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// Copyright 2007-2008 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef V8_GLOBAL_HANDLES_H_
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#define V8_GLOBAL_HANDLES_H_
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#include "list-inl.h"
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namespace v8 {
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namespace internal {
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// Structure for tracking global handles.
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// A single list keeps all the allocated global handles.
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// Destroyed handles stay in the list but is added to the free list.
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// At GC the destroyed global handles are removed from the free list
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// and deallocated.
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// Callback function on handling weak global handles.
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// typedef bool (*WeakSlotCallback)(Object** pointer);
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// An object group is treated like a single JS object: if one of object in
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// the group is alive, all objects in the same group are considered alive.
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// An object group is used to simulate object relationship in a DOM tree.
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class ObjectGroup : public Malloced {
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public:
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ObjectGroup() : objects_(4) {}
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explicit ObjectGroup(size_t capacity)
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: objects_(static_cast<int>(capacity)) { }
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List<Object**> objects_;
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};
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typedef void (*WeakReferenceGuest)(Object* object, void* parameter);
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class GlobalHandles : public AllStatic {
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public:
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// Creates a new global handle that is alive until Destroy is called.
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static Handle<Object> Create(Object* value);
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// Destroy a global handle.
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static void Destroy(Object** location);
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// Make the global handle weak and set the callback parameter for the
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// handle. When the garbage collector recognizes that only weak global
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// handles point to an object the handles are cleared and the callback
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// function is invoked (for each handle) with the handle and corresponding
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// parameter as arguments. Note: cleared means set to Smi::FromInt(0). The
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// reason is that Smi::FromInt(0) does not change during garage collection.
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static void MakeWeak(Object** location,
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void* parameter,
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WeakReferenceCallback callback);
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// Returns the current number of weak handles.
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static int NumberOfWeakHandles() { return number_of_weak_handles_; }
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static void RecordStats(HeapStats* stats);
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// Returns the current number of weak handles to global objects.
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// These handles are also included in NumberOfWeakHandles().
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static int NumberOfGlobalObjectWeakHandles() {
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return number_of_global_object_weak_handles_;
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}
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// Clear the weakness of a global handle.
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static void ClearWeakness(Object** location);
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// Tells whether global handle is near death.
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static bool IsNearDeath(Object** location);
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// Tells whether global handle is weak.
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static bool IsWeak(Object** location);
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// Process pending weak handles. Returns true if any weak handle
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// callback has been invoked.
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static bool PostGarbageCollectionProcessing();
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// Iterates over all strong handles.
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static void IterateStrongRoots(ObjectVisitor* v);
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// Iterates over all handles.
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static void IterateAllRoots(ObjectVisitor* v);
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// Iterates over all weak roots in heap.
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static void IterateWeakRoots(ObjectVisitor* v);
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// Iterates over weak roots that are bound to a given callback.
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static void IterateWeakRoots(WeakReferenceGuest f,
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WeakReferenceCallback callback);
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// Find all weak handles satisfying the callback predicate, mark
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// them as pending.
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static void IdentifyWeakHandles(WeakSlotCallback f);
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// Add an object group.
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// Should only used in GC callback function before a collection.
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// All groups are destroyed after a mark-compact collection.
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static void AddGroup(Object*** handles, size_t length);
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// Returns the object groups.
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static List<ObjectGroup*>* ObjectGroups();
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// Remove bags, this should only happen after GC.
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static void RemoveObjectGroups();
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// Tear down the global handle structure.
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static void TearDown();
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#ifdef DEBUG
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static void PrintStats();
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static void Print();
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#endif
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class Pool;
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private:
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// Internal node structure, one for each global handle.
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class Node;
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// Field always containing the number of weak and near-death handles.
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static int number_of_weak_handles_;
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// Field always containing the number of weak and near-death handles
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// to global objects. These objects are also included in
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// number_of_weak_handles_.
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static int number_of_global_object_weak_handles_;
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// Global handles are kept in a single linked list pointed to by head_.
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static Node* head_;
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static Node* head() { return head_; }
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static void set_head(Node* value) { head_ = value; }
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// Free list for DESTROYED global handles not yet deallocated.
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static Node* first_free_;
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static Node* first_free() { return first_free_; }
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static void set_first_free(Node* value) { first_free_ = value; }
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// List of deallocated nodes.
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// Deallocated nodes form a prefix of all the nodes and
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// |first_deallocated| points to last deallocated node before
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// |head|. Those deallocated nodes are additionally linked
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// by |next_free|:
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// 1st deallocated head
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// | |
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// V V
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// node node ... node node
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// .next -> .next -> .next ->
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// <- .next_free <- .next_free <- .next_free
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static Node* first_deallocated_;
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static Node* first_deallocated() { return first_deallocated_; }
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static void set_first_deallocated(Node* value) {
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first_deallocated_ = value;
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}
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};
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} } // namespace v8::internal
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#endif // V8_GLOBAL_HANDLES_H_
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