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// Copyright 2007-2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_GLOBAL_HANDLES_H_
#define V8_GLOBAL_HANDLES_H_
#include "../include/v8-profiler.h"
#include "list-inl.h"
namespace v8 {
namespace internal {
// Structure for tracking global handles.
// A single list keeps all the allocated global handles.
// Destroyed handles stay in the list but is added to the free list.
// At GC the destroyed global handles are removed from the free list
// and deallocated.
// An object group is treated like a single JS object: if one of object in
// the group is alive, all objects in the same group are considered alive.
// An object group is used to simulate object relationship in a DOM tree.
class ObjectGroup {
public:
static ObjectGroup* New(Object*** handles,
size_t length,
v8::RetainedObjectInfo* info) {
ASSERT(length > 0);
ObjectGroup* group = reinterpret_cast<ObjectGroup*>(
malloc(OFFSET_OF(ObjectGroup, objects_[length])));
group->length_ = length;
group->info_ = info;
CopyWords(group->objects_, handles, static_cast<int>(length));
return group;
}
void Dispose() {
if (info_ != NULL) info_->Dispose();
free(this);
}
size_t length_;
v8::RetainedObjectInfo* info_;
Object** objects_[1]; // Variable sized array.
private:
void* operator new(size_t size);
void operator delete(void* p);
~ObjectGroup();
DISALLOW_IMPLICIT_CONSTRUCTORS(ObjectGroup);
};
// An implicit references group consists of two parts: a parent object and
// a list of children objects. If the parent is alive, all the children
// are alive too.
class ImplicitRefGroup {
public:
static ImplicitRefGroup* New(HeapObject** parent,
Object*** children,
size_t length) {
ASSERT(length > 0);
ImplicitRefGroup* group = reinterpret_cast<ImplicitRefGroup*>(
malloc(OFFSET_OF(ImplicitRefGroup, children_[length])));
group->parent_ = parent;
group->length_ = length;
CopyWords(group->children_, children, static_cast<int>(length));
return group;
}
void Dispose() {
free(this);
}
HeapObject** parent_;
size_t length_;
Object** children_[1]; // Variable sized array.
private:
void* operator new(size_t size);
void operator delete(void* p);
~ImplicitRefGroup();
DISALLOW_IMPLICIT_CONSTRUCTORS(ImplicitRefGroup);
};
typedef void (*WeakReferenceGuest)(Object* object, void* parameter);
class GlobalHandles {
public:
~GlobalHandles();
// Creates a new global handle that is alive until Destroy is called.
Handle<Object> Create(Object* value);
// Destroy a global handle.
void Destroy(Object** location);
// Make the global handle weak and set the callback parameter for the
// handle. When the garbage collector recognizes that only weak global
// handles point to an object the handles are cleared and the callback
// function is invoked (for each handle) with the handle and corresponding
// parameter as arguments. Note: cleared means set to Smi::FromInt(0). The
// reason is that Smi::FromInt(0) does not change during garage collection.
void MakeWeak(Object** location,
void* parameter,
WeakReferenceCallback callback);
static void SetWrapperClassId(Object** location, uint16_t class_id);
// Returns the current number of weak handles.
int NumberOfWeakHandles() { return number_of_weak_handles_; }
void RecordStats(HeapStats* stats);
// Returns the current number of weak handles to global objects.
// These handles are also included in NumberOfWeakHandles().
int NumberOfGlobalObjectWeakHandles() {
return number_of_global_object_weak_handles_;
}
// Clear the weakness of a global handle.
void ClearWeakness(Object** location);
// Tells whether global handle is near death.
static bool IsNearDeath(Object** location);
// Tells whether global handle is weak.
static bool IsWeak(Object** location);
// Process pending weak handles.
// Returns true if next major GC is likely to collect more garbage.
bool PostGarbageCollectionProcessing();
// Iterates over all strong handles.
void IterateStrongRoots(ObjectVisitor* v);
// Iterates over all handles.
void IterateAllRoots(ObjectVisitor* v);
// Iterates over all handles that have embedder-assigned class ID.
void IterateAllRootsWithClassIds(ObjectVisitor* v);
// Iterates over all weak roots in heap.
void IterateWeakRoots(ObjectVisitor* v);
// Iterates over weak roots that are bound to a given callback.
void IterateWeakRoots(WeakReferenceGuest f,
WeakReferenceCallback callback);
// Find all weak handles satisfying the callback predicate, mark
// them as pending.
void IdentifyWeakHandles(WeakSlotCallback f);
// Add an object group.
// Should be only used in GC callback function before a collection.
// All groups are destroyed after a mark-compact collection.
void AddObjectGroup(Object*** handles,
size_t length,
v8::RetainedObjectInfo* info);
// Add an implicit references' group.
// Should be only used in GC callback function before a collection.
// All groups are destroyed after a mark-compact collection.
void AddImplicitReferences(HeapObject** parent,
Object*** children,
size_t length);
// Returns the object groups.
List<ObjectGroup*>* object_groups() { return &object_groups_; }
// Returns the implicit references' groups.
List<ImplicitRefGroup*>* implicit_ref_groups() {
return &implicit_ref_groups_;
}
// Remove bags, this should only happen after GC.
void RemoveObjectGroups();
void RemoveImplicitRefGroups();
// Tear down the global handle structure.
void TearDown();
Isolate* isolate() { return isolate_; }
#ifdef DEBUG
void PrintStats();
void Print();
#endif
class Pool;
private:
explicit GlobalHandles(Isolate* isolate);
// Internal node structure, one for each global handle.
class Node;
Isolate* isolate_;
// Field always containing the number of weak and near-death handles.
int number_of_weak_handles_;
// Field always containing the number of weak and near-death handles
// to global objects. These objects are also included in
// number_of_weak_handles_.
int number_of_global_object_weak_handles_;
// Global handles are kept in a single linked list pointed to by head_.
Node* head_;
Node* head() { return head_; }
void set_head(Node* value) { head_ = value; }
// Free list for DESTROYED global handles not yet deallocated.
Node* first_free_;
Node* first_free() { return first_free_; }
void set_first_free(Node* value) { first_free_ = value; }
// List of deallocated nodes.
// Deallocated nodes form a prefix of all the nodes and
// |first_deallocated| points to last deallocated node before
// |head|. Those deallocated nodes are additionally linked
// by |next_free|:
// 1st deallocated head
// | |
// V V
// node node ... node node
// .next -> .next -> .next ->
// <- .next_free <- .next_free <- .next_free
Node* first_deallocated_;
Node* first_deallocated() { return first_deallocated_; }
void set_first_deallocated(Node* value) {
first_deallocated_ = value;
}
Pool* pool_;
int post_gc_processing_count_;
List<ObjectGroup*> object_groups_;
List<ImplicitRefGroup*> implicit_ref_groups_;
friend class Isolate;
DISALLOW_COPY_AND_ASSIGN(GlobalHandles);
};
} } // namespace v8::internal
#endif // V8_GLOBAL_HANDLES_H_