Hi
The guo da li is exchanging betrothal gifts ( This is the promise of marraige, today we call it engagement), like JoJo mentioned, usually happens 2 weeks before the wedding ceremony (actual day). Cakes given by the groom at this time, are then delivered to all the bride's relatives together with invitations to announce the coming wedding event.(now can get bangawan solo cake vouchers) There are many, many items... my mother cannot even remember all....No roast pig given here, only Big piece of whole RAW pig leg, also suppose to chop portions to give relatives. I have opted to have a big slab of roast pork instead ....for obvious reasons!!! Some bride's mothers ask for 6-12 tin cans of pork leg (ma ling brand)
On the wedding ceremony day, after the tea ceremony at groom's place, will go back to bride's place,( olden days, this happens 3 days later) that's when he brings the roast pig. This is to signify that the groom's family is very pleased with the bride.