Function addk

3rd/lua-5.4.3/src/lcode.c:542–568

** Add constant 'v' to prototype's list of constants (field 'k'). ** Use scanner's table to cache position of constants in constant list ** and try to reuse constants. Because some values should not be used ** as keys (nil cannot be a key, integer keys can collapse with float ** keys), the caller must provide a useful 'key' for indexing the cache. ** Note that all functions share the same table, s

** a function can make some indices wrong.
*/
static int addk (FuncState *fs, TValue *key, TValue *v) {
  TValue val;
  lua_State *L = fs->ls->L;
  Proto *f = fs->f;
  const TValue *idx = luaH_get(fs->ls->h, key);  /* query scanner table */
  int k, oldsize;
  if (ttisinteger(idx)) {  /* is there an index there? */
    k = cast_int(ivalue(idx));
    /* correct value? (warning: must distinguish floats from integers!) */
    if (k < fs->nk && ttypetag(&f->k[k]) == ttypetag(v) &&
                      luaV_rawequalobj(&f->k[k], v))
      return k;  /* reuse index */
  }
  /* constant not found; create a new entry */
  oldsize = f->sizek;
  k = fs->nk;
  /* numerical value does not need GC barrier;
     table has no metatable, so it does not need to invalidate cache */
  setivalue(&val, k);
  luaH_finishset(L, fs->ls->h, key, idx, &val);
  luaM_growvector(L, f->k, k, f->sizek, TValue, MAXARG_Ax, "constants");
  while (oldsize < f->sizek) setnilvalue(&f->k[oldsize++]);
  setobj(L, &f->k[k], v);
  fs->nk++;
  luaC_barrier(L, f, v);
  return k;
}


/*