mirror of
https://github.com/lua/lua
synced 2024-12-14 14:57:10 +03:00
505 lines
12 KiB
C
505 lines
12 KiB
C
/*
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** $Id: lgc.c,v 1.139 2002/06/25 19:17:42 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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#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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Table *tmark; /* list of marked tables to be visited */
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Table *toclear; /* list of visited weak tables (to be cleared after GC) */
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lua_State *L;
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} GCState;
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/* mark a string; marks larger than 1 cannot be changed */
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#define strmark(s) {if ((s)->tsv.marked == 0) (s)->tsv.marked = 1;}
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/* unmarked tables are represented by pointing `mark' to themselves */
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#define ismarked(x) ((x)->mark != (x))
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/* `Table.flag' bits to indicate whether table is key-weak and/or value-weak */
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#define KEYWEAKBIT (TM_MODE+1) /* ORDER TM */
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#define VALUEWEAKBIT (TM_MODE+2)
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#define KEYWEAK (1<<KEYWEAKBIT)
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#define VALUEWEAK (1<<VALUEWEAKBIT)
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/* mark tricks for userdata */
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#define isudmarked(u) (u->uv.len & 1)
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#define markud(u) (u->uv.len |= 1)
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#define unmarkud(u) (u->uv.len &= (~(size_t)1))
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#define isfinalized(u) (u->uv.len & 2)
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#define markfinalized(u) (u->uv.len |= 2)
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/* mark tricks for upvalues (assume that open upvalues are always marked) */
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#define isupvalmarked(uv) ((uv)->v != &(uv)->value)
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#define ismarkable(o) (!((1 << ttype(o)) & \
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((1 << LUA_TNIL) | (1 << LUA_TNUMBER) | \
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(1 << LUA_TBOOLEAN) | (1 << LUA_TUDATAVAL))))
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static void reallymarkobject (GCState *st, TObject *o);
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#define markobject(st,o) if (ismarkable(o)) reallymarkobject(st,o)
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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->sizek; i++) {
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if (ttype(f->k+i) == LUA_TSTRING)
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strmark(tsvalue(f->k+i));
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}
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for (i=0; i<f->sizep; i++)
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protomark(f->p[i]);
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for (i=0; i<f->sizelocvars; i++) /* mark local-variable names */
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strmark(f->locvars[i].varname);
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}
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lua_assert(luaG_checkcode(f));
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}
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static void marktable (GCState *st, Table *h) {
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if (!ismarked(h)) {
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h->mark = st->tmark; /* chain it for later traversal */
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st->tmark = h;
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}
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}
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static void markclosure (GCState *st, Closure *cl) {
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if (!cl->c.marked) {
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cl->c.marked = 1;
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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->nupvalues);
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marktable(st, hvalue(&cl->l.g));
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protomark(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 (!isupvalmarked(u)) {
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markobject(st, &u->value);
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u->v = NULL; /* mark it! */
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}
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}
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}
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}
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}
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static void markudata (GCState *st, Udata *u) {
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markud(u);
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marktable(st, u->uv.metatable);
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}
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static void reallymarkobject (GCState *st, TObject *o) {
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switch (ttype(o)) {
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case LUA_TSTRING:
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strmark(tsvalue(o));
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break;
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case LUA_TUSERDATA:
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if (!isudmarked(uvalue(o)))
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markudata(st, uvalue(o));
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break;
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case LUA_TFUNCTION:
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markclosure(st, clvalue(o));
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break;
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case LUA_TTABLE: {
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marktable(st, hvalue(o));
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break;
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}
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default: lua_assert(0); /* should not be called with other types */
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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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used = max - L->stack; /* part of stack in use */
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if (4*used < L->stacksize && 2*BASIC_STACK_SIZE < L->stacksize)
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luaD_reallocstack(L, L->stacksize/2); /* still big enough... */
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}
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static void markstacks (GCState *st) {
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lua_State *L1 = st->L;
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do { /* for each thread */
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StkId o, lim;
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CallInfo *ci;
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if (L1->base_ci == NULL) { /* incomplete state? */
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lua_assert(L1 != st->L);
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L1 = L1->next;
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luaE_closethread(st->L, L1->previous); /* collect it */
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continue;
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}
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markobject(st, defaultmeta(L1));
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markobject(st, gt(L1));
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markobject(st, registry(L1));
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for (o=L1->stack; o<L1->top; o++)
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markobject(st, o);
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lim = o;
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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<=lim; o++) setnilvalue(o);
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checkstacksizes(L1, lim);
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lua_assert(L1->previous->next == L1 && L1->next->previous == L1);
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L1 = L1->next;
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} while (L1 != st->L);
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}
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static void marktmu (GCState *st) {
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Udata *u;
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for (u = G(st->L)->tmudata; u; u = u->uv.next)
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markudata(st, u);
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}
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/* move `dead' udata that need finalization to list `tmudata' */
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static void separateudata (lua_State *L) {
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Udata **p = &G(L)->rootudata;
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Udata *curr;
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Udata *collected = NULL; /* to collect udata with gc event */
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Udata **lastcollected = &collected;
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while ((curr = *p) != NULL) {
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if (isudmarked(curr) || isfinalized(curr) ||
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(fasttm(L, curr->uv.metatable, TM_GC) == NULL))
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p = &curr->uv.next;
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else { /* must call its gc method */
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*p = curr->uv.next;
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curr->uv.next = NULL; /* link `curr' at the end of `collected' list */
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*lastcollected = curr;
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lastcollected = &curr->uv.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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}
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static void removekey (Node *n) {
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setnilvalue(val(n)); /* remove corresponding value ... */
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if (ismarkable(key(n)))
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setttype(key(n), LUA_TNONE); /* dead key; remove it */
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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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const TObject *mode;
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int weakkey = 0;
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int weakvalue = 0;
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marktable(st, h->metatable);
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lua_assert(h->lsizenode || h->node == G(st->L)->dummynode);
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mode = fasttm(st->L, h->metatable, TM_MODE);
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if (mode && ttype(mode) == LUA_TSTRING) { /* weak table? */
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h->mark = st->toclear; /* must be cleared after GC, ... */
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st->toclear = h; /* ...put in the appropriate list */
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weakkey = (strchr(svalue(mode), 'k') != NULL);
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weakvalue = (strchr(svalue(mode), 'v') != NULL);
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h->flags &= ~(KEYWEAK | VALUEWEAK); /* clear bits */
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h->flags |= (weakkey << KEYWEAKBIT) | (weakvalue << VALUEWEAKBIT);
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}
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if (!weakvalue) {
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i = sizearray(h);
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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 = node(h, i);
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if (ttype(val(n)) != LUA_TNIL) {
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lua_assert(ttype(key(n)) != LUA_TNIL);
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if (!weakkey) markobject(st, key(n));
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if (!weakvalue) markobject(st, val(n));
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}
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}
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}
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static void propagatemarks (GCState *st) {
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while (st->tmark) { /* traverse marked tables */
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Table *h = st->tmark; /* get first table from list */
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st->tmark = h->mark; /* remove it from list */
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traversetable(st, h);
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}
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}
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static int hasmark (const TObject *o) {
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switch (ttype(o)) {
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case LUA_TSTRING:
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return tsvalue(o)->tsv.marked;
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case LUA_TUSERDATA:
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return isudmarked(uvalue(o));
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case LUA_TTABLE:
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return ismarked(hvalue(o));
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case LUA_TFUNCTION:
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return clvalue(o)->c.marked;
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default: /* number, nil, boolean */
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return 1;
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}
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}
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/*
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** clear collected keys from weaktables
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*/
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static void cleartablekeys (GCState *st) {
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Table *h;
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for (h = st->toclear; h; h = h->mark) {
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int i;
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if (!(h->flags & KEYWEAK)) continue;
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lua_assert(strchr(svalue(fasttm(st->L, h->metatable, TM_MODE)), 'k'));
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i = sizenode(h);
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while (i--) {
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Node *n = node(h, i);
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if (!hasmark(key(n)))
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removekey(n); /* ... and key */
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}
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}
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}
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/*
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** clear collected values from weaktables
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*/
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static void cleartablevalues (GCState *st) {
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Table *h;
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for (h = st->toclear; h; h = h->mark) {
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int i;
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if (!(h->flags & VALUEWEAK)) continue;
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lua_assert(strchr(svalue(fasttm(st->L, h->metatable, TM_MODE)), 'v'));
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i = sizearray(h);
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while (i--) {
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TObject *o = &h->array[i];
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if (!hasmark(o))
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setnilvalue(o); /* remove value */
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}
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i = sizenode(h);
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while (i--) {
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Node *n = node(h, i);
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if (!hasmark(val(n)))
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removekey(n); /* ... and key */
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}
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}
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}
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static void collectproto (lua_State *L) {
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Proto **p = &G(L)->rootproto;
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Proto *curr;
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while ((curr = *p) != NULL) {
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if (curr->marked) {
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curr->marked = 0;
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p = &curr->next;
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}
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else {
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*p = curr->next;
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luaF_freeproto(L, curr);
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}
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}
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}
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static void collectclosures (lua_State *L) {
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Closure **p = &G(L)->rootcl;
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Closure *curr;
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while ((curr = *p) != NULL) {
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if (curr->c.marked) {
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curr->c.marked = 0;
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p = &curr->c.next;
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}
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else {
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*p = curr->c.next;
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luaF_freeclosure(L, curr);
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}
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}
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}
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static void collectupval (lua_State *L) {
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UpVal **v = &G(L)->rootupval;
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UpVal *curr;
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while ((curr = *v) != NULL) {
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if (isupvalmarked(curr)) {
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lua_assert(curr->v == NULL);
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curr->v = &curr->value; /* unmark */
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v = &curr->next; /* next */
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}
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else {
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*v = curr->next; /* next */
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luaM_freelem(L, curr);
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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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Table **p = &G(L)->roottable;
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Table *curr;
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while ((curr = *p) != NULL) {
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if (ismarked(curr)) {
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curr->mark = curr; /* unmark */
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p = &curr->next;
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}
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else {
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*p = curr->next;
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luaH_free(L, curr);
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}
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}
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}
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static void collectudata (lua_State *L) {
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Udata **p = &G(L)->rootudata;
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Udata *curr;
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while ((curr = *p) != NULL) {
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if (isudmarked(curr)) {
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unmarkud(curr);
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p = &curr->uv.next;
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}
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else {
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*p = curr->uv.next;
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luaM_free(L, curr, sizeudata(curr->uv.len & (~(size_t)3)));
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}
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}
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}
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static void collectstrings (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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TString **p = &G(L)->strt.hash[i];
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TString *curr;
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while ((curr = *p) != NULL) {
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if (curr->tsv.marked && !all) { /* preserve? */
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if (curr->tsv.marked < FIXMARK) /* does not change FIXMARKs */
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curr->tsv.marked = 0;
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p = &curr->tsv.nexthash;
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}
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else { /* collect */
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*p = curr->tsv.nexthash;
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G(L)->strt.nuse--;
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luaM_free(L, curr, sizestring(curr->tsv.len));
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}
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}
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}
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if (G(L)->strt.nuse < cast(ls_nstr, 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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}
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#define MINBUFFER 256
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static void checkMbuffer (lua_State *L) {
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if (G(L)->Mbuffsize > MINBUFFER*2) { /* is buffer too big? */
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size_t newsize = G(L)->Mbuffsize/2; /* still larger than MINBUFFER */
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luaM_reallocvector(L, G(L)->Mbuffer, G(L)->Mbuffsize, newsize, char);
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G(L)->Mbuffsize = newsize;
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}
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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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setobj(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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static void callGCTM (lua_State *L) {
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int oldah = L->allowhooks;
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L->allowhooks = 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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Udata *udata = G(L)->tmudata;
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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 = udata;
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setuvalue(L->top - 1, udata); /* keep a reference to it */
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unmarkud(udata);
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markfinalized(udata);
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do1gcTM(L, udata);
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}
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L->top--;
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L->allowhooks = oldah; /* restore hooks */
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}
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void luaC_callallgcTM (lua_State *L) {
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separateudata(L);
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callGCTM(L); /* call their GC tag methods */
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}
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void luaC_collect (lua_State *L, int all) {
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collectudata(L);
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collectstrings(L, all);
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collecttable(L);
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collectproto(L);
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collectupval(L);
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collectclosures(L);
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}
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void luaC_collectgarbage (lua_State *L) {
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GCState st;
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st.L = L;
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st.tmark = NULL;
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st.toclear = NULL;
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markstacks(&st); /* mark all stacks */
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propagatemarks(&st); /* mark all reachable objects */
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cleartablevalues(&st);
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separateudata(L); /* separate userdata to be preserved */
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marktmu(&st); /* mark `preserved' userdata */
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propagatemarks(&st); /* remark */
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cleartablekeys(&st);
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luaC_collect(L, 0);
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checkMbuffer(L);
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G(L)->GCthreshold = 2*G(L)->nblocks; /* new threshold */
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callGCTM(L);
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}
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