/*

 * Copyright (c) 2003, 2014, 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/dictionary.hpp"

#include "classfile/systemDictionary.hpp"

#include "memory/iterator.hpp"

#include "oops/oop.inline.hpp"

#include "prims/jvmtiRedefineClassesTrace.hpp"

#include "runtime/orderAccess.inline.hpp"

#include "utilities/hashtable.inline.hpp"

DictionaryEntry*  Dictionary::_current_class_entry = NULL;

int               Dictionary::_current_class_index =    0;

Dictionary::Dictionary(int table_size)

  : TwoOopHashtable<Klass*, mtClass>(table_size, sizeof(DictionaryEntry)) {

  _current_class_index = 0;

  _current_class_entry = NULL;

  _pd_cache_table = new ProtectionDomainCacheTable(defaultProtectionDomainCacheSize);

};

Dictionary::Dictionary(int table_size, HashtableBucket<mtClass>* t,

                       int number_of_entries)

  : TwoOopHashtable<Klass*, mtClass>(table_size, sizeof(DictionaryEntry), t, number_of_entries) {

  _current_class_index = 0;

  _current_class_entry = NULL;

  _pd_cache_table = new ProtectionDomainCacheTable(defaultProtectionDomainCacheSize);

};

ProtectionDomainCacheEntry* Dictionary::cache_get(oop protection_domain) {

  return _pd_cache_table->get(protection_domain);

}

DictionaryEntry* Dictionary::new_entry(unsigned int hash, Klass* klass,

                                       ClassLoaderData* loader_data) {

  DictionaryEntry* entry = (DictionaryEntry*)Hashtable<Klass*, mtClass>::new_entry(hash, klass);

  entry->set_loader_data(loader_data);

  entry->set_pd_set(NULL);

  assert(klass->oop_is_instance(), "Must be");

  return entry;

}

void Dictionary::free_entry(DictionaryEntry* entry) {

  // avoid recursion when deleting linked list

  while (entry->pd_set() != NULL) {

    ProtectionDomainEntry* to_delete = entry->pd_set();

    entry->set_pd_set(to_delete->next());

    delete to_delete;

  }

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

}

bool DictionaryEntry::contains_protection_domain(oop protection_domain) const {

#ifdef ASSERT

  if (protection_domain == InstanceKlass::cast(klass())->protection_domain()) {

    // Ensure this doesn't show up in the pd_set (invariant)

    bool in_pd_set = false;

    for (ProtectionDomainEntry* current = _pd_set;

                                current != NULL;

                                current = current->next()) {

      if (current->protection_domain() == protection_domain) {

        in_pd_set = true;

        break;

      }

    }

    if (in_pd_set) {

      assert(false, "A klass's protection domain should not show up "

                    "in its sys. dict. PD set");

    }

  }

#endif /* ASSERT */

  if (protection_domain == InstanceKlass::cast(klass())->protection_domain()) {

    // Succeeds trivially

    return true;

  }

  for (ProtectionDomainEntry* current = _pd_set;

                              current != NULL;

                              current = current->next()) {

    if (current->protection_domain() == protection_domain) return true;

  }

  return false;

}

void DictionaryEntry::add_protection_domain(Dictionary* dict, oop protection_domain) {

  assert_locked_or_safepoint(SystemDictionary_lock);

  if (!contains_protection_domain(protection_domain)) {

    ProtectionDomainCacheEntry* entry = dict->cache_get(protection_domain);

    ProtectionDomainEntry* new_head =

                new ProtectionDomainEntry(entry, _pd_set);

    // Warning: Preserve store ordering.  The SystemDictionary is read

    //          without locks.  The new ProtectionDomainEntry must be

    //          complete before other threads can be allowed to see it

    //          via a store to _pd_set.

    OrderAccess::release_store_ptr(&_pd_set, new_head);

  }

  if (TraceProtectionDomainVerification && WizardMode) {

    print();

  }

}

bool Dictionary::do_unloading() {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

  bool class_was_unloaded = false;

  int  index = 0; // Defined here for portability! Do not move

  // Remove unloadable entries and classes from system dictionary

  // The placeholder array has been handled in always_strong_oops_do.

  DictionaryEntry* probe = NULL;

  for (index = 0; index < table_size(); index++) {

    for (DictionaryEntry** p = bucket_addr(index); *p != NULL; ) {

      probe = *p;

      Klass* e = probe->klass();

      ClassLoaderData* loader_data = probe->loader_data();

      InstanceKlass* ik = InstanceKlass::cast(e);

      // Non-unloadable classes were handled in always_strong_oops_do

      if (!is_strongly_reachable(loader_data, e)) {

        // Entry was not visited in phase1 (negated test from phase1)

        assert(!loader_data->is_the_null_class_loader_data(), "unloading entry with null class loader");

        ClassLoaderData* k_def_class_loader_data = ik->class_loader_data();

        // Do we need to delete this system dictionary entry?

        bool purge_entry = false;

        // Do we need to delete this system dictionary entry?

        if (loader_data->is_unloading()) {

          // If the loader is not live this entry should always be

          // removed (will never be looked up again). Note that this is

          // not the same as unloading the referred class.

          if (k_def_class_loader_data == loader_data) {

            // This is the defining entry, so the referred class is about

            // to be unloaded.

            class_was_unloaded = true;

          }

          // Also remove this system dictionary entry.

          purge_entry = true;

        } else {

          // The loader in this entry is alive. If the klass is dead,

          // (determined by checking the defining class loader)

          // the loader must be an initiating loader (rather than the

          // defining loader). Remove this entry.

          if (k_def_class_loader_data->is_unloading()) {

            // If we get here, the class_loader_data must not be the defining

            // loader, it must be an initiating one.

            assert(k_def_class_loader_data != loader_data,

                   "cannot have live defining loader and unreachable klass");

            // Loader is live, but class and its defining loader are dead.

            // Remove the entry. The class is going away.

            purge_entry = true;

          }

        }

        if (purge_entry) {

          *p = probe->next();

          if (probe == _current_class_entry) {

            _current_class_entry = NULL;

          }

          free_entry(probe);

          continue;

        }

      }

      p = probe->next_addr();

    }

  }

  return class_was_unloaded;

}

void Dictionary::always_strong_oops_do(OopClosure* blk) {

  // Follow all system classes and temporary placeholders in dictionary; only

  // protection domain oops contain references into the heap. In a first

  // pass over the system dictionary determine which need to be treated as

  // strongly reachable and mark them as such.

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

    for (DictionaryEntry *probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      Klass* e = probe->klass();

      ClassLoaderData* loader_data = probe->loader_data();

      if (is_strongly_reachable(loader_data, e)) {

        probe->set_strongly_reachable();

      }

    }

  }

  // Then iterate over the protection domain cache to apply the closure on the

  // previously marked ones.

  _pd_cache_table->always_strong_oops_do(blk);

}

void Dictionary::always_strong_classes_do(KlassClosure* closure) {

  // Follow all system classes and temporary placeholders in dictionary

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      Klass* e = probe->klass();

      ClassLoaderData* loader_data = probe->loader_data();

      if (is_strongly_reachable(loader_data, e)) {

        closure->do_klass(e);

      }

    }

  }

}

//   Just the classes from defining class loaders

void Dictionary::classes_do(void f(Klass*)) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      Klass* k = probe->klass();

      if (probe->loader_data() == InstanceKlass::cast(k)->class_loader_data()) {

        f(k);

      }

    }

  }

}

// Added for initialize_itable_for_klass to handle exceptions

//   Just the classes from defining class loaders

void Dictionary::classes_do(void f(Klass*, TRAPS), TRAPS) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      Klass* k = probe->klass();

      if (probe->loader_data() == InstanceKlass::cast(k)->class_loader_data()) {

        f(k, CHECK);

      }

    }

  }

}

//   All classes, and their class loaders

// Don't iterate over placeholders

void Dictionary::classes_do(void f(Klass*, ClassLoaderData*)) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      Klass* k = probe->klass();

      f(k, probe->loader_data());

    }

  }

}

void Dictionary::oops_do(OopClosure* f) {

  // Only the protection domain oops contain references into the heap. Iterate

  // over all of them.

  _pd_cache_table->oops_do(f);

}

void Dictionary::methods_do(void f(Method*)) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      Klass* k = probe->klass();

      if (probe->loader_data() == InstanceKlass::cast(k)->class_loader_data()) {

        // only take klass is we have the entry with the defining class loader

        InstanceKlass::cast(k)->methods_do(f);

      }

    }

  }

}

void Dictionary::unlink(BoolObjectClosure* is_alive) {

  // Only the protection domain cache table may contain references to the heap

  // that need to be unlinked.

  _pd_cache_table->unlink(is_alive);

}

Klass* Dictionary::try_get_next_class() {

  while (true) {

    if (_current_class_entry != NULL) {

      Klass* k = _current_class_entry->klass();

      _current_class_entry = _current_class_entry->next();

      return k;

    }

    _current_class_index = (_current_class_index + 1) % table_size();

    _current_class_entry = bucket(_current_class_index);

  }

  // never reached

}

// Add a loaded class to the system dictionary.

// Readers of the SystemDictionary aren't always locked, so _buckets

// is volatile. The store of the next field in the constructor is

// also cast to volatile;  we do this to ensure store order is maintained

// by the compilers.

void Dictionary::add_klass(Symbol* class_name, ClassLoaderData* loader_data,

                           KlassHandle obj) {

  assert_locked_or_safepoint(SystemDictionary_lock);

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

  assert(obj()->name() == class_name, "sanity check on name");

  assert(loader_data != NULL, "Must be non-NULL");

  unsigned int hash = compute_hash(class_name, loader_data);

  int index = hash_to_index(hash);

  DictionaryEntry* entry = new_entry(hash, obj(), loader_data);

  add_entry(index, entry);

}

// This routine does not lock the system dictionary.

//

// Since readers don't hold a lock, we must make sure that system

// dictionary entries are only removed at a safepoint (when only one

// thread is running), and are added to in a safe way (all links must

// be updated in an MT-safe manner).

//

// Callers should be aware that an entry could be added just after

// _buckets[index] is read here, so the caller will not see the new entry.

DictionaryEntry* Dictionary::get_entry(int index, unsigned int hash,

                                       Symbol* class_name,

                                       ClassLoaderData* loader_data) {

  debug_only(_lookup_count++);

  for (DictionaryEntry* entry = bucket(index);

                        entry != NULL;

                        entry = entry->next()) {

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

      return entry;

    }

    debug_only(_lookup_length++);

  }

  return NULL;

}

Klass* Dictionary::find(int index, unsigned int hash, Symbol* name,

                          ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {

  DictionaryEntry* entry = get_entry(index, hash, name, loader_data);

  if (entry != NULL && entry->is_valid_protection_domain(protection_domain)) {

    return entry->klass();

  } else {

    return NULL;

  }

}

Klass* Dictionary::find_class(int index, unsigned int hash,

                                Symbol* name, ClassLoaderData* loader_data) {

  assert_locked_or_safepoint(SystemDictionary_lock);

  assert (index == index_for(name, loader_data), "incorrect index?");

  DictionaryEntry* entry = get_entry(index, hash, name, loader_data);

  return (entry != NULL) ? entry->klass() : (Klass*)NULL;

}

// Variant of find_class for shared classes.  No locking required, as

// that table is static.

Klass* Dictionary::find_shared_class(int index, unsigned int hash,

                                       Symbol* name) {

  assert (index == index_for(name, NULL), "incorrect index?");

  DictionaryEntry* entry = get_entry(index, hash, name, NULL);

  return (entry != NULL) ? entry->klass() : (Klass*)NULL;

}

void Dictionary::add_protection_domain(int index, unsigned int hash,

                                       instanceKlassHandle klass,

                                       ClassLoaderData* loader_data, Handle protection_domain,

                                       TRAPS) {

  Symbol*  klass_name = klass->name();

  DictionaryEntry* entry = get_entry(index, hash, klass_name, loader_data);

  assert(entry != NULL,"entry must be present, we just created it");

  assert(protection_domain() != NULL,

         "real protection domain should be present");

  entry->add_protection_domain(this, protection_domain());

  assert(entry->contains_protection_domain(protection_domain()),

         "now protection domain should be present");

}

bool Dictionary::is_valid_protection_domain(int index, unsigned int hash,

                                            Symbol* name,

                                            ClassLoaderData* loader_data,

                                            Handle protection_domain) {

  DictionaryEntry* entry = get_entry(index, hash, name, loader_data);

  return entry->is_valid_protection_domain(protection_domain);

}

void Dictionary::reorder_dictionary() {

  // Copy all the dictionary entries into a single master list.

  DictionaryEntry* master_list = NULL;

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

    DictionaryEntry* p = bucket(i);

    while (p != NULL) {

      DictionaryEntry* tmp;

      tmp = p->next();

      p->set_next(master_list);

      master_list = p;

      p = tmp;

    }

    set_entry(i, NULL);

  }

  // Add the dictionary entries back to the list in the correct buckets.

  while (master_list != NULL) {

    DictionaryEntry* p = master_list;

    master_list = master_list->next();

    p->set_next(NULL);

    Symbol* class_name = InstanceKlass::cast((Klass*)(p->klass()))->name();

    // Since the null class loader data isn't copied to the CDS archive,

    // compute the hash with NULL for loader data.

    unsigned int hash = compute_hash(class_name, NULL);

    int index = hash_to_index(hash);

    p->set_hash(hash);

    p->set_loader_data(NULL);   // loader_data isn't copied to CDS

    p->set_next(bucket(index));

    set_entry(index, p);

  }

}

ProtectionDomainCacheTable::ProtectionDomainCacheTable(int table_size)

  : Hashtable<oop, mtClass>(table_size, sizeof(ProtectionDomainCacheEntry))

{

}

void ProtectionDomainCacheTable::unlink(BoolObjectClosure* is_alive) {

  assert(SafepointSynchronize::is_at_safepoint(), "must be");

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

    ProtectionDomainCacheEntry** p = bucket_addr(i);

    ProtectionDomainCacheEntry* entry = bucket(i);

    while (entry != NULL) {

      if (is_alive->do_object_b(entry->literal())) {

        p = entry->next_addr();

      } else {

        *p = entry->next();

        free_entry(entry);

      }

      entry = *p;

    }

  }

}

void ProtectionDomainCacheTable::oops_do(OopClosure* f) {

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

    for (ProtectionDomainCacheEntry* probe = bucket(index);

                                     probe != NULL;

                                     probe = probe->next()) {

      probe->oops_do(f);

    }

  }

}

uint ProtectionDomainCacheTable::bucket_size() {

  return sizeof(ProtectionDomainCacheEntry);

}

#ifndef PRODUCT

void ProtectionDomainCacheTable::print() {

  tty->print_cr("Protection domain cache table (table_size=%d, classes=%d)",

                table_size(), number_of_entries());

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

    for (ProtectionDomainCacheEntry* probe = bucket(index);

                                     probe != NULL;

                                     probe = probe->next()) {

      probe->print();

    }

  }