/*

 * Copyright (c) 2003, 2018, 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/systemDictionary.hpp"

#include "gc/shared/collectedHeap.hpp"

#include "memory/universe.hpp"

#include "prims/jvmtiGetLoadedClasses.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/jniHandles.inline.hpp"

#include "runtime/thread.hpp"

#include "utilities/stack.inline.hpp"

// The closure for GetLoadedClasses

class LoadedClassesClosure : public KlassClosure {

private:

  Stack<jclass, mtInternal> _classStack;

  JvmtiEnv* _env;

  Thread*   _cur_thread;

public:

  LoadedClassesClosure(Thread* thread, JvmtiEnv* env) : _cur_thread(thread), _env(env) {

    assert(_cur_thread == Thread::current(), "must be current thread");

  }

  void do_klass(Klass* k) {

    // Collect all jclasses

    _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));

  }

  int extract(jclass* result_list) {

    // The size of the Stack will be 0 after extract, so get it here

    int count = (int)_classStack.size();

    int i = count;

    // Pop all jclasses, fill backwards

    while (!_classStack.is_empty()) {

      result_list[--i] = _classStack.pop();

    }

    // Return the number of elements written

    return count;

  }

  // Return current size of the Stack

  int get_count() {

    return (int)_classStack.size();

  }

};

// The closure for GetClassLoaderClasses

class JvmtiGetLoadedClassesClosure : public StackObj {

  // Since the ClassLoaderDataGraph::dictionary_all_entries_do callback

  // doesn't pass a closureData pointer,

  // we use a thread-local slot to hold a pointer to

  // a stack allocated instance of this structure.

 private:

  jobject _initiatingLoader;

  int     _count;

  Handle* _list;

  int     _index;

 private:

  // Getting and setting the thread local pointer

  static JvmtiGetLoadedClassesClosure* get_this() {

    JvmtiGetLoadedClassesClosure* result = NULL;

    JavaThread* thread = JavaThread::current();

    result = thread->get_jvmti_get_loaded_classes_closure();

    return result;

  }

  static void set_this(JvmtiGetLoadedClassesClosure* that) {

    JavaThread* thread = JavaThread::current();

    thread->set_jvmti_get_loaded_classes_closure(that);

  }

 public:

  // Constructor/Destructor

  JvmtiGetLoadedClassesClosure() {

    JvmtiGetLoadedClassesClosure* that = get_this();

    assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");

    _initiatingLoader = NULL;

    _count = 0;

    _list = NULL;

    _index = 0;

    set_this(this);

  }

  JvmtiGetLoadedClassesClosure(jobject initiatingLoader) {

    JvmtiGetLoadedClassesClosure* that = get_this();

    assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");

    _initiatingLoader = initiatingLoader;

    _count = 0;

    _list = NULL;

    _index = 0;

    set_this(this);

  }

  ~JvmtiGetLoadedClassesClosure() {

    JvmtiGetLoadedClassesClosure* that = get_this();

    assert(that != NULL, "JvmtiGetLoadedClassesClosure not found");

    set_this(NULL);

    _initiatingLoader = NULL;

    _count = 0;

    if (_list != NULL) {

      FreeHeap(_list);

      _list = NULL;

    }

    _index = 0;

  }

  // Accessors.

  jobject get_initiatingLoader() {

    return _initiatingLoader;

  }

  int get_count() {

    return _count;

  }

  void set_count(int value) {

    _count = value;

  }

  Handle* get_list() {

    return _list;

  }

  void set_list(Handle* value) {

    _list = value;

  }

  int get_index() {

    return _index;

  }

  void set_index(int value) {

    _index = value;

  }

  Handle get_element(int index) {

    if ((_list != NULL) && (index < _count)) {

      return _list[index];

    } else {

      assert(false, "empty get_element");

      return Handle();

    }

  }

  void set_element(int index, Handle value) {

    if ((_list != NULL) && (index < _count)) {

      _list[index] = value;

    } else {

      assert(false, "bad set_element");

    }

  }

  // Other predicates

  bool available() {

    return (_list != NULL);

  }

#ifdef ASSERT

  // For debugging.

  void check(int limit) {

    for (int i = 0; i < limit; i += 1) {

      assert(Universe::heap()->is_in(get_element(i)()), "check fails");

    }

  }

#endif

  // Public methods that get called within the scope of the closure

  void allocate() {

    _list = NEW_C_HEAP_ARRAY(Handle, _count, mtInternal);

    assert(_list != NULL, "Out of memory");

    if (_list == NULL) {

      _count = 0;

    }

  }

  void extract(JvmtiEnv *env, jclass* result) {

    for (int index = 0; index < _count; index += 1) {

      result[index] = (jclass) env->jni_reference(get_element(index));

    }

  }

  static void increment_with_loader(InstanceKlass* k, ClassLoaderData* loader_data) {

    JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

    oop class_loader = loader_data->class_loader();

    if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {

      for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

        that->set_count(that->get_count() + 1);

      }

    }

  }

  static void add_with_loader(InstanceKlass* k, ClassLoaderData* loader_data) {

    JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

    if (that->available()) {

      oop class_loader = loader_data->class_loader();

      if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {

        Thread *thread = Thread::current();

        for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

          Handle mirror(thread, l->java_mirror());

          that->set_element(that->get_index(), mirror);

          that->set_index(that->get_index() + 1);

        }

      }

    }

  }

  // increment the count for the given basic type array class (and any

  // multi-dimensional arrays). For example, for [B we check for

  // [[B, [[[B, .. and the count is incremented for each one that exists.

  static void increment_for_basic_type_arrays(Klass* k) {

    JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

    assert(that != NULL, "no JvmtiGetLoadedClassesClosure");

    for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

      that->set_count(that->get_count() + 1);

    }

  }

  // add the basic type array class and its multi-dimensional array classes to the list

  static void add_for_basic_type_arrays(Klass* k) {

    JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

    assert(that != NULL, "no JvmtiGetLoadedClassesClosure");

    assert(that->available(), "no list");

    Thread *thread = Thread::current();

    for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

      Handle mirror(thread, l->java_mirror());

      that->set_element(that->get_index(), mirror);

      that->set_index(that->get_index() + 1);

    }

  }

};

jvmtiError

JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {

  LoadedClassesClosure closure(Thread::current(), env);

  {

    // To get a consistent list of classes we need MultiArray_lock to ensure

    // array classes aren't created.

    MutexLocker ma(MultiArray_lock);

    // Iterate through all classes in ClassLoaderDataGraph

    // and collect them using the LoadedClassesClosure

    ClassLoaderDataGraph::loaded_classes_do(&closure);

  }

  // Return results by extracting the collected contents into a list

  // allocated via JvmtiEnv

  jclass* result_list;

  jvmtiError error = env->Allocate(closure.get_count() * sizeof(jclass),

                               (unsigned char**)&result_list);

  if (error == JVMTI_ERROR_NONE) {

    int count = closure.extract(result_list);

    *classCountPtr = count;

    *classesPtr = result_list;

  }

  return error;

}

jvmtiError

JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,

                                             jint* classCountPtr, jclass** classesPtr) {

  // Since ClassLoaderDataGraph::dictionary_all_entries_do only takes a function pointer

  // and doesn't call back with a closure data pointer,

  // we can only pass static methods.

  JvmtiGetLoadedClassesClosure closure(initiatingLoader);

  {

    // To get a consistent list of classes we need MultiArray_lock to ensure

    // array classes aren't created, and SystemDictionary_lock to ensure that

    // classes aren't added to the class loader data dictionaries.

    MutexLocker ma(MultiArray_lock);

    MutexLocker sd(SystemDictionary_lock);

    // First, count the classes in the class loader data dictionaries which have this loader recorded

    // as an initiating loader. For basic type arrays this information is not recorded

    // so GetClassLoaderClasses will return all of the basic type arrays. This is okay

    // because the defining loader for basic type arrays is always the boot class loader

    // and these classes are "visible" to all loaders.

    ClassLoaderDataGraph::dictionary_all_entries_do(&JvmtiGetLoadedClassesClosure::increment_with_loader);

    Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::increment_for_basic_type_arrays);

    // Next, fill in the classes

    closure.allocate();

    ClassLoaderDataGraph::dictionary_all_entries_do(&JvmtiGetLoadedClassesClosure::add_with_loader);

    Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::add_for_basic_type_arrays);

    // Drop the SystemDictionary_lock, so the results could be wrong from here,

    // but we still have a snapshot.

  }

  // Post results

  jclass* result_list;

  jvmtiError err = env->Allocate(closure.get_count() * sizeof(jclass),

                                 (unsigned char**)&result_list);

  if (err != JVMTI_ERROR_NONE) {

    return err;

  }

  closure.extract(env, result_list);

  *classCountPtr = closure.get_count();

  *classesPtr = result_list;

  return JVMTI_ERROR_NONE;

}