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      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 "WriteBarrier.h"
     31 #include <wtf/FixedArray.h>
     32 #include <wtf/OwnPtr.h>
     33 
     34 namespace JSC {
     35 
     36     class HeapRootMarker;
     37     class JSGlobalData;
     38     class JSString;
     39     class MarkStack;
     40     class SmallStringsStorage;
     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 markChildren(HeapRootMarker&);
     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
     87