runtime/StructureIDTable.h

   1 /*
   2  * Copyright (C) 2013 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. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef StructureIDTable_h
  27 #define StructureIDTable_h
  28
  29 #include "UnusedPointer.h"
  30 #include <wtf/Vector.h>
  31
  32 namespace JSC {
  33
  34 class Structure;
  35
  36 #if USE(JSVALUE64)
  37 typedef uint32_t StructureID;
  38 #else
  39 typedef Structure* StructureID;
  40 #endif
  41
  42 class StructureIDTable {
  43     friend class LLIntOffsetsExtractor;
  44 public:
  45     StructureIDTable();
  46
  47     void** base() { return reinterpret_cast<void**>(&m_table); }
  48
  49     Structure* get(StructureID);
  50     void deallocateID(Structure*, StructureID);
  51     StructureID allocateID(Structure*);
  52
  53     void flushOldTables();
  54
  55 private:
  56     void resize(size_t newCapacity);
  57
  58     union StructureOrOffset {
  59         WTF_MAKE_FAST_ALLOCATED;
  60     public:
  61         Structure* structure;
  62         StructureID offset;
  63     };
  64
  65     StructureOrOffset* table() const { return m_table.get(); }
  66
  67     static const size_t s_initialSize = 256;
  68
  69     Vector<std::unique_ptr<StructureOrOffset[]>> m_oldTables;
  70
  71     uint32_t m_firstFreeOffset;
  72     std::unique_ptr<StructureOrOffset[]> m_table;
  73
  74     size_t m_size;
  75     size_t m_capacity;
  76
  77 #if USE(JSVALUE64)
  78     static const StructureID s_unusedID = unusedPointer;
  79 #endif
  80 };
  81
  82 inline Structure* StructureIDTable::get(StructureID structureID)
  83 {
  84 #if USE(JSVALUE64)
  85     ASSERT_WITH_SECURITY_IMPLICATION(structureID && structureID < m_capacity);
  86     return table()[structureID].structure;
  87 #else
  88     return structureID;
  89 #endif
  90 }
  91
  92 } // namespace JSC
  93
  94 #endif // StructureIDTable_h