1  /*
 2   * Copyright (C) 2017 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  #pragma once
27  
28  #include "StructureIDTable.h"
29  #include "VM.h"
30  #include <wtf/Vector.h>
31  
32  namespace JSC {
33  
34  class JSCell;
35  class JSGlobalObject;
36  class JSObject;
37  class PropertySlot;
38  class Structure;
39  
40  class PolyProtoAccessChain {
41      WTF_MAKE_FAST_ALLOCATED;
42  
43  public:
44      PolyProtoAccessChain(PolyProtoAccessChain&) = default;
45  
46      // Returns nullptr when invalid.
47      static std::unique_ptr<PolyProtoAccessChain> create(JSGlobalObject*, JSCell* base, const PropertySlot&);
48      static std::unique_ptr<PolyProtoAccessChain> create(JSGlobalObject*, JSCell* base, JSObject* target);
49  
50      std::unique_ptr<PolyProtoAccessChain> clone()
51      {
52          return makeUnique<PolyProtoAccessChain>(*this);
53      }
54  
55      const Vector<StructureID>& chain() const { return m_chain; }
56  
57      void dump(Structure* baseStructure, PrintStream& out) const;
58  
59      bool operator==(const PolyProtoAccessChain& other) const;
60      bool operator!=(const PolyProtoAccessChain& other) const
61      {
62          return !(*this == other);
63      }
64  
65      bool needImpurePropertyWatchpoint(VM&) const;
66  
67      template <typename Func>
68      void forEach(VM& vm, Structure* baseStructure, const Func& func) const
69      {
70          bool atEnd = !m_chain.size();
71          func(baseStructure, atEnd);
72          for (unsigned i = 0; i < m_chain.size(); ++i) {
73              atEnd = i + 1 == m_chain.size();
74              func(vm.getStructure(m_chain[i]), atEnd);
75          }
76      }
77  
78      Structure* slotBaseStructure(VM& vm, Structure* baseStructure) const
79      {
80          if (m_chain.size())
81              return vm.getStructure(m_chain.last());
82          return baseStructure;
83      }
84  
85  private:
86      PolyProtoAccessChain() = default;
87  
88      // This does not include the base. We rely on AccessCase providing it for us. That said, this data
89      // structure is tied to the base that it was created with.
90      Vector<StructureID> m_chain; 
91  };
92  
93  }