/*

 * Copyright (c) 2012, 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_CLASSFILE_CLASSLOADERDATA_HPP

#define SHARE_CLASSFILE_CLASSLOADERDATA_HPP

#include "memory/allocation.hpp"

#include "memory/memRegion.hpp"

#include "oops/oopHandle.hpp"

#include "oops/weakHandle.hpp"

#include "runtime/atomic.hpp"

#include "runtime/mutex.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/macros.hpp"

#if INCLUDE_JFR

#include "jfr/support/jfrTraceIdExtension.hpp"

#endif

// external name (synthetic) for the primordial "bootstrap" class loader instance

#define BOOTSTRAP_LOADER_NAME "bootstrap"

#define BOOTSTRAP_LOADER_NAME_LEN 9

//

// A class loader represents a linkset. Conceptually, a linkset identifies

// the complete transitive closure of resolved links that a dynamic linker can

// produce.

//

// A ClassLoaderData also encapsulates the allocation space, called a metaspace,

// used by the dynamic linker to allocate the runtime representation of all

// the types it defines.

//

// ClassLoaderData are stored in the runtime representation of classes,

// and provides iterators for root tracing and other GC operations.

class ClassLoaderDataGraph;

class JNIMethodBlock;

class ModuleEntry;

class PackageEntry;

class ModuleEntryTable;

class PackageEntryTable;

class DictionaryEntry;

class Dictionary;

namespace metaspace {

  class ClassLoaderMetaspace;

}

// ClassLoaderData class

class ClassLoaderData : public CHeapObj<mtClass> {

  friend class VMStructs;

 private:

  class ChunkedHandleList {

    struct Chunk : public CHeapObj<mtClass> {

      static const size_t CAPACITY = 32;

      oop _data[CAPACITY];

      volatile juint _size;

      Chunk* _next;

      Chunk(Chunk* c) : _size(0), _next(c) { }

    };

    Chunk* volatile _head;

    void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);

   public:

    ChunkedHandleList() : _head(NULL) {}

    ~ChunkedHandleList();

    // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().

    // However, multiple threads can execute oops_do concurrently with add.

    oop* add(oop o);

    bool contains(oop p);

    NOT_PRODUCT(bool owner_of(oop* p);)

    void oops_do(OopClosure* f);

    int count() const;

  };

  friend class ClassLoaderDataGraph;

  friend class ClassLoaderDataGraphIterator;

  friend class ClassLoaderDataGraphKlassIteratorAtomic;

  friend class ClassLoaderDataGraphKlassIteratorStatic;

  friend class ClassLoaderDataGraphMetaspaceIterator;

  friend class Klass;

  friend class MetaDataFactory;

  friend class Method;

  static ClassLoaderData * _the_null_class_loader_data;

  WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader

  OopHandle _class_loader;    // The instance of java/lang/ClassLoader associated with

                              // this ClassLoaderData

  metaspace::ClassLoaderMetaspace* volatile _metaspace;  // Meta-space where meta-data defined by the

                                    // classes in the class loader are allocated.

  Mutex* _metaspace_lock;  // Locks the metaspace for allocations and setup.

  bool _unloading;         // true if this class loader goes away

  bool _is_unsafe_anonymous; // CLD is dedicated to one class and that class determines the CLDs lifecycle.

                             // For example, an unsafe anonymous class.

  // Remembered sets support for the oops in the class loader data.

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

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

  int _keep_alive;         // if this CLD is kept alive.

                           // Used for unsafe anonymous classes and the boot class

                           // loader. _keep_alive does not need to be volatile or

                           // atomic since there is one unique CLD per unsafe anonymous class.

  volatile int _claim; // non-zero if claimed, for example during GC traces.

                       // To avoid applying oop closure more than once.

  ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which

                              // have the same life cycle of the corresponding ClassLoader.

  NOT_PRODUCT(volatile int _dependency_count;)  // number of class loader dependencies

  Klass* volatile _klasses;              // The classes defined by the class loader.

  PackageEntryTable* volatile _packages; // The packages defined by the class loader.

  ModuleEntryTable*  volatile _modules;  // The modules defined by the class loader.

  ModuleEntry* _unnamed_module;          // This class loader's unnamed module.

  Dictionary*  _dictionary;              // The loaded InstanceKlasses, including initiated by this class loader

  // These method IDs are created for the class loader and set to NULL when the

  // class loader is unloaded.  They are rarely freed, only for redefine classes

  // and if they lose a data race in InstanceKlass.

  JNIMethodBlock*                  _jmethod_ids;

  // Metadata to be deallocated when it's safe at class unloading, when

  // this class loader isn't unloaded itself.

  GrowableArray<Metadata*>*      _deallocate_list;

  // Support for walking class loader data objects

  ClassLoaderData* _next; /// Next loader_datas created

  Klass*  _class_loader_klass;

  Symbol* _name;

  Symbol* _name_and_id;

  JFR_ONLY(DEFINE_TRACE_ID_FIELD;)

  void set_next(ClassLoaderData* next) { _next = next; }

  ClassLoaderData* next() const        { return Atomic::load(&_next); }

  ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous);

  ~ClassLoaderData();

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

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

  // The CT and MUT bits saves this information for the whole class loader data.

  void clear_modified_oops()             { _modified_oops = false; }

 public:

  void record_modified_oops()            { _modified_oops = true; }

  bool has_modified_oops()               { return _modified_oops; }

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

  void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }

  bool has_accumulated_modified_oops()   { return _accumulated_modified_oops; }

  oop holder_no_keepalive() const;

  oop holder_phantom() const;

 private:

  void unload();

  bool keep_alive() const       { return _keep_alive > 0; }

  void classes_do(void f(Klass* const));

  void loaded_classes_do(KlassClosure* klass_closure);

  void classes_do(void f(InstanceKlass*));

  void methods_do(void f(Method*));

  void modules_do(void f(ModuleEntry*));

  void packages_do(void f(PackageEntry*));

  // Deallocate free list during class unloading.

  void free_deallocate_list();                      // for the classes that are not unloaded

  void free_deallocate_list_C_heap_structures();    // for the classes that are unloaded

  // Allocate out of this class loader data

  MetaWord* allocate(size_t size);

  Dictionary* create_dictionary();

  void initialize_name(Handle class_loader);

 public:

  // GC interface.

  // The "claim" is typically used to check if oops_do needs to be applied on

  // the CLD or not. Most GCs only perform strong marking during the marking phase.

  enum Claim {

    _claim_none         = 0,

    _claim_finalizable  = 2,

    _claim_strong       = 3,

    _claim_other        = 4

  };

  void clear_claim() { _claim = 0; }

  void clear_claim(int claim);

  bool claimed() const { return _claim != 0; }

  bool claimed(int claim) const { return (_claim & claim) == claim; }

  bool try_claim(int claim);

  // Computes if the CLD is alive or not. This is safe to call in concurrent

  // contexts.

  bool is_alive() const;

  // Accessors

  metaspace::ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }

  static ClassLoaderData* the_null_class_loader_data() {

    return _the_null_class_loader_data;

  }

  Mutex* metaspace_lock() const { return _metaspace_lock; }

  bool is_unsafe_anonymous() const { return _is_unsafe_anonymous; }

  static void init_null_class_loader_data();

  bool is_the_null_class_loader_data() const {

    return this == _the_null_class_loader_data;

  }

  // Returns true if this class loader data is for the system class loader.

  // (Note that the class loader data may be unsafe anonymous.)

  bool is_system_class_loader_data() const;

  // Returns true if this class loader data is for the platform class loader.

  // (Note that the class loader data may be unsafe anonymous.)

  bool is_platform_class_loader_data() const;

  // Returns true if this class loader data is for the boot class loader.

  // (Note that the class loader data may be unsafe anonymous.)

  inline bool is_boot_class_loader_data() const;

  bool is_builtin_class_loader_data() const;

  bool is_permanent_class_loader_data() const;

  // The Metaspace is created lazily so may be NULL.  This

  // method will allocate a Metaspace if needed.

  metaspace::ClassLoaderMetaspace* metaspace_non_null();

  inline oop class_loader() const;

  // Returns true if this class loader data is for a loader going away.

  // Note that this is only safe after the GC has computed if the CLD is

  // unloading or not. In concurrent contexts where there are no such

  // guarantees, is_alive() should be used instead.

  bool is_unloading() const     {

    assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");

    return _unloading;

  }

  // Used to refcount an unsafe anonymous class's CLD in order to

  // indicate their aliveness.

  void inc_keep_alive();

  void dec_keep_alive();

  void initialize_holder(Handle holder);

  void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false);

  void classes_do(KlassClosure* klass_closure);

  Klass* klasses() { return _klasses; }

  JNIMethodBlock* jmethod_ids() const              { return _jmethod_ids; }

  void set_jmethod_ids(JNIMethodBlock* new_block)  { _jmethod_ids = new_block; }

  void print() const;

  void print_on(outputStream* out) const PRODUCT_RETURN;

  void print_value() const;

  void print_value_on(outputStream* out) const;

  void verify();

  OopHandle add_handle(Handle h);

  void remove_handle(OopHandle h);

  void init_handle_locked(OopHandle& pd, Handle h);  // used for concurrent access to ModuleEntry::_pd field

  void add_class(Klass* k, bool publicize = true);

  void remove_class(Klass* k);

  bool contains_klass(Klass* k);

  void record_dependency(const Klass* to);

  PackageEntryTable* packages() { return _packages; }

  ModuleEntry* unnamed_module() { return _unnamed_module; }

  ModuleEntryTable* modules();

  bool modules_defined() { return (_modules != NULL); }

  // Offsets

  static ByteSize holder_offset()     { return in_ByteSize(offset_of(ClassLoaderData, _holder)); }

  static ByteSize keep_alive_offset() { return in_ByteSize(offset_of(ClassLoaderData, _keep_alive)); }

  // Loaded class dictionary

  Dictionary* dictionary() const { return _dictionary; }

  void add_to_deallocate_list(Metadata* m);

  static ClassLoaderData* class_loader_data(oop loader);

  static ClassLoaderData* class_loader_data_or_null(oop loader);

  static ClassLoaderData* unsafe_anonymous_class_loader_data(Handle loader);

  // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.

  // Also works if unloading.

  Klass* class_loader_klass() const { return _class_loader_klass; }

  // Returns the class loader's explict name as specified during

  // construction or the class loader's qualified class name.

  // Works during unloading.

  const char* loader_name() const;

  // Returns the explicitly specified class loader name or NULL.

  Symbol* name() const { return _name; }

  // Obtain the class loader's _name_and_id, works during unloading.

  const char* loader_name_and_id() const;

  Symbol* name_and_id() const { return _name_and_id; }

  JFR_ONLY(DEFINE_TRACE_ID_METHODS;)

};

#endif // SHARE_CLASSFILE_CLASSLOADERDATA_HPP