Updating C structeres from Lua?

[Allan Odgaard <Allan@...>]

I am still not subscribed, but it seems I can post to the list and 
access the archive at YahooGroups (though please do Cc me in a 
potential reply).

I am writing a text editor (for OS X) and have chosen Lua as the 
scripting langauge, because this quite frankly seems to be the best 
choice :-)

My questions is twofold:

I would like to expose a lot of stuff to the scripts started from my 
text editor, but this would probably add a rather big memory (and 
performance) overhead, if I had to add all the stuff to Lua, e.g. the 
text buffer itself would be a table used as an array consisting of 
strings (and I would have to re-add it when text is changed from the 
editor).

Instead I can for example provide my "text buffer" table with a 
metatable that points to a function for 'index' which will pull the 
proper line from C, convert it to Lua, add it and return it.

Problem with this approach is that the user won't be able to do stuff 
like "table.foreach(textbuffer,print)" to print all lines.

Is there anyway around this?

Another problem is that there is also a settings table and the user 
could change this as he pleases.

Rather than having to go through the entire table when the script exits 
(to see what is changed) then I would prefer to supply some sort of 
callback function -- unfortunately it seems that 'newindex' (from the 
metatable) is only called when new indexes are created, and not when 
old ones are updated.

Any way around that?

I gues basically what I ask for is virtual tables, i.e. where all get 
and set would go through C code, rather than have to initially map all 
C structures to Lua and when the script exits, map it all back again.

I know I could provide my own Lua get/set functions and impose these on 
the user, but that would suck big time...

Thanks in advance, Allan