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  1. /*
  2. ** $Id: lgc.h,v 2.91.1.1 2017/04/19 17:39:34 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. /* how much to allocate before next GC step */
  30. #if !defined(GCSTEPSIZE)
  31. /* ~100 small strings */
  32. #define GCSTEPSIZE      (cast_int(100 * sizeof(TString)))
  33. #endif
  34.  
  35.  
  36. /*
  37. ** Possible states of the Garbage Collector
  38. */
  39. #define GCSpropagate    0
  40. #define GCSatomic       1
  41. #define GCSswpallgc     2
  42. #define GCSswpfinobj    3
  43. #define GCSswptobefnz   4
  44. #define GCSswpend       5
  45. #define GCScallfin      6
  46. #define GCSpause        7
  47.  
  48.  
  49. #define issweepphase(g)  \
  50.         (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
  51.  
  52.  
  53. /*
  54. ** macro to tell when main invariant (white objects cannot point to black
  55. ** ones) must be kept. During a collection, the sweep
  56. ** phase may break the invariant, as objects turned white may point to
  57. ** still-black objects. The invariant is restored when sweep ends and
  58. ** all objects are white again.
  59. */
  60.  
  61. #define keepinvariant(g)        ((g)->gcstate <= GCSatomic)
  62.  
  63.  
  64. /*
  65. ** some useful bit tricks
  66. */
  67. #define resetbits(x,m)          ((x) &= cast(lu_byte, ~(m)))
  68. #define setbits(x,m)            ((x) |= (m))
  69. #define testbits(x,m)           ((x) & (m))
  70. #define bitmask(b)              (1<<(b))
  71. #define bit2mask(b1,b2)         (bitmask(b1) | bitmask(b2))
  72. #define l_setbit(x,b)           setbits(x, bitmask(b))
  73. #define resetbit(x,b)           resetbits(x, bitmask(b))
  74. #define testbit(x,b)            testbits(x, bitmask(b))
  75.  
  76.  
  77. /* Layout for bit use in 'marked' field: */
  78. #define WHITE0BIT       0  /* object is white (type 0) */
  79. #define WHITE1BIT       1  /* object is white (type 1) */
  80. #define BLACKBIT        2  /* object is black */
  81. #define FINALIZEDBIT    3  /* object has been marked for finalization */
  82. /* bit 7 is currently used by tests (luaL_checkmemory) */
  83.  
  84. #define WHITEBITS       bit2mask(WHITE0BIT, WHITE1BIT)
  85.  
  86.  
  87. #define iswhite(x)      testbits((x)->marked, WHITEBITS)
  88. #define isblack(x)      testbit((x)->marked, BLACKBIT)
  89. #define isgray(x)  /* neither white nor black */  \
  90.         (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
  91.  
  92. #define tofinalize(x)   testbit((x)->marked, FINALIZEDBIT)
  93.  
  94. #define otherwhite(g)   ((g)->currentwhite ^ WHITEBITS)
  95. #define isdeadm(ow,m)   (!(((m) ^ WHITEBITS) & (ow)))
  96. #define isdead(g,v)     isdeadm(otherwhite(g), (v)->marked)
  97.  
  98. #define changewhite(x)  ((x)->marked ^= WHITEBITS)
  99. #define gray2black(x)   l_setbit((x)->marked, BLACKBIT)
  100.  
  101. #define luaC_white(g)   cast(lu_byte, (g)->currentwhite & WHITEBITS)
  102.  
  103.  
  104. /*
  105. ** Does one step of collection when debt becomes positive. 'pre'/'pos'
  106. ** allows some adjustments to be done only when needed. macro
  107. ** 'condchangemem' is used only for heavy tests (forcing a full
  108. ** GC cycle on every opportunity)
  109. */
  110. #define luaC_condGC(L,pre,pos) \
  111.         { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
  112.           condchangemem(L,pre,pos); }
  113.  
  114. /* more often than not, 'pre'/'pos' are empty */
  115. #define luaC_checkGC(L)         luaC_condGC(L,(void)0,(void)0)
  116.  
  117.  
  118. #define luaC_barrier(L,p,v) (  \
  119.         (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ?  \
  120.         luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
  121.  
  122. #define luaC_barrierback(L,p,v) (  \
  123.         (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
  124.         luaC_barrierback_(L,p) : cast_void(0))
  125.  
  126. #define luaC_objbarrier(L,p,o) (  \
  127.         (isblack(p) && iswhite(o)) ? \
  128.         luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
  129.  
  130. #define luaC_upvalbarrier(L,uv) ( \
  131.         (iscollectable((uv)->v) && !upisopen(uv)) ? \
  132.          luaC_upvalbarrier_(L,uv) : cast_void(0))
  133.  
  134. LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
  135. LUAI_FUNC void luaC_freeallobjects (lua_State *L);
  136. LUAI_FUNC void luaC_step (lua_State *L);
  137. LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
  138. LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
  139. LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
  140. LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
  141. LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o);
  142. LUAI_FUNC void luaC_upvalbarrier_ (lua_State *L, UpVal *uv);
  143. LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
  144. LUAI_FUNC void luaC_upvdeccount (lua_State *L, UpVal *uv);
  145.  
  146.  
  147. #endif
  148.