Re: String equality?

[Chris Marrin <chris@...>]

Mark Hamburg wrote:
> ...
> 3. Look at ways of making pushing the comparison string faster. For example,
> if you have a constant C string, you could store them in the registry keyed
> by the constant address by implementing something like the following:
>
>     void pushConstantString( lua_State* L, const char* s, size_t len ) {
>         lua_pushlightuserdata( L, s );
>         lua_rawget( L, LUA_REGISTRYINDEX );
>         if( lua_isnil( L, -1 ) ) {
>             lua_pop( L, 1 );
>             lua_pushlstring( L, s, len );
>             /* Save it in the registry. */
>             lua_pushlightuserdata( L, s );
>             lua_pushvalue( L, -2 );
>             lua_rawset( L, LUA_REGISTRYINDEX );
>         }
>     }
>
> Given that, you can then avoid repeated hashing of the string when pushing
> it.

This is very similar to what I have tried with luaL_ref(), except that 
you are using a lightuserdata rather than an integer. The nice thing 
about using luaL_ref() is that it works for non-constant strings.

But I think I will just continue using the ad-hoc technique I am using 
now. At least that allows me to do little optimizations like:

    const char* prop = lua_tostring(L,-1);
    if (prop[0] == 'f' && prop[1] == 'o' && prop[2] == 'o') ...

Oh well, on to bigger issues!

Thanks for all the ideas...

--
chris marrin              ,""$, "As a general rule,don't solve puzzles
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