client/deps/liblua/lgc.h

   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_objbarrier(L,p,o) (  \
 176         (isblack(p) && iswhite(o)) ? \
 177         luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
 178
 179 #define luaC_barrier(L,p,v) (  \
 180         iscollectable(v) ? luaC_objbarrier(L,p,gcvalue(v)) : cast_void(0))
 181
 182 #define luaC_objbarrierback(L,p,o) (  \
 183         (isblack(p) && iswhite(o)) ? luaC_barrierback_(L,p) : cast_void(0))
 184
 185 #define luaC_barrierback(L,p,v) (  \
 186         iscollectable(v) ? luaC_objbarrierback(L, p, gcvalue(v)) : cast_void(0))
 187
 188 LUAI_FUNC void luaC_fix(lua_State *L, GCObject *o);
 189 LUAI_FUNC void luaC_freeallobjects(lua_State *L);
 190 LUAI_FUNC void luaC_step(lua_State *L);
 191 LUAI_FUNC void luaC_runtilstate(lua_State *L, int statesmask);
 192 LUAI_FUNC void luaC_fullgc(lua_State *L, int isemergency);
 193 LUAI_FUNC GCObject *luaC_newobj(lua_State *L, int tt, size_t sz);
 194 LUAI_FUNC GCObject *luaC_newobjdt(lua_State *L, int tt, size_t sz,
 195                                   size_t offset);
 196 LUAI_FUNC void luaC_barrier_(lua_State *L, GCObject *o, GCObject *v);
 197 LUAI_FUNC void luaC_barrierback_(lua_State *L, GCObject *o);
 198 LUAI_FUNC void luaC_checkfinalizer(lua_State *L, GCObject *o, Table *mt);
 199 LUAI_FUNC void luaC_changemode(lua_State *L, int newmode);
 200
 201
 202 #endif