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** $Id: lgc.h $

** 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. (Open

** upvalues are an exception to this rule.) These lists have no meaning

** when the invariant is not being enforced (e.g., sweep phase).

** Possible states of the Garbage Collector

#define GCSpropagate 0

#define GCSenteratomic 1

#define GCSatomic 2

#define GCSswpallgc 3

#define GCSswpfinobj 4

#define GCSswptobefnz 5

#define GCSswpend 6

#define GCScallfin 7

#define GCSpause 8

#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_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. First three bits are

** used for object "age" in generational mode. Last bit is used

** by tests.

#define WHITE0BIT 3 /* object is white (type 0) */

#define WHITE1BIT 4 /* object is white (type 1) */

#define BLACKBIT 5 /* object is black */

#define FINALIZEDBIT 6 /* object has been marked for finalization */

#define TESTBIT 7

#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) & (ow))

#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)

#define changewhite(x) ((x)->marked ^= WHITEBITS)

#define nw2black(x) \

check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))

#define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS)

/* object age in generational mode */

#define G_NEW 0 /* created in current cycle */

#define G_SURVIVAL 1 /* created in previous cycle */

#define G_OLD0 2 /* marked old by frw. barrier in this cycle */

#define G_OLD1 3 /* first full cycle as old */

#define G_OLD 4 /* really old object (not to be visited) */

#define G_TOUCHED1 5 /* old object touched this cycle */

#define G_TOUCHED2 6 /* old object touched in previous cycle */

#define AGEBITS 7 /* all age bits (111) */

#define getage(o) ((o)->marked & AGEBITS)

#define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))

#define isold(o) (getage(o) > G_SURVIVAL)

#define changeage(o,f,t) \

check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t)))

/* Default Values for GC parameters */

#define LUAI_GENMAJORMUL 100

#define LUAI_GENMINORMUL 20

/* wait memory to double before starting new cycle */

#define LUAI_GCPAUSE 200

** some gc parameters are stored divided by 4 to allow a maximum value

** up to 1023 in a 'lu_byte'.

#define getgcparam(p) ((p) * 4)

#define setgcparam(p,v) ((p) = (v) / 4)

#define LUAI_GCMUL 100

/* how much to allocate before next GC step (log2) */

#define LUAI_GCSTEPSIZE 13 /* 8 KB */

** Check whether the declared GC mode is generational. While in

** generational mode, the collector can go temporarily to incremental

** mode to improve performance. This is signaled by 'g->lastatomic != 0'.

#define isdecGCmodegen(g) (g->gckind == KGC_GEN || g->lastatomic != 0)

** Control when GC is running:

#define GCSTPUSR 1 /* bit true when GC stopped by user */

#define GCSTPGC 2 /* bit true when GC stopped by itself */

#define GCSTPCLS 4 /* bit true when closing Lua state */

#define gcrunning(g) ((g)->gcstp == 0)

** 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_objbarrier(L,p,o) ( \

(isblack(p) && iswhite(o)) ? \

luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))

#define luaC_barrier(L,p,v) ( \

iscollectable(v) ? luaC_objbarrier(L,p,gcvalue(v)) : cast_void(0))

#define luaC_objbarrierback(L,p,o) ( \

(isblack(p) && iswhite(o)) ? luaC_barrierback_(L,p) : cast_void(0))

#define luaC_barrierback(L,p,v) ( \

iscollectable(v) ? luaC_objbarrierback(L, p, gcvalue(v)) : 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 GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz,

size_t offset);

LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);

LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);

LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);

LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);

#endif

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