runtime/SmallStrings.h

   1 /*
   2  * Copyright (C) 2008, 2009, 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  * 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 #ifndef SmallStrings_h
  27 #define SmallStrings_h
  28
  29 #include "TypeofType.h"
  30 #include "WriteBarrier.h"
  31 #include <wtf/Noncopyable.h>
  32
  33 #define JSC_COMMON_STRINGS_EACH_NAME(macro) \
  34     macro(boolean) \
  35     macro(false) \
  36     macro(function) \
  37     macro(number) \
  38     macro(null) \
  39     macro(object) \
  40     macro(undefined) \
  41     macro(string) \
  42     macro(symbol) \
  43     macro(true)
  44
  45 namespace WTF {
  46 class StringImpl;
  47 }
  48
  49 namespace JSC {
  50
  51 class HeapRootVisitor;
  52 class VM;
  53 class JSString;
  54 class SmallStringsStorage;
  55 class SlotVisitor;
  56
  57 static const unsigned maxSingleCharacterString = 0xFF;
  58
  59 class SmallStrings {
  60     WTF_MAKE_NONCOPYABLE(SmallStrings);
  61 public:
  62     SmallStrings();
  63     ~SmallStrings();
  64
  65     JSString* emptyString()
  66     {
  67         return m_emptyString;
  68     }
  69
  70     JSString* singleCharacterString(unsigned char character)
  71     {
  72         return m_singleCharacterStrings[character];
  73     }
  74
  75     JS_EXPORT_PRIVATE WTF::StringImpl* singleCharacterStringRep(unsigned char character);
  76
  77     JSString** singleCharacterStrings() { return &m_singleCharacterStrings[0]; }
  78
  79     void initializeCommonStrings(VM&);
  80     void visitStrongReferences(SlotVisitor&);
  81
  82 #define JSC_COMMON_STRINGS_ACCESSOR_DEFINITION(name) \
  83     JSString* name##String() const                   \
  84     {                                                \
  85         return m_##name;                             \
  86     }
  87     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ACCESSOR_DEFINITION)
  88 #undef JSC_COMMON_STRINGS_ACCESSOR_DEFINITION
  89
  90     JSString* typeString(TypeofType type) const
  91     {
  92         switch (type) {
  93         case TypeofType::Undefined:
  94             return undefinedString();
  95         case TypeofType::Boolean:
  96             return booleanString();
  97         case TypeofType::Number:
  98             return numberString();
  99         case TypeofType::String:
 100             return stringString();
 101         case TypeofType::Symbol:
 102             return symbolString();
 103         case TypeofType::Object:
 104             return objectString();
 105         case TypeofType::Function:
 106             return functionString();
 107         }
 108
 109         RELEASE_ASSERT_NOT_REACHED();
 110         return nullptr;
 111     }
 112
 113     JSString* nullObjectString() const { return m_nullObjectString; }
 114     JSString* undefinedObjectString() const { return m_undefinedObjectString; }
 115
 116     bool needsToBeVisited(HeapOperation collectionType) const
 117     {
 118         if (collectionType == FullCollection)
 119             return true;
 120         return m_needsToBeVisited;
 121     }
 122
 123 private:
 124     static const unsigned singleCharacterStringCount = maxSingleCharacterString + 1;
 125
 126     JS_EXPORT_PRIVATE void createEmptyString(VM*);
 127     JS_EXPORT_PRIVATE void createSingleCharacterString(VM*, unsigned char);
 128
 129     void initialize(VM*, JSString*&, const char* value);
 130
 131     JSString* m_emptyString;
 132 #define JSC_COMMON_STRINGS_ATTRIBUTE_DECLARATION(name) JSString* m_##name;
 133     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_DECLARATION)
 134 #undef JSC_COMMON_STRINGS_ATTRIBUTE_DECLARATION
 135     JSString* m_nullObjectString;
 136     JSString* m_undefinedObjectString;
 137     JSString* m_singleCharacterStrings[singleCharacterStringCount];
 138     std::unique_ptr<SmallStringsStorage> m_storage;
 139     bool m_needsToBeVisited;
 140 };
 141
 142 } // namespace JSC
 143
 144 #endif // SmallStrings_h