heap/CardSet.h

   1 /*
   2  * Copyright (C) 2011 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 CardSet_h
  27 #define CardSet_h
  28
  29 #include <stdint.h>
  30 #include <wtf/Assertions.h>
  31 #include <wtf/Noncopyable.h>
  32
  33 namespace JSC {
  34
  35 template <size_t cardSize, size_t blockSize> class CardSet {
  36     WTF_MAKE_NONCOPYABLE(CardSet);
  37
  38 public:
  39     static const size_t cardCount = (blockSize + cardSize - 1) / cardSize;
  40
  41     CardSet()
  42     {
  43         memset(m_cards, 0, cardCount);
  44     }
  45
  46     bool isCardMarkedForAtom(const void*);
  47     void markCardForAtom(const void*);
  48     uint8_t& cardForAtom(const void*);
  49     bool isCardMarked(size_t);
  50     bool testAndClear(size_t);
  51
  52 private:
  53     uint8_t m_cards[cardCount];
  54     COMPILE_ASSERT(!(cardSize & (cardSize - 1)), cardSet_cardSize_is_power_of_two);
  55     COMPILE_ASSERT(!(cardCount & (cardCount - 1)), cardSet_cardCount_is_power_of_two);
  56 };
  57
  58 template <size_t cardSize, size_t blockSize> uint8_t& CardSet<cardSize, blockSize>::cardForAtom(const void* ptr)
  59 {
  60     ASSERT(ptr > this && ptr < (reinterpret_cast<char*>(this) + cardCount * cardSize));
  61     uintptr_t card = (reinterpret_cast<uintptr_t>(ptr) / cardSize) % cardCount;
  62     return m_cards[card];
  63 }
  64
  65 template <size_t cardSize, size_t blockSize> bool CardSet<cardSize, blockSize>::isCardMarkedForAtom(const void* ptr)
  66 {
  67     return cardForAtom(ptr);
  68 }
  69
  70 template <size_t cardSize, size_t blockSize> void CardSet<cardSize, blockSize>::markCardForAtom(const void* ptr)
  71 {
  72     cardForAtom(ptr) = 1;
  73 }
  74
  75 template <size_t cardSize, size_t blockSize> bool CardSet<cardSize, blockSize>::isCardMarked(size_t i)
  76 {
  77     ASSERT(i < cardCount);
  78     return m_cards[i];
  79 }
  80
  81 template <size_t cardSize, size_t blockSize> bool CardSet<cardSize, blockSize>::testAndClear(size_t i)
  82 {
  83     ASSERT(i < cardCount);
  84     bool result = m_cards[i];
  85     m_cards[i] = 0;
  86     return result;
  87 }
  88
  89 }
  90
  91 #endif