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(much) smarter way to clear weak tables

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This commit is contained in:
Roberto Ierusalimschy 2003-05-16 15:58:39 -03:00
parent b10bfd4934
commit ecf5730c0c
1 changed files with 39 additions and 59 deletions
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98
lgc.c
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@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 1.171 2003/04/03 13:35:34 roberto Exp roberto $
** $Id: lgc.c,v 1.172 2003/04/28 19:26:16 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@ -24,9 +24,7 @@
typedef struct GCState {
GCObject *tmark; /* list of marked objects to be traversed */
GCObject *wk; /* list of traversed key-weak tables (to be cleared) */
GCObject *wv; /* list of traversed value-weak tables */
GCObject *wkv; /* list of traversed key-value weak tables */
GCObject *w; /* list of traversed weak tables (to be cleared) */
global_State *g;
} GCState;
@ -125,6 +123,7 @@ void luaC_separateudata (lua_State *L) {
p = &curr->gch.next;
}
else { /* must call its gc method */
markfinalized(gcotou(curr));
*p = curr->gch.next;
curr->gch.next = NULL; /* link `curr' at the end of `collected' list */
*lastcollected = curr;
@ -137,13 +136,6 @@ void luaC_separateudata (lua_State *L) {
}
static void removekey (Node *n) {
setnilvalue(gval(n)); /* remove corresponding value ... */
if (iscollectable(gkey(n)))
setttype(gkey(n), LUA_TNONE); /* dead key; remove it */
}
static void traversetable (GCState *st, Table *h) {
int i;
int weakkey = 0;
@ -156,17 +148,14 @@ static void traversetable (GCState *st, Table *h) {
weakkey = (strchr(svalue(mode), 'k') != NULL);
weakvalue = (strchr(svalue(mode), 'v') != NULL);
if (weakkey || weakvalue) { /* is really weak? */
GCObject **weaklist;
h->marked &= ~(KEYWEAK | VALUEWEAK); /* clear bits */
h->marked |= cast(lu_byte, (weakkey << KEYWEAKBIT) |
(weakvalue << VALUEWEAKBIT));
weaklist = (weakkey && weakvalue) ? &st->wkv :
(weakkey) ? &st->wk :
&st->wv;
h->gclist = *weaklist; /* must be cleared after GC, ... */
*weaklist = valtogco(h); /* ... so put in the appropriate list */
h->gclist = st->w; /* must be cleared after GC, ... */
st->w = valtogco(h); /* ... so put in the appropriate list */
}
}
if (weakkey && weakvalue) return;
if (!weakvalue) {
i = h->sizearray;
while (i--)
@ -288,48 +277,51 @@ static void propagatemarks (GCState *st) {
}
static int valismarked (const TObject *o) {
if (ttisstring(o))
/*
** The next function tells whether a key or value can be cleared from
** a weak table. Non-collectable objects are never removed from weak
** tables. Strings behave as `values', so are never removed too. for
** other objects: if really collected, cannot keep them; for userdata
** being finalized, keep them in keys, but not in values
*/
static int iscleared (const TObject *o, int iskey) {
if (!iscollectable(o)) return 0;
if (ttisstring(o)) {
stringmark(tsvalue(o)); /* strings are `values', so are never weak */
return !iscollectable(o) || testbit(o->value.gc->gch.marked, 0);
}
/*
** clear collected keys from weaktables
*/
static void cleartablekeys (GCObject *l) {
while (l) {
Table *h = gcotoh(l);
int i = sizenode(h);
lua_assert(h->marked & KEYWEAK);
while (i--) {
Node *n = gnode(h, i);
if (!valismarked(gkey(n))) /* key was collected? */
removekey(n); /* remove entry from table */
}
l = h->gclist;
return 0;
}
return !ismarked(gcvalue(o)) ||
(ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
}
static void removekey (Node *n) {
setnilvalue(gval(n)); /* remove corresponding value ... */
if (iscollectable(gkey(n)))
setttype(gkey(n), LUA_TNONE); /* dead key; remove it */
}
/*
** clear collected values from weaktables
** clear collected entries from weaktables
*/
static void cleartablevalues (GCObject *l) {
static void cleartable (GCObject *l) {
while (l) {
Table *h = gcotoh(l);
int i = h->sizearray;
lua_assert(h->marked & VALUEWEAK);
while (i--) {
TObject *o = &h->array[i];
if (!valismarked(o)) /* value was collected? */
setnilvalue(o); /* remove value */
lua_assert(h->marked & (KEYWEAK | VALUEWEAK));
if (h->marked & VALUEWEAK) {
while (i--) {
TObject *o = &h->array[i];
if (iscleared(o, 0)) /* value was collected? */
setnilvalue(o); /* remove value */
}
}
i = sizenode(h);
while (i--) {
Node *n = gnode(h, i);
if (!valismarked(gval(n))) /* value was collected? */
if (!ttisnil(gval(n)) && /* non-empty entry? */
(iscleared(gkey(n), 1) || iscleared(gval(n), 0)))
removekey(n); /* remove entry from table */
}
l = h->gclist;
@ -424,7 +416,6 @@ void luaC_callGCTM (lua_State *L) {
G(L)->rootudata = o;
setuvalue(L->top - 1, udata); /* keep a reference to it */
unmark(o);
markfinalized(udata);
do1gcTM(L, udata);
}
L->top--;
@ -453,26 +444,15 @@ static void markroot (GCState *st, lua_State *L) {
static void mark (lua_State *L) {
GCState st;
GCObject *wkv;
st.g = G(L);
st.tmark = NULL;
st.wkv = st.wk = st.wv = NULL;
st.w = NULL;
markroot(&st, L);
propagatemarks(&st); /* mark all reachable objects */
cleartablevalues(st.wkv);
cleartablevalues(st.wv);
wkv = st.wkv; /* keys must be cleared after preserving udata */
st.wkv = NULL;
st.wv = NULL;
luaC_separateudata(L); /* separate userdata to be preserved */
marktmu(&st); /* mark `preserved' userdata */
propagatemarks(&st); /* remark, to propagate `preserveness' */
cleartablekeys(wkv);
/* `propagatemarks' may resuscitate some weak tables; clear them too */
cleartablekeys(st.wk);
cleartablevalues(st.wv);
cleartablekeys(st.wkv);
cleartablevalues(st.wkv);
cleartable(st.w); /* remove collected objects from weak tables */
}