runtime/JSEnvironmentRecord.h

   1 /*
   2  * Copyright (C) 2007, 2008, 2012, 2015 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  *
   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.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef JSEnvironmentRecord_h
  30 #define JSEnvironmentRecord_h
  31
  32 #include "JSObject.h"
  33 #include "JSSymbolTableObject.h"
  34 #include "Register.h"
  35 #include "SymbolTable.h"
  36
  37 namespace JSC {
  38
  39 class LLIntOffsetsExtractor;
  40 class Register;
  41
  42 class JSEnvironmentRecord : public JSSymbolTableObject {
  43     friend class JIT;
  44     friend class LLIntOffsetsExtractor;
  45
  46 public:
  47     typedef JSSymbolTableObject Base;
  48     static const unsigned StructureFlags = Base::StructureFlags;
  49
  50     WriteBarrierBase<Unknown>* variables()
  51     {
  52         return bitwise_cast<WriteBarrierBase<Unknown>*>(bitwise_cast<char*>(this) + offsetOfVariables());
  53     }
  54
  55     bool isValid(ScopeOffset offset)
  56     {
  57         return !!offset && offset.offset() < symbolTable()->scopeSize();
  58     }
  59
  60     WriteBarrierBase<Unknown>& variableAt(ScopeOffset offset)
  61     {
  62         ASSERT(isValid(offset));
  63         return variables()[offset.offset()];
  64     }
  65
  66     static size_t offsetOfVariables()
  67     {
  68         return WTF::roundUpToMultipleOf<sizeof(WriteBarrier<Unknown>)>(sizeof(JSEnvironmentRecord));
  69     }
  70
  71     static ptrdiff_t offsetOfVariable(ScopeOffset offset)
  72     {
  73         return offsetOfVariables() + offset.offset() * sizeof(WriteBarrier<Unknown>);
  74     }
  75
  76     DECLARE_INFO;
  77
  78     static size_t allocationSizeForScopeSize(unsigned scopeSize)
  79     {
  80         return offsetOfVariables() + scopeSize * sizeof(WriteBarrier<Unknown>);
  81     }
  82
  83     static size_t allocationSize(SymbolTable* symbolTable)
  84     {
  85         return allocationSizeForScopeSize(symbolTable->scopeSize());
  86     }
  87
  88 protected:
  89     JSEnvironmentRecord(
  90         VM& vm,
  91         Structure* structure,
  92         JSScope* scope,
  93         SymbolTable* symbolTable)
  94         : Base(vm, structure, scope, symbolTable)
  95     {
  96     }
  97
  98     void finishCreationUninitialized(VM& vm)
  99     {
 100         Base::finishCreation(vm);
 101     }
 102
 103     void finishCreation(VM& vm)
 104     {
 105         finishCreationUninitialized(vm);
 106         for (unsigned i = symbolTable()->scopeSize(); i--;) {
 107             // Filling this with undefined is useful because that's what variables start out as.
 108             variableAt(ScopeOffset(i)).setUndefined();
 109         }
 110     }
 111
 112     static void visitChildren(JSCell*, SlotVisitor&);
 113 };
 114
 115 } // namespace JSC
 116
 117 #endif // JSEnvironmentRecord_h