Function lua_gc

deps/lua/src/lapi.c:899–955

*/

LUA_API int lua_gc (lua_State *L, int what, int data) {
  int res = 0;
  global_State *g;
  lua_lock(L);
  g = G(L);
  switch (what) {
    case LUA_GCSTOP: {
      g->GCthreshold = MAX_LUMEM;
      break;
    }
    case LUA_GCRESTART: {
      g->GCthreshold = g->totalbytes;
      break;
    }
    case LUA_GCCOLLECT: {
      luaC_fullgc(L);
      break;
    }
    case LUA_GCCOUNT: {
      /* GC values are expressed in Kbytes: #bytes/2^10 */
      res = cast_int(g->totalbytes >> 10);
      break;
    }
    case LUA_GCCOUNTB: {
      res = cast_int(g->totalbytes & 0x3ff);
      break;
    }
    case LUA_GCSTEP: {
      lu_mem a = (cast(lu_mem, data) << 10);
      if (a <= g->totalbytes)
        g->GCthreshold = g->totalbytes - a;
      else
        g->GCthreshold = 0;
      while (g->GCthreshold <= g->totalbytes) {
        luaC_step(L);
        if (g->gcstate == GCSpause) {  /* end of cycle? */
          res = 1;  /* signal it */
          break;
        }
      }
      break;
    }
    case LUA_GCSETPAUSE: {
      res = g->gcpause;
      g->gcpause = data;
      break;
    }
    case LUA_GCSETSTEPMUL: {
      res = g->gcstepmul;
      g->gcstepmul = data;
      break;
    }
    default: res = -1;  /* invalid option */
  }
  lua_unlock(L);
  return res;
}