src/global-handles.h - platform/external/v8 - Git at Google

 // 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"

 #include "../include/v8-profiler.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_
	// 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"

	#include "../include/v8-profiler.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_