/*

 * Copyright (c) 2003, 2010, 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 "oops/oop.inline.hpp"

#include "prims/jvmtiRedefineClassesTrace.hpp"

#include "services/classLoadingService.hpp"

#include "utilities/hashtable.inline.hpp"

DictionaryEntry*  Dictionary::_current_class_entry = NULL;

int               Dictionary::_current_class_index =    0;

Dictionary::Dictionary(int table_size)

  : TwoOopHashtable(table_size, sizeof(DictionaryEntry)) {

  _current_class_index = 0;

  _current_class_entry = NULL;

};

Dictionary::Dictionary(int table_size, HashtableBucket* t,

                       int number_of_entries)

  : TwoOopHashtable(table_size, sizeof(DictionaryEntry), t, number_of_entries) {

  _current_class_index = 0;

  _current_class_entry = NULL;

};

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

                                       oop loader) {

  DictionaryEntry* entry;

  entry = (DictionaryEntry*)Hashtable::new_entry(hash, klass);

  entry->set_loader(loader);

  entry->set_pd_set(NULL);

  return entry;

}

DictionaryEntry* Dictionary::new_entry() {

  DictionaryEntry* entry = (DictionaryEntry*)Hashtable::new_entry(0L, NULL);

  entry->set_loader(NULL);

  entry->set_pd_set(NULL);

  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::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(oop protection_domain) {

  assert_locked_or_safepoint(SystemDictionary_lock);

  if (!contains_protection_domain(protection_domain)) {

    ProtectionDomainEntry* new_head =

                new ProtectionDomainEntry(protection_domain, _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(BoolObjectClosure* is_alive) {

  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;

      klassOop e = probe->klass();

      oop class_loader = probe->loader();

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

      if (ik->previous_versions() != NULL) {

        // This klass has previous versions so see what we can cleanup

        // while it is safe to do so.

        int gc_count = 0;    // leave debugging breadcrumbs

        int live_count = 0;

        // RC_TRACE macro has an embedded ResourceMark

        RC_TRACE(0x00000200, ("unload: %s: previous version length=%d",

          ik->external_name(), ik->previous_versions()->length()));

        for (int i = ik->previous_versions()->length() - 1; i >= 0; i--) {

          // check the previous versions array for GC'ed weak refs

          PreviousVersionNode * pv_node = ik->previous_versions()->at(i);

          jobject cp_ref = pv_node->prev_constant_pool();

          assert(cp_ref != NULL, "cp ref was unexpectedly cleared");

          if (cp_ref == NULL) {

            delete pv_node;

            ik->previous_versions()->remove_at(i);

            // Since we are traversing the array backwards, we don't have to

            // do anything special with the index.

            continue;  // robustness

          }

          constantPoolOop pvcp = (constantPoolOop)JNIHandles::resolve(cp_ref);

          if (pvcp == NULL) {

            // this entry has been GC'ed so remove it

            delete pv_node;

            ik->previous_versions()->remove_at(i);

            // Since we are traversing the array backwards, we don't have to

            // do anything special with the index.

            gc_count++;

            continue;

          } else {

            RC_TRACE(0x00000200, ("unload: previous version @%d is alive", i));

            if (is_alive->do_object_b(pvcp)) {

              live_count++;

            } else {

              guarantee(false, "sanity check");

            }

          }

          GrowableArray<jweak>* method_refs = pv_node->prev_EMCP_methods();

          if (method_refs != NULL) {

            RC_TRACE(0x00000200, ("unload: previous methods length=%d",

              method_refs->length()));

            for (int j = method_refs->length() - 1; j >= 0; j--) {

              jweak method_ref = method_refs->at(j);

              assert(method_ref != NULL, "weak method ref was unexpectedly cleared");

              if (method_ref == NULL) {

                method_refs->remove_at(j);

                // Since we are traversing the array backwards, we don't have to

                // do anything special with the index.

                continue;  // robustness

              }

              methodOop method = (methodOop)JNIHandles::resolve(method_ref);

              if (method == NULL) {

                // this method entry has been GC'ed so remove it

                JNIHandles::destroy_weak_global(method_ref);

                method_refs->remove_at(j);

              } else {

                // RC_TRACE macro has an embedded ResourceMark

                RC_TRACE(0x00000200,

                  ("unload: %s(%s): prev method @%d in version @%d is alive",

                  method->name()->as_C_string(),

                  method->signature()->as_C_string(), j, i));

              }

            }

          }

        }

        assert(ik->previous_versions()->length() == live_count, "sanity check");

        RC_TRACE(0x00000200,

          ("unload: previous version stats: live=%d, GC'ed=%d", live_count,

          gc_count));

      }

      // Non-unloadable classes were handled in always_strong_oops_do

      if (!is_strongly_reachable(class_loader, e)) {

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

        assert(class_loader != NULL, "unloading entry with null class loader");

        oop k_def_class_loader = ik->class_loader();

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

        bool purge_entry = false;

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

        if (!is_alive->do_object_b(class_loader)) {

          // 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 == class_loader) {

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

            // to be unloaded.

            // Notify the debugger and clean up the class.

            guarantee(!is_alive->do_object_b(e),

                      "klass should not be live if defining loader is not");

            class_was_unloaded = true;

            // notify the debugger

            if (JvmtiExport::should_post_class_unload()) {

              JvmtiExport::post_class_unload(ik->as_klassOop());

            }

            // notify ClassLoadingService of class unload

            ClassLoadingService::notify_class_unloaded(ik);

            // Clean up C heap

            ik->release_C_heap_structures();

          }

          // Also remove this system dictionary entry.

          purge_entry = true;

        } else {

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

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

          // defining loader). Remove this entry.

          if (!is_alive->do_object_b(e)) {

            guarantee(!is_alive->do_object_b(k_def_class_loader),

                      "defining loader should not be live if klass is not");

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

            // loader, it must be an initiating one.

            assert(k_def_class_loader != class_loader,

                   "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_classes_do(OopClosure* blk) {

  // 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()) {

      oop e = probe->klass();

      oop class_loader = probe->loader();

      if (is_strongly_reachable(class_loader, e)) {

        blk->do_oop((oop*)probe->klass_addr());

        if (class_loader != NULL) {

          blk->do_oop(probe->loader_addr());

        }

        probe->protection_domain_set_oops_do(blk);

      }

    }

  }

}

//   Just the classes from defining class loaders

void Dictionary::classes_do(void f(klassOop)) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      klassOop k = probe->klass();

      if (probe->loader() == instanceKlass::cast(k)->class_loader()) {

        f(k);

      }

    }

  }

}

// Added for initialize_itable_for_klass to handle exceptions

//   Just the classes from defining class loaders

void Dictionary::classes_do(void f(klassOop, TRAPS), TRAPS) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      klassOop k = probe->klass();

      if (probe->loader() == instanceKlass::cast(k)->class_loader()) {

        f(k, CHECK);

      }

    }

  }

}

//   All classes, and their class loaders

//   (added for helpers that use HandleMarks and ResourceMarks)

// Don't iterate over placeholders

void Dictionary::classes_do(void f(klassOop, oop, TRAPS), TRAPS) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      klassOop k = probe->klass();

      f(k, probe->loader(), CHECK);

    }

  }

}

//   All classes, and their class loaders

// Don't iterate over placeholders

void Dictionary::classes_do(void f(klassOop, oop)) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      klassOop k = probe->klass();

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

    }

  }

}

void Dictionary::oops_do(OopClosure* f) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      f->do_oop((oop*)probe->klass_addr());

      if (probe->loader() != NULL) {

        f->do_oop(probe->loader_addr());

      }

      probe->protection_domain_set_oops_do(f);

    }

  }

}

void Dictionary::methods_do(void f(methodOop)) {

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

    for (DictionaryEntry* probe = bucket(index);

                          probe != NULL;

                          probe = probe->next()) {

      klassOop k = probe->klass();

      if (probe->loader() == instanceKlass::cast(k)->class_loader()) {

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

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

      }

    }

  }

}

klassOop Dictionary::try_get_next_class() {

  while (true) {

    if (_current_class_entry != NULL) {

      klassOop 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(symbolHandle class_name, Handle class_loader,

                           KlassHandle obj) {

  assert_locked_or_safepoint(SystemDictionary_lock);

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

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

  unsigned int hash = compute_hash(class_name, class_loader);

  int index = hash_to_index(hash);

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

  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,

                                       symbolHandle class_name,

                                       Handle class_loader) {

  symbolOop name_ = class_name();

  oop loader_ = class_loader();

  debug_only(_lookup_count++);

  for (DictionaryEntry* entry = bucket(index);

                        entry != NULL;

                        entry = entry->next()) {

    if (entry->hash() == hash && entry->equals(name_, loader_)) {

      return entry;

    }

    debug_only(_lookup_length++);

  }

  return NULL;

}

klassOop Dictionary::find(int index, unsigned int hash, symbolHandle name,

                          Handle loader, Handle protection_domain, TRAPS) {

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

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

    return entry->klass();

  } else {

    return NULL;

  }

}

klassOop Dictionary::find_class(int index, unsigned int hash,

                                symbolHandle name, Handle loader) {

  assert_locked_or_safepoint(SystemDictionary_lock);

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

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

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

}

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

// that table is static.

klassOop Dictionary::find_shared_class(int index, unsigned int hash,

                                       symbolHandle name) {

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

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

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

}

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

                                       instanceKlassHandle klass,

                                       Handle loader, Handle protection_domain,

                                       TRAPS) {

  symbolHandle klass_name(THREAD, klass->name());

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

  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(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,

                                            symbolHandle name,

                                            Handle loader,

                                            Handle protection_domain) {

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

  return entry->is_valid_protection_domain(protection_domain);

}

void Dictionary::reorder_dictionary() {

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