#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);
}
uintptr_t scrambledNext;
};
class FreeList {
public:
FreeList(unsigned cellSize);
~FreeList();
void clear();
void initializeList(FreeCell* head, uintptr_t secret, unsigned bytes);
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); }
void dump(PrintStream&) const;
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 };
};
}