def putkeep (k, v)

      k = k.to_s; v = v.to_s

      lib.abs_putkeep(@db, k, Rufus::Tokyo.blen(k), v, Rufus::Tokyo.blen(v))
    end
def putkeep (k, v)

      k = k.to_s; v = v.to_s

      lib.abs_putkeep(@db, k, Rufus::Tokyo.blen(k), v, Rufus::Tokyo.blen(v))
    end
Like #put but doesn't overwrite the value if already set. Returns true
 only if there no previous entry for k.