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  1. /*
  2. ** $Id: lgc.h $
  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 means
  16. ** the object is not marked; gray, which means the object is marked, but
  17. ** its references may be not marked; and black, which means that the
  18. ** object and all its references are marked.  The main invariant of the
  19. ** garbage collector, while marking objects, is that a black object can
  20. ** never point to a white one. Moreover, any gray object must be in a
  21. ** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
  22. ** can be visited again before finishing the collection cycle. (Open
  23. ** upvalues are an exception to this rule.)  These lists have no meaning
  24. ** when the invariant 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 GCSenteratomic  1
  33. #define GCSatomic       2
  34. #define GCSswpallgc     3
  35. #define GCSswpfinobj    4
  36. #define GCSswptobefnz   5
  37. #define GCSswpend       6
  38. #define GCScallfin      7
  39. #define GCSpause        8
  40.  
  41.  
  42. #define issweepphase(g)  \
  43.         (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
  44.  
  45.  
  46. /*
  47. ** macro to tell when main invariant (white objects cannot point to black
  48. ** ones) must be kept. During a collection, the sweep
  49. ** phase may break the invariant, as objects turned white may point to
  50. ** still-black objects. The invariant is restored when sweep ends and
  51. ** all objects are white again.
  52. */
  53.  
  54. #define keepinvariant(g)        ((g)->gcstate <= GCSatomic)
  55.  
  56.  
  57. /*
  58. ** some useful bit tricks
  59. */
  60. #define resetbits(x,m)          ((x) &= cast_byte(~(m)))
  61. #define setbits(x,m)            ((x) |= (m))
  62. #define testbits(x,m)           ((x) & (m))
  63. #define bitmask(b)              (1<<(b))
  64. #define bit2mask(b1,b2)         (bitmask(b1) | bitmask(b2))
  65. #define l_setbit(x,b)           setbits(x, bitmask(b))
  66. #define resetbit(x,b)           resetbits(x, bitmask(b))
  67. #define testbit(x,b)            testbits(x, bitmask(b))
  68.  
  69.  
  70. /*
  71. ** Layout for bit use in 'marked' field. First three bits are
  72. ** used for object "age" in generational mode. Last bit is used
  73. ** by tests.
  74. */
  75. #define WHITE0BIT       3  /* object is white (type 0) */
  76. #define WHITE1BIT       4  /* object is white (type 1) */
  77. #define BLACKBIT        5  /* object is black */
  78. #define FINALIZEDBIT    6  /* object has been marked for finalization */
  79.  
  80. #define TESTBIT         7
  81.  
  82.  
  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) & (ow))
  96. #define isdead(g,v)     isdeadm(otherwhite(g), (v)->marked)
  97.  
  98. #define changewhite(x)  ((x)->marked ^= WHITEBITS)
  99. #define nw2black(x)  \
  100.         check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))
  101.  
  102. #define luaC_white(g)   cast_byte((g)->currentwhite & WHITEBITS)
  103.  
  104.  
  105. /* object age in generational mode */
  106. #define G_NEW           0       /* created in current cycle */
  107. #define G_SURVIVAL      1       /* created in previous cycle */
  108. #define G_OLD0          2       /* marked old by frw. barrier in this cycle */
  109. #define G_OLD1          3       /* first full cycle as old */
  110. #define G_OLD           4       /* really old object (not to be visited) */
  111. #define G_TOUCHED1      5       /* old object touched this cycle */
  112. #define G_TOUCHED2      6       /* old object touched in previous cycle */
  113.  
  114. #define AGEBITS         7  /* all age bits (111) */
  115.  
  116. #define getage(o)       ((o)->marked & AGEBITS)
  117. #define setage(o,a)  ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))
  118. #define isold(o)        (getage(o) > G_SURVIVAL)
  119.  
  120. #define changeage(o,f,t)  \
  121.         check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t)))
  122.  
  123.  
  124. /* Default Values for GC parameters */
  125. #define LUAI_GENMAJORMUL         100
  126. #define LUAI_GENMINORMUL         20
  127.  
  128. /* wait memory to double before starting new cycle */
  129. #define LUAI_GCPAUSE    200
  130.  
  131. /*
  132. ** some gc parameters are stored divided by 4 to allow a maximum value
  133. ** up to 1023 in a 'lu_byte'.
  134. */
  135. #define getgcparam(p)   ((p) * 4)
  136. #define setgcparam(p,v) ((p) = (v) / 4)
  137.  
  138. #define LUAI_GCMUL      100
  139.  
  140. /* how much to allocate before next GC step (log2) */
  141. #define LUAI_GCSTEPSIZE 13      /* 8 KB */
  142.  
  143.  
  144. /*
  145. ** Check whether the declared GC mode is generational. While in
  146. ** generational mode, the collector can go temporarily to incremental
  147. ** mode to improve performance. This is signaled by 'g->lastatomic != 0'.
  148. */
  149. #define isdecGCmodegen(g)       (g->gckind == KGC_GEN || g->lastatomic != 0)
  150.  
  151.  
  152. /*
  153. ** Control when GC is running:
  154. */
  155. #define GCSTPUSR        1  /* bit true when GC stopped by user */
  156. #define GCSTPGC         2  /* bit true when GC stopped by itself */
  157. #define GCSTPCLS        4  /* bit true when closing Lua state */
  158. #define gcrunning(g)    ((g)->gcstp == 0)
  159.  
  160.  
  161. /*
  162. ** Does one step of collection when debt becomes positive. 'pre'/'pos'
  163. ** allows some adjustments to be done only when needed. macro
  164. ** 'condchangemem' is used only for heavy tests (forcing a full
  165. ** GC cycle on every opportunity)
  166. */
  167. #define luaC_condGC(L,pre,pos) \
  168.         { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
  169.           condchangemem(L,pre,pos); }
  170.  
  171. /* more often than not, 'pre'/'pos' are empty */
  172. #define luaC_checkGC(L)         luaC_condGC(L,(void)0,(void)0)
  173.  
  174.  
  175. #define luaC_barrier(L,p,v) (  \
  176.         (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ?  \
  177.         luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
  178.  
  179. #define luaC_barrierback(L,p,v) (  \
  180.         (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
  181.         luaC_barrierback_(L,p) : cast_void(0))
  182.  
  183. #define luaC_objbarrier(L,p,o) (  \
  184.         (isblack(p) && iswhite(o)) ? \
  185.         luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
  186.  
  187. LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
  188. LUAI_FUNC void luaC_freeallobjects (lua_State *L);
  189. LUAI_FUNC void luaC_step (lua_State *L);
  190. LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
  191. LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
  192. LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
  193. LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
  194. LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
  195. LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
  196. LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);
  197.  
  198.  
  199. #endif
  200.