/*

 * Copyright (c) 2003, 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_PLACEHOLDERS_HPP

#define SHARE_CLASSFILE_PLACEHOLDERS_HPP

#include "runtime/thread.hpp"

#include "utilities/hashtable.hpp"

class PlaceholderEntry;

// Placeholder objects. These represent classes currently

// being loaded, as well as arrays of primitives.

//

class PlaceholderTable : public Hashtable<Symbol*, mtClass> {

public:

  PlaceholderTable(int table_size);

  PlaceholderEntry* new_entry(int hash, Symbol* name, ClassLoaderData* loader_data, bool havesupername, Symbol* supername);

  void free_entry(PlaceholderEntry* entry);

  PlaceholderEntry* bucket(int i) const {

    return (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::bucket(i);

  }

  PlaceholderEntry** bucket_addr(int i) {

    return (PlaceholderEntry**)Hashtable<Symbol*, mtClass>::bucket_addr(i);

  }

  void add_entry(int index, PlaceholderEntry* new_entry) {

    Hashtable<Symbol*, mtClass>::add_entry(index, (HashtableEntry<Symbol*, mtClass>*)new_entry);

  }

  void add_entry(int index, unsigned int hash, Symbol* name,

                ClassLoaderData* loader_data, bool havesupername, Symbol* supername);

  // This returns a Symbol* to match type for SystemDictionary

  Symbol* find_entry(int index, unsigned int hash,

                       Symbol* name, ClassLoaderData* loader_data);

  PlaceholderEntry* get_entry(int index, unsigned int hash,

                       Symbol* name, ClassLoaderData* loader_data);

// caller to create a placeholder entry must enumerate an action

// caller claims ownership of that action

// For parallel classloading:

// multiple LOAD_INSTANCE threads can proceed in parallel

// multiple LOAD_SUPER threads can proceed in parallel

// LOAD_SUPER needed to check for class circularity

// DEFINE_CLASS: ultimately define class must be single threaded

// on a class/classloader basis

// so the head of that queue owns the token

// and the rest of the threads return the result the first thread gets

 enum classloadAction {

    LOAD_INSTANCE = 1,             // calling load_instance_class

    LOAD_SUPER = 2,                // loading superclass for this class

    DEFINE_CLASS = 3               // find_or_define class

 };

  // find_and_add returns probe pointer - old or new

  // If no entry exists, add a placeholder entry and push SeenThread for classloadAction

  // If entry exists, reuse entry and push SeenThread for classloadAction

  PlaceholderEntry* find_and_add(int index, unsigned int hash,

                                 Symbol* name, ClassLoaderData* loader_data,

                                 classloadAction action, Symbol* supername,

                                 Thread* thread);

  void remove_entry(int index, unsigned int hash,

                    Symbol* name, ClassLoaderData* loader_data);

  // find_and_remove first removes SeenThread for classloadAction

  // If all queues are empty and definer is null, remove the PlacheholderEntry completely

  void find_and_remove(int index, unsigned int hash,

                       Symbol* name, ClassLoaderData* loader_data,

                       classloadAction action, Thread* thread);

  void print_on(outputStream* st) const;

  void verify();

};

// SeenThread objects represent list of threads that are

// currently performing a load action on a class.

// For class circularity, set before loading a superclass.

// For bootclasssearchpath, set before calling load_instance_class.

// Defining must be single threaded on a class/classloader basis

// For DEFINE_CLASS, the head of the queue owns the

// define token and the rest of the threads wait to return the

// result the first thread gets.

class SeenThread: public CHeapObj<mtInternal> {

private:

   Thread *_thread;

   SeenThread* _stnext;

   SeenThread* _stprev;

public:

   SeenThread(Thread *thread) {

       _thread = thread;

       _stnext = NULL;

       _stprev = NULL;

   }

   Thread* thread()                const { return _thread;}

   void set_thread(Thread *thread) { _thread = thread; }

   SeenThread* next()              const { return _stnext;}

   void set_next(SeenThread *seen) { _stnext = seen; }

   void set_prev(SeenThread *seen) { _stprev = seen; }

  void print_action_queue(outputStream* st) {

    SeenThread* seen = this;

    while (seen != NULL) {

      seen->thread()->print_value_on(st);

      st->print(", ");

      seen = seen->next();

    }

  }

};

// Placeholder objects represent classes currently being loaded.

// All threads examining the placeholder table must hold the

// SystemDictionary_lock, so we don't need special precautions

// on store ordering here.

// The system dictionary is the only user of this class.

class PlaceholderEntry : public HashtableEntry<Symbol*, mtClass> {

 private:

  ClassLoaderData*  _loader_data;   // initiating loader

  bool              _havesupername; // distinguish between null supername, and unknown

  Symbol*           _supername;

  Thread*           _definer;       // owner of define token

  InstanceKlass*    _instanceKlass; // InstanceKlass from successful define

  SeenThread*       _superThreadQ;  // doubly-linked queue of Threads loading a superclass for this class

  SeenThread*       _loadInstanceThreadQ;  // loadInstance thread

                                    // can be multiple threads if classloader object lock broken by application

                                    // or if classloader supports parallel classloading

  SeenThread*       _defineThreadQ; // queue of Threads trying to define this class

                                    // including _definer

                                    // _definer owns token

                                    // queue waits for and returns results from _definer

 public:

  // Simple accessors, used only by SystemDictionary

  Symbol*            klassname()           const { return literal(); }

  ClassLoaderData*   loader_data()         const { return _loader_data; }

  void               set_loader_data(ClassLoaderData* loader_data) { _loader_data = loader_data; }

  bool               havesupername()       const { return _havesupername; }

  void               set_havesupername(bool havesupername) { _havesupername = havesupername; }

  Symbol*            supername()           const { return _supername; }

  void               set_supername(Symbol* supername) {

    _supername = supername;

    if (_supername != NULL) _supername->increment_refcount();

  }

  Thread*            definer()             const {return _definer; }

  void               set_definer(Thread* definer) { _definer = definer; }

  InstanceKlass*     instance_klass()      const {return _instanceKlass; }

  void               set_instance_klass(InstanceKlass* ik) { _instanceKlass = ik; }

  SeenThread*        superThreadQ()        const { return _superThreadQ; }

  void               set_superThreadQ(SeenThread* SeenThread) { _superThreadQ = SeenThread; }

  SeenThread*        loadInstanceThreadQ() const { return _loadInstanceThreadQ; }

  void               set_loadInstanceThreadQ(SeenThread* SeenThread) { _loadInstanceThreadQ = SeenThread; }

  SeenThread*        defineThreadQ()        const { return _defineThreadQ; }

  void               set_defineThreadQ(SeenThread* SeenThread) { _defineThreadQ = SeenThread; }

  PlaceholderEntry* next() const {

    return (PlaceholderEntry*)HashtableEntry<Symbol*, mtClass>::next();

  }

  PlaceholderEntry** next_addr() {

    return (PlaceholderEntry**)HashtableEntry<Symbol*, mtClass>::next_addr();

  }

  // Test for equality

  // Entries are unique for class/classloader name pair

  bool equals(Symbol* class_name, ClassLoaderData* loader) const {

    return (klassname() == class_name && loader_data() == loader);

  }

  SeenThread* actionToQueue(PlaceholderTable::classloadAction action) {

    SeenThread* queuehead = NULL;

    switch (action) {

      case PlaceholderTable::LOAD_INSTANCE:

         queuehead = _loadInstanceThreadQ;

         break;

      case PlaceholderTable::LOAD_SUPER:

         queuehead = _superThreadQ;

         break;

      case PlaceholderTable::DEFINE_CLASS:

         queuehead = _defineThreadQ;

         break;

      default: Unimplemented();

    }

    return queuehead;

  }

  void set_threadQ(SeenThread* seenthread, PlaceholderTable::classloadAction action) {

    switch (action) {

      case PlaceholderTable::LOAD_INSTANCE:

         _loadInstanceThreadQ = seenthread;

         break;

      case PlaceholderTable::LOAD_SUPER:

         _superThreadQ = seenthread;

         break;

      case PlaceholderTable::DEFINE_CLASS:

         _defineThreadQ = seenthread;

         break;

      default: Unimplemented();

    }

    return;

  }

  bool super_load_in_progress() {

     return (_superThreadQ != NULL);

  }

  bool instance_load_in_progress() {

    return (_loadInstanceThreadQ != NULL);

  }

  bool define_class_in_progress() {

    return (_defineThreadQ != NULL);

  }

// Doubly-linked list of Threads per action for class/classloader pair

// Class circularity support: links in thread before loading superclass

// bootstrapsearchpath support: links in a thread before load_instance_class

// definers: use as queue of define requestors, including owner of

// define token. Appends for debugging of requestor order

  void add_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {

    assert_lock_strong(SystemDictionary_lock);

    SeenThread* threadEntry = new SeenThread(thread);

    SeenThread* seen = actionToQueue(action);

    if (seen == NULL) {

      set_threadQ(threadEntry, action);

      return;

    }

    SeenThread* next;

    while ((next = seen->next()) != NULL) {

      seen = next;

    }

    seen->set_next(threadEntry);

    threadEntry->set_prev(seen);

    return;

  }

  bool check_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {

    assert_lock_strong(SystemDictionary_lock);

    SeenThread* threadQ = actionToQueue(action);

    SeenThread* seen = threadQ;

    while (seen) {

      if (thread == seen->thread()) {

        return true;

      }

      seen = seen->next();

    }

    return false;

  }

  // returns true if seenthreadQ is now empty

  // Note, caller must ensure probe still exists while holding

  // SystemDictionary_lock

  // ignores if cleanup has already been done

  // if found, deletes SeenThread

  bool remove_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {

    assert_lock_strong(SystemDictionary_lock);

    SeenThread* threadQ = actionToQueue(action);

    SeenThread* seen = threadQ;

    SeenThread* prev = NULL;

    while (seen) {

      if (thread == seen->thread()) {

        if (prev) {

          prev->set_next(seen->next());

        } else {

          set_threadQ(seen->next(), action);

        }

        if (seen->next()) {

          seen->next()->set_prev(prev);

        }

        delete seen;

        break;

      }

      prev = seen;

      seen = seen->next();

    }

    return (actionToQueue(action) == NULL);

  }

  // Print method doesn't append a cr

  void print_entry(outputStream* st) const;

  void verify() const;

};

#endif // SHARE_CLASSFILE_PLACEHOLDERS_HPP