mirror of
https://github.com/lua/lua
synced 2024-11-23 13:19:57 +03:00
487 lines
13 KiB
C
487 lines
13 KiB
C
/*
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** $Id: lgc.c,v 1.176 2003/07/29 19:25:37 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 <string.h>
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#define lgc_c
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#include "lua.h"
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#include "ldebug.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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GCObject *tmark; /* list of marked objects to be traversed */
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GCObject *w; /* list of traversed weak tables (to be cleared) */
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global_State *g;
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} GCState;
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/*
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** some userful bit tricks
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*/
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#define setbit(x,b) ((x) |= (1<<(b)))
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#define resetbit(x,b) ((x) &= cast(lu_byte, ~(1<<(b))))
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#define testbit(x,b) ((x) & (1<<(b)))
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#define unmark(x) resetbit((x)->gch.marked, 0)
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#define ismarked(x) ((x)->gch.marked & ((1<<4)|1))
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#define stringmark(s) setbit((s)->tsv.marked, 0)
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#define isfinalized(u) (!testbit((u)->uv.marked, 1))
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#define markfinalized(u) resetbit((u)->uv.marked, 1)
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#define KEYWEAKBIT 1
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#define VALUEWEAKBIT 2
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#define KEYWEAK (1<<KEYWEAKBIT)
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#define VALUEWEAK (1<<VALUEWEAKBIT)
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#define markobject(st,o) { checkconsistency(o); \
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if (iscollectable(o) && !ismarked(gcvalue(o))) reallymarkobject(st,gcvalue(o)); }
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#define condmarkobject(st,o,c) { checkconsistency(o); \
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if (iscollectable(o) && !ismarked(gcvalue(o)) && (c)) \
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reallymarkobject(st,gcvalue(o)); }
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#define markvalue(st,t) { if (!ismarked(valtogco(t))) \
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reallymarkobject(st, valtogco(t)); }
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static void reallymarkobject (GCState *st, GCObject *o) {
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lua_assert(!ismarked(o));
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setbit(o->gch.marked, 0); /* mark object */
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switch (o->gch.tt) {
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case LUA_TUSERDATA: {
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markvalue(st, gcotou(o)->uv.metatable);
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break;
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}
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case LUA_TFUNCTION: {
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gcotocl(o)->c.gclist = st->tmark;
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st->tmark = o;
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break;
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}
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case LUA_TTABLE: {
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gcotoh(o)->gclist = st->tmark;
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st->tmark = o;
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break;
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}
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case LUA_TTHREAD: {
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gcototh(o)->gclist = st->tmark;
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st->tmark = o;
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break;
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}
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case LUA_TPROTO: {
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gcotop(o)->gclist = st->tmark;
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st->tmark = o;
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break;
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}
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default: lua_assert(o->gch.tt == LUA_TSTRING);
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}
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}
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static void marktmu (GCState *st) {
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GCObject *u;
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for (u = st->g->tmudata; u; u = u->gch.next) {
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unmark(u); /* may be marked, if left from previous GC */
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reallymarkobject(st, u);
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}
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}
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/* move `dead' udata that need finalization to list `tmudata' */
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size_t luaC_separateudata (lua_State *L) {
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size_t deadmem = 0;
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GCObject **p = &G(L)->rootudata;
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GCObject *curr;
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GCObject *collected = NULL; /* to collect udata with gc event */
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GCObject **lastcollected = &collected;
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while ((curr = *p) != NULL) {
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lua_assert(curr->gch.tt == LUA_TUSERDATA);
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if (ismarked(curr) || isfinalized(gcotou(curr)))
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p = &curr->gch.next; /* don't bother with them */
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else if (fasttm(L, gcotou(curr)->uv.metatable, TM_GC) == NULL) {
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markfinalized(gcotou(curr)); /* don't need finalization */
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p = &curr->gch.next;
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}
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else { /* must call its gc method */
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deadmem += sizeudata(gcotou(curr)->uv.len);
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markfinalized(gcotou(curr));
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*p = curr->gch.next;
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curr->gch.next = NULL; /* link `curr' at the end of `collected' list */
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*lastcollected = curr;
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lastcollected = &curr->gch.next;
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}
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}
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/* insert collected udata with gc event into `tmudata' list */
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*lastcollected = G(L)->tmudata;
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G(L)->tmudata = collected;
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return deadmem;
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}
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static void traversetable (GCState *st, Table *h) {
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int i;
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int weakkey = 0;
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int weakvalue = 0;
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const TObject *mode;
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markvalue(st, h->metatable);
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lua_assert(h->lsizenode || h->node == st->g->dummynode);
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mode = gfasttm(st->g, h->metatable, TM_MODE);
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if (mode && ttisstring(mode)) { /* is there a weak mode? */
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weakkey = (strchr(svalue(mode), 'k') != NULL);
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weakvalue = (strchr(svalue(mode), 'v') != NULL);
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if (weakkey || weakvalue) { /* is really weak? */
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h->marked &= ~(KEYWEAK | VALUEWEAK); /* clear bits */
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h->marked |= cast(lu_byte, (weakkey << KEYWEAKBIT) |
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(weakvalue << VALUEWEAKBIT));
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h->gclist = st->w; /* must be cleared after GC, ... */
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st->w = valtogco(h); /* ... so put in the appropriate list */
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}
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}
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if (weakkey && weakvalue) return;
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if (!weakvalue) {
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i = h->sizearray;
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while (i--)
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markobject(st, &h->array[i]);
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}
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i = sizenode(h);
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while (i--) {
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Node *n = gnode(h, i);
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if (!ttisnil(gval(n))) {
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lua_assert(!ttisnil(gkey(n)));
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condmarkobject(st, gkey(n), !weakkey);
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condmarkobject(st, gval(n), !weakvalue);
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}
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}
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}
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/*
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** All marks are conditional because a GC may happen while the
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** prototype is still being created
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*/
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static void traverseproto (GCState *st, Proto *f) {
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int i;
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if (f->source) stringmark(f->source);
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for (i=0; i<f->sizek; i++) { /* mark literal strings */
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if (ttisstring(f->k+i))
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stringmark(tsvalue(f->k+i));
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}
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for (i=0; i<f->sizeupvalues; i++) { /* mark upvalue names */
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if (f->upvalues[i])
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stringmark(f->upvalues[i]);
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}
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for (i=0; i<f->sizep; i++) { /* mark nested protos */
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if (f->p[i])
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markvalue(st, f->p[i]);
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}
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for (i=0; i<f->sizelocvars; i++) { /* mark local-variable names */
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if (f->locvars[i].varname)
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stringmark(f->locvars[i].varname);
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}
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}
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static void traverseclosure (GCState *st, Closure *cl) {
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if (cl->c.isC) {
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int i;
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for (i=0; i<cl->c.nupvalues; i++) /* mark its upvalues */
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markobject(st, &cl->c.upvalue[i]);
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}
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else {
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int i;
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lua_assert(cl->l.nupvalues == cl->l.p->nups);
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markvalue(st, hvalue(&cl->l.g));
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markvalue(st, cl->l.p);
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for (i=0; i<cl->l.nupvalues; i++) { /* mark its upvalues */
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UpVal *u = cl->l.upvals[i];
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if (!u->marked) {
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markobject(st, &u->value);
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u->marked = 1;
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}
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}
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}
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}
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static void checkstacksizes (lua_State *L, StkId max) {
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int used = L->ci - L->base_ci; /* number of `ci' in use */
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if (4*used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
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luaD_reallocCI(L, L->size_ci/2); /* still big enough... */
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else condhardstacktests(luaD_reallocCI(L, L->size_ci));
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used = max - L->stack; /* part of stack in use */
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if (4*used < L->stacksize && 2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
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luaD_reallocstack(L, L->stacksize/2); /* still big enough... */
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else condhardstacktests(luaD_reallocstack(L, L->stacksize));
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}
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static void traversestack (GCState *st, lua_State *L1) {
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StkId o, lim;
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CallInfo *ci;
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markobject(st, gt(L1));
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lim = L1->top;
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for (ci = L1->base_ci; ci <= L1->ci; ci++) {
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lua_assert(ci->top <= L1->stack_last);
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if (lim < ci->top) lim = ci->top;
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}
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for (o = L1->stack; o < L1->top; o++)
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markobject(st, o);
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for (; o <= lim; o++)
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setnilvalue(o);
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checkstacksizes(L1, lim);
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}
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static void propagatemarks (GCState *st) {
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while (st->tmark) { /* traverse marked objects */
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switch (st->tmark->gch.tt) {
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case LUA_TTABLE: {
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Table *h = gcotoh(st->tmark);
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st->tmark = h->gclist;
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traversetable(st, h);
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break;
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}
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case LUA_TFUNCTION: {
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Closure *cl = gcotocl(st->tmark);
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st->tmark = cl->c.gclist;
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traverseclosure(st, cl);
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break;
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}
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case LUA_TTHREAD: {
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lua_State *th = gcototh(st->tmark);
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st->tmark = th->gclist;
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traversestack(st, th);
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break;
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}
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case LUA_TPROTO: {
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Proto *p = gcotop(st->tmark);
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st->tmark = p->gclist;
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traverseproto(st, p);
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break;
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}
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default: lua_assert(0);
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}
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}
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}
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/*
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** The next function tells whether a key or value can be cleared from
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** a weak table. Non-collectable objects are never removed from weak
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** tables. Strings behave as `values', so are never removed too. for
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** other objects: if really collected, cannot keep them; for userdata
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** being finalized, keep them in keys, but not in values
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*/
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static int iscleared (const TObject *o, int iskey) {
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if (!iscollectable(o)) return 0;
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if (ttisstring(o)) {
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stringmark(tsvalue(o)); /* strings are `values', so are never weak */
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return 0;
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}
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return !ismarked(gcvalue(o)) ||
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(ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
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}
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static void removekey (Node *n) {
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setnilvalue(gval(n)); /* remove corresponding value ... */
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if (iscollectable(gkey(n)))
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setttype(gkey(n), LUA_TNONE); /* dead key; remove it */
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}
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/*
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** clear collected entries from weaktables
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*/
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static void cleartable (GCObject *l) {
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while (l) {
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Table *h = gcotoh(l);
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int i = h->sizearray;
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lua_assert(h->marked & (KEYWEAK | VALUEWEAK));
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if (h->marked & VALUEWEAK) {
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while (i--) {
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TObject *o = &h->array[i];
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if (iscleared(o, 0)) /* value was collected? */
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setnilvalue(o); /* remove value */
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}
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}
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i = sizenode(h);
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while (i--) {
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Node *n = gnode(h, i);
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if (!ttisnil(gval(n)) && /* non-empty entry? */
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(iscleared(gkey(n), 1) || iscleared(gval(n), 0)))
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removekey(n); /* remove entry from table */
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}
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l = h->gclist;
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}
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}
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static void freeobj (lua_State *L, GCObject *o) {
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switch (o->gch.tt) {
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case LUA_TPROTO: luaF_freeproto(L, gcotop(o)); break;
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case LUA_TFUNCTION: luaF_freeclosure(L, gcotocl(o)); break;
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case LUA_TUPVAL: luaM_freelem(L, gcotouv(o)); break;
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case LUA_TTABLE: luaH_free(L, gcotoh(o)); break;
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case LUA_TTHREAD: {
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lua_assert(gcototh(o) != L && gcototh(o) != G(L)->mainthread);
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luaE_freethread(L, gcototh(o));
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break;
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}
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case LUA_TSTRING: {
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luaM_free(L, o, sizestring(gcotots(o)->tsv.len));
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break;
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}
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case LUA_TUSERDATA: {
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luaM_free(L, o, sizeudata(gcotou(o)->uv.len));
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break;
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}
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default: lua_assert(0);
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}
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}
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static int sweeplist (lua_State *L, GCObject **p, int limit) {
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GCObject *curr;
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int count = 0; /* number of collected items */
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while ((curr = *p) != NULL) {
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if (curr->gch.marked > limit) {
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unmark(curr);
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p = &curr->gch.next;
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}
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else {
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count++;
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*p = curr->gch.next;
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freeobj(L, curr);
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}
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}
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return count;
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}
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static void sweepstrings (lua_State *L, int all) {
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int i;
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for (i=0; i<G(L)->strt.size; i++) { /* for each list */
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G(L)->strt.nuse -= sweeplist(L, &G(L)->strt.hash[i], all);
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}
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}
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static void checkSizes (lua_State *L, size_t deadmem) {
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/* check size of string hash */
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if (G(L)->strt.nuse < cast(lu_int32, G(L)->strt.size/4) &&
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G(L)->strt.size > MINSTRTABSIZE*2)
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luaS_resize(L, G(L)->strt.size/2); /* table is too big */
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/* check size of buffer */
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if (luaZ_sizebuffer(&G(L)->buff) > LUA_MINBUFFER*2) { /* buffer too big? */
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size_t newsize = luaZ_sizebuffer(&G(L)->buff) / 2;
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luaZ_resizebuffer(L, &G(L)->buff, newsize);
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}
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lua_assert(G(L)->nblocks > deadmem);
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G(L)->GCthreshold = 2*G(L)->nblocks - deadmem; /* new threshold */
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}
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static void do1gcTM (lua_State *L, Udata *udata) {
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const TObject *tm = fasttm(L, udata->uv.metatable, TM_GC);
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if (tm != NULL) {
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setobj2s(L->top, tm);
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setuvalue(L->top+1, udata);
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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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void luaC_callGCTM (lua_State *L) {
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lu_byte oldah = L->allowhook;
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L->allowhook = 0; /* stop debug hooks during GC tag methods */
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L->top++; /* reserve space to keep udata while runs its gc method */
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while (G(L)->tmudata != NULL) {
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GCObject *o = G(L)->tmudata;
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Udata *udata = gcotou(o);
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G(L)->tmudata = udata->uv.next; /* remove udata from `tmudata' */
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udata->uv.next = G(L)->rootudata; /* return it to `root' list */
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G(L)->rootudata = o;
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setuvalue(L->top - 1, udata); /* keep a reference to it */
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unmark(o);
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do1gcTM(L, udata);
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}
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L->top--;
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L->allowhook = oldah; /* restore hooks */
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}
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void luaC_sweep (lua_State *L, int all) {
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if (all) all = 256; /* larger than any mark */
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sweeplist(L, &G(L)->rootudata, all);
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sweepstrings(L, all);
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sweeplist(L, &G(L)->rootgc, all);
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}
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/* mark root set */
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static void markroot (GCState *st, lua_State *L) {
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global_State *g = st->g;
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markobject(st, defaultmeta(L));
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markobject(st, registry(L));
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traversestack(st, g->mainthread);
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if (L != g->mainthread) /* another thread is running? */
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markvalue(st, L); /* cannot collect it */
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}
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static size_t mark (lua_State *L) {
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size_t deadmem;
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GCState st;
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st.g = G(L);
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st.tmark = NULL;
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st.w = NULL;
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markroot(&st, L);
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propagatemarks(&st); /* mark all reachable objects */
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deadmem = luaC_separateudata(L); /* separate userdata to be preserved */
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marktmu(&st); /* mark `preserved' userdata */
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propagatemarks(&st); /* remark, to propagate `preserveness' */
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cleartable(st.w); /* remove collected objects from weak tables */
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return deadmem;
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}
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void luaC_collectgarbage (lua_State *L) {
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size_t deadmem = mark(L);
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luaC_sweep(L, 0);
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checkSizes(L, deadmem);
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luaC_callGCTM(L);
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}
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void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
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o->gch.next = G(L)->rootgc;
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G(L)->rootgc = o;
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o->gch.marked = 0;
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o->gch.tt = tt;
|
|
}
|
|
|