persistant tables

[Asko Kauppi <asko.kauppi@...>]

A pre-information about a feature in upcoming LuaX that might be 
beneficial for others, too.

Persistant tables (no trademark applied :) is a way to make Lua tables 
that sync automatically to a disk image.  It works as a module, using 
SQLite3, but that is just an implementation detail.

The API:

	-----
	-- Opens a persistant table to work with (creates the database file if 
not there).
	--
	-- 'section' is an optional string, allowing to have several, 
independent tables
	-- of data within the one filename.
	--
	[per_obj] [,err_str]= open( fname_str [,section_str] )

	-- Closing the handle is not really required, GC will do it 
automatically.
	--
	void= close( per_obj )


The 'per_obj' value can be used as any regular table, writing numbers, 
strings, booleans and/or tables to it.  Tables are written on disk as a 
transaction, supposedly guaranteeing data integrity.  Reading data is 
fast, writing _can_ be fast (if syncing is turned off).

Iterating over the contents is possible in LuaX (but not in plain Lua) 
using the regular 'pairs' and 'ipairs' functions.

-ak