compiler support

  static int super_offset_in_bytes()         { return offset_of(Klass, _super); }

  static int super_check_offset_offset_in_bytes() { return offset_of(Klass, _super_check_offset); }

  static int primary_supers_offset_in_bytes(){ return offset_of(Klass, _primary_supers); }

  static int secondary_super_cache_offset_in_bytes() { return offset_of(Klass, _secondary_super_cache); }

  static int secondary_supers_offset_in_bytes() { return offset_of(Klass, _secondary_supers); }

  static int java_mirror_offset_in_bytes()   { return offset_of(Klass, _java_mirror); }

  static int modifier_flags_offset_in_bytes(){ return offset_of(Klass, _modifier_flags); }

  static int layout_helper_offset_in_bytes() { return offset_of(Klass, _layout_helper); }

  static int access_flags_offset_in_bytes()  { return 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_type_value    = ~0x00,  // 0xC0000000 >> 30

    _lh_array_tag_obj_value     = ~0x01   // 0x80000000 >> 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_javaArray(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;

  }

  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");

    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 << LogHeapWordSize)

      |    (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 >> LogHeapWordSize;

  }

  // 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

  virtual klassVtable* vtable() const        { return NULL; }

  static int klass_size_in_bytes()           { return offset_of(Klass, _alloc_count) + sizeof(juint); }  // all "visible" fields

  // subclass check

  bool is_subclass_of(klassOop k) const;

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

  bool is_subtype_of(klassOop k) const {

    juint    off = k->klass_part()->super_check_offset();

    klassOop sup = *(klassOop*)( (address)as_klassOop() + off );

    const juint secondary_offset = secondary_super_cache_offset_in_bytes() + sizeof(oopDesc);

    if (sup == k) {

      return true;

    } else if (off != secondary_offset) {

      return false;

    } else {

      return search_secondary_supers(k);

    }

  }

  bool search_secondary_supers(klassOop 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);

  // Casting

  static Klass* cast(klassOop k) {

    assert(k->is_klass(), "cast to Klass");

    return k->klass_part();

  }

  // 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 methodOop uncached_lookup_method(symbolOop name, symbolOop signature) const;

 public:

  methodOop lookup_method(symbolOop name, symbolOop signature) const {

    return uncached_lookup_method(name, signature);

  }

  // array class with specific rank

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

  // array class with this klass as element type

  klassOop 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.

  klassOop array_klass_or_null(int rank);

  klassOop array_klass_or_null();

  virtual oop protection_domain()       { return NULL; }

  virtual oop class_loader()  const     { return NULL; }

 protected:

  virtual klassOop array_klass_impl(bool or_null, int rank, TRAPS);

  virtual klassOop array_klass_impl(bool or_null, TRAPS);

 public:

  virtual void remove_unshareable_info();

 protected:

  // computes the subtype relationship

  virtual bool compute_is_subtype_of(klassOop k);

 public:

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