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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* GC-internal definition of relocation overlay used while moving cells.
*/
#ifndef gc_RelocationOverlay_h
#define gc_RelocationOverlay_h
#include "mozilla/Assertions.h"
#include "mozilla/EndianUtils.h"
#include <stdint.h>
#include "gc/Cell.h"
#include "js/HeapAPI.h"
#include "vm/JSObject.h"
#include "vm/Shape.h"
namespace js {
namespace gc {
/*
* This structure overlays a Cell that has been moved and provides a way to find
* its new location. It's used during generational and compacting GC.
*/
class RelocationOverlay : public Cell {
// First word of a Cell has additional requirements from GC. The GC flags
// determine if a Cell is a normal entry or is a RelocationOverlay.
// 3 0
// -------------------------
// | NewLocation | GCFlags |
// -------------------------
uintptr_t dataWithTag_;
/* A list entry to track all relocated things. */
RelocationOverlay* next_;
public:
static const RelocationOverlay* fromCell(const Cell* cell) {
return static_cast<const RelocationOverlay*>(cell);
}
static RelocationOverlay* fromCell(Cell* cell) {
return static_cast<RelocationOverlay*>(cell);
}
Cell* forwardingAddress() const {
MOZ_ASSERT(isForwarded());
uintptr_t newLocation = dataWithTag_ & ~Cell::RESERVED_MASK;
return reinterpret_cast<Cell*>(newLocation);
}
void forwardTo(Cell* cell);
RelocationOverlay*& nextRef() {
MOZ_ASSERT(isForwarded());
return next_;
}
RelocationOverlay* next() const {
MOZ_ASSERT(isForwarded());
return next_;
}
};
} // namespace gc
} // namespace js
#endif /* gc_RelocationOverlay_h */