F.BATAbsolute sector offset of a data block, where a data block contains a sector bitmap and then data
val get : t -> int -> int32get t i returns the ith entry
val set : t -> int -> int32 -> unitset t i j sets the ith entry to j
val fold : (int -> int64 -> 'a -> 'a) -> t -> 'a -> 'afold f t initial folds f across all valid entries
val length : t -> intlength t the number of entries in the table
val to_string : t -> stringto_string t creates a debug-printable string