js/src/jscell.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  *
   3  * ***** BEGIN LICENSE BLOCK *****
   4  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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   7  * 1.1 (the "License"); you may not use this file except in compliance with
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  16  * The Original Code is SpiderMonkey code.
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  20  * Portions created by the Initial Developer are Copyright (C) 2010
  21  * the Initial Developer. All Rights Reserved.
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  23  * Contributor(s):
  24  * Gregor Wagner <anygregor@gmail.com>
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  38  * ***** END LICENSE BLOCK ***** */
  39
  40 #ifndef jscell_h___
  41 #define jscell_h___
  42
  43 struct JSCompartment;
  44
  45 namespace js {
  46 namespace gc {
  47
  48 template <typename T> struct Arena;
  49 struct ArenaBitmap;
  50 struct MarkingDelay;
  51 struct Chunk;
  52 struct FreeCell;
  53
  54 /*
  55  * A GC cell is the base class for GC Things like JSObject, JSShortString,
  56  * JSFunction, JSXML and for an empty cell called FreeCell. It helps avoiding
  57  * casts from an Object to a Cell whenever we call GC related mark functions.
  58  * Cell is not the base Class for JSString because static initialization
  59  * (used for unitStringTables) does not work with inheritance.
  60  */
  61
  62 struct Cell {
  63     static const size_t CellShift = 3;
  64     static const size_t CellSize = size_t(1) << CellShift;
  65     static const size_t CellMask = CellSize - 1;
  66
  67     inline Arena<Cell> *arena() const;
  68     inline Chunk *chunk() const;
  69     inline ArenaBitmap *bitmap() const;
  70     JS_ALWAYS_INLINE size_t cellIndex() const;
  71
  72     JS_ALWAYS_INLINE bool isMarked(uint32 color) const;
  73     JS_ALWAYS_INLINE bool markIfUnmarked(uint32 color) const;
  74     JS_ALWAYS_INLINE void unmark(uint32 color) const;
  75
  76     inline JSCompartment *compartment() const;
  77
  78     /* Needed for compatibility reasons because Cell can't be a base class of JSString */
  79     JS_ALWAYS_INLINE js::gc::Cell *asCell() { return this; }
  80
  81     JS_ALWAYS_INLINE js::gc::FreeCell *asFreeCell() {
  82         return reinterpret_cast<FreeCell *>(this);
  83     }
  84 };
  85
  86 /* FreeCell has always size 8 */
  87 struct FreeCell : Cell {
  88     union {
  89         FreeCell *link;
  90         double data;
  91     };
  92 };
  93
  94 JS_STATIC_ASSERT(sizeof(FreeCell) == 8);
  95
  96 } /* namespace gc */
  97 } /* namespace js */
  98
  99 #endif /* jscell_h___ */