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authorJeffrey Armstrong <jeff@approximatrix.com>2020-09-28 20:25:16 -0400
committerJeffrey Armstrong <jeff@approximatrix.com>2020-09-28 20:25:16 -0400
commit334ee3f66a7aad17c9865bd9952b0c501b97721a (patch)
tree0ee71269e8c482e6a2df9cbb37dbe15302136799 /src/lgc.h
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Initial import based on Lua 5.3.5
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+/*
+** $Id: lgc.h,v 2.91.1.1 2017/04/19 17:39:34 roberto Exp $
+** Garbage Collector
+** See Copyright Notice in lua.h
+*/
+
+#ifndef lgc_h
+#define lgc_h
+
+
+#include "lobject.h"
+#include "lstate.h"
+
+/*
+** Collectable objects may have one of three colors: white, which
+** means the object is not marked; gray, which means the
+** object is marked, but its references may be not marked; and
+** black, which means that the object and all its references are marked.
+** The main invariant of the garbage collector, while marking objects,
+** is that a black object can never point to a white one. Moreover,
+** any gray object must be in a "gray list" (gray, grayagain, weak,
+** allweak, ephemeron) so that it can be visited again before finishing
+** the collection cycle. These lists have no meaning when the invariant
+** is not being enforced (e.g., sweep phase).
+*/
+
+
+
+/* how much to allocate before next GC step */
+#if !defined(GCSTEPSIZE)
+/* ~100 small strings */
+#define GCSTEPSIZE (cast_int(100 * sizeof(TString)))
+#endif
+
+
+/*
+** Possible states of the Garbage Collector
+*/
+#define GCSpropagate 0
+#define GCSatomic 1
+#define GCSswpallgc 2
+#define GCSswpfinobj 3
+#define GCSswptobefnz 4
+#define GCSswpend 5
+#define GCScallfin 6
+#define GCSpause 7
+
+
+#define issweepphase(g) \
+ (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
+
+
+/*
+** macro to tell when main invariant (white objects cannot point to black
+** ones) must be kept. During a collection, the sweep
+** phase may break the invariant, as objects turned white may point to
+** still-black objects. The invariant is restored when sweep ends and
+** all objects are white again.
+*/
+
+#define keepinvariant(g) ((g)->gcstate <= GCSatomic)
+
+
+/*
+** some useful bit tricks
+*/
+#define resetbits(x,m) ((x) &= cast(lu_byte, ~(m)))
+#define setbits(x,m) ((x) |= (m))
+#define testbits(x,m) ((x) & (m))
+#define bitmask(b) (1<<(b))
+#define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
+#define l_setbit(x,b) setbits(x, bitmask(b))
+#define resetbit(x,b) resetbits(x, bitmask(b))
+#define testbit(x,b) testbits(x, bitmask(b))
+
+
+/* Layout for bit use in 'marked' field: */
+#define WHITE0BIT 0 /* object is white (type 0) */
+#define WHITE1BIT 1 /* object is white (type 1) */
+#define BLACKBIT 2 /* object is black */
+#define FINALIZEDBIT 3 /* object has been marked for finalization */
+/* bit 7 is currently used by tests (luaL_checkmemory) */
+
+#define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)
+
+
+#define iswhite(x) testbits((x)->marked, WHITEBITS)
+#define isblack(x) testbit((x)->marked, BLACKBIT)
+#define isgray(x) /* neither white nor black */ \
+ (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
+
+#define tofinalize(x) testbit((x)->marked, FINALIZEDBIT)
+
+#define otherwhite(g) ((g)->currentwhite ^ WHITEBITS)
+#define isdeadm(ow,m) (!(((m) ^ WHITEBITS) & (ow)))
+#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
+
+#define changewhite(x) ((x)->marked ^= WHITEBITS)
+#define gray2black(x) l_setbit((x)->marked, BLACKBIT)
+
+#define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS)
+
+
+/*
+** Does one step of collection when debt becomes positive. 'pre'/'pos'
+** allows some adjustments to be done only when needed. macro
+** 'condchangemem' is used only for heavy tests (forcing a full
+** GC cycle on every opportunity)
+*/
+#define luaC_condGC(L,pre,pos) \
+ { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
+ condchangemem(L,pre,pos); }
+
+/* more often than not, 'pre'/'pos' are empty */
+#define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0)
+
+
+#define luaC_barrier(L,p,v) ( \
+ (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
+ luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
+
+#define luaC_barrierback(L,p,v) ( \
+ (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
+ luaC_barrierback_(L,p) : cast_void(0))
+
+#define luaC_objbarrier(L,p,o) ( \
+ (isblack(p) && iswhite(o)) ? \
+ luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
+
+#define luaC_upvalbarrier(L,uv) ( \
+ (iscollectable((uv)->v) && !upisopen(uv)) ? \
+ luaC_upvalbarrier_(L,uv) : cast_void(0))
+
+LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
+LUAI_FUNC void luaC_freeallobjects (lua_State *L);
+LUAI_FUNC void luaC_step (lua_State *L);
+LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
+LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
+LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
+LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
+LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o);
+LUAI_FUNC void luaC_upvalbarrier_ (lua_State *L, UpVal *uv);
+LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
+LUAI_FUNC void luaC_upvdeccount (lua_State *L, UpVal *uv);
+
+
+#endif