external/mit/lua/dist/src/lgc.h

   1 /*
   2 ** $Id: lgc.h,v 1.3 2015/02/02 14:03:05 lneto 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 #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) {  \
 110         if (iscollectable(v) && isblack(p) && iswhite(gcvalue(v)))  \
 111         luaC_barrier_(L,obj2gco(p),gcvalue(v)); }
 112
 113 #define luaC_barrierback(L,p,v) {  \
 114         if (iscollectable(v) && isblack(p) && iswhite(gcvalue(v)))  \
 115         luaC_barrierback_(L,p); }
 116
 117 #define luaC_objbarrier(L,p,o) {  \
 118         if (isblack(p) && iswhite(o)) \
 119                 luaC_barrier_(L,obj2gco(p),obj2gco(o)); }
 120
 121 #define luaC_upvalbarrier(L,uv) \
 122   { if (iscollectable((uv)->v) && !upisopen(uv)) \
 123          luaC_upvalbarrier_(L,uv); }
 124
 125 LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
 126 LUAI_FUNC void luaC_freeallobjects (lua_State *L);
 127 LUAI_FUNC void luaC_step (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 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
 132 LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o);
 133 LUAI_FUNC void luaC_upvalbarrier_ (lua_State *L, UpVal *uv);
 134 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
 135 LUAI_FUNC void luaC_upvdeccount (lua_State *L, UpVal *uv);
 136
 137
 138 #endif