blob: f2e059d6bc428a866bf6566e2640961ce1fa7408 [file] [log] [blame]
* Copyright (C) 2014 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "base/logging.h"
#include "base/macros.h"
#include "handle.h"
#include "stack.h"
#include "utils.h"
namespace art {
namespace mirror {
class Object;
class Thread;
// HandleScopes can be allocated within the bridge frame between managed and native code backed by
// stack storage or manually allocated in native.
class HandleScope {
~HandleScope() {}
// Number of references contained within this handle scope.
uint32_t NumberOfReferences() const {
return number_of_references_;
// We have versions with and without explicit pointer size of the following. The first two are
// used at runtime, so OFFSETOF_MEMBER computes the right offsets automatically. The last one
// takes the pointer size explicitly so that at compile time we can cross-compile correctly.
// Returns the size of a HandleScope containing num_references handles.
static size_t SizeOf(uint32_t num_references) {
size_t header_size = OFFSETOF_MEMBER(HandleScope, references_);
size_t data_size = sizeof(StackReference<mirror::Object>) * num_references;
return header_size + data_size;
// Get the size of the handle scope for the number of entries, with padding added for potential alignment.
static size_t GetAlignedHandleScopeSize(uint32_t num_references) {
size_t handle_scope_size = SizeOf(num_references);
return RoundUp(handle_scope_size, 8);
// Get the size of the handle scope for the number of entries, with padding added for potential alignment.
static size_t GetAlignedHandleScopeSizeTarget(size_t pointer_size, uint32_t num_references) {
// Assume that the layout is packed.
size_t header_size = pointer_size + sizeof(number_of_references_);
// This assumes there is no layout change between 32 and 64b.
size_t data_size = sizeof(StackReference<mirror::Object>) * num_references;
size_t handle_scope_size = header_size + data_size;
return RoundUp(handle_scope_size, 8);
// Link to previous HandleScope or null.
HandleScope* GetLink() const {
return link_;
void SetLink(HandleScope* link) {
DCHECK_NE(this, link);
link_ = link;
// Sets the number_of_references_ field for constructing tables out of raw memory. Warning: will
// not resize anything.
void SetNumberOfReferences(uint32_t num_references) {
number_of_references_ = num_references;
mirror::Object* GetReference(size_t i) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
DCHECK_LT(i, number_of_references_);
return references_[i].AsMirrorPtr();
Handle<mirror::Object> GetHandle(size_t i) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
DCHECK_LT(i, number_of_references_);
return Handle<mirror::Object>(&references_[i]);
void SetReference(size_t i, mirror::Object* object) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
DCHECK_LT(i, number_of_references_);
bool Contains(StackReference<mirror::Object>* handle_scope_entry) const {
// A HandleScope should always contain something. One created by the
// jni_compiler should have a jobject/jclass as a native method is
// passed in a this pointer or a class
DCHECK_GT(number_of_references_, 0U);
return ((&references_[0] <= handle_scope_entry)
&& (handle_scope_entry <= (&references_[number_of_references_ - 1])));
// Offset of link within HandleScope, used by generated code
static size_t LinkOffset(size_t pointer_size) {
return 0;
// Offset of length within handle scope, used by generated code
static size_t NumberOfReferencesOffset(size_t pointer_size) {
return pointer_size;
// Offset of link within handle scope, used by generated code
static size_t ReferencesOffset(size_t pointer_size) {
return pointer_size + sizeof(number_of_references_);
explicit HandleScope(size_t number_of_references) :
link_(nullptr), number_of_references_(number_of_references) {
HandleScope* link_;
uint32_t number_of_references_;
// number_of_references_ are available if this is allocated and filled in by jni_compiler.
StackReference<mirror::Object> references_[0];
template<size_t kNumReferences> friend class StackHandleScope;
// A wrapper which wraps around Object** and restores the pointer in the destructor.
// TODO: Add more functionality.
template<class T>
class HandleWrapper : public Handle<T> {
HandleWrapper(T** obj, const Handle<T>& handle)
: Handle<T>(handle), obj_(obj) {
~HandleWrapper() {
*obj_ = Handle<T>::Get();
T** obj_;
// Scoped handle storage of a fixed size that is usually stack allocated.
template<size_t kNumReferences>
class StackHandleScope : public HandleScope {
explicit StackHandleScope(Thread* self);
template<class T>
Handle<T> NewHandle(T* object) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
SetReference(pos_, object);
return Handle<T>(GetHandle(pos_++));
template<class T>
HandleWrapper<T> NewHandleWrapper(T** object) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
SetReference(pos_, *object);
Handle<T> h(GetHandle(pos_++));
return HandleWrapper<T>(object, h);
// references_storage_ needs to be first so that it matches the address of references_.
StackReference<mirror::Object> references_storage_[kNumReferences];
Thread* const self_;
size_t pos_;
template<size_t kNumRefs> friend class StackHandleScope;
} // namespace art