runtime/SmallStrings.h

   1 /*
   2  * Copyright (C) 2008, 2009 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 "UString.h"
  30 #include <wtf/FixedArray.h>
  31 #include <wtf/OwnPtr.h>
  32
  33 namespace JSC {
  34
  35     class HeapRootVisitor;
  36     class JSGlobalData;
  37     class JSString;
  38     class MarkStack;
  39     class SmallStringsStorage;
  40     typedef MarkStack SlotVisitor;
  41
  42     static const unsigned maxSingleCharacterString = 0xFF;
  43
  44     class SmallStrings {
  45         WTF_MAKE_NONCOPYABLE(SmallStrings);
  46     public:
  47         SmallStrings();
  48         ~SmallStrings();
  49
  50         JSString* emptyString(JSGlobalData* globalData)
  51         {
  52             if (!m_emptyString)
  53                 createEmptyString(globalData);
  54             return m_emptyString;
  55         }
  56
  57         JSString* singleCharacterString(JSGlobalData* globalData, unsigned char character)
  58         {
  59             if (!m_singleCharacterStrings[character])
  60                 createSingleCharacterString(globalData, character);
  61             return m_singleCharacterStrings[character];
  62         }
  63
  64         StringImpl* singleCharacterStringRep(unsigned char character);
  65
  66         void visitChildren(HeapRootVisitor&);
  67         void clear();
  68
  69         unsigned count() const;
  70
  71         JSString** singleCharacterStrings() { return &m_singleCharacterStrings[0]; }
  72
  73     private:
  74         static const unsigned singleCharacterStringCount = maxSingleCharacterString + 1;
  75
  76         void createEmptyString(JSGlobalData*);
  77         void createSingleCharacterString(JSGlobalData*, unsigned char);
  78
  79         JSString* m_emptyString;
  80         JSString* m_singleCharacterStrings[singleCharacterStringCount];
  81         OwnPtr<SmallStringsStorage> m_storage;
  82     };
  83
  84 } // namespace JSC
  85
  86 #endif // SmallStrings_h