Re: Possible enhancements for Lua 5.2

[Rebel Neurofog <rebelneurofog@...>]

> But that takes a table lookup for the key...

I'm not sure, but it is probably faster than sequential string
comparison (especially for lots of strings).
But of course it is slower than hashing.
It's kind of simple intermediate workaround.

There's also another trick (which works fast for single Lua state per
executable):

static const char *points_string;

static void func ()
{
    lua_State *L = lua_newstate (...);

    lua_pushliteral (L, "points"); /* There is a simpler way in Lua 5.2 */
    points_string = lua_tostring (L, -1);
    lua_setfield (L, LUA_REGISTRYINDEX, "points_string"); /* to
prevent garbage collection */
}

static void some_lua_func (lua_State *L)
{
    const char *st = lua_tostring (L, 1);
    if (points_string == st) { /* That's the magic */
        /* We've got a match here */
    }
    return 0;
}

If you have several Lua states, then you may do something like that:

typedef struct some_ud_t {
    const char *points_string;
} some_ud_t;

static void func ()
{
    some_ud_t *ud = malloc (sizeof (some_ud_t));
    lua_State *L = lua_newstate (allocator, ud);

    lua_pushliteral (L, "points"); /* There is a simpler way in Lua 5.2 */
    ud->points_string = lua_tostring (L, -1);
    lua_setfield (L, LUA_REGISTRYINDEX, "points_string"); /* to
prevent garbage collection */
}

static void some_lua_func (lua_State *L)
{
    some_ud_t *ud;
    lua_getallocf (L, &ud);
    const char *st = lua_tostring (L, 1);
    if (ud->points_string == st) { /* That's the magic */
        /* We've got a match here */
    }
    return 0;
}

Once again, I didn't test all these mad things