openjdkjvmti/jvmti_weak_table-inl.h - LeafOS-Project/android_art - Gitiles

 /* Copyright (C) 2017 The Android Open Source Project
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This file implements interfaces from the file jvmti.h. This implementation
  * is licensed under the same terms as the file jvmti.h.  The
  * copyright and license information for the file jvmti.h follows.
  *
  * Copyright (c) 2003, 2011, 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.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * 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.
  */

 #ifndef ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_INL_H_
 #define ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_INL_H_

 #include "jvmti_weak_table.h"

 #include <limits>

 #include <android-base/logging.h>

 #include "art_jvmti.h"
 #include "gc/allocation_listener.h"
 #include "instrumentation.h"
 #include "jni_env_ext-inl.h"
 #include "jvmti_allocator.h"
 #include "mirror/class.h"
 #include "mirror/object.h"
 #include "nativehelper/scoped_local_ref.h"
 #include "runtime.h"

 namespace openjdkjvmti {

 template <typename T>
 void JvmtiWeakTable<T>::Lock() {
   allow_disallow_lock_.ExclusiveLock(art::Thread::Current());
 }
 template <typename T>
 void JvmtiWeakTable<T>::Unlock() {
   allow_disallow_lock_.ExclusiveUnlock(art::Thread::Current());
 }
 template <typename T>
 void JvmtiWeakTable<T>::AssertLocked() {
   allow_disallow_lock_.AssertHeld(art::Thread::Current());
 }

 template <typename T>
 void JvmtiWeakTable<T>::UpdateTableWithReadBarrier() {
   update_since_last_sweep_ = true;

   auto WithReadBarrierUpdater = [&](const art::GcRoot<art::mirror::Object>& original_root,
                                     art::mirror::Object* original_obj ATTRIBUTE_UNUSED)
      REQUIRES_SHARED(art::Locks::mutator_lock_) {
     return original_root.Read<art::kWithReadBarrier>();
   };

   UpdateTableWith<decltype(WithReadBarrierUpdater), kIgnoreNull>(WithReadBarrierUpdater);
 }

 template <typename T>
 bool JvmtiWeakTable<T>::GetTagSlowPath(art::Thread* self, art::mirror::Object* obj, T* result) {
   // Under concurrent GC, there is a window between moving objects and sweeping of system
   // weaks in which mutators are active. We may receive a to-space object pointer in obj,
   // but still have from-space pointers in the table. Explicitly update the table once.
   // Note: this will keep *all* objects in the table live, but should be a rare occurrence.
   UpdateTableWithReadBarrier();
   return GetTagLocked(self, obj, result);
 }

 template <typename T>
 bool JvmtiWeakTable<T>::Remove(art::mirror::Object* obj, /* out */ T* tag) {
   art::Thread* self = art::Thread::Current();
   art::MutexLock mu(self, allow_disallow_lock_);
   Wait(self);

   return RemoveLocked(self, obj, tag);
 }
 template <typename T>
 bool JvmtiWeakTable<T>::RemoveLocked(art::mirror::Object* obj, T* tag) {
   art::Thread* self = art::Thread::Current();
   allow_disallow_lock_.AssertHeld(self);
   Wait(self);

   return RemoveLocked(self, obj, tag);
 }

 template <typename T>
 bool JvmtiWeakTable<T>::RemoveLocked(art::Thread* self, art::mirror::Object* obj, T* tag) {
   auto it = tagged_objects_.find(art::GcRoot<art::mirror::Object>(obj));
   if (it != tagged_objects_.end()) {
     if (tag != nullptr) {
       *tag = it->second;
     }
     tagged_objects_.erase(it);
     return true;
   }

   if (art::kUseReadBarrier && self->GetIsGcMarking() && !update_since_last_sweep_) {
     // Under concurrent GC, there is a window between moving objects and sweeping of system
     // weaks in which mutators are active. We may receive a to-space object pointer in obj,
     // but still have from-space pointers in the table. Explicitly update the table once.
     // Note: this will keep *all* objects in the table live, but should be a rare occurrence.

     // Update the table.
     UpdateTableWithReadBarrier();

     // And try again.
     return RemoveLocked(self, obj, tag);
   }

   // Not in here.
   return false;
 }

 template <typename T>
 bool JvmtiWeakTable<T>::Set(art::mirror::Object* obj, T new_tag) {
   art::Thread* self = art::Thread::Current();
   art::MutexLock mu(self, allow_disallow_lock_);
   Wait(self);

   return SetLocked(self, obj, new_tag);
 }
 template <typename T>
 bool JvmtiWeakTable<T>::SetLocked(art::mirror::Object* obj, T new_tag) {
   art::Thread* self = art::Thread::Current();
   allow_disallow_lock_.AssertHeld(self);
   Wait(self);

   return SetLocked(self, obj, new_tag);
 }

 template <typename T>
 bool JvmtiWeakTable<T>::SetLocked(art::Thread* self, art::mirror::Object* obj, T new_tag) {
   auto it = tagged_objects_.find(art::GcRoot<art::mirror::Object>(obj));
   if (it != tagged_objects_.end()) {
     it->second = new_tag;
     return true;
   }

   if (art::kUseReadBarrier && self->GetIsGcMarking() && !update_since_last_sweep_) {
     // Under concurrent GC, there is a window between moving objects and sweeping of system
     // weaks in which mutators are active. We may receive a to-space object pointer in obj,
     // but still have from-space pointers in the table. Explicitly update the table once.
     // Note: this will keep *all* objects in the table live, but should be a rare occurrence.

     // Update the table.
     UpdateTableWithReadBarrier();

     // And try again.
     return SetLocked(self, obj, new_tag);
   }

   // New element.
   auto insert_it = tagged_objects_.emplace(art::GcRoot<art::mirror::Object>(obj), new_tag);
   DCHECK(insert_it.second);
   return false;
 }

 template <typename T>
 void JvmtiWeakTable<T>::Sweep(art::IsMarkedVisitor* visitor) {
   if (DoesHandleNullOnSweep()) {
     SweepImpl<true>(visitor);
   } else {
     SweepImpl<false>(visitor);
   }

   // Under concurrent GC, there is a window between moving objects and sweeping of system
   // weaks in which mutators are active. We may receive a to-space object pointer in obj,
   // but still have from-space pointers in the table. We explicitly update the table then
   // to ensure we compare against to-space pointers. But we want to do this only once. Once
   // sweeping is done, we know all objects are to-space pointers until the next GC cycle,
   // so we re-enable the explicit update for the next marking.
   update_since_last_sweep_ = false;
 }

 template <typename T>
 template <bool kHandleNull>
 void JvmtiWeakTable<T>::SweepImpl(art::IsMarkedVisitor* visitor) {
   art::Thread* self = art::Thread::Current();
   art::MutexLock mu(self, allow_disallow_lock_);

   auto IsMarkedUpdater = [&](const art::GcRoot<art::mirror::Object>& original_root ATTRIBUTE_UNUSED,
                              art::mirror::Object* original_obj) {
     return visitor->IsMarked(original_obj);
   };

   UpdateTableWith<decltype(IsMarkedUpdater),
                   kHandleNull ? kCallHandleNull : kRemoveNull>(IsMarkedUpdater);
 }

 template <typename T>
 template <typename Updater, typename JvmtiWeakTable<T>::TableUpdateNullTarget kTargetNull>
 ALWAYS_INLINE inline void JvmtiWeakTable<T>::UpdateTableWith(Updater& updater) {
   // We optimistically hope that elements will still be well-distributed when re-inserting them.
   // So play with the map mechanics, and postpone rehashing. This avoids the need of a side
   // vector and two passes.
   float original_max_load_factor = tagged_objects_.max_load_factor();
   tagged_objects_.max_load_factor(std::numeric_limits<float>::max());
   // For checking that a max load-factor actually does what we expect.
   size_t original_bucket_count = tagged_objects_.bucket_count();

   for (auto it = tagged_objects_.begin(); it != tagged_objects_.end();) {
     DCHECK(!it->first.IsNull());
     art::mirror::Object* original_obj = it->first.template Read<art::kWithoutReadBarrier>();
     art::mirror::Object* target_obj = updater(it->first, original_obj);
     if (original_obj != target_obj) {
       if (kTargetNull == kIgnoreNull && target_obj == nullptr) {
         // Ignore null target, don't do anything.
       } else {
         T tag = it->second;
         it = tagged_objects_.erase(it);
         if (target_obj != nullptr) {
           tagged_objects_.emplace(art::GcRoot<art::mirror::Object>(target_obj), tag);
           DCHECK_EQ(original_bucket_count, tagged_objects_.bucket_count());
         } else if (kTargetNull == kCallHandleNull) {
           HandleNullSweep(tag);
         }
         continue;  // Iterator was implicitly updated by erase.
       }
     }
     it++;
   }

   tagged_objects_.max_load_factor(original_max_load_factor);
   // TODO: consider rehash here.
 }

 template <typename T>
 template <typename Storage, class Allocator>
 struct JvmtiWeakTable<T>::ReleasableContainer {
   using allocator_type = Allocator;

   explicit ReleasableContainer(const allocator_type& alloc, size_t reserve = 10)
       : allocator(alloc),
         data(reserve > 0 ? allocator.allocate(reserve) : nullptr),
         size(0),
         capacity(reserve) {
   }

   ~ReleasableContainer() {
     if (data != nullptr) {
       allocator.deallocate(data, capacity);
       capacity = 0;
       size = 0;
     }
   }

   Storage* Release() {
     Storage* tmp = data;

     data = nullptr;
     size = 0;
     capacity = 0;

     return tmp;
   }

   void Resize(size_t new_capacity) {
     CHECK_GT(new_capacity, capacity);

     Storage* tmp = allocator.allocate(new_capacity);
     DCHECK(tmp != nullptr);
     if (data != nullptr) {
       memcpy(tmp, data, sizeof(Storage) * size);
     }
     Storage* old = data;
     data = tmp;
     allocator.deallocate(old, capacity);
     capacity = new_capacity;
   }

   void Pushback(const Storage& elem) {
     if (size == capacity) {
       size_t new_capacity = 2 * capacity + 1;
       Resize(new_capacity);
     }
     data[size++] = elem;
   }

   Allocator allocator;
   Storage* data;
   size_t size;
   size_t capacity;
 };

 template <typename T>
 jvmtiError JvmtiWeakTable<T>::GetTaggedObjects(jvmtiEnv* jvmti_env,
                                                jint tag_count,
                                                const T* tags,
                                                jint* count_ptr,
                                                jobject** object_result_ptr,
                                                T** tag_result_ptr) {
   if (tag_count < 0) {
     return ERR(ILLEGAL_ARGUMENT);
   }
   if (tag_count > 0) {
     for (size_t i = 0; i != static_cast<size_t>(tag_count); ++i) {
       if (tags[i] == 0) {
         return ERR(ILLEGAL_ARGUMENT);
       }
     }
   }
   if (tags == nullptr) {
     return ERR(NULL_POINTER);
   }
   if (count_ptr == nullptr) {
     return ERR(NULL_POINTER);
   }

   art::Thread* self = art::Thread::Current();
   art::MutexLock mu(self, allow_disallow_lock_);
   Wait(self);

   art::JNIEnvExt* jni_env = self->GetJniEnv();

   constexpr size_t kDefaultSize = 10;
   size_t initial_object_size;
   size_t initial_tag_size;
   if (tag_count == 0) {
     initial_object_size = (object_result_ptr != nullptr) ? tagged_objects_.size() : 0;
     initial_tag_size = (tag_result_ptr != nullptr) ? tagged_objects_.size() : 0;
   } else {
     initial_object_size = initial_tag_size = kDefaultSize;
   }
   JvmtiAllocator<void> allocator(jvmti_env);
   ReleasableContainer<jobject, JvmtiAllocator<jobject>> selected_objects(allocator,
                                                                          initial_object_size);
   ReleasableContainer<T, JvmtiAllocator<T>> selected_tags(allocator, initial_tag_size);

   size_t count = 0;
   for (auto& pair : tagged_objects_) {
     bool select;
     if (tag_count > 0) {
       select = false;
       for (size_t i = 0; i != static_cast<size_t>(tag_count); ++i) {
         if (tags[i] == pair.second) {
           select = true;
           break;
         }
       }
     } else {
       select = true;
     }

     if (select) {
       art::mirror::Object* obj = pair.first.template Read<art::kWithReadBarrier>();
       if (obj != nullptr) {
         count++;
         if (object_result_ptr != nullptr) {
           selected_objects.Pushback(jni_env->AddLocalReference<jobject>(obj));
         }
         if (tag_result_ptr != nullptr) {
           selected_tags.Pushback(pair.second);
         }
       }
     }
   }

   if (object_result_ptr != nullptr) {
     *object_result_ptr = selected_objects.Release();
   }
   if (tag_result_ptr != nullptr) {
     *tag_result_ptr = selected_tags.Release();
   }
   *count_ptr = static_cast<jint>(count);
   return ERR(NONE);
 }

 template <typename T>
 art::mirror::Object* JvmtiWeakTable<T>::Find(T tag) {
   art::Thread* self = art::Thread::Current();
   art::MutexLock mu(self, allow_disallow_lock_);
   Wait(self);

   for (auto& pair : tagged_objects_) {
     if (tag == pair.second) {
       art::mirror::Object* obj = pair.first.template Read<art::kWithReadBarrier>();
       if (obj != nullptr) {
         return obj;
       }
     }
   }
   return nullptr;
 }

 }  // namespace openjdkjvmti

 #endif  // ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_INL_H_
	/* Copyright (C) 2017 The Android Open Source Project
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This file implements interfaces from the file jvmti.h. This implementation
	* is licensed under the same terms as the file jvmti.h. The
	* copyright and license information for the file jvmti.h follows.
	*
	* Copyright (c) 2003, 2011, 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. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* 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.
	*/

	#ifndef ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_INL_H_
	#define ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_INL_H_

	#include "jvmti_weak_table.h"

	#include <limits>

	#include <android-base/logging.h>

	#include "art_jvmti.h"
	#include "gc/allocation_listener.h"
	#include "instrumentation.h"
	#include "jni_env_ext-inl.h"
	#include "jvmti_allocator.h"
	#include "mirror/class.h"
	#include "mirror/object.h"
	#include "nativehelper/scoped_local_ref.h"
	#include "runtime.h"

	namespace openjdkjvmti {

	template <typename T>
	void JvmtiWeakTable<T>::Lock() {
	allow_disallow_lock_.ExclusiveLock(art::Thread::Current());
	}
	template <typename T>
	void JvmtiWeakTable<T>::Unlock() {
	allow_disallow_lock_.ExclusiveUnlock(art::Thread::Current());
	}
	template <typename T>
	void JvmtiWeakTable<T>::AssertLocked() {
	allow_disallow_lock_.AssertHeld(art::Thread::Current());
	}

	template <typename T>
	void JvmtiWeakTable<T>::UpdateTableWithReadBarrier() {
	update_since_last_sweep_ = true;

	auto WithReadBarrierUpdater = [&](const art::GcRoot<art::mirror::Object>& original_root,
	art::mirror::Object* original_obj ATTRIBUTE_UNUSED)
	REQUIRES_SHARED(art::Locks::mutator_lock_) {
	return original_root.Read<art::kWithReadBarrier>();
	};

	UpdateTableWith<decltype(WithReadBarrierUpdater), kIgnoreNull>(WithReadBarrierUpdater);
	}

	template <typename T>
	bool JvmtiWeakTable<T>::GetTagSlowPath(art::Thread* self, art::mirror::Object* obj, T* result) {
	// Under concurrent GC, there is a window between moving objects and sweeping of system
	// weaks in which mutators are active. We may receive a to-space object pointer in obj,
	// but still have from-space pointers in the table. Explicitly update the table once.
	// Note: this will keep all objects in the table live, but should be a rare occurrence.
	UpdateTableWithReadBarrier();
	return GetTagLocked(self, obj, result);
	}

	template <typename T>
	bool JvmtiWeakTable<T>::Remove(art::mirror::Object* obj, /* out / T tag) {
	art::Thread* self = art::Thread::Current();
	art::MutexLock mu(self, allow_disallow_lock_);
	Wait(self);

	return RemoveLocked(self, obj, tag);
	}
	template <typename T>
	bool JvmtiWeakTable<T>::RemoveLocked(art::mirror::Object* obj, T* tag) {
	art::Thread* self = art::Thread::Current();
	allow_disallow_lock_.AssertHeld(self);
	Wait(self);

	return RemoveLocked(self, obj, tag);
	}

	template <typename T>
	bool JvmtiWeakTable<T>::RemoveLocked(art::Thread* self, art::mirror::Object* obj, T* tag) {
	auto it = tagged_objects_.find(art::GcRoot<art::mirror::Object>(obj));
	if (it != tagged_objects_.end()) {
	if (tag != nullptr) {
	*tag = it->second;
	}
	tagged_objects_.erase(it);
	return true;
	}

	if (art::kUseReadBarrier && self->GetIsGcMarking() && !update_since_last_sweep_) {
	// Under concurrent GC, there is a window between moving objects and sweeping of system
	// weaks in which mutators are active. We may receive a to-space object pointer in obj,
	// but still have from-space pointers in the table. Explicitly update the table once.
	// Note: this will keep all objects in the table live, but should be a rare occurrence.

	// Update the table.
	UpdateTableWithReadBarrier();

	// And try again.
	return RemoveLocked(self, obj, tag);
	}

	// Not in here.
	return false;
	}

	template <typename T>
	bool JvmtiWeakTable<T>::Set(art::mirror::Object* obj, T new_tag) {
	art::Thread* self = art::Thread::Current();
	art::MutexLock mu(self, allow_disallow_lock_);
	Wait(self);

	return SetLocked(self, obj, new_tag);
	}
	template <typename T>
	bool JvmtiWeakTable<T>::SetLocked(art::mirror::Object* obj, T new_tag) {
	art::Thread* self = art::Thread::Current();
	allow_disallow_lock_.AssertHeld(self);
	Wait(self);

	return SetLocked(self, obj, new_tag);
	}

	template <typename T>
	bool JvmtiWeakTable<T>::SetLocked(art::Thread* self, art::mirror::Object* obj, T new_tag) {
	auto it = tagged_objects_.find(art::GcRoot<art::mirror::Object>(obj));
	if (it != tagged_objects_.end()) {
	it->second = new_tag;
	return true;
	}

	if (art::kUseReadBarrier && self->GetIsGcMarking() && !update_since_last_sweep_) {
	// Under concurrent GC, there is a window between moving objects and sweeping of system
	// weaks in which mutators are active. We may receive a to-space object pointer in obj,
	// but still have from-space pointers in the table. Explicitly update the table once.
	// Note: this will keep all objects in the table live, but should be a rare occurrence.

	// Update the table.
	UpdateTableWithReadBarrier();

	// And try again.
	return SetLocked(self, obj, new_tag);
	}

	// New element.
	auto insert_it = tagged_objects_.emplace(art::GcRoot<art::mirror::Object>(obj), new_tag);
	DCHECK(insert_it.second);
	return false;
	}

	template <typename T>
	void JvmtiWeakTable<T>::Sweep(art::IsMarkedVisitor* visitor) {
	if (DoesHandleNullOnSweep()) {
	SweepImpl<true>(visitor);
	} else {
	SweepImpl<false>(visitor);
	}

	// Under concurrent GC, there is a window between moving objects and sweeping of system
	// weaks in which mutators are active. We may receive a to-space object pointer in obj,
	// but still have from-space pointers in the table. We explicitly update the table then
	// to ensure we compare against to-space pointers. But we want to do this only once. Once
	// sweeping is done, we know all objects are to-space pointers until the next GC cycle,
	// so we re-enable the explicit update for the next marking.
	update_since_last_sweep_ = false;
	}

	template <typename T>
	template <bool kHandleNull>
	void JvmtiWeakTable<T>::SweepImpl(art::IsMarkedVisitor* visitor) {
	art::Thread* self = art::Thread::Current();
	art::MutexLock mu(self, allow_disallow_lock_);

	auto IsMarkedUpdater = [&](const art::GcRoot<art::mirror::Object>& original_root ATTRIBUTE_UNUSED,
	art::mirror::Object* original_obj) {
	return visitor->IsMarked(original_obj);
	};

	UpdateTableWith<decltype(IsMarkedUpdater),
	kHandleNull ? kCallHandleNull : kRemoveNull>(IsMarkedUpdater);
	}

	template <typename T>
	template <typename Updater, typename JvmtiWeakTable<T>::TableUpdateNullTarget kTargetNull>
	ALWAYS_INLINE inline void JvmtiWeakTable<T>::UpdateTableWith(Updater& updater) {
	// We optimistically hope that elements will still be well-distributed when re-inserting them.
	// So play with the map mechanics, and postpone rehashing. This avoids the need of a side
	// vector and two passes.
	float original_max_load_factor = tagged_objects_.max_load_factor();
	tagged_objects_.max_load_factor(std::numeric_limits<float>::max());
	// For checking that a max load-factor actually does what we expect.
	size_t original_bucket_count = tagged_objects_.bucket_count();

	for (auto it = tagged_objects_.begin(); it != tagged_objects_.end();) {
	DCHECK(!it->first.IsNull());
	art::mirror::Object* original_obj = it->first.template Read<art::kWithoutReadBarrier>();
	art::mirror::Object* target_obj = updater(it->first, original_obj);
	if (original_obj != target_obj) {
	if (kTargetNull == kIgnoreNull && target_obj == nullptr) {
	// Ignore null target, don't do anything.
	} else {
	T tag = it->second;
	it = tagged_objects_.erase(it);
	if (target_obj != nullptr) {
	tagged_objects_.emplace(art::GcRoot<art::mirror::Object>(target_obj), tag);
	DCHECK_EQ(original_bucket_count, tagged_objects_.bucket_count());
	} else if (kTargetNull == kCallHandleNull) {
	HandleNullSweep(tag);
	}
	continue; // Iterator was implicitly updated by erase.
	}
	}
	it++;
	}

	tagged_objects_.max_load_factor(original_max_load_factor);
	// TODO: consider rehash here.
	}

	template <typename T>
	template <typename Storage, class Allocator>
	struct JvmtiWeakTable<T>::ReleasableContainer {
	using allocator_type = Allocator;

	explicit ReleasableContainer(const allocator_type& alloc, size_t reserve = 10)
	: allocator(alloc),
	data(reserve > 0 ? allocator.allocate(reserve) : nullptr),
	size(0),
	capacity(reserve) {
	}

	~ReleasableContainer() {
	if (data != nullptr) {
	allocator.deallocate(data, capacity);
	capacity = 0;
	size = 0;
	}
	}

	Storage* Release() {
	Storage* tmp = data;

	data = nullptr;
	size = 0;
	capacity = 0;

	return tmp;
	}

	void Resize(size_t new_capacity) {
	CHECK_GT(new_capacity, capacity);

	Storage* tmp = allocator.allocate(new_capacity);
	DCHECK(tmp != nullptr);
	if (data != nullptr) {
	memcpy(tmp, data, sizeof(Storage) * size);
	}
	Storage* old = data;
	data = tmp;
	allocator.deallocate(old, capacity);
	capacity = new_capacity;
	}

	void Pushback(const Storage& elem) {
	if (size == capacity) {
	size_t new_capacity = 2 * capacity + 1;
	Resize(new_capacity);
	}
	data[size++] = elem;
	}

	Allocator allocator;
	Storage* data;
	size_t size;
	size_t capacity;
	};

	template <typename T>
	jvmtiError JvmtiWeakTable<T>::GetTaggedObjects(jvmtiEnv* jvmti_env,
	jint tag_count,
	const T* tags,
	jint* count_ptr,
	jobject** object_result_ptr,
	T** tag_result_ptr) {
	if (tag_count < 0) {
	return ERR(ILLEGAL_ARGUMENT);
	}
	if (tag_count > 0) {
	for (size_t i = 0; i != static_cast<size_t>(tag_count); ++i) {
	if (tags[i] == 0) {
	return ERR(ILLEGAL_ARGUMENT);
	}
	}
	}
	if (tags == nullptr) {
	return ERR(NULL_POINTER);
	}
	if (count_ptr == nullptr) {
	return ERR(NULL_POINTER);
	}

	art::Thread* self = art::Thread::Current();
	art::MutexLock mu(self, allow_disallow_lock_);
	Wait(self);

	art::JNIEnvExt* jni_env = self->GetJniEnv();

	constexpr size_t kDefaultSize = 10;
	size_t initial_object_size;
	size_t initial_tag_size;
	if (tag_count == 0) {
	initial_object_size = (object_result_ptr != nullptr) ? tagged_objects_.size() : 0;
	initial_tag_size = (tag_result_ptr != nullptr) ? tagged_objects_.size() : 0;
	} else {
	initial_object_size = initial_tag_size = kDefaultSize;
	}
	JvmtiAllocator<void> allocator(jvmti_env);
	ReleasableContainer<jobject, JvmtiAllocator<jobject>> selected_objects(allocator,
	initial_object_size);
	ReleasableContainer<T, JvmtiAllocator<T>> selected_tags(allocator, initial_tag_size);

	size_t count = 0;
	for (auto& pair : tagged_objects_) {
	bool select;
	if (tag_count > 0) {
	select = false;
	for (size_t i = 0; i != static_cast<size_t>(tag_count); ++i) {
	if (tags[i] == pair.second) {
	select = true;
	break;
	}
	}
	} else {
	select = true;
	}

	if (select) {
	art::mirror::Object* obj = pair.first.template Read<art::kWithReadBarrier>();
	if (obj != nullptr) {
	count++;
	if (object_result_ptr != nullptr) {
	selected_objects.Pushback(jni_env->AddLocalReference<jobject>(obj));
	}
	if (tag_result_ptr != nullptr) {
	selected_tags.Pushback(pair.second);
	}
	}
	}
	}

	if (object_result_ptr != nullptr) {
	*object_result_ptr = selected_objects.Release();
	}
	if (tag_result_ptr != nullptr) {
	*tag_result_ptr = selected_tags.Release();
	}
	*count_ptr = static_cast<jint>(count);
	return ERR(NONE);
	}

	template <typename T>
	art::mirror::Object* JvmtiWeakTable<T>::Find(T tag) {
	art::Thread* self = art::Thread::Current();
	art::MutexLock mu(self, allow_disallow_lock_);
	Wait(self);

	for (auto& pair : tagged_objects_) {
	if (tag == pair.second) {
	art::mirror::Object* obj = pair.first.template Read<art::kWithReadBarrier>();
	if (obj != nullptr) {
	return obj;
	}
	}
	}
	return nullptr;
	}

	} // namespace openjdkjvmti

	#endif // ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_INL_H_