The OpenBSD Ada Library

This library was written to help my easing into Ada programming, as I struggle with this language so
different from all others I've known.  This is a package I can be proud of, however.  This defines a
simple package for  OpenBSD's extra facilities,  namely pledge and unveil.   There is an enumeration
type common to both,  two more enumeration types,  two array types thereof, two exceptions, and then
two procedures Pledge and Unveil.  This is a simple and high-level interface to OpenBSD's pledge and
unveil facilities that came to mind in my errant thought.   The procedures are expected and designed
to be used exclusively with array aggregates and not with the type names.   Here is the example that
inspired the library:

with OpenBSD; use OpenBSD;
...
Unveil("/tmp/", (Read | Write => Allowed, others => Disallowed));
...
Pledge((Stdio | Fattr => Allowed, others => Disallowed));
...

These procedures work by fixing Ada's enumeration types over the strings OpenBSD uses to approximate
such a  language facility.   The pledge accepts a simple string of  designated keywords separated by
spaces and terminated according to the usual C convention.  The unveil accepts a filename and string
of designated characters terminated according to the usual C convention, as well.  Failure cases are
invalid pointers,  malformed strings, invalid requests, attempts to increase permissions, and so on.
Several of these failure cases simply won't occur in Ada;  the permission errors are those  that are
particularly relevant  and correspond to the exceptions,  with unveil conflating some of the failure
cases for simplicity, and this is a reasonable decision given that the precise error can be learned.

I'm, of course, still rather green to Ada and so it can be expected the body of this package will be
improved over time.  I likely won't change any of the names used in the specification, but this is a
reason you should only use array aggregates with it.  This library is not currently robust to change
as I believe it should be, but I intend to correct this.  It has been a valuable learning experience
and I expect to update this library as  OpenBSD changes the semantics of  pledge and unveil  or adds
new facilities that would be worthwhile to expose to Ada.

Written in 2019 by Prince Trippy.
This document is available under the CC0 Public Domain Dedication.
.