1 /* 2 * Copyright (C) 2007, 2008 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 Computer, 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 SymbolTable_h 30 #define SymbolTable_h 31 32 #include "JSObject.h" 33 #include "UString.h" 34 #include <wtf/AlwaysInline.h> 35 36 namespace JSC { 37 missingSymbolMarker()38 static ALWAYS_INLINE int missingSymbolMarker() { return std::numeric_limits<int>::max(); } 39 40 // The bit twiddling in this class assumes that every register index is a 41 // reasonably small positive or negative number, and therefore has its high 42 // four bits all set or all unset. 43 44 struct SymbolTableEntry { SymbolTableEntrySymbolTableEntry45 SymbolTableEntry() 46 : m_bits(0) 47 { 48 } 49 SymbolTableEntrySymbolTableEntry50 SymbolTableEntry(int index) 51 { 52 ASSERT(isValidIndex(index)); 53 pack(index, false, false); 54 } 55 SymbolTableEntrySymbolTableEntry56 SymbolTableEntry(int index, unsigned attributes) 57 { 58 ASSERT(isValidIndex(index)); 59 pack(index, attributes & ReadOnly, attributes & DontEnum); 60 } 61 isNullSymbolTableEntry62 bool isNull() const 63 { 64 return !m_bits; 65 } 66 getIndexSymbolTableEntry67 int getIndex() const 68 { 69 return m_bits >> FlagBits; 70 } 71 getAttributesSymbolTableEntry72 unsigned getAttributes() const 73 { 74 unsigned attributes = 0; 75 if (m_bits & ReadOnlyFlag) 76 attributes |= ReadOnly; 77 if (m_bits & DontEnumFlag) 78 attributes |= DontEnum; 79 return attributes; 80 } 81 setAttributesSymbolTableEntry82 void setAttributes(unsigned attributes) 83 { 84 pack(getIndex(), attributes & ReadOnly, attributes & DontEnum); 85 } 86 isReadOnlySymbolTableEntry87 bool isReadOnly() const 88 { 89 return m_bits & ReadOnlyFlag; 90 } 91 92 private: 93 static const unsigned ReadOnlyFlag = 0x1; 94 static const unsigned DontEnumFlag = 0x2; 95 static const unsigned NotNullFlag = 0x4; 96 static const unsigned FlagBits = 3; 97 packSymbolTableEntry98 void pack(int index, bool readOnly, bool dontEnum) 99 { 100 m_bits = (index << FlagBits) | NotNullFlag; 101 if (readOnly) 102 m_bits |= ReadOnlyFlag; 103 if (dontEnum) 104 m_bits |= DontEnumFlag; 105 } 106 isValidIndexSymbolTableEntry107 bool isValidIndex(int index) 108 { 109 return ((index << FlagBits) >> FlagBits) == index; 110 } 111 112 int m_bits; 113 }; 114 115 struct SymbolTableIndexHashTraits { 116 typedef SymbolTableEntry TraitType; emptyValueSymbolTableIndexHashTraits117 static SymbolTableEntry emptyValue() { return SymbolTableEntry(); } 118 static const bool emptyValueIsZero = true; 119 static const bool needsDestruction = false; 120 }; 121 122 typedef HashMap<RefPtr<StringImpl>, SymbolTableEntry, IdentifierRepHash, HashTraits<RefPtr<StringImpl> >, SymbolTableIndexHashTraits> SymbolTable; 123 124 class SharedSymbolTable : public SymbolTable, public RefCounted<SharedSymbolTable> { 125 WTF_MAKE_FAST_ALLOCATED; 126 public: create()127 static PassRefPtr<SharedSymbolTable> create() { return adoptRef(new SharedSymbolTable); } 128 private: SharedSymbolTable()129 SharedSymbolTable() { } 130 }; 131 132 } // namespace JSC 133 134 #endif // SymbolTable_h 135