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/*
* Copyright (C) 2016-2019 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.
*/
#pragma once
#include <wtf/Noncopyable.h>
#include <wtf/PrintStream.h>
namespace JSC {
class HeapCell;
struct FreeCell {
static uintptr_t scramble(FreeCell* cell, uintptr_t secret)
{
return bitwise_cast<uintptr_t>(cell) ^ secret;
}
static FreeCell* descramble(uintptr_t cell, uintptr_t secret)
{
return bitwise_cast<FreeCell*>(cell ^ secret);
}
void setNext(FreeCell* next, uintptr_t secret)
{
scrambledNext = scramble(next, secret);
}
FreeCell* next(uintptr_t secret) const
{
return descramble(scrambledNext, secret);
}
static ptrdiff_t offsetOfScrambledNext() { return OBJECT_OFFSETOF(FreeCell, scrambledNext); }
uint64_t preservedBitsForCrashAnalysis;
uintptr_t scrambledNext;
};
class FreeList {
public:
FreeList(unsigned cellSize);
~FreeList();
void clear();
JS_EXPORT_PRIVATE void initializeList(FreeCell* head, uintptr_t secret, unsigned bytes);
JS_EXPORT_PRIVATE void initializeBump(char* payloadEnd, unsigned remaining);
bool allocationWillFail() const { return !head() && !m_remaining; }
bool allocationWillSucceed() const { return !allocationWillFail(); }
template<typename Func>
HeapCell* allocate(const Func& slowPath);
bool contains(HeapCell*) const;
template<typename Func>
void forEach(const Func&) const;
unsigned originalSize() const { return m_originalSize; }
static ptrdiff_t offsetOfScrambledHead() { return OBJECT_OFFSETOF(FreeList, m_scrambledHead); }
static ptrdiff_t offsetOfSecret() { return OBJECT_OFFSETOF(FreeList, m_secret); }
static ptrdiff_t offsetOfPayloadEnd() { return OBJECT_OFFSETOF(FreeList, m_payloadEnd); }
static ptrdiff_t offsetOfRemaining() { return OBJECT_OFFSETOF(FreeList, m_remaining); }
static ptrdiff_t offsetOfOriginalSize() { return OBJECT_OFFSETOF(FreeList, m_originalSize); }
static ptrdiff_t offsetOfCellSize() { return OBJECT_OFFSETOF(FreeList, m_cellSize); }
JS_EXPORT_PRIVATE void dump(PrintStream&) const;
unsigned cellSize() const { return m_cellSize; }
private:
FreeCell* head() const { return FreeCell::descramble(m_scrambledHead, m_secret); }
uintptr_t m_scrambledHead { 0 };
uintptr_t m_secret { 0 };
char* m_payloadEnd { nullptr };
unsigned m_remaining { 0 };
unsigned m_originalSize { 0 };
unsigned m_cellSize { 0 };
};
} // namespace JSC
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