+ Should use db->flags as errno, and should have an errorlist, so that
  we can return reasonable error indicators.

+ Should use db->blkno to track the page file pointer, so we can avoid a
  seek or two, by noting that we are already positioned on the block we
  need. (does this make any difference ?? I heard not.)

+ Must have a much better "bit-scrambling" hash function. This is crucial
  for the performance of sdbm: a better hash function means a better
  balanced trie, lesser holes, better splits, lesser number of pages.
  possibilities: crc-based hashing, cryptographic techniques. [I think I
  have found a very simple, but very effective hash function, even better
  than that of ndbm. Is there anything better ??]

+ It would be nice to re-construct a bitmap given the data file without
  having to re-hash all keys. (dba) This is easily doable, by using one
  key per page, and the identical hash function.

+ dbm is much like 9th Edition cbt utility. could be turned into something
  more useful.