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lua/lgc.c

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/*
** $Id: lgc.c,v 1.144 2002/08/05 14:50:39 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
#include <string.h>
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
typedef struct GCState {
Table *tmark; /* list of marked tables to be visited */
Table *toclear; /* list of visited weak tables (to be cleared after GC) */
lua_State *L;
} GCState;
/* mark a string; marks larger than 1 cannot be changed */
#define strmark(s) {if ((s)->tsv.marked == 0) (s)->tsv.marked = 1;}
/* unmarked tables are represented by pointing `mark' to themselves */
#define ismarked(x) ((x)->mark != (x))
/* mark tricks for userdata */
#define isudmarked(u) (u->uv.len & 1)
#define markud(u) (u->uv.len |= 1)
#define unmarkud(u) (u->uv.len &= (~(size_t)1))
#define isfinalized(u) (u->uv.len & 2)
#define markfinalized(u) (u->uv.len |= 2)
/* mark tricks for upvalues (assume that open upvalues are always marked) */
#define isupvalmarked(uv) ((uv)->v != &(uv)->value)
#define ismarkable(o) (!((1 << ttype(o)) & \
((1 << LUA_TNIL) | (1 << LUA_TNUMBER) | \
(1 << LUA_TBOOLEAN) | (1 << LUA_TLIGHTUSERDATA))))
static void reallymarkobject (GCState *st, TObject *o);
#define markobject(st,o) if (ismarkable(o)) reallymarkobject(st,o)
static void protomark (Proto *f) {
if (!f->marked) {
int i;
f->marked = 1;
strmark(f->source);
for (i=0; i<f->sizek; i++) {
if (ttisstring(f->k+i))
strmark(tsvalue(f->k+i));
}
for (i=0; i<f->sizep; i++)
protomark(f->p[i]);
for (i=0; i<f->sizelocvars; i++) /* mark local-variable names */
strmark(f->locvars[i].varname);
}
lua_assert(luaG_checkcode(f));
}
static void marktable (GCState *st, Table *h) {
if (!ismarked(h)) {
h->mark = st->tmark; /* chain it for later traversal */
st->tmark = h;
}
}
static void markclosure (GCState *st, Closure *cl) {
if (!cl->c.marked) {
cl->c.marked = 1;
if (cl->c.isC) {
int i;
for (i=0; i<cl->c.nupvalues; i++) /* mark its upvalues */
markobject(st, &cl->c.upvalue[i]);
}
else {
int i;
lua_assert(cl->l.nupvalues == cl->l.p->nupvalues);
marktable(st, hvalue(&cl->l.g));
protomark(cl->l.p);
for (i=0; i<cl->l.nupvalues; i++) { /* mark its upvalues */
UpVal *u = cl->l.upvals[i];
if (!isupvalmarked(u)) {
markobject(st, &u->value);
u->v = NULL; /* mark it! */
}
}
}
}
}
static void markudata (GCState *st, Udata *u) {
markud(u);
marktable(st, u->uv.metatable);
}
static void reallymarkobject (GCState *st, TObject *o) {
switch (ttype(o)) {
case LUA_TSTRING:
strmark(tsvalue(o));
break;
case LUA_TUSERDATA:
if (!isudmarked(uvalue(o)))
markudata(st, uvalue(o));
break;
case LUA_TFUNCTION:
markclosure(st, clvalue(o));
break;
case LUA_TTABLE: {
marktable(st, hvalue(o));
break;
}
default: lua_assert(0); /* should not be called with other types */
}
}
static void checkstacksizes (lua_State *L, StkId max) {
int used = L->ci - L->base_ci; /* number of `ci' in use */
if (4*used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
luaD_reallocCI(L, L->size_ci/2); /* still big enough... */
used = max - L->stack; /* part of stack in use */
if (4*used < L->stacksize && 2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
luaD_reallocstack(L, L->stacksize/2); /* still big enough... */
}
static void markstacks (GCState *st) {
lua_State *L1 = st->L;
do { /* for each thread */
StkId o, lim;
CallInfo *ci;
if (ttisnil(defaultmeta(L1))) { /* incomplete state? */
lua_assert(L1 != st->L);
L1 = L1->next;
luaE_closethread(st->L, L1->previous); /* collect it */
continue;
}
markobject(st, defaultmeta(L1));
markobject(st, gt(L1));
markobject(st, registry(L1));
for (o=L1->stack; o<L1->top; o++)
markobject(st, o);
lim = o;
for (ci = L1->base_ci; ci <= L1->ci; ci++) {
lua_assert(ci->top <= L1->stack_last);
if (lim < ci->top) lim = ci->top;
}
for (; o<=lim; o++) setnilvalue(o);
checkstacksizes(L1, lim);
lua_assert(L1->previous->next == L1 && L1->next->previous == L1);
L1 = L1->next;
} while (L1 != st->L);
}
static void marktmu (GCState *st) {
Udata *u;
for (u = G(st->L)->tmudata; u; u = u->uv.next)
markudata(st, u);
}
/* move `dead' udata that need finalization to list `tmudata' */
static void separateudata (lua_State *L) {
Udata **p = &G(L)->rootudata;
Udata *curr;
Udata *collected = NULL; /* to collect udata with gc event */
Udata **lastcollected = &collected;
while ((curr = *p) != NULL) {
if (isudmarked(curr) || isfinalized(curr) ||
(fasttm(L, curr->uv.metatable, TM_GC) == NULL))
p = &curr->uv.next;
else { /* must call its gc method */
*p = curr->uv.next;
curr->uv.next = NULL; /* link `curr' at the end of `collected' list */
*lastcollected = curr;
lastcollected = &curr->uv.next;
}
}
/* insert collected udata with gc event into `tmudata' list */
*lastcollected = G(L)->tmudata;
G(L)->tmudata = collected;
}
static void removekey (Node *n) {
setnilvalue(val(n)); /* remove corresponding value ... */
if (ismarkable(key(n)))
setttype(key(n), LUA_TNONE); /* dead key; remove it */
}
static void traversetable (GCState *st, Table *h) {
int i;
int weakkey = 0;
int weakvalue = 0;
marktable(st, h->metatable);
lua_assert(h->lsizenode || h->node == G(st->L)->dummynode);
if (h->mode & (WEAKKEY | WEAKVALUE)) { /* weak table? */
weakkey = h->mode & WEAKKEY;
weakvalue = h->mode & WEAKVALUE;
h->mark = st->toclear; /* must be cleared after GC, ... */
st->toclear = h; /* ... so put in the appropriate list */
}
if (!weakvalue) {
i = sizearray(h);
while (i--)
markobject(st, &h->array[i]);
}
i = sizenode(h);
while (i--) {
Node *n = node(h, i);
if (!ttisnil(val(n))) {
lua_assert(!ttisnil(key(n)));
if (!weakkey) markobject(st, key(n));
if (!weakvalue) markobject(st, val(n));
}
}
}
static void propagatemarks (GCState *st) {
while (st->tmark) { /* traverse marked tables */
Table *h = st->tmark; /* get first table from list */
st->tmark = h->mark; /* remove it from list */
traversetable(st, h);
}
}
static int hasmark (const TObject *o) {
switch (ttype(o)) {
case LUA_TUSERDATA:
return isudmarked(uvalue(o));
case LUA_TTABLE:
return ismarked(hvalue(o));
case LUA_TFUNCTION:
return clvalue(o)->c.marked;
case LUA_TSTRING:
strmark(tsvalue(o)); /* strings are `values', so are never weak */
/* go through */
default: /* number, nil, boolean, udataval */
return 1;
}
}
/*
** clear collected keys from weaktables
*/
static void cleartablekeys (GCState *st) {
Table *h;
for (h = st->toclear; h; h = h->mark) {
lua_assert(h->mode & (WEAKKEY | WEAKVALUE));
if ((h->mode & WEAKKEY)) { /* table may have collected keys? */
int i = sizenode(h);
while (i--) {
Node *n = node(h, i);
if (!hasmark(key(n))) /* key was collected? */
removekey(n); /* remove entry from table */
}
}
}
}
/*
** clear collected values from weaktables
*/
static void cleartablevalues (GCState *st) {
Table *h;
for (h = st->toclear; h; h = h->mark) {
if ((h->mode & WEAKVALUE)) { /* table may have collected values? */
int i = sizearray(h);
while (i--) {
TObject *o = &h->array[i];
if (!hasmark(o)) /* value was collected? */
setnilvalue(o); /* remove value */
}
i = sizenode(h);
while (i--) {
Node *n = node(h, i);
if (!hasmark(val(n))) /* value was collected? */
removekey(n); /* remove entry from table */
}
}
}
}
static void collectproto (lua_State *L) {
Proto **p = &G(L)->rootproto;
Proto *curr;
while ((curr = *p) != NULL) {
if (curr->marked) {
curr->marked = 0;
p = &curr->next;
}
else {
*p = curr->next;
luaF_freeproto(L, curr);
}
}
}
static void collectclosures (lua_State *L) {
Closure **p = &G(L)->rootcl;
Closure *curr;
while ((curr = *p) != NULL) {
if (curr->c.marked) {
curr->c.marked = 0;
p = &curr->c.next;
}
else {
*p = curr->c.next;
luaF_freeclosure(L, curr);
}
}
}
static void collectupval (lua_State *L) {
UpVal **v = &G(L)->rootupval;
UpVal *curr;
while ((curr = *v) != NULL) {
if (isupvalmarked(curr)) {
lua_assert(curr->v == NULL);
curr->v = &curr->value; /* unmark */
v = &curr->next; /* next */
}
else {
*v = curr->next; /* next */
luaM_freelem(L, curr);
}
}
}
static void collecttable (lua_State *L) {
Table **p = &G(L)->roottable;
Table *curr;
while ((curr = *p) != NULL) {
if (ismarked(curr)) {
curr->mark = curr; /* unmark */
p = &curr->next;
}
else {
*p = curr->next;
luaH_free(L, curr);
}
}
}
static void collectudata (lua_State *L) {
Udata **p = &G(L)->rootudata;
Udata *curr;
while ((curr = *p) != NULL) {
if (isudmarked(curr)) {
unmarkud(curr);
p = &curr->uv.next;
}
else {
*p = curr->uv.next;
luaM_free(L, curr, sizeudata(curr->uv.len & (~(size_t)3)));
}
}
}
static void collectstrings (lua_State *L, int all) {
int i;
for (i=0; i<G(L)->strt.size; i++) { /* for each list */
TString **p = &G(L)->strt.hash[i];
TString *curr;
while ((curr = *p) != NULL) {
if (curr->tsv.marked && !all) { /* preserve? */
if (curr->tsv.marked < FIXMARK) /* does not change FIXMARKs */
curr->tsv.marked = 0;
p = &curr->tsv.nexthash;
}
else { /* collect */
*p = curr->tsv.nexthash;
G(L)->strt.nuse--;
luaM_free(L, curr, sizestring(curr->tsv.len));
}
}
}
if (G(L)->strt.nuse < cast(ls_nstr, G(L)->strt.size/4) &&
G(L)->strt.size > MINSTRTABSIZE*2)
luaS_resize(L, G(L)->strt.size/2); /* table is too big */
}
#define MINBUFFER 256
static void checkMbuffer (lua_State *L) {
if (G(L)->Mbuffsize > MINBUFFER*2) { /* is buffer too big? */
size_t newsize = G(L)->Mbuffsize/2; /* still larger than MINBUFFER */
luaM_reallocvector(L, G(L)->Mbuffer, G(L)->Mbuffsize, newsize, char);
G(L)->Mbuffsize = newsize;
}
}
static void do1gcTM (lua_State *L, Udata *udata) {
const TObject *tm = fasttm(L, udata->uv.metatable, TM_GC);
if (tm != NULL) {
setobj(L->top, tm);
setuvalue(L->top+1, udata);
L->top += 2;
luaD_call(L, L->top - 2, 0);
}
}
static void callGCTM (lua_State *L) {
int oldah = allowhook(L);
setallowhook(L, 0); /* stop debug hooks during GC tag methods */
L->top++; /* reserve space to keep udata while runs its gc method */
while (G(L)->tmudata != NULL) {
Udata *udata = G(L)->tmudata;
G(L)->tmudata = udata->uv.next; /* remove udata from `tmudata' */
udata->uv.next = G(L)->rootudata; /* return it to `root' list */
G(L)->rootudata = udata;
setuvalue(L->top - 1, udata); /* keep a reference to it */
unmarkud(udata);
markfinalized(udata);
do1gcTM(L, udata);
}
L->top--;
setallowhook(L, oldah); /* restore hooks */
}
void luaC_callallgcTM (lua_State *L) {
separateudata(L);
callGCTM(L); /* call their GC tag methods */
}
void luaC_collect (lua_State *L, int all) {
collectudata(L);
collectstrings(L, all);
collecttable(L);
collectproto(L);
collectupval(L);
collectclosures(L);
}
void luaC_collectgarbage (lua_State *L) {
GCState st;
st.L = L;
st.tmark = NULL;
st.toclear = NULL;
markstacks(&st); /* mark all stacks */
propagatemarks(&st); /* mark all reachable objects */
cleartablevalues(&st);
separateudata(L); /* separate userdata to be preserved */
marktmu(&st); /* mark `preserved' userdata */
propagatemarks(&st); /* remark */
cleartablekeys(&st);
luaC_collect(L, 0);
checkMbuffer(L);
G(L)->GCthreshold = 2*G(L)->nblocks; /* new threshold */
callGCTM(L);
}
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