[c-host] initial agnostic option api and parser

common/include/common/option.h

@@ -0,0 +1,75 @@
+/*
+KVMGFX Client - A KVM Client for VGA Passthrough
+Copyright (C) 2017-2019 Geoffrey McRae <geoff@hostfission.com>
+https://looking-glass.hostfission.com
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 2 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#include <stdint.h>
+#include <stdbool.h>
+
+enum OptionType
+{
+  OPTION_TYPE_NONE = 0,
+  OPTION_TYPE_INT,
+  OPTION_TYPE_STRING,
+  OPTION_TYPE_BOOL
+};
+
+struct OptionState;
+
+struct OptionValue
+{
+  enum OptionType type;
+  union
+  {
+    int    x_int;
+    char * x_string;
+    bool   x_bool;
+  }
+  v;
+
+  // internal state
+  struct OptionState * state;
+};
+
+struct Option
+{
+  const char         * module;
+  const char         * name;
+  const char         * description;
+  struct OptionValue   value;
+
+  bool (*validator)(struct OptionValue * value);
+  void (*printHelp)();
+};
+
+// register an NULL terminated array of options
+bool option_register(struct Option options[]);
+
+// lookup the value of an option
+struct OptionValue * option_get       (const char * module, const char * name);
+int                  option_get_int   (const char * module, const char * name);
+const char *         option_get_string(const char * module, const char * name);
+bool                 option_get_bool  (const char * module, const char * name);
+
+// called by the main application to parse the command line arguments
+bool option_parse(int argc, char * argv[]);
+
+// print out the options, help, and their current values
+void option_print();
+
+// final cleanup
+void option_free();