For me, the ASSIGN technique is not best practice, so max bianchi is in my view pointing in the correct direction. However, I'd implement his suggestion like this:
If the whole table is accessible in a place you can get to before the BADI, then
1. Create a STATIC attribute on the BADI implementation class, that has the type of the data you need
2. In the bit before your BADI (maybe even an implicit enhancement) have
the_badi_class=>your_attribute = the_table
3. In your badi implementation, your_attribute now has the data
In this way, you don't need to export anything to memory, you're keeping all the "bits" of your development in one place, and you're keeping with the OO concept that BADI is built on.