/*

 * Copyright (c) 2003, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "classfile/placeholders.hpp"

#include "classfile/systemDictionary.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/fieldType.hpp"

#include "utilities/hashtable.inline.hpp"

// Placeholder methods

PlaceholderEntry* PlaceholderTable::new_entry(int hash, Symbol* name,

                                              ClassLoaderData* loader_data,

                                              bool havesupername,

                                              Symbol* supername) {

  PlaceholderEntry* entry = (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::new_entry(hash, name);

  // Hashtable with Symbol* literal must increment and decrement refcount.

  name->increment_refcount();

  entry->set_loader_data(loader_data);

  entry->set_havesupername(havesupername);

  entry->set_supername(supername);

  entry->set_superThreadQ(NULL);

  entry->set_loadInstanceThreadQ(NULL);

  entry->set_defineThreadQ(NULL);

  entry->set_definer(NULL);

  entry->set_instance_klass(NULL);

  return entry;

}

void PlaceholderTable::free_entry(PlaceholderEntry* entry) {

  // decrement Symbol refcount here because Hashtable doesn't.

  entry->literal()->decrement_refcount();

  if (entry->supername() != NULL) entry->supername()->decrement_refcount();

  Hashtable<Symbol*, mtClass>::free_entry(entry);

}

// 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.

void PlaceholderTable::add_entry(int index, unsigned int hash,

                                 Symbol* class_name, ClassLoaderData* loader_data,

                                 bool havesupername, Symbol* supername){

  assert_locked_or_safepoint(SystemDictionary_lock);

  assert(class_name != NULL, "adding NULL obj");

  // Both readers and writers are locked so it's safe to just

  // create the placeholder and insert it in the list without a membar.

  PlaceholderEntry* entry = new_entry(hash, class_name, loader_data, havesupername, supername);

  add_entry(index, entry);

}

// Remove a placeholder object.

void PlaceholderTable::remove_entry(int index, unsigned int hash,

                                    Symbol* class_name,

                                    ClassLoaderData* loader_data) {

  assert_locked_or_safepoint(SystemDictionary_lock);

  PlaceholderEntry** p = bucket_addr(index);

  while (*p) {

    PlaceholderEntry *probe = *p;

    if (probe->hash() == hash && probe->equals(class_name, loader_data)) {

      // Delete entry

      *p = probe->next();

      free_entry(probe);

      return;

    }

    p = probe->next_addr();

  }

}

PlaceholderEntry* PlaceholderTable::get_entry(int index, unsigned int hash,

                                       Symbol* class_name,

                                       ClassLoaderData* loader_data) {

  assert_locked_or_safepoint(SystemDictionary_lock);

  for (PlaceholderEntry *place_probe = bucket(index);

                         place_probe != NULL;

                         place_probe = place_probe->next()) {

    if (place_probe->hash() == hash &&

        place_probe->equals(class_name, loader_data)) {

      return place_probe;

    }

  }

  return NULL;

}

Symbol* PlaceholderTable::find_entry(int index, unsigned int hash,

                                       Symbol* class_name,

                                       ClassLoaderData* loader_data) {

  PlaceholderEntry* probe = get_entry(index, hash, class_name, loader_data);

  return (probe? probe->klassname(): (Symbol*)NULL);

}

  // find_and_add returns probe pointer - old or new

  // If no entry exists, add a placeholder entry

  // If entry exists, reuse entry

  // For both, push SeenThread for classloadAction

  // if havesupername: this is used for circularity for instanceklass loading

PlaceholderEntry* PlaceholderTable::find_and_add(int index, unsigned int hash,

                                                 Symbol* name,

                                                 ClassLoaderData* loader_data,

                                                 classloadAction action,

                                                 Symbol* supername,

                                                 Thread* thread) {

  PlaceholderEntry* probe = get_entry(index, hash, name, loader_data);

  if (probe == NULL) {

    // Nothing found, add place holder

    add_entry(index, hash, name, loader_data, (action == LOAD_SUPER), supername);

    probe = get_entry(index, hash, name, loader_data);

  } else {

    if (action == LOAD_SUPER) {

      probe->set_havesupername(true);

      probe->set_supername(supername);

    }

  }

  if (probe) probe->add_seen_thread(thread, action);

  return probe;

}

// placeholder is used to track class loading internal states

// placeholder existence now for loading superclass/superinterface

// superthreadQ tracks class circularity, while loading superclass/superinterface

// loadInstanceThreadQ tracks load_instance_class calls

// definer() tracks the single thread that owns define token

// defineThreadQ tracks waiters on defining thread's results

// 1st claimant creates placeholder

// find_and_add adds SeenThread entry for appropriate queue

// All claimants remove SeenThread after completing action

// On removal: if definer and all queues empty, remove entry

// Note: you can be in both placeholders and systemDictionary

// Therefore - must always check SD first

// Ignores the case where entry is not found

void PlaceholderTable::find_and_remove(int index, unsigned int hash,

                                       Symbol* name, ClassLoaderData* loader_data,

                                       classloadAction action,

                                       Thread* thread) {

    assert_locked_or_safepoint(SystemDictionary_lock);

    PlaceholderEntry *probe = get_entry(index, hash, name, loader_data);

    if (probe != NULL) {

       probe->remove_seen_thread(thread, action);

       // If no other threads using this entry, and this thread is not using this entry for other states

       if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL)

          && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) {

         remove_entry(index, hash, name, loader_data);

       }

    }

  }

PlaceholderTable::PlaceholderTable(int table_size)

    : Hashtable<Symbol*, mtClass>(table_size, sizeof(PlaceholderEntry)) {

}

void PlaceholderEntry::verify() const {

  guarantee(loader_data() != NULL, "Must have been setup.");

  guarantee(loader_data()->class_loader() == NULL || loader_data()->class_loader()->is_instance(),

            "checking type of _loader");

  guarantee(instance_klass() == NULL

            || instance_klass()->is_instance_klass(),

            "checking type of instance_klass result");

}

void PlaceholderTable::verify() {

  verify_table<PlaceholderEntry>("Placeholder Table");

}

// Note, doesn't append a cr

// Can't call this print_on because HashtableEntry doesn't initialize its vptr

// and print_on is a virtual function so the vptr call crashes.

void PlaceholderEntry::print_entry(outputStream* st) const {

  klassname()->print_value_on(st);

  if (loader_data() != NULL) {

    st->print(", loader ");

    loader_data()->print_value_on(st);

  }

  if (supername() != NULL) {

    st->print(", supername ");

    supername()->print_value_on(st);

  }

  if (definer() != NULL) {

    st->print(", definer ");

    definer()->print_value_on(st);

  }

  if (instance_klass() != NULL) {

    st->print(", InstanceKlass ");

    instance_klass()->print_value_on(st);

  }

  st->cr();

  st->print("loadInstanceThreadQ threads:");

  loadInstanceThreadQ()->print_action_queue(st);

  st->cr();

  st->print("superThreadQ threads:");

  superThreadQ()->print_action_queue(st);

  st->cr();

  st->print("defineThreadQ threads:");

  defineThreadQ()->print_action_queue(st);

  st->cr();

}

void PlaceholderTable::print_on(outputStream* st) const {

  st->print_cr("Placeholder table (table_size=%d, placeholders=%d)",

                table_size(), number_of_entries());

  for (int pindex = 0; pindex < table_size(); pindex++) {

    for (PlaceholderEntry* probe = bucket(pindex);

                           probe != NULL;

                           probe = probe->next()) {

      st->print("%4d: placeholder ", pindex);

      probe->print_entry(st);

    }

  }

}