1/*
2 * Copyright (C) 2013, 2016 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef PrototypeMap_h
27#define PrototypeMap_h
28
29#include "WeakGCMap.h"
30#include <wtf/TriState.h>
31
32namespace JSC {
33
34class JSObject;
35class Structure;
36class VM;
37
38// Tracks the canonical structure an object should be allocated with when inheriting from a given prototype.
39class PrototypeMap {
40public:
41 explicit PrototypeMap(VM& vm)
42 : m_prototypes(vm)
43 , m_structures(vm)
44 {
45 }
46
47 JS_EXPORT_PRIVATE Structure* emptyObjectStructureForPrototype(JSObject*, unsigned inlineCapacity);
48 JS_EXPORT_PRIVATE Structure* emptyStructureForPrototypeFromBaseStructure(JSObject*, Structure*);
49 void clearEmptyObjectStructureForPrototype(JSObject*, unsigned inlineCapacity);
50 JS_EXPORT_PRIVATE void addPrototype(JSObject*);
51 TriState isPrototype(JSObject*) const; // Returns a conservative estimate.
52
53private:
54 Structure* createEmptyStructure(JSObject* prototype, const TypeInfo&, const ClassInfo*, IndexingType, unsigned inlineCapacity);
55
56 WeakGCMap<JSObject*, JSObject> m_prototypes;
57 typedef WeakGCMap<std::pair<JSObject*, std::pair<unsigned, const ClassInfo*>>, Structure> StructureMap;
58 StructureMap m_structures;
59};
60
61inline TriState PrototypeMap::isPrototype(JSObject* object) const
62{
63 if (!m_prototypes.contains(object))
64 return FalseTriState;
65
66 // We know that 'object' was used as a prototype at one time, so be
67 // conservative and say that it might still be so. (It would be expensive
68 // to find out for sure, and we don't know of any cases where being precise
69 // would improve performance.)
70 return MixedTriState;
71}
72
73} // namespace JSC
74
75#endif // PrototypeMap_h
76