api change - change []bool to byte array

[dajohi]

API needs to be changed to have it 'encapsulated'; Internally just have a byte array with bits of meaning, which is the form it is stored in the db, so faster on db load/store.

[davecgh]

To be a little more clear about what this issue is suggesting, currently the spent tracking data is kept in the memory using a []bool. Unfortunately, Go does not bit pack them, so it is using quite a bit more memory than it needs to.

Ideally, a new type such as type SpendData []byte could be created which packs the spend information into the byte slice using a single bit per output along with methods such as IsSpent(output uint32) (bool, error) and Spend(output uint32) error which do the bit twiddling to set/test the output. It is already stored in the database in this packed form, so it would require less time to load the information, and perhaps more importantly, lower the amount of garbage generated.

Once that is in place, all of the places up the dependency chain would have to be changed to accommodate the change.

[davecgh]

This will be part of overhaul described in #6.

[davecgh]

This has been moved to btcsuite/btcd#254.