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39 | |
40 | #include "config.h" |
41 | #include "qscriptstaticscopeobject_p.h" |
42 | |
43 | namespace JSC |
44 | { |
45 | ASSERT_CLASS_FITS_IN_CELL(QT_PREPEND_NAMESPACE(QScriptStaticScopeObject)); |
46 | } |
47 | |
48 | QT_BEGIN_NAMESPACE |
49 | |
50 | /*! |
51 | \class QScriptStaticScopeObject |
52 | \internal |
53 | |
54 | Represents a static scope object. |
55 | |
56 | This class allows the VM to determine at JS script compile time whether |
57 | the object has a given property or not. If the object has the property, |
58 | a fast, index-based read/write operation will be used. If the object |
59 | doesn't have the property, the compiler knows it can safely skip this |
60 | object when dynamically resolving the property. Either way, this can |
61 | greatly improve performance. |
62 | |
63 | \sa QScriptContext::pushScope() |
64 | */ |
65 | |
66 | const JSC::ClassInfo QScriptStaticScopeObject::info = { .className: "QScriptStaticScopeObject" , .parentClass: 0, .staticPropHashTable: 0, .classPropHashTableGetterFunction: 0 }; |
67 | |
68 | /*! |
69 | Creates a static scope object with a fixed set of undeletable properties. |
70 | |
71 | It's not possible to add new properties to the object after construction. |
72 | */ |
73 | QScriptStaticScopeObject::QScriptStaticScopeObject(WTF::NonNullPassRefPtr<JSC::Structure> structure, |
74 | int propertyCount, const PropertyInfo* props) |
75 | : JSC::JSVariableObject(structure, new Data(/*canGrow=*/false)) |
76 | { |
77 | int index = growRegisterArray(propertyCount); |
78 | for (int i = 0; i < propertyCount; ++i, --index) { |
79 | const PropertyInfo& prop = props[i]; |
80 | JSC::SymbolTableEntry entry(index, prop.attributes); |
81 | symbolTable().add(key: prop.identifier.ustring().rep(), mapped: entry); |
82 | registerAt(index) = prop.value; |
83 | } |
84 | } |
85 | |
86 | /*! |
87 | Creates an empty static scope object. |
88 | |
89 | Properties can be added to the object after construction, either by |
90 | calling QScriptValue::setProperty(), or by pushing the object on the |
91 | scope chain; variable declarations ("var" statements) and function |
92 | declarations in JavaScript will create properties on the scope object. |
93 | |
94 | Note that once the scope object has been used in a closure and the |
95 | resulting function has been compiled, it's no longer safe to add |
96 | properties to the scope object (because the VM will bypass this |
97 | object the next time the function is executed). |
98 | */ |
99 | QScriptStaticScopeObject::QScriptStaticScopeObject(WTF::NonNullPassRefPtr<JSC::Structure> structure) |
100 | : JSC::JSVariableObject(structure, new Data(/*canGrow=*/true)) |
101 | { |
102 | } |
103 | |
104 | QScriptStaticScopeObject::~QScriptStaticScopeObject() |
105 | { |
106 | delete d_ptr(); |
107 | } |
108 | |
109 | bool QScriptStaticScopeObject::getOwnPropertySlot(JSC::ExecState*, const JSC::Identifier& propertyName, JSC::PropertySlot& slot) |
110 | { |
111 | return symbolTableGet(propertyName, slot); |
112 | } |
113 | |
114 | bool QScriptStaticScopeObject::getOwnPropertyDescriptor(JSC::ExecState*, const JSC::Identifier& propertyName, JSC::PropertyDescriptor& descriptor) |
115 | { |
116 | return symbolTableGet(propertyName, descriptor); |
117 | } |
118 | |
119 | void QScriptStaticScopeObject::putWithAttributes(JSC::ExecState* exec, const JSC::Identifier &propertyName, JSC::JSValue value, unsigned attributes) |
120 | { |
121 | if (symbolTablePutWithAttributes(propertyName, value, attributes)) |
122 | return; |
123 | Q_ASSERT(d_ptr()->canGrow); |
124 | addSymbolTableProperty(propertyName, value, attributes); |
125 | } |
126 | |
127 | void QScriptStaticScopeObject::put(JSC::ExecState* exec, const JSC::Identifier& propertyName, JSC::JSValue value, JSC::PutPropertySlot&) |
128 | { |
129 | if (symbolTablePut(propertyName, value)) |
130 | return; |
131 | Q_ASSERT(d_ptr()->canGrow); |
132 | addSymbolTableProperty(propertyName, value, /*attributes=*/0); |
133 | } |
134 | |
135 | bool QScriptStaticScopeObject::deleteProperty(JSC::ExecState*, const JSC::Identifier&) |
136 | { |
137 | return false; |
138 | } |
139 | |
140 | void QScriptStaticScopeObject::markChildren(JSC::MarkStack& markStack) |
141 | { |
142 | JSC::Register* registerArray = d_ptr()->registerArray.get(); |
143 | if (!registerArray) |
144 | return; |
145 | markStack.appendValues(values: reinterpret_cast<JSC::JSValue*>(registerArray), count: d_ptr()->registerArraySize); |
146 | } |
147 | |
148 | void QScriptStaticScopeObject::addSymbolTableProperty(const JSC::Identifier& name, JSC::JSValue value, unsigned attributes) |
149 | { |
150 | int index = growRegisterArray(1); |
151 | JSC::SymbolTableEntry newEntry(index, attributes | JSC::DontDelete); |
152 | symbolTable().add(key: name.ustring().rep(), mapped: newEntry); |
153 | registerAt(index) = value; |
154 | } |
155 | |
156 | /*! |
157 | Grows the register array by \a count elements, and returns the offset of |
158 | the newly added elements (note that the register file grows downwards, |
159 | starting at index -1). |
160 | */ |
161 | int QScriptStaticScopeObject::growRegisterArray(int count) |
162 | { |
163 | size_t oldSize = d_ptr()->registerArraySize; |
164 | size_t newSize = oldSize + count; |
165 | JSC::Register* registerArray = new JSC::Register[newSize]; |
166 | if (d_ptr()->registerArray) |
167 | memcpy(dest: registerArray + count, src: d_ptr()->registerArray.get(), n: oldSize * sizeof(JSC::Register)); |
168 | setRegisters(registers: registerArray + newSize, registerArray); |
169 | d_ptr()->registerArraySize = newSize; |
170 | return -oldSize - 1; |
171 | } |
172 | |
173 | QT_END_NAMESPACE |
174 | |