This "util" directory is provided for utility header files and
implementations that are internally used in the DNS library
(libdns++).

The functionality provided in these tools is generally available in
other external or perhaps system supplied libraries.  The basic
development policy of BIND 10 is to avoid "reinventing wheels" unless
they belong to the exact technology area that BIND 10 targets (e.g.,
DNS).  However, libdns++ is a very core part of BIND 10, and is also
intended to be used as a public library, so dependency from libdns++
to external libraries should be minimized.  The utilities in this
directory are provided balancing two policies and as a kind of
compromise.

The header files in this directory are therefore not intended to be
installed.  Likewise, classes and public functions defined in this
directory are not intended to be used outside libdns++, although we
cannot prohibit it at the language level.

They are not even expected to be used in other modules of BIND 10 than
libdns++ based on the basic policy explained above.  Other modules
should only rely on the DNS specific interface that may internally
rely on these utility interfaces, or should use external libraries if
the other module really needs to use the utility feature directly.
There seem to be some violations as of this writing, but we should
eventually fix it.  A notable example is the SHA1 interfaces.  They
are defined here in the context of NSEC3 processing, but, in fact,
they are not even used from any of the other libdns++ classes or
functions.  The SHA1 related interfaces should be moved to the
application that needs it or the application should only access it
through DNS specific interfaces defined in libdns++.