rework config management

* Add standard way to do str2val and val2str conversion
* Add support for a config file
* Add support for reading and writing settings via ioctl

src/func.cpp

@@ -0,0 +1,39 @@
+/*
+  ISC License
+
+  Copyright (c) 2019, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "func.hpp"
+
+int
+Func::from_string(const std::string &s_)
+{
+  const Policy *tmp;
+
+  tmp = &Policy::find(s_);
+  if(tmp == Policy::invalid)
+    return -EINVAL;
+
+  policy = tmp;
+
+  return 0;
+}
+
+std::string
+Func::to_string(void) const
+{
+  return policy->to_string();
+}