Re: [ANN] Lua 5.2.0 (beta-rc2) now available

[Tom N Harris <telliamed@...>]

On 06/22/2011 09:52 AM, Roberto Ierusalimschy wrote:
> The advantage of exporting the structure is that the user may add her
> own extra fields, if needed. (Are there real cases for this need?)

In that case the library likely also provides its own functions that use 
the extra data. And since the purpose of customizing FILE* is to be able 
to use the built-in functions, it seems superfluous. However, the 
exported FILE* factory could offer to add extra size to the structure 
that can be written to. Any internal Lua fields would be in front of the 
public fields, then extended data after. It also allows the userdata to 
be created prior to opening the handle. Something like:

lua_file* F = luaL_createfilehandle(L, extrasize);
F->fclose = myclose;
F->fptr = fopen(...);
((MyFile*)F)->extra = whatever;

--
- tom
telliamed@whoopdedo.org