Steve Block | a7e24c1 | 2009-10-30 11:49:00 +0000 | [diff] [blame] | 1 | // Copyright 2007-2008 the V8 project authors. All rights reserved. |
| 2 | // Redistribution and use in source and binary forms, with or without |
| 3 | // modification, are permitted provided that the following conditions are |
| 4 | // met: |
| 5 | // |
| 6 | // * Redistributions of source code must retain the above copyright |
| 7 | // notice, this list of conditions and the following disclaimer. |
| 8 | // * Redistributions in binary form must reproduce the above |
| 9 | // copyright notice, this list of conditions and the following |
| 10 | // disclaimer in the documentation and/or other materials provided |
| 11 | // with the distribution. |
| 12 | // * Neither the name of Google Inc. nor the names of its |
| 13 | // contributors may be used to endorse or promote products derived |
| 14 | // from this software without specific prior written permission. |
| 15 | // |
| 16 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | |
| 28 | #ifndef V8_GLOBAL_HANDLES_H_ |
| 29 | #define V8_GLOBAL_HANDLES_H_ |
| 30 | |
| 31 | #include "list-inl.h" |
| 32 | |
| 33 | namespace v8 { |
| 34 | namespace internal { |
| 35 | |
| 36 | // Structure for tracking global handles. |
| 37 | // A single list keeps all the allocated global handles. |
| 38 | // Destroyed handles stay in the list but is added to the free list. |
| 39 | // At GC the destroyed global handles are removed from the free list |
| 40 | // and deallocated. |
| 41 | |
| 42 | // Callback function on handling weak global handles. |
| 43 | // typedef bool (*WeakSlotCallback)(Object** pointer); |
| 44 | |
| 45 | // An object group is treated like a single JS object: if one of object in |
| 46 | // the group is alive, all objects in the same group are considered alive. |
| 47 | // An object group is used to simulate object relationship in a DOM tree. |
| 48 | class ObjectGroup : public Malloced { |
| 49 | public: |
| 50 | ObjectGroup() : objects_(4) {} |
| 51 | explicit ObjectGroup(size_t capacity) : objects_(capacity) {} |
| 52 | |
| 53 | List<Object**> objects_; |
| 54 | }; |
| 55 | |
| 56 | |
Steve Block | 3ce2e20 | 2009-11-05 08:53:23 +0000 | [diff] [blame^] | 57 | typedef void (*WeakReferenceGuest)(Object* object, void* parameter); |
| 58 | |
Steve Block | a7e24c1 | 2009-10-30 11:49:00 +0000 | [diff] [blame] | 59 | class GlobalHandles : public AllStatic { |
| 60 | public: |
| 61 | // Creates a new global handle that is alive until Destroy is called. |
| 62 | static Handle<Object> Create(Object* value); |
| 63 | |
| 64 | // Destroy a global handle. |
| 65 | static void Destroy(Object** location); |
| 66 | |
| 67 | // Make the global handle weak and set the callback parameter for the |
| 68 | // handle. When the garbage collector recognizes that only weak global |
| 69 | // handles point to an object the handles are cleared and the callback |
| 70 | // function is invoked (for each handle) with the handle and corresponding |
| 71 | // parameter as arguments. Note: cleared means set to Smi::FromInt(0). The |
| 72 | // reason is that Smi::FromInt(0) does not change during garage collection. |
| 73 | static void MakeWeak(Object** location, |
| 74 | void* parameter, |
| 75 | WeakReferenceCallback callback); |
| 76 | |
| 77 | // Returns the current number of weak handles. |
| 78 | static int NumberOfWeakHandles() { return number_of_weak_handles_; } |
| 79 | |
| 80 | // Returns the current number of weak handles to global objects. |
| 81 | // These handles are also included in NumberOfWeakHandles(). |
| 82 | static int NumberOfGlobalObjectWeakHandles() { |
| 83 | return number_of_global_object_weak_handles_; |
| 84 | } |
| 85 | |
| 86 | // Clear the weakness of a global handle. |
| 87 | static void ClearWeakness(Object** location); |
| 88 | |
| 89 | // Tells whether global handle is near death. |
| 90 | static bool IsNearDeath(Object** location); |
| 91 | |
| 92 | // Tells whether global handle is weak. |
| 93 | static bool IsWeak(Object** location); |
| 94 | |
| 95 | // Process pending weak handles. |
| 96 | static void PostGarbageCollectionProcessing(); |
| 97 | |
| 98 | // Iterates over all handles. |
| 99 | static void IterateRoots(ObjectVisitor* v); |
| 100 | |
| 101 | // Iterates over all weak roots in heap. |
| 102 | static void IterateWeakRoots(ObjectVisitor* v); |
| 103 | |
Steve Block | 3ce2e20 | 2009-11-05 08:53:23 +0000 | [diff] [blame^] | 104 | // Iterates over weak roots that are bound to a given callback. |
| 105 | static void IterateWeakRoots(WeakReferenceGuest f, |
| 106 | WeakReferenceCallback callback); |
| 107 | |
Steve Block | a7e24c1 | 2009-10-30 11:49:00 +0000 | [diff] [blame] | 108 | // Find all weak handles satisfying the callback predicate, mark |
| 109 | // them as pending. |
| 110 | static void IdentifyWeakHandles(WeakSlotCallback f); |
| 111 | |
| 112 | // Add an object group. |
| 113 | // Should only used in GC callback function before a collection. |
| 114 | // All groups are destroyed after a mark-compact collection. |
| 115 | static void AddGroup(Object*** handles, size_t length); |
| 116 | |
| 117 | // Returns the object groups. |
| 118 | static List<ObjectGroup*>* ObjectGroups(); |
| 119 | |
| 120 | // Remove bags, this should only happen after GC. |
| 121 | static void RemoveObjectGroups(); |
| 122 | |
| 123 | // Tear down the global handle structure. |
| 124 | static void TearDown(); |
| 125 | |
| 126 | #ifdef DEBUG |
| 127 | static void PrintStats(); |
| 128 | static void Print(); |
| 129 | #endif |
| 130 | private: |
| 131 | // Internal node structure, one for each global handle. |
| 132 | class Node; |
| 133 | |
| 134 | // Field always containing the number of weak and near-death handles. |
| 135 | static int number_of_weak_handles_; |
| 136 | |
| 137 | // Field always containing the number of weak and near-death handles |
| 138 | // to global objects. These objects are also included in |
| 139 | // number_of_weak_handles_. |
| 140 | static int number_of_global_object_weak_handles_; |
| 141 | |
| 142 | // Global handles are kept in a single linked list pointed to by head_. |
| 143 | static Node* head_; |
| 144 | static Node* head() { return head_; } |
| 145 | static void set_head(Node* value) { head_ = value; } |
| 146 | |
| 147 | // Free list for DESTROYED global handles not yet deallocated. |
| 148 | static Node* first_free_; |
| 149 | static Node* first_free() { return first_free_; } |
| 150 | static void set_first_free(Node* value) { first_free_ = value; } |
| 151 | }; |
| 152 | |
| 153 | |
| 154 | } } // namespace v8::internal |
| 155 | |
| 156 | #endif // V8_GLOBAL_HANDLES_H_ |