mirror of
https://github.com/lua/lua.git
synced 2024-11-28 12:45:29 +08:00
359 lines
8.6 KiB
C
359 lines
8.6 KiB
C
/*
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** $Id: lgc.c,v 1.66 2000/09/19 08:42:35 roberto Exp roberto $
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** Garbage Collector
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** See Copyright Notice in lua.h
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*/
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#include "lua.h"
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#include "ldo.h"
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#include "lfunc.h"
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#include "lgc.h"
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#include "lmem.h"
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#include "lobject.h"
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#include "lstate.h"
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#include "lstring.h"
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#include "ltable.h"
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#include "ltm.h"
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typedef struct GCState {
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Hash *tmark; /* list of marked tables to be visited */
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Closure *cmark; /* list of marked closures to be visited */
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} GCState;
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static int markobject (GCState *st, TObject *o);
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/* mark a string; marks larger than 1 cannot be changed */
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#define strmark(s) {if ((s)->marked == 0) (s)->marked = 1;}
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static void protomark (Proto *f) {
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if (!f->marked) {
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int i;
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f->marked = 1;
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strmark(f->source);
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for (i=0; i<f->nkstr; i++)
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strmark(f->kstr[i]);
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for (i=0; i<f->nkproto; i++)
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protomark(f->kproto[i]);
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for (i=0; i<f->nlocvars; i++) /* mark local-variable names */
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strmark(f->locvars[i].varname);
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}
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}
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static void markstack (lua_State *L, GCState *st) {
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StkId o;
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for (o=L->stack; o<L->top; o++)
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markobject(st, o);
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}
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static void marklock (lua_State *L, GCState *st) {
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int i;
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for (i=0; i<L->refSize; i++) {
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if (L->refArray[i].st == LOCK)
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markobject(st, &L->refArray[i].o);
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}
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}
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static void marktagmethods (lua_State *L, GCState *st) {
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int e;
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for (e=0; e<IM_N; e++) {
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int t;
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for (t=0; t<=L->last_tag; t++)
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markobject(st, luaT_getim(L, t,e));
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}
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}
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static int markobject (GCState *st, TObject *o) {
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switch (ttype(o)) {
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case TAG_USERDATA: case TAG_STRING:
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strmark(tsvalue(o));
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break;
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case TAG_TABLE: {
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if (!ismarked(hvalue(o))) {
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hvalue(o)->mark = st->tmark; /* chain it in list of marked */
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st->tmark = hvalue(o);
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}
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break;
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}
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case TAG_LMARK: {
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Closure *cl = infovalue(o)->func;
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if (!ismarked(cl)) {
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protomark(cl->f.l);
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cl->mark = st->cmark; /* chain it for later traversal */
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st->cmark = cl;
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}
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break;
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}
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case TAG_LCLOSURE:
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protomark(clvalue(o)->f.l);
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/* go through */
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case TAG_CCLOSURE: case TAG_CMARK:
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if (!ismarked(clvalue(o))) {
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clvalue(o)->mark = st->cmark; /* chain it for later traversal */
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st->cmark = clvalue(o);
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}
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break;
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default: break; /* numbers, etc */
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}
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return 0;
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}
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static void markall (lua_State *L) {
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GCState st;
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st.cmark = NULL;
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st.tmark = L->gt; /* put table of globals in mark list */
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L->gt->mark = NULL;
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marktagmethods(L, &st); /* mark tag methods */
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markstack(L, &st); /* mark stack objects */
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marklock(L, &st); /* mark locked objects */
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for (;;) { /* mark tables and closures */
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if (st.cmark) {
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int i;
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Closure *f = st.cmark; /* get first closure from list */
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st.cmark = f->mark; /* remove it from list */
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for (i=0; i<f->nupvalues; i++) /* mark its upvalues */
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markobject(&st, &f->upvalue[i]);
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}
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else if (st.tmark) {
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int i;
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Hash *h = st.tmark; /* get first table from list */
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st.tmark = h->mark; /* remove it from list */
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for (i=0; i<h->size; i++) {
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Node *n = node(h, i);
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if (ttype(key(n)) != TAG_NIL) {
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if (ttype(val(n)) == TAG_NIL)
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luaH_remove(h, key(n)); /* dead element; try to remove it */
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markobject(&st, &n->key);
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markobject(&st, &n->val);
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}
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}
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}
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else break; /* nothing else to mark */
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}
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}
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static int hasmark (const TObject *o) {
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/* valid only for locked objects */
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switch (o->ttype) {
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case TAG_STRING: case TAG_USERDATA:
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return tsvalue(o)->marked;
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case TAG_TABLE:
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return ismarked(hvalue(o));
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case TAG_LCLOSURE: case TAG_CCLOSURE:
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return ismarked(clvalue(o));
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default: /* number */
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return 1;
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}
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}
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/* macro for internal debugging; check if a link of free refs is valid */
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#define VALIDLINK(L, st,n) (NONEXT <= (st) && (st) < (n))
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static void invalidaterefs (lua_State *L) {
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int n = L->refSize;
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int i;
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for (i=0; i<n; i++) {
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struct Ref *r = &L->refArray[i];
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if (r->st == HOLD && !hasmark(&r->o))
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r->st = COLLECTED;
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LUA_ASSERT((r->st == LOCK && hasmark(&r->o)) ||
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(r->st == HOLD && hasmark(&r->o)) ||
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r->st == COLLECTED ||
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r->st == NONEXT ||
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(r->st < n && VALIDLINK(L, L->refArray[r->st].st, n)),
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"inconsistent ref table");
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}
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LUA_ASSERT(VALIDLINK(L, L->refFree, n), "inconsistent ref table");
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}
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static void collectproto (lua_State *L) {
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Proto **p = &L->rootproto;
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Proto *next;
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while ((next = *p) != NULL) {
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if (next->marked) {
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next->marked = 0;
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p = &next->next;
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}
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else {
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*p = next->next;
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luaF_freeproto(L, next);
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}
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}
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}
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static void collectclosure (lua_State *L) {
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Closure **p = &L->rootcl;
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Closure *next;
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while ((next = *p) != NULL) {
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if (ismarked(next)) {
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next->mark = next; /* unmark */
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p = &next->next;
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}
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else {
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*p = next->next;
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luaF_freeclosure(L, next);
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}
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}
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}
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static void collecttable (lua_State *L) {
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Hash **p = &L->roottable;
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Hash *next;
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while ((next = *p) != NULL) {
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if (ismarked(next)) {
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next->mark = next; /* unmark */
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p = &next->next;
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}
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else {
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*p = next->next;
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luaH_free(L, next);
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}
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}
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}
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static void checktab (lua_State *L, stringtable *tb) {
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if (tb->nuse < (lint32)(tb->size/4) && tb->size > 10)
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luaS_resize(L, tb, tb->size/2); /* table is too big */
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}
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/*
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** collect all elements with `marked' <= `limit'.
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** with limit=0, that means all unmarked elements;
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** with limit=MAX_INT, that means all elements.
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*/
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static void collectstringtab (lua_State *L, int limit) {
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int i;
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for (i=0; i<L->strt.size; i++) { /* for each list */
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TString **p = &L->strt.hash[i];
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TString *next;
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while ((next = *p) != NULL) {
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if ((int)next->marked > limit) { /* preserve? */
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if (next->marked < FIXMARK) /* does not change FIXMARKs */
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next->marked = 0;
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p = &next->nexthash;
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}
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else { /* collect */
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*p = next->nexthash;
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L->strt.nuse--;
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L->nblocks -= gcsizestring(L, next->u.s.len);
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luaM_free(L, next);
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}
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}
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}
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checktab(L, &L->strt);
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}
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static void collectudatatab (lua_State *L, int all) {
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int i;
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for (i=0; i<L->udt.size; i++) { /* for each list */
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TString **p = &L->udt.hash[i];
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TString *next;
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while ((next = *p) != NULL) {
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LUA_ASSERT(next->marked <= 1, "udata cannot be fixed");
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if ((int)next->marked > all) { /* preserve? */
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next->marked = 0;
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p = &next->nexthash;
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}
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else { /* collect */
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int tag = next->u.d.tag;
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if (tag > L->last_tag) tag = TAG_USERDATA;
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*p = next->nexthash;
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next->nexthash = L->IMtable[tag].collected; /* chain udata */
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L->IMtable[tag].collected = next;
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L->nblocks -= gcsizeudata;
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L->udt.nuse--;
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}
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}
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}
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checktab(L, &L->udt);
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}
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static void callgcTM (lua_State *L, const TObject *o) {
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const TObject *im = luaT_getimbyObj(L, o, IM_GC);
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if (ttype(im) != TAG_NIL) {
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luaD_checkstack(L, 2);
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*(L->top) = *im;
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*(L->top+1) = *o;
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L->top += 2;
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luaD_call(L, L->top-2, 0);
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}
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}
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static void callgcTMudata (lua_State *L) {
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int tag;
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TObject o;
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ttype(&o) = TAG_USERDATA;
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for (tag=L->last_tag; tag>=0; tag--) {
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TString *udata = L->IMtable[tag].collected;
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L->IMtable[tag].collected = NULL;
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while (udata) {
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TString *next = udata->nexthash;
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tsvalue(&o) = udata;
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callgcTM(L, &o);
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luaM_free(L, udata);
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udata = next;
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}
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}
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}
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void luaC_collect (lua_State *L, int all) {
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int oldah = L->allowhooks;
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L->allowhooks = 0; /* stop debug hooks during GC */
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L->GCthreshold *= 4; /* to avoid GC during GC */
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collectudatatab(L, all);
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callgcTMudata(L);
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collectstringtab(L, all?MAX_INT:0);
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collecttable(L);
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collectproto(L);
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collectclosure(L);
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L->allowhooks = oldah; /* restore hooks */
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}
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#define MINBUFFER 256
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long lua_collectgarbage (lua_State *L, long limit) {
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unsigned long recovered = L->nblocks; /* to subtract `nblocks' after gc */
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markall(L);
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invalidaterefs(L);
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luaC_collect(L, 0);
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recovered = recovered - L->nblocks;
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L->GCthreshold = (limit == 0) ? 2*L->nblocks : L->nblocks+limit;
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if (L->Mbuffsize > MINBUFFER*2) { /* is buffer too big? */
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L->Mbuffsize /= 2; /* still larger than MINBUFFER */
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luaM_reallocvector(L, L->Mbuffer, L->Mbuffsize, char);
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}
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callgcTM(L, &luaO_nilobject);
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return recovered;
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}
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void luaC_checkGC (lua_State *L) {
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if (L->nblocks >= L->GCthreshold)
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lua_collectgarbage(L, 0);
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}
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