Re: Lua strings as "atoms"???

[Ben Sunshine-Hill <sneftel@...>]

It makes the C code a bit uglier, but I try to use upvalues for all my
Lua string constants in C functions that need to be efficient. By
pre-interning the strings, string equality is reduced to a pointer
compare. Using the registry is another approach, and one that looks a
lot cleaner, but isn't quite as efficient.

Ben

On 5/16/05, Chris Marrin <chris@marrin.com> wrote:
> I want to optimize string compares and pushes when interacting with Lua.
> For instance, in my __index() function I want to do this:
> 
>     const char* prop = lua_getstring(L, -1);
>     if (prop == mygPrototypeString)
>         ...
>     else if (prop == mygParentString)
>         ...
> 
> and so on. The global strings would be created in some init code like this:
> 
>     // global variables
>     const char* mygPrototypeString = NULL;
>     const char* mygParentString = NULL;
> 
>     ...
> 
>     lua_pushstring(L, "prototype");
>     mygPrototypeString = lua_tostring(L, -1);
>     lua_pop(L, 1);
>     lua_pushstring(L, "parent");
>     mygParentString = lua_tostring(L, -1);
>     lua_pop(L, 1);
> 
> By doing some experimentation it looks like, whenever you push a string
> and then ask for a pointer to it, the same address is always returned
> for that pointer, whether it is still on the stack or not. Is this
> always true? Can the above reliably be used to handle strings as atoms?
> 
> Or is there another, better way to do this?
> 
> PS - I am imagining also adding some refs (luaL_ref/luaL_unref) to
> global strings like this so I can push them by just pushing the ref. I
> would do this to save the time of hashing the string. Would this save
> enough to be worth it?
> 
> --
> chris marrin                ,""$,
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>  ```"```'"    `"`         `""`        ""`                          ,P`
> "As a general rule,don't solve puzzles that open portals to Hell"'
>