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/*
* Copyright (C) 2010, 2013 Apple Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#ifndef StackBounds_h
#define StackBounds_h
namespace WTF {
class StackBounds {
// isSafeToRecurse() / recursionLimit() tests (by default)
// that we are at least this far from the end of the stack.
//
// This 64k number was picked because a sampling of stack usage differences
// between consecutive entries into one of the Interpreter::execute...()
// functions was seen to be as high as 27k. Hence, 64k is chosen as a
// conservative availability value that is not too large but comfortably
// exceeds 27k with some buffer for error.
const static size_t s_defaultAvailabilityDelta = 64 * 1024;
public:
static StackBounds currentThreadStackBounds()
{
StackBounds bounds;
bounds.initialize();
bounds.checkConsistency();
return bounds;
}
bool isSafeToRecurse(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
{
checkConsistency();
if (isGrowingDownward())
return current() >= recursionLimit(minAvailableDelta);
return current() <= recursionLimit(minAvailableDelta);
}
void* origin() const
{
ASSERT(m_origin);
return m_origin;
}
size_t size() const
{
if (isGrowingDownward())
return static_cast<char*>(m_origin) - static_cast<char*>(m_bound);
return static_cast<char*>(m_bound) - static_cast<char*>(m_origin);
}
private:
StackBounds()
: m_origin(0)
, m_bound(0)
{
}
WTF_EXPORT_PRIVATE void initialize();
void* current() const
{
checkConsistency();
void* currentPosition = ¤tPosition;
return currentPosition;
}
void* recursionLimit(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
{
checkConsistency();
if (isGrowingDownward())
return static_cast<char*>(m_bound) + minAvailableDelta;
return static_cast<char*>(m_bound) - minAvailableDelta;
}
bool isGrowingDownward() const
{
ASSERT(m_origin && m_bound);
#if OS(WINCE)
return m_origin > m_bound;
#else
return true;
#endif
}
void checkConsistency() const
{
#if !ASSERT_DISABLED
void* currentPosition = ¤tPosition;
ASSERT(m_origin != m_bound);
ASSERT(isGrowingDownward()
? (currentPosition < m_origin && currentPosition > m_bound)
: (currentPosition > m_origin && currentPosition < m_bound));
#endif
}
void* m_origin;
void* m_bound;
friend class StackStats;
};
} // namespace WTF
using WTF::StackBounds;
#endif
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