1/*
2** $Id: lgc.h,v 2.58 2012/09/11 12:53:08 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 GCSsweepstring	2
42#define GCSsweepudata	3
43#define GCSsweep	4
44#define GCSpause	5
45
46
47#define issweepphase(g)  \
48	(GCSsweepstring <= (g)->gcstate && (g)->gcstate <= GCSsweep)
49
50#define isgenerational(g)	((g)->gckind == KGC_GEN)
51
52/*
53** macros to tell when main invariant (white objects cannot point to black
54** ones) must be kept. During a non-generational collection, the sweep
55** phase may break the invariant, as objects turned white may point to
56** still-black objects. The invariant is restored when sweep ends and
57** all objects are white again. During a generational collection, the
58** invariant must be kept all times.
59*/
60
61#define keepinvariant(g)	(isgenerational(g) || g->gcstate <= GCSatomic)
62
63
64/*
65** Outside the collector, the state in generational mode is kept in
66** 'propagate', so 'keepinvariant' is always true.
67*/
68#define keepinvariantout(g)  \
69  check_exp(g->gcstate == GCSpropagate || !isgenerational(g),  \
70            g->gcstate <= GCSatomic)
71
72
73/*
74** some useful bit tricks
75*/
76#define resetbits(x,m)		((x) &= cast(lu_byte, ~(m)))
77#define setbits(x,m)		((x) |= (m))
78#define testbits(x,m)		((x) & (m))
79#define bitmask(b)		(1<<(b))
80#define bit2mask(b1,b2)		(bitmask(b1) | bitmask(b2))
81#define l_setbit(x,b)		setbits(x, bitmask(b))
82#define resetbit(x,b)		resetbits(x, bitmask(b))
83#define testbit(x,b)		testbits(x, bitmask(b))
84
85
86/* Layout for bit use in `marked' field: */
87#define WHITE0BIT	0  /* object is white (type 0) */
88#define WHITE1BIT	1  /* object is white (type 1) */
89#define BLACKBIT	2  /* object is black */
90#define FINALIZEDBIT	3  /* object has been separated for finalization */
91#define SEPARATED	4  /* object is in 'finobj' list or in 'tobefnz' */
92#define FIXEDBIT	5  /* object is fixed (should not be collected) */
93#define OLDBIT		6  /* object is old (only in generational mode) */
94/* bit 7 is currently used by tests (luaL_checkmemory) */
95
96#define WHITEBITS	bit2mask(WHITE0BIT, WHITE1BIT)
97
98
99#define iswhite(x)      testbits((x)->gch.marked, WHITEBITS)
100#define isblack(x)      testbit((x)->gch.marked, BLACKBIT)
101#define isgray(x)  /* neither white nor black */  \
102	(!testbits((x)->gch.marked, WHITEBITS | bitmask(BLACKBIT)))
103
104#define isold(x)	testbit((x)->gch.marked, OLDBIT)
105
106/* MOVE OLD rule: whenever an object is moved to the beginning of
107   a GC list, its old bit must be cleared */
108#define resetoldbit(o)	resetbit((o)->gch.marked, OLDBIT)
109
110#define otherwhite(g)	(g->currentwhite ^ WHITEBITS)
111#define isdeadm(ow,m)	(!(((m) ^ WHITEBITS) & (ow)))
112#define isdead(g,v)	isdeadm(otherwhite(g), (v)->gch.marked)
113
114#define changewhite(x)	((x)->gch.marked ^= WHITEBITS)
115#define gray2black(x)	l_setbit((x)->gch.marked, BLACKBIT)
116
117#define valiswhite(x)	(iscollectable(x) && iswhite(gcvalue(x)))
118
119#define luaC_white(g)	cast(lu_byte, (g)->currentwhite & WHITEBITS)
120
121
122#define luaC_condGC(L,c) \
123	{if (G(L)->GCdebt > 0) {c;}; condchangemem(L);}
124#define luaC_checkGC(L)		luaC_condGC(L, luaC_step(L);)
125
126
127#define luaC_barrier(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p)))  \
128	luaC_barrier_(L,obj2gco(p),gcvalue(v)); }
129
130#define luaC_barrierback(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p)))  \
131	luaC_barrierback_(L,p); }
132
133#define luaC_objbarrier(L,p,o)  \
134	{ if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) \
135		luaC_barrier_(L,obj2gco(p),obj2gco(o)); }
136
137#define luaC_objbarrierback(L,p,o)  \
138   { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) luaC_barrierback_(L,p); }
139
140#define luaC_barrierproto(L,p,c) \
141   { if (isblack(obj2gco(p))) luaC_barrierproto_(L,p,c); }
142
143LUAI_FUNC void luaC_freeallobjects (lua_State *L);
144LUAI_FUNC void luaC_step (lua_State *L);
145LUAI_FUNC void luaC_forcestep (lua_State *L);
146LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
147LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
148LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz,
149                                 GCObject **list, int offset);
150LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
151LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
152LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c);
153LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
154LUAI_FUNC void luaC_checkupvalcolor (global_State *g, UpVal *uv);
155LUAI_FUNC void luaC_changemode (lua_State *L, int mode);
156
157#endif
158