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  1. /*
  2. ** $Id: lgc.h,v 2.52 2011/10/03 17:54:25 roberto Exp $
  3. ** Garbage Collector
  4. ** See Copyright Notice in lua.h
  5. */
  6.  
  7. #ifndef lgc_h
  8. #define lgc_h
  9.  
  10.  
  11. #include "lobject.h"
  12. #include "lstate.h"
  13.  
  14. /*
  15. ** Collectable objects may have one of three colors: white, which
  16. ** means the object is not marked; gray, which means the
  17. ** object is marked, but its references may be not marked; and
  18. ** black, which means that the object and all its references are marked.
  19. ** The main invariant of the garbage collector, while marking objects,
  20. ** is that a black object can never point to a white one. Moreover,
  21. ** any gray object must be in a "gray list" (gray, grayagain, weak,
  22. ** allweak, ephemeron) so that it can be visited again before finishing
  23. ** the collection cycle. These lists have no meaning when the invariant
  24. ** is not being enforced (e.g., sweep phase).
  25. */
  26.  
  27.  
  28. /*
  29. ** Possible states of the Garbage Collector
  30. */
  31. #define GCSpropagate    0
  32. #define GCSatomic       1
  33. #define GCSsweepstring  2
  34. #define GCSsweepudata   3
  35. #define GCSsweep        4
  36. #define GCSpause        5
  37.  
  38.  
  39. #define issweepphase(g)  \
  40.         (GCSsweepstring <= (g)->gcstate && (g)->gcstate <= GCSsweep)
  41.  
  42. #define isgenerational(g)       ((g)->gckind == KGC_GEN)
  43.  
  44. /*
  45. ** macro to tell when main invariant (white objects cannot point to black
  46. ** ones) must be kept. During a non-generational collection, the sweep
  47. ** phase may break the invariant, as objects turned white may point to
  48. ** still-black objects. The invariant is restored when sweep ends and
  49. ** all objects are white again. During a generational collection, the
  50. ** invariant must be kept all times.
  51. */
  52. #define keepinvariant(g)  (isgenerational(g) || g->gcstate <= GCSatomic)
  53.  
  54.  
  55. /*
  56. ** some useful bit tricks
  57. */
  58. #define resetbits(x,m)          ((x) &= cast(lu_byte, ~(m)))
  59. #define setbits(x,m)            ((x) |= (m))
  60. #define testbits(x,m)           ((x) & (m))
  61. #define bitmask(b)              (1<<(b))
  62. #define bit2mask(b1,b2)         (bitmask(b1) | bitmask(b2))
  63. #define l_setbit(x,b)           setbits(x, bitmask(b))
  64. #define resetbit(x,b)           resetbits(x, bitmask(b))
  65. #define testbit(x,b)            testbits(x, bitmask(b))
  66.  
  67.  
  68. /* Layout for bit use in `marked' field: */
  69. #define WHITE0BIT       0  /* object is white (type 0) */
  70. #define WHITE1BIT       1  /* object is white (type 1) */
  71. #define BLACKBIT        2  /* object is black */
  72. #define FINALIZEDBIT    3  /* object has been separated for finalization */
  73. #define SEPARATED       4  /* object is in 'finobj' list or in 'tobefnz' */
  74. #define FIXEDBIT        5  /* object is fixed (should not be collected) */
  75. #define OLDBIT          6  /* object is old (only in generational mode) */
  76. /* bit 7 is currently used by tests (luaL_checkmemory) */
  77.  
  78. #define WHITEBITS       bit2mask(WHITE0BIT, WHITE1BIT)
  79.  
  80.  
  81. #define iswhite(x)      testbits((x)->gch.marked, WHITEBITS)
  82. #define isblack(x)      testbit((x)->gch.marked, BLACKBIT)
  83. #define isgray(x)  /* neither white nor black */  \
  84.         (!testbits((x)->gch.marked, WHITEBITS | bitmask(BLACKBIT)))
  85.  
  86. #define isold(x)        testbit((x)->gch.marked, OLDBIT)
  87.  
  88. /* MOVE OLD rule: whenever an object is moved to the beginning of
  89.    a GC list, its old bit must be cleared */
  90. #define resetoldbit(o)  resetbit((o)->gch.marked, OLDBIT)
  91.  
  92. #define otherwhite(g)   (g->currentwhite ^ WHITEBITS)
  93. #define isdeadm(ow,m)   (!(((m) ^ WHITEBITS) & (ow)))
  94. #define isdead(g,v)     isdeadm(otherwhite(g), (v)->gch.marked)
  95.  
  96. #define changewhite(x)  ((x)->gch.marked ^= WHITEBITS)
  97. #define gray2black(x)   l_setbit((x)->gch.marked, BLACKBIT)
  98.  
  99. #define valiswhite(x)   (iscollectable(x) && iswhite(gcvalue(x)))
  100.  
  101. #define luaC_white(g)   cast(lu_byte, (g)->currentwhite & WHITEBITS)
  102.  
  103.  
  104. #define luaC_condGC(L,c) \
  105.         {if (G(L)->GCdebt > 0) {c;}; condchangemem(L);}
  106. #define luaC_checkGC(L)         luaC_condGC(L, luaC_step(L);)
  107.  
  108.  
  109. #define luaC_barrier(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p)))  \
  110.         luaC_barrier_(L,obj2gco(p),gcvalue(v)); }
  111.  
  112. #define luaC_barrierback(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p)))  \
  113.         luaC_barrierback_(L,p); }
  114.  
  115. #define luaC_objbarrier(L,p,o)  \
  116.         { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) \
  117.                 luaC_barrier_(L,obj2gco(p),obj2gco(o)); }
  118.  
  119. #define luaC_objbarrierback(L,p,o)  \
  120.    { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) luaC_barrierback_(L,p); }
  121.  
  122. #define luaC_barrierproto(L,p,c) \
  123.    { if (isblack(obj2gco(p))) luaC_barrierproto_(L,p,c); }
  124.  
  125. LUAI_FUNC void luaC_freeallobjects (lua_State *L);
  126. LUAI_FUNC void luaC_step (lua_State *L);
  127. LUAI_FUNC void luaC_forcestep (lua_State *L);
  128. LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
  129. LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
  130. LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz,
  131.                                  GCObject **list, int offset);
  132. LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
  133. LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
  134. LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c);
  135. LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
  136. LUAI_FUNC void luaC_checkupvalcolor (global_State *g, UpVal *uv);
  137. LUAI_FUNC void luaC_changemode (lua_State *L, int mode);
  138.  
  139. #endif
  140.