class type digest_ctx =object..end
method add_memory : Netsys_types.memory -> unitAdd data
method add_subbytes : Stdlib.Bytes.t -> int -> int -> unitAdd data
method add_substring : string -> int -> int -> unitAdd data
method add_tstring : Netsys_types.tstring -> int -> int -> unitAdd data
method finish : unit -> stringFinish digestion, and return the digest
