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/*
* Copyright (C) 2011 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 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 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 CopiedAllocator_h
#define CopiedAllocator_h
#include "CopiedBlock.h"
#include <wtf/CheckedBoolean.h>
#include <wtf/DataLog.h>
namespace JSC {
class CopiedAllocator {
public:
CopiedAllocator();
bool fastPathShouldSucceed(size_t bytes) const;
CheckedBoolean tryAllocate(size_t bytes, void** outPtr);
CheckedBoolean tryReallocate(void *oldPtr, size_t oldBytes, size_t newBytes);
void* forceAllocate(size_t bytes);
CopiedBlock* resetCurrentBlock();
void setCurrentBlock(CopiedBlock*);
size_t currentCapacity();
bool isValid() { return !!m_currentBlock; }
CopiedBlock* currentBlock() { return m_currentBlock; }
// Yes, these are public. No, that doesn't mean you can play with them.
// If I had made them private then I'd have to list off all of the JIT
// classes and functions that are entitled to modify these directly, and
// that would have been gross.
size_t m_currentRemaining;
char* m_currentPayloadEnd;
CopiedBlock* m_currentBlock;
};
inline CopiedAllocator::CopiedAllocator()
: m_currentRemaining(0)
, m_currentPayloadEnd(0)
, m_currentBlock(0)
{
}
inline bool CopiedAllocator::fastPathShouldSucceed(size_t bytes) const
{
ASSERT(is8ByteAligned(reinterpret_cast<void*>(bytes)));
return bytes <= m_currentRemaining;
}
inline CheckedBoolean CopiedAllocator::tryAllocate(size_t bytes, void** outPtr)
{
ASSERT(is8ByteAligned(reinterpret_cast<void*>(bytes)));
// This code is written in a gratuitously low-level manner, in order to
// serve as a kind of template for what the JIT would do. Note that the
// way it's written it ought to only require one register, which doubles
// as the result, provided that the compiler does a minimal amount of
// control flow simplification and the bytes argument is a constant.
size_t currentRemaining = m_currentRemaining;
if (bytes > currentRemaining)
return false;
currentRemaining -= bytes;
m_currentRemaining = currentRemaining;
*outPtr = m_currentPayloadEnd - currentRemaining - bytes;
ASSERT(is8ByteAligned(*outPtr));
return true;
}
inline CheckedBoolean CopiedAllocator::tryReallocate(
void* oldPtr, size_t oldBytes, size_t newBytes)
{
ASSERT(is8ByteAligned(oldPtr));
ASSERT(is8ByteAligned(reinterpret_cast<void*>(oldBytes)));
ASSERT(is8ByteAligned(reinterpret_cast<void*>(newBytes)));
ASSERT(newBytes > oldBytes);
size_t additionalBytes = newBytes - oldBytes;
size_t currentRemaining = m_currentRemaining;
if (m_currentPayloadEnd - currentRemaining - oldBytes != static_cast<char*>(oldPtr))
return false;
if (additionalBytes > currentRemaining)
return false;
m_currentRemaining = currentRemaining - additionalBytes;
return true;
}
inline void* CopiedAllocator::forceAllocate(size_t bytes)
{
void* result = 0; // Needed because compilers don't realize this will always be assigned.
CheckedBoolean didSucceed = tryAllocate(bytes, &result);
ASSERT(didSucceed);
return result;
}
inline CopiedBlock* CopiedAllocator::resetCurrentBlock()
{
CopiedBlock* result = m_currentBlock;
if (result) {
result->m_remaining = m_currentRemaining;
m_currentBlock = 0;
m_currentRemaining = 0;
m_currentPayloadEnd = 0;
}
return result;
}
inline void CopiedAllocator::setCurrentBlock(CopiedBlock* newBlock)
{
ASSERT(!m_currentBlock);
m_currentBlock = newBlock;
ASSERT(newBlock);
m_currentRemaining = newBlock->m_remaining;
m_currentPayloadEnd = newBlock->payloadEnd();
}
inline size_t CopiedAllocator::currentCapacity()
{
if (!m_currentBlock)
return 0;
return m_currentBlock->capacity();
}
} // namespace JSC
#endif
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