cfec9567b6746ddd06e464133121a9dd021deea2
[WebKit-https.git] / Source / JavaScriptCore / runtime / JSLexicalEnvironment.h
1 /*
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6  * are met:
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8  * 1.  Redistributions of source code must retain the above copyright
9  *     notice, this list of conditions and the following disclaimer.
10  * 2.  Redistributions in binary form must reproduce the above copyright
11  *     notice, this list of conditions and the following disclaimer in the
12  *     documentation and/or other materials provided with the distribution.
13  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
14  *     its contributors may be used to endorse or promote products derived
15  *     from this software without specific prior written permission.
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27  */
28  
29 #pragma once
30
31 #include "CodeBlock.h"
32 #include "JSSymbolTableObject.h"
33 #include "SymbolTable.h"
34
35 namespace JSC {
36
37 class LLIntOffsetsExtractor;
38
39 class JSLexicalEnvironment : public JSSymbolTableObject {
40     friend class JIT;
41     friend class LLIntOffsetsExtractor;
42 public:
43     template<typename CellType>
44     static CompleteSubspace* subspaceFor(VM& vm)
45     {
46         RELEASE_ASSERT(!CellType::needsDestruction);
47         return &vm.jsValueGigacageCellSpace;
48     }
49
50     using Base = JSSymbolTableObject;
51     static const unsigned StructureFlags = Base::StructureFlags | OverridesGetOwnPropertySlot | OverridesGetPropertyNames;
52
53     WriteBarrierBase<Unknown>* variables()
54     {
55         return bitwise_cast<WriteBarrierBase<Unknown>*>(bitwise_cast<char*>(this) + offsetOfVariables());
56     }
57
58     bool isValidScopeOffset(ScopeOffset offset)
59     {
60         return !!offset && offset.offset() < symbolTable()->scopeSize();
61     }
62
63     WriteBarrierBase<Unknown>& variableAt(ScopeOffset offset)
64     {
65         ASSERT(isValidScopeOffset(offset));
66         return variables()[offset.offset()];
67     }
68
69     static size_t offsetOfVariables()
70     {
71         return WTF::roundUpToMultipleOf<sizeof(WriteBarrier<Unknown>)>(sizeof(JSLexicalEnvironment));
72     }
73
74     static size_t offsetOfVariable(ScopeOffset offset)
75     {
76         Checked<size_t> scopeOffset = offset.offset();
77         return (offsetOfVariables() + scopeOffset * sizeof(WriteBarrier<Unknown>)).unsafeGet();
78     }
79
80     static size_t allocationSizeForScopeSize(Checked<size_t> scopeSize)
81     {
82         return (offsetOfVariables() + scopeSize * sizeof(WriteBarrier<Unknown>)).unsafeGet();
83     }
84
85     static size_t allocationSize(SymbolTable* symbolTable)
86     {
87         return allocationSizeForScopeSize(symbolTable->scopeSize());
88     }
89
90     static JSLexicalEnvironment* create(
91         VM& vm, Structure* structure, JSScope* currentScope, SymbolTable* symbolTable, JSValue initialValue)
92     {
93         JSLexicalEnvironment* result = 
94             new (
95                 NotNull,
96                 allocateCell<JSLexicalEnvironment>(vm.heap, allocationSize(symbolTable)))
97             JSLexicalEnvironment(vm, structure, currentScope, symbolTable);
98         result->finishCreation(vm, initialValue);
99         return result;
100     }
101
102     static JSLexicalEnvironment* create(VM& vm, JSGlobalObject* globalObject, JSScope* currentScope, SymbolTable* symbolTable, JSValue initialValue)
103     {
104         Structure* structure = globalObject->activationStructure();
105         return create(vm, structure, currentScope, symbolTable, initialValue);
106     }
107         
108     static bool getOwnPropertySlot(JSObject*, ExecState*, PropertyName, PropertySlot&);
109     static void getOwnNonIndexPropertyNames(JSObject*, ExecState*, PropertyNameArray&, EnumerationMode);
110
111     static bool put(JSCell*, ExecState*, PropertyName, JSValue, PutPropertySlot&);
112
113     static bool deleteProperty(JSCell*, ExecState*, PropertyName);
114
115     DECLARE_INFO;
116
117     static Structure* createStructure(VM& vm, JSGlobalObject* globalObject) { return Structure::create(vm, globalObject, jsNull(), TypeInfo(LexicalEnvironmentType, StructureFlags), info()); }
118
119 protected:
120     JSLexicalEnvironment(VM&, Structure*, JSScope*, SymbolTable*);
121
122     void finishCreationUninitialized(VM& vm)
123     {
124         Base::finishCreation(vm);
125     }
126
127     void finishCreation(VM& vm, JSValue value)
128     {
129         finishCreationUninitialized(vm);
130         ASSERT(value == jsUndefined() || value == jsTDZValue());
131         for (unsigned i = symbolTable()->scopeSize(); i--;) {
132             // Filling this with undefined/TDZEmptyValue is useful because that's what variables start out as.
133             variableAt(ScopeOffset(i)).setStartingValue(value);
134         }
135     }
136
137     static void visitChildren(JSCell*, SlotVisitor&);
138     static void heapSnapshot(JSCell*, HeapSnapshotBuilder&);
139 };
140
141 inline JSLexicalEnvironment::JSLexicalEnvironment(VM& vm, Structure* structure, JSScope* currentScope, SymbolTable* symbolTable)
142     : Base(vm, structure, currentScope, symbolTable)
143 {
144 }
145
146 } // namespace JSC