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// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_FREE_SPACE_H_
#define V8_OBJECTS_FREE_SPACE_H_
#include "src/objects/heap-object.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
#include "torque-generated/src/objects/free-space-tq.inc"
// FreeSpace are fixed-size free memory blocks used by the heap and GC.
// They look like heap objects (are heap object tagged and have a map) so that
// the heap remains iterable. They have a size and a next pointer.
// The next pointer is the raw address of the next FreeSpace object (or NULL)
// in the free list.
//
// When external code space is enabled next pointer is stored as Smi values
// representing a diff from current FreeSpace object address in kObjectAlignment
// chunks. Terminating FreeSpace value is represented as Smi zero.
// Such a representation has the following properties:
// a) it can hold both positive an negative diffs for full pointer compression
// cage size (HeapObject address has only valuable 30 bits while Smis have
// 31 bits),
// b) it's independent of the pointer compression base and pointer compression
// scheme.
class FreeSpace : public TorqueGeneratedFreeSpace<FreeSpace, HeapObject> {
public:
// [size]: size of the free space including the header.
DECL_RELAXED_SMI_ACCESSORS(size)
inline int Size();
// Accessors for the next field.
inline FreeSpace next() const;
inline void set_next(FreeSpace next);
inline static FreeSpace cast(HeapObject obj);
inline static FreeSpace unchecked_cast(const Object obj);
// Dispatched behavior.
DECL_PRINTER(FreeSpace)
class BodyDescriptor;
private:
inline bool IsValid() const;
TQ_OBJECT_CONSTRUCTORS(FreeSpace)
};
} // namespace internal
} // namespace v8
#include "src/objects/object-macros-undef.h"
#endif // V8_OBJECTS_FREE_SPACE_H_
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