Line data    Source code

       1             : // Copyright 2018 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #ifndef V8_OBJECTS_FREE_SPACE_H_
       6             : #define V8_OBJECTS_FREE_SPACE_H_
       7             : 
       8             : #include "src/objects/heap-object.h"
       9             : 
      10             : // Has to be the last include (doesn't have include guards):
      11             : #include "src/objects/object-macros.h"
      12             : 
      13             : namespace v8 {
      14             : namespace internal {
      15             : 
      16             : // FreeSpace are fixed-size free memory blocks used by the heap and GC.
      17             : // They look like heap objects (are heap object tagged and have a map) so that
      18             : // the heap remains iterable.  They have a size and a next pointer.
      19             : // The next pointer is the raw address of the next FreeSpace object (or NULL)
      20             : // in the free list.
      21             : class FreeSpace : public HeapObject {
      22             :  public:
      23             :   // [size]: size of the free space including the header.
      24             :   inline int size() const;
      25             :   inline void set_size(int value);
      26             : 
      27             :   inline int relaxed_read_size() const;
      28             :   inline void relaxed_write_size(int value);
      29             : 
      30             :   inline int Size();
      31             : 
      32             :   // Accessors for the next field.
      33             :   inline FreeSpace next();
      34             :   inline void set_next(FreeSpace next);
      35             : 
      36             :   inline static FreeSpace cast(HeapObject obj);
      37             :   inline static FreeSpace unchecked_cast(const Object obj);
      38             : 
      39             :   // Dispatched behavior.
      40             :   DECL_PRINTER(FreeSpace)
      41             :   DECL_VERIFIER(FreeSpace)
      42             : 
      43             :   // Layout description.
      44             : #define FREE_SPACE_FIELDS(V)  \
      45             :   V(kSizeOffset, kTaggedSize) \
      46             :   V(kNextOffset, kTaggedSize) \
      47             :   /* Header size. */          \
      48             :   V(kSize, 0)
      49             : 
      50             :   DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, FREE_SPACE_FIELDS)
      51             : #undef FREE_SPACE_FIELDS
      52             : 
      53           2 :   OBJECT_CONSTRUCTORS(FreeSpace, HeapObject);
      54             : };
      55             : 
      56             : }  // namespace internal
      57             : }  // namespace v8
      58             : 
      59             : #include "src/objects/object-macros-undef.h"
      60             : 
      61             : #endif  // V8_OBJECTS_FREE_SPACE_H_