ApplyDAOHardFork modifies the state database according to the DAO hard-fork rules, transferring all balances of a set of DAO accounts to a single refund contract.

VerifyDAOHeaderExtraData validates the extra-data field of a block header to ensure it conforms to DAO hard-fork rules.

VerifyForkHashes verifies that blocks conforming to network hard-forks do have the correct hashes, to avoid clients going off on different chains.

ErrBadNoDAOExtra is returned if a header does support the DAO fork on a no- fork client.

ErrBadProDAOExtra is returned if a header doens't support the DAO fork on a pro-fork client.