mudgangster

Tiny, scriptable MUD client
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lgc.h (4742B)

      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