wtf/StackBounds.h

   1 /*
   2  * Copyright (C) 2010 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 COMPUTER, 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 COMPUTER, 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
  27 #ifndef StackBounds_h
  28 #define StackBounds_h
  29
  30 namespace WTF {
  31
  32 class StackBounds {
  33     // recursionCheck() / recursionLimit() tests (by default)
  34     // that we are at least this far from the end of the stack.
  35     const static size_t s_defaultAvailabilityDelta = 4096;
  36
  37 public:
  38     StackBounds()
  39         : m_origin(0)
  40         , m_bound(0)
  41     {
  42     }
  43
  44     static StackBounds currentThreadStackBounds()
  45     {
  46         StackBounds bounds;
  47         bounds.initialize();
  48         bounds.checkConsistency();
  49         return bounds;
  50     }
  51
  52     void* origin() const
  53     {
  54         ASSERT(m_origin);
  55         return m_origin;
  56     }
  57
  58     void* current() const
  59     {
  60         checkConsistency();
  61         void* currentPosition = &currentPosition;
  62         return currentPosition;
  63     }
  64
  65     void* recursionLimit(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
  66     {
  67         checkConsistency();
  68         return isGrowingDownward()
  69             ? static_cast<char*>(m_bound) + minAvailableDelta
  70             : static_cast<char*>(m_bound) - minAvailableDelta;
  71     }
  72
  73     bool recursionCheck(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
  74     {
  75         checkConsistency();
  76         return isGrowingDownward()
  77             ? current() >= recursionLimit(minAvailableDelta)
  78             : current() <= recursionLimit(minAvailableDelta);
  79     }
  80
  81 private:
  82     void initialize();
  83
  84
  85     bool isGrowingDownward() const
  86     {
  87         ASSERT(m_origin && m_bound);
  88 #if OS(WINCE)
  89         return m_origin > m_bound;
  90 #else
  91         return true;
  92 #endif
  93     }
  94
  95     void checkConsistency() const;
  96
  97     void* m_origin;
  98     void* m_bound;
  99 };
 100
 101 } // namespace WTF
 102
 103 using WTF::StackBounds;
 104
 105 #endif