database

type DB interface {
	SaveBlock(block *types.Block, sender, miner string, wo *opt.WriteOptions) error
	LastBlock(ro *opt.ReadOptions) (*types.Block, error)
	// retrieve block by hash
	GetBlockH(hash []byte, ro *opt.ReadOptions) (*types.Block, error)
	// retrieve block by index
	GetBlockI(index uint64, ro *opt.ReadOptions) (*types.Block, error)
	// retrieve block hash by index
	GetBlkHash(index uint64, ro *opt.ReadOptions) ([]byte, error)

	SaveState(ss map[types.Account][]*types.UTXO, height uint64, wo *opt.WriteOptions) error
	ReadState() (map[types.Account][]*types.UTXO, error)
}